diff --git a/cmds/atrace/atrace.cpp b/cmds/atrace/atrace.cpp
index 79419d3..021fdb5 100644
--- a/cmds/atrace/atrace.cpp
+++ b/cmds/atrace/atrace.cpp
@@ -245,6 +245,7 @@
         { OPT,      "events/kmem/ion_heap_shrink/enable" },
         { OPT,      "events/ion/ion_stat/enable" },
         { OPT,      "events/gpu_mem/gpu_mem_total/enable" },
+        { OPT,      "events/fastrpc/fastrpc_dma_stat/enable" },
     } },
     { "thermal",  "Thermal event", 0, {
         { REQ,      "events/thermal/thermal_temperature/enable" },
diff --git a/include/ftl/cast.h b/include/ftl/cast.h
new file mode 100644
index 0000000..ff1b58a
--- /dev/null
+++ b/include/ftl/cast.h
@@ -0,0 +1,84 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <limits>
+#include <type_traits>
+
+#include <ftl/details/cast.h>
+
+namespace android::ftl {
+
+enum class CastSafety { kSafe, kUnderflow, kOverflow };
+
+// Returns whether static_cast<R>(v) is safe, or would result in underflow or overflow.
+//
+//   static_assert(ftl::cast_safety<uint8_t>(-1) == ftl::CastSafety::kUnderflow);
+//   static_assert(ftl::cast_safety<int8_t>(128u) == ftl::CastSafety::kOverflow);
+//
+//   static_assert(ftl::cast_safety<uint32_t>(-.1f) == ftl::CastSafety::kUnderflow);
+//   static_assert(ftl::cast_safety<int32_t>(static_cast<float>(INT32_MAX)) ==
+//                                           ftl::CastSafety::kOverflow);
+//
+//   static_assert(ftl::cast_safety<float>(-DBL_MAX) == ftl::CastSafety::kUnderflow);
+//
+template <typename R, typename T>
+constexpr CastSafety cast_safety(T v) {
+  static_assert(std::is_arithmetic_v<T>);
+  static_assert(std::is_arithmetic_v<R>);
+
+  constexpr bool kFromSigned = std::is_signed_v<T>;
+  constexpr bool kToSigned = std::is_signed_v<R>;
+
+  using details::max_exponent;
+
+  // If the R range contains the T range, then casting is always safe.
+  if constexpr ((kFromSigned == kToSigned && max_exponent<R> >= max_exponent<T>) ||
+                (!kFromSigned && kToSigned && max_exponent<R> > max_exponent<T>)) {
+    return CastSafety::kSafe;
+  }
+
+  using C = std::common_type_t<R, T>;
+
+  if constexpr (kFromSigned) {
+    using L = details::safe_limits<R, T>;
+
+    if constexpr (kToSigned) {
+      // Signed to signed.
+      if (v < L::lowest()) return CastSafety::kUnderflow;
+      return v <= L::max() ? CastSafety::kSafe : CastSafety::kOverflow;
+    } else {
+      // Signed to unsigned.
+      if (v < 0) return CastSafety::kUnderflow;
+      return static_cast<C>(v) <= static_cast<C>(L::max()) ? CastSafety::kSafe
+                                                           : CastSafety::kOverflow;
+    }
+  } else {
+    using L = std::numeric_limits<R>;
+
+    if constexpr (kToSigned) {
+      // Unsigned to signed.
+      return static_cast<C>(v) <= static_cast<C>(L::max()) ? CastSafety::kSafe
+                                                           : CastSafety::kOverflow;
+    } else {
+      // Unsigned to unsigned.
+      return v <= L::max() ? CastSafety::kSafe : CastSafety::kOverflow;
+    }
+  }
+}
+
+}  // namespace android::ftl
diff --git a/include/ftl/details/cast.h b/include/ftl/details/cast.h
new file mode 100644
index 0000000..87b9f1e
--- /dev/null
+++ b/include/ftl/details/cast.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <limits>
+#include <type_traits>
+
+namespace android::ftl::details {
+
+// Exponent whose power of 2 is the (exclusive) upper bound of T.
+template <typename T, typename L = std::numeric_limits<T>>
+constexpr int max_exponent = std::is_floating_point_v<T> ? L::max_exponent : L::digits;
+
+// Extension of std::numeric_limits<T> that reduces the maximum for integral types T such that it
+// has an exact representation for floating-point types F. For example, the maximum int32_t value
+// is 2'147'483'647, but casting it to float commonly rounds up to 2'147'483'650.f, which cannot
+// be safely converted back lest the signed overflow invokes undefined behavior. This pitfall is
+// avoided by clearing the lower (31 - 24 =) 7 bits of precision to 2'147'483'520. Note that the
+// minimum is representable.
+template <typename T, typename F>
+struct safe_limits : std::numeric_limits<T> {
+  static constexpr T max() {
+    using Base = std::numeric_limits<T>;
+
+    if constexpr (std::is_integral_v<T> && std::is_floating_point_v<F>) {
+      // Assume the mantissa is 24 bits for float, or 53 bits for double.
+      using Float = std::numeric_limits<F>;
+      static_assert(Float::is_iec559);
+
+      // If the integer is wider than the mantissa, clear the excess bits of precision.
+      constexpr int kShift = Base::digits - Float::digits;
+      if constexpr (kShift > 0) {
+        using U = std::make_unsigned_t<T>;
+        constexpr U kOne = static_cast<U>(1);
+        return static_cast<U>(Base::max()) & ~((kOne << kShift) - kOne);
+      }
+    }
+
+    return Base::max();
+  }
+};
+
+}  // namespace android::ftl::details
diff --git a/include/ftl/small_map.h b/include/ftl/small_map.h
index 84c15eb..bcaba82 100644
--- a/include/ftl/small_map.h
+++ b/include/ftl/small_map.h
@@ -19,6 +19,7 @@
 #include <ftl/initializer_list.h>
 #include <ftl/small_vector.h>
 
+#include <algorithm>
 #include <functional>
 #include <optional>
 #include <type_traits>
@@ -28,7 +29,10 @@
 
 // Associative container with unique, unordered keys. Unlike std::unordered_map, key-value pairs are
 // stored in contiguous storage for cache efficiency. The map is allocated statically until its size
-// exceeds N, at which point mappings are relocated to dynamic memory.
+// exceeds N, at which point mappings are relocated to dynamic memory. The try_emplace operation has
+// a non-standard analogue try_replace that destructively emplaces. The API also defines an in-place
+// counterpart to insert_or_assign: emplace_or_replace. Lookup is done not via a subscript operator,
+// but immutable getters that can optionally transform the value.
 //
 // SmallMap<K, V, 0> unconditionally allocates on the heap.
 //
@@ -43,16 +47,19 @@
 //   assert(!map.dynamic());
 //
 //   assert(map.contains(123));
-//   assert(map.find(42, [](const std::string& s) { return s.size(); }) == 3u);
+//   assert(map.get(42, [](const std::string& s) { return s.size(); }) == 3u);
 //
-//   const auto opt = map.find(-1);
+//   const auto opt = map.get(-1);
 //   assert(opt);
 //
 //   std::string& ref = *opt;
 //   assert(ref.empty());
 //   ref = "xyz";
 //
-//   assert(map == SmallMap(ftl::init::map(-1, "xyz")(42, "???")(123, "abc")));
+//   map.emplace_or_replace(0, "vanilla", 2u, 3u);
+//   assert(map.dynamic());
+//
+//   assert(map == SmallMap(ftl::init::map(-1, "xyz")(0, "nil")(42, "???")(123, "abc")));
 //
 template <typename K, typename V, std::size_t N>
 class SmallMap final {
@@ -80,12 +87,7 @@
   // The syntax for listing pairs is as follows:
   //
   //   ftl::SmallMap map = ftl::init::map<int, std::string>(123, "abc")(-1)(42, 3u, '?');
-  //
   //   static_assert(std::is_same_v<decltype(map), ftl::SmallMap<int, std::string, 3>>);
-  //   assert(map.size() == 3u);
-  //   assert(map.contains(-1) && map.find(-1)->get().empty());
-  //   assert(map.contains(42) && map.find(42)->get() == "???");
-  //   assert(map.contains(123) && map.find(123)->get() == "abc");
   //
   // The types of the key and value are deduced if the first pair contains exactly two arguments:
   //
@@ -95,7 +97,7 @@
   template <typename U, std::size_t... Sizes, typename... Types>
   SmallMap(InitializerList<U, std::index_sequence<Sizes...>, Types...>&& list)
       : map_(std::move(list)) {
-    // TODO: Enforce unique keys.
+    deduplicate();
   }
 
   size_type max_size() const { return map_.max_size(); }
@@ -115,27 +117,27 @@
 
   // Returns whether a mapping exists for the given key.
   bool contains(const key_type& key) const {
-    return find(key, [](const mapped_type&) {});
+    return get(key, [](const mapped_type&) {});
   }
 
   // Returns a reference to the value for the given key, or std::nullopt if the key was not found.
   //
   //   ftl::SmallMap map = ftl::init::map('a', 'A')('b', 'B')('c', 'C');
   //
-  //   const auto opt = map.find('c');
+  //   const auto opt = map.get('c');
   //   assert(opt == 'C');
   //
   //   char d = 'd';
-  //   const auto ref = map.find('d').value_or(std::ref(d));
+  //   const auto ref = map.get('d').value_or(std::ref(d));
   //   ref.get() = 'D';
   //   assert(d == 'D');
   //
-  auto find(const key_type& key) const -> std::optional<std::reference_wrapper<const mapped_type>> {
-    return find(key, [](const mapped_type& v) { return std::cref(v); });
+  auto get(const key_type& key) const -> std::optional<std::reference_wrapper<const mapped_type>> {
+    return get(key, [](const mapped_type& v) { return std::cref(v); });
   }
 
-  auto find(const key_type& key) -> std::optional<std::reference_wrapper<mapped_type>> {
-    return find(key, [](mapped_type& v) { return std::ref(v); });
+  auto get(const key_type& key) -> std::optional<std::reference_wrapper<mapped_type>> {
+    return get(key, [](mapped_type& v) { return std::ref(v); });
   }
 
   // Returns the result R of a unary operation F on (a constant or mutable reference to) the value
@@ -144,11 +146,11 @@
   //
   //   ftl::SmallMap map = ftl::init::map('a', 'x')('b', 'y')('c', 'z');
   //
-  //   assert(map.find('c', [](char c) { return std::toupper(c); }) == 'Z');
-  //   assert(map.find('c', [](char& c) { c = std::toupper(c); }));
+  //   assert(map.get('c', [](char c) { return std::toupper(c); }) == 'Z');
+  //   assert(map.get('c', [](char& c) { c = std::toupper(c); }));
   //
   template <typename F, typename R = std::invoke_result_t<F, const mapped_type&>>
-  auto find(const key_type& key, F f) const
+  auto get(const key_type& key, F f) const
       -> std::conditional_t<std::is_void_v<R>, bool, std::optional<R>> {
     for (auto& [k, v] : *this) {
       if (k == key) {
@@ -165,12 +167,96 @@
   }
 
   template <typename F>
-  auto find(const key_type& key, F f) {
-    return std::as_const(*this).find(
+  auto get(const key_type& key, F f) {
+    return std::as_const(*this).get(
         key, [&f](const mapped_type& v) { return f(const_cast<mapped_type&>(v)); });
   }
 
+  // Returns an iterator to an existing mapping for the given key, or the end() iterator otherwise.
+  const_iterator find(const key_type& key) const { return const_cast<SmallMap&>(*this).find(key); }
+  iterator find(const key_type& key) { return find(key, begin()); }
+
+  // Inserts a mapping unless it exists. Returns an iterator to the inserted or existing mapping,
+  // and whether the mapping was inserted.
+  //
+  // On emplace, if the map reaches its static or dynamic capacity, then all iterators are
+  // invalidated. Otherwise, only the end() iterator is invalidated.
+  //
+  template <typename... Args>
+  std::pair<iterator, bool> try_emplace(const key_type& key, Args&&... args) {
+    if (const auto it = find(key); it != end()) {
+      return {it, false};
+    }
+
+    auto& ref = map_.emplace_back(std::piecewise_construct, std::forward_as_tuple(key),
+                                  std::forward_as_tuple(std::forward<Args>(args)...));
+    return {&ref, true};
+  }
+
+  // Replaces a mapping if it exists, and returns an iterator to it. Returns the end() iterator
+  // otherwise.
+  //
+  // The value is replaced via move constructor, so type V does not need to define copy/move
+  // assignment, e.g. its data members may be const.
+  //
+  // The arguments may directly or indirectly refer to the mapping being replaced.
+  //
+  // Iterators to the replaced mapping point to its replacement, and others remain valid.
+  //
+  template <typename... Args>
+  iterator try_replace(const key_type& key, Args&&... args) {
+    const auto it = find(key);
+    if (it == end()) return it;
+    map_.replace(it, std::piecewise_construct, std::forward_as_tuple(key),
+                 std::forward_as_tuple(std::forward<Args>(args)...));
+    return it;
+  }
+
+  // In-place counterpart of std::unordered_map's insert_or_assign. Returns true on emplace, or
+  // false on replace.
+  //
+  // The value is emplaced and replaced via move constructor, so type V does not need to define
+  // copy/move assignment, e.g. its data members may be const.
+  //
+  // On emplace, if the map reaches its static or dynamic capacity, then all iterators are
+  // invalidated. Otherwise, only the end() iterator is invalidated. On replace, iterators
+  // to the replaced mapping point to its replacement, and others remain valid.
+  //
+  template <typename... Args>
+  std::pair<iterator, bool> emplace_or_replace(const key_type& key, Args&&... args) {
+    const auto [it, ok] = try_emplace(key, std::forward<Args>(args)...);
+    if (ok) return {it, ok};
+    map_.replace(it, std::piecewise_construct, std::forward_as_tuple(key),
+                 std::forward_as_tuple(std::forward<Args>(args)...));
+    return {it, ok};
+  }
+
+  // Removes a mapping if it exists, and returns whether it did.
+  //
+  // The last() and end() iterators, as well as those to the erased mapping, are invalidated.
+  //
+  bool erase(const key_type& key) { return erase(key, begin()); }
+
  private:
+  iterator find(const key_type& key, iterator first) {
+    return std::find_if(first, end(), [&key](const auto& pair) { return pair.first == key; });
+  }
+
+  bool erase(const key_type& key, iterator first) {
+    const auto it = find(key, first);
+    if (it == end()) return false;
+    map_.unstable_erase(it);
+    return true;
+  }
+
+  void deduplicate() {
+    for (auto it = begin(); it != end();) {
+      if (const auto key = it->first; ++it != end()) {
+        while (erase(key, it));
+      }
+    }
+  }
+
   Map map_;
 };
 
@@ -186,7 +272,7 @@
 
   for (const auto& [k, v] : lhs) {
     const auto& lv = v;
-    if (!rhs.find(k, [&lv](const auto& rv) { return lv == rv; }).value_or(false)) {
+    if (!rhs.get(k, [&lv](const auto& rv) { return lv == rv; }).value_or(false)) {
       return false;
     }
   }
diff --git a/include/ftl/small_vector.h b/include/ftl/small_vector.h
index cb0ae35..0341435 100644
--- a/include/ftl/small_vector.h
+++ b/include/ftl/small_vector.h
@@ -348,7 +348,7 @@
   using Impl::pop_back;
 
   void unstable_erase(iterator it) {
-    if (it != last()) std::iter_swap(it, last());
+    if (it != last()) replace(it, std::move(back()));
     pop_back();
   }
 
diff --git a/include/ftl/string.h b/include/ftl/string.h
new file mode 100644
index 0000000..2d96b06
--- /dev/null
+++ b/include/ftl/string.h
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <cassert>
+#include <charconv>
+#include <limits>
+#include <string>
+#include <string_view>
+#include <type_traits>
+
+namespace android::ftl {
+
+enum class Radix { kBin = 2, kDec = 10, kHex = 16 };
+
+template <typename T>
+struct to_chars_length {
+  static_assert(std::is_integral_v<T>);
+  // Maximum binary digits, plus minus sign and radix prefix.
+  static constexpr std::size_t value = std::numeric_limits<std::make_unsigned_t<T>>::digits + 3;
+};
+
+template <typename T>
+constexpr std::size_t to_chars_length_v = to_chars_length<T>::value;
+
+template <typename T = std::int64_t>
+using to_chars_buffer_t = char[to_chars_length_v<T>];
+
+// Lightweight (not allocating nor sprintf-based) alternative to std::to_string for integers, with
+// optional radix. See also ftl::to_string below.
+//
+//   ftl::to_chars_buffer_t<> buffer;
+//
+//   assert(ftl::to_chars(buffer, 123u) == "123");
+//   assert(ftl::to_chars(buffer, -42, ftl::Radix::kBin) == "-0b101010");
+//   assert(ftl::to_chars(buffer, 0xcafe, ftl::Radix::kHex) == "0xcafe");
+//   assert(ftl::to_chars(buffer, '*', ftl::Radix::kHex) == "0x2a");
+//
+template <typename T, std::size_t N>
+std::string_view to_chars(char (&buffer)[N], T v, Radix radix = Radix::kDec) {
+  static_assert(N >= to_chars_length_v<T>);
+
+  auto begin = buffer + 2;
+  const auto [end, err] = std::to_chars(begin, buffer + N, v, static_cast<int>(radix));
+  assert(err == std::errc());
+
+  if (radix == Radix::kDec) {
+    // TODO: Replace with {begin, end} in C++20.
+    return {begin, static_cast<std::size_t>(end - begin)};
+  }
+
+  const auto prefix = radix == Radix::kBin ? 'b' : 'x';
+  if constexpr (std::is_unsigned_v<T>) {
+    buffer[0] = '0';
+    buffer[1] = prefix;
+  } else {
+    if (*begin == '-') {
+      *buffer = '-';
+    } else {
+      --begin;
+    }
+
+    *begin-- = prefix;
+    *begin = '0';
+  }
+
+  // TODO: Replace with {buffer, end} in C++20.
+  return {buffer, static_cast<std::size_t>(end - buffer)};
+}
+
+// Lightweight (not sprintf-based) alternative to std::to_string for integers, with optional radix.
+//
+//   assert(ftl::to_string(123u) == "123");
+//   assert(ftl::to_string(-42, ftl::Radix::kBin) == "-0b101010");
+//   assert(ftl::to_string(0xcafe, ftl::Radix::kHex) == "0xcafe");
+//   assert(ftl::to_string('*', ftl::Radix::kHex) == "0x2a");
+//
+template <typename T>
+inline std::string to_string(T v, Radix radix = Radix::kDec) {
+  to_chars_buffer_t<T> buffer;
+  return std::string(to_chars(buffer, v, radix));
+}
+
+std::string to_string(bool) = delete;
+std::string to_string(bool, Radix) = delete;
+
+}  // namespace android::ftl
diff --git a/include/input/Input.h b/include/input/Input.h
index e8678d2..438121b 100644
--- a/include/input/Input.h
+++ b/include/input/Input.h
@@ -368,8 +368,6 @@
     float getAxisValue(int32_t axis) const;
     status_t setAxisValue(int32_t axis, float value);
 
-    void scale(float globalScale);
-
     // Scale the pointer coordinates according to a global scale and a
     // window scale. The global scale will be applied to TOUCH/TOOL_MAJOR/MINOR
     // axes, however the window scaling will not.
diff --git a/libs/ftl/Android.bp b/libs/ftl/Android.bp
index 97626be..4366203 100644
--- a/libs/ftl/Android.bp
+++ b/libs/ftl/Android.bp
@@ -14,10 +14,12 @@
         address: true,
     },
     srcs: [
+        "cast_test.cpp",
         "future_test.cpp",
         "small_map_test.cpp",
         "small_vector_test.cpp",
         "static_vector_test.cpp",
+        "string_test.cpp",
     ],
     cflags: [
         "-Wall",
diff --git a/libs/ftl/cast_test.cpp b/libs/ftl/cast_test.cpp
new file mode 100644
index 0000000..2abcb8f
--- /dev/null
+++ b/libs/ftl/cast_test.cpp
@@ -0,0 +1,200 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <ftl/cast.h>
+#include <gtest/gtest.h>
+
+#include <cfloat>
+#include <cmath>
+#include <limits>
+
+namespace android::test {
+
+using ftl::cast_safety;
+using ftl::CastSafety;
+
+template <typename T>
+constexpr T min = std::numeric_limits<T>::lowest();
+
+template <typename T>
+constexpr T max = std::numeric_limits<T>::max();
+
+template <typename T>
+constexpr T inf = std::numeric_limits<T>::infinity();
+
+template <typename T>
+constexpr T NaN = std::numeric_limits<T>::quiet_NaN();
+
+// Keep in sync with example usage in header file.
+
+static_assert(cast_safety<uint8_t>(-1) == CastSafety::kUnderflow);
+static_assert(cast_safety<int8_t>(128u) == CastSafety::kOverflow);
+
+static_assert(cast_safety<uint32_t>(-.1f) == CastSafety::kUnderflow);
+static_assert(cast_safety<int32_t>(static_cast<float>(INT32_MAX)) == CastSafety::kOverflow);
+
+static_assert(cast_safety<float>(-DBL_MAX) == CastSafety::kUnderflow);
+
+// Unsigned to unsigned.
+
+static_assert(cast_safety<uint8_t>(0u) == CastSafety::kSafe);
+static_assert(cast_safety<uint16_t>(max<uint8_t>) == CastSafety::kSafe);
+static_assert(cast_safety<uint8_t>(static_cast<uint32_t>(max<uint8_t>)) == CastSafety::kSafe);
+
+static_assert(cast_safety<uint32_t>(max<uint64_t>) == CastSafety::kOverflow);
+static_assert(cast_safety<uint8_t>(static_cast<uint32_t>(max<uint8_t>) + 1) ==
+              CastSafety::kOverflow);
+
+// Unsigned to signed.
+
+static_assert(cast_safety<int16_t>(0u) == CastSafety::kSafe);
+static_assert(cast_safety<int16_t>(max<uint8_t>) == CastSafety::kSafe);
+static_assert(cast_safety<int16_t>(max<uint16_t>) == CastSafety::kOverflow);
+
+static_assert(cast_safety<int64_t>(static_cast<uint64_t>(max<int64_t>) - 1) == CastSafety::kSafe);
+static_assert(cast_safety<int64_t>(static_cast<uint64_t>(max<int64_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<int64_t>(static_cast<uint64_t>(max<int64_t>) + 1) ==
+              CastSafety::kOverflow);
+
+// Signed to unsigned.
+
+static_assert(cast_safety<uint16_t>(0) == CastSafety::kSafe);
+static_assert(cast_safety<uint16_t>(max<int8_t>) == CastSafety::kSafe);
+static_assert(cast_safety<uint16_t>(max<int16_t>) == CastSafety::kSafe);
+
+static_assert(cast_safety<uint32_t>(-1) == CastSafety::kUnderflow);
+static_assert(cast_safety<uint32_t>(max<int64_t>) == CastSafety::kOverflow);
+
+static_assert(cast_safety<uint32_t>(static_cast<int64_t>(max<uint32_t>) - 1) == CastSafety::kSafe);
+static_assert(cast_safety<uint32_t>(static_cast<int64_t>(max<uint32_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<uint32_t>(static_cast<int64_t>(max<uint32_t>) + 1) ==
+              CastSafety::kOverflow);
+
+// Signed to signed.
+
+static_assert(cast_safety<int8_t>(-129) == CastSafety::kUnderflow);
+static_assert(cast_safety<int8_t>(-128) == CastSafety::kSafe);
+static_assert(cast_safety<int8_t>(127) == CastSafety::kSafe);
+static_assert(cast_safety<int8_t>(128) == CastSafety::kOverflow);
+
+static_assert(cast_safety<int32_t>(static_cast<int64_t>(min<int32_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<int32_t>(static_cast<int64_t>(max<int32_t>)) == CastSafety::kSafe);
+
+static_assert(cast_safety<int16_t>(min<int32_t>) == CastSafety::kUnderflow);
+static_assert(cast_safety<int32_t>(max<int64_t>) == CastSafety::kOverflow);
+
+// Float to float.
+
+static_assert(cast_safety<double>(max<float>) == CastSafety::kSafe);
+static_assert(cast_safety<double>(min<float>) == CastSafety::kSafe);
+
+static_assert(cast_safety<float>(min<double>) == CastSafety::kUnderflow);
+static_assert(cast_safety<float>(max<double>) == CastSafety::kOverflow);
+
+TEST(CastSafety, FloatToFloat) {
+  EXPECT_EQ(cast_safety<float>(std::nexttoward(static_cast<double>(min<float>), min<double>)),
+            CastSafety::kUnderflow);
+  EXPECT_EQ(cast_safety<float>(std::nexttoward(static_cast<double>(max<float>), max<double>)),
+            CastSafety::kOverflow);
+}
+
+// Unsigned to float.
+
+static_assert(cast_safety<float>(0u) == CastSafety::kSafe);
+static_assert(cast_safety<float>(max<uint64_t>) == CastSafety::kSafe);
+
+static_assert(cast_safety<double>(0u) == CastSafety::kSafe);
+static_assert(cast_safety<double>(max<uint64_t>) == CastSafety::kSafe);
+
+// Signed to float.
+
+static_assert(cast_safety<float>(min<int64_t>) == CastSafety::kSafe);
+static_assert(cast_safety<float>(max<int64_t>) == CastSafety::kSafe);
+
+static_assert(cast_safety<double>(min<int64_t>) == CastSafety::kSafe);
+static_assert(cast_safety<double>(max<int64_t>) == CastSafety::kSafe);
+
+// Float to unsigned.
+
+static_assert(cast_safety<uint32_t>(0.f) == CastSafety::kSafe);
+static_assert(cast_safety<uint32_t>(min<float>) == CastSafety::kUnderflow);
+static_assert(cast_safety<uint32_t>(max<float>) == CastSafety::kOverflow);
+static_assert(cast_safety<uint32_t>(-.1f) == CastSafety::kUnderflow);
+
+static_assert(cast_safety<uint16_t>(-inf<float>) == CastSafety::kUnderflow);
+static_assert(cast_safety<uint32_t>(inf<float>) == CastSafety::kOverflow);
+static_assert(cast_safety<uint64_t>(NaN<float>) == CastSafety::kOverflow);
+
+static_assert(cast_safety<uint32_t>(static_cast<float>(max<int32_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<uint32_t>(static_cast<float>(max<uint32_t>)) == CastSafety::kOverflow);
+static_assert(cast_safety<uint32_t>(static_cast<double>(max<int32_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<uint32_t>(static_cast<double>(max<uint32_t>)) == CastSafety::kSafe);
+
+static_assert(cast_safety<uint64_t>(0.0) == CastSafety::kSafe);
+static_assert(cast_safety<uint64_t>(min<double>) == CastSafety::kUnderflow);
+static_assert(cast_safety<uint64_t>(max<double>) == CastSafety::kOverflow);
+static_assert(cast_safety<uint64_t>(-.1) == CastSafety::kUnderflow);
+
+static_assert(cast_safety<uint64_t>(static_cast<float>(max<int64_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<uint64_t>(static_cast<float>(max<uint64_t>)) == CastSafety::kOverflow);
+static_assert(cast_safety<uint64_t>(static_cast<double>(max<int64_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<uint64_t>(static_cast<double>(max<uint64_t>)) == CastSafety::kOverflow);
+
+// Float to signed.
+
+static_assert(cast_safety<int32_t>(0.f) == CastSafety::kSafe);
+static_assert(cast_safety<int32_t>(min<float>) == CastSafety::kUnderflow);
+static_assert(cast_safety<int32_t>(max<float>) == CastSafety::kOverflow);
+
+static_assert(cast_safety<int16_t>(-inf<double>) == CastSafety::kUnderflow);
+static_assert(cast_safety<int32_t>(inf<double>) == CastSafety::kOverflow);
+static_assert(cast_safety<int64_t>(NaN<double>) == CastSafety::kOverflow);
+
+static_assert(cast_safety<int32_t>(static_cast<float>(min<int32_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<int32_t>(static_cast<float>(max<int32_t>)) == CastSafety::kOverflow);
+static_assert(cast_safety<int32_t>(static_cast<double>(min<int32_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<int32_t>(static_cast<double>(max<int32_t>)) == CastSafety::kSafe);
+
+static_assert(cast_safety<int64_t>(0.0) == CastSafety::kSafe);
+static_assert(cast_safety<int64_t>(min<double>) == CastSafety::kUnderflow);
+static_assert(cast_safety<int64_t>(max<double>) == CastSafety::kOverflow);
+
+static_assert(cast_safety<int64_t>(static_cast<float>(min<int64_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<int64_t>(static_cast<float>(max<int64_t>)) == CastSafety::kOverflow);
+static_assert(cast_safety<int64_t>(static_cast<double>(min<int64_t>)) == CastSafety::kSafe);
+static_assert(cast_safety<int64_t>(static_cast<double>(max<int64_t>)) == CastSafety::kOverflow);
+
+TEST(CastSafety, FloatToSigned) {
+  constexpr int32_t kMax = ftl::details::safe_limits<int32_t, float>::max();
+  static_assert(kMax == 2'147'483'520);
+  EXPECT_EQ(kMax, static_cast<int32_t>(std::nexttowardf(max<int32_t>, 0)));
+
+  EXPECT_EQ(cast_safety<int32_t>(std::nexttowardf(min<int32_t>, 0)), CastSafety::kSafe);
+  EXPECT_EQ(cast_safety<int32_t>(std::nexttowardf(max<int32_t>, 0)), CastSafety::kSafe);
+  EXPECT_EQ(cast_safety<int64_t>(std::nexttoward(min<int64_t>, 0)), CastSafety::kSafe);
+  EXPECT_EQ(cast_safety<int64_t>(std::nexttoward(max<int64_t>, 0)), CastSafety::kSafe);
+
+  EXPECT_EQ(cast_safety<int32_t>(std::nexttowardf(min<int32_t>, min<float>)),
+            CastSafety::kUnderflow);
+  EXPECT_EQ(cast_safety<int32_t>(std::nexttowardf(max<int32_t>, max<float>)),
+            CastSafety::kOverflow);
+  EXPECT_EQ(cast_safety<int64_t>(std::nexttoward(min<int64_t>, min<double>)),
+            CastSafety::kUnderflow);
+  EXPECT_EQ(cast_safety<int64_t>(std::nexttoward(max<int64_t>, max<double>)),
+            CastSafety::kOverflow);
+}
+
+}  // namespace android::test
diff --git a/libs/ftl/small_map_test.cpp b/libs/ftl/small_map_test.cpp
index 323b9f9..2e81022 100644
--- a/libs/ftl/small_map_test.cpp
+++ b/libs/ftl/small_map_test.cpp
@@ -18,6 +18,9 @@
 #include <gtest/gtest.h>
 
 #include <cctype>
+#include <string>
+
+using namespace std::string_literals;
 
 namespace android::test {
 
@@ -35,16 +38,19 @@
 
   EXPECT_TRUE(map.contains(123));
 
-  EXPECT_EQ(map.find(42, [](const std::string& s) { return s.size(); }), 3u);
+  EXPECT_EQ(map.get(42, [](const std::string& s) { return s.size(); }), 3u);
 
-  const auto opt = map.find(-1);
+  const auto opt = map.get(-1);
   ASSERT_TRUE(opt);
 
   std::string& ref = *opt;
   EXPECT_TRUE(ref.empty());
   ref = "xyz";
 
-  EXPECT_EQ(map, SmallMap(ftl::init::map(-1, "xyz")(42, "???")(123, "abc")));
+  map.emplace_or_replace(0, "vanilla", 2u, 3u);
+  EXPECT_TRUE(map.dynamic());
+
+  EXPECT_EQ(map, SmallMap(ftl::init::map(-1, "xyz")(0, "nil")(42, "???")(123, "abc")));
 }
 
 TEST(SmallMap, Construct) {
@@ -90,42 +96,253 @@
   }
 }
 
+TEST(SmallMap, UniqueKeys) {
+  {
+    // Duplicate mappings are discarded.
+    const SmallMap map = ftl::init::map<int, float>(1)(2)(3)(2)(3)(1)(3)(2)(1);
+
+    EXPECT_EQ(map.size(), 3u);
+    EXPECT_EQ(map.max_size(), 9u);
+
+    using Map = decltype(map);
+    EXPECT_EQ(map, Map(ftl::init::map(1, 0.f)(2, 0.f)(3, 0.f)));
+  }
+  {
+    // Duplicate mappings may be reordered.
+    const SmallMap map = ftl::init::map('a', 'A')(
+        'b', 'B')('b')('b')('c', 'C')('a')('d')('c')('e', 'E')('d', 'D')('a')('f', 'F');
+
+    EXPECT_EQ(map.size(), 6u);
+    EXPECT_EQ(map.max_size(), 12u);
+
+    using Map = decltype(map);
+    EXPECT_EQ(map, Map(ftl::init::map('a', 'A')('b', 'B')('c', 'C')('d', 'D')('e', 'E')('f', 'F')));
+  }
+}
+
 TEST(SmallMap, Find) {
   {
     // Constant reference.
-    const ftl::SmallMap map = ftl::init::map('a', 'A')('b', 'B')('c', 'C');
+    const SmallMap map = ftl::init::map('a', 'A')('b', 'B')('c', 'C');
 
-    const auto opt = map.find('b');
+    const auto opt = map.get('b');
     EXPECT_EQ(opt, 'B');
 
     const char d = 'D';
-    const auto ref = map.find('d').value_or(std::cref(d));
+    const auto ref = map.get('d').value_or(std::cref(d));
     EXPECT_EQ(ref.get(), 'D');
   }
   {
     // Mutable reference.
-    ftl::SmallMap map = ftl::init::map('a', 'A')('b', 'B')('c', 'C');
+    SmallMap map = ftl::init::map('a', 'A')('b', 'B')('c', 'C');
 
-    const auto opt = map.find('c');
+    const auto opt = map.get('c');
     EXPECT_EQ(opt, 'C');
 
     char d = 'd';
-    const auto ref = map.find('d').value_or(std::ref(d));
+    const auto ref = map.get('d').value_or(std::ref(d));
     ref.get() = 'D';
     EXPECT_EQ(d, 'D');
   }
   {
     // Constant unary operation.
-    const ftl::SmallMap map = ftl::init::map('a', 'x')('b', 'y')('c', 'z');
-    EXPECT_EQ(map.find('c', [](char c) { return std::toupper(c); }), 'Z');
+    const SmallMap map = ftl::init::map('a', 'x')('b', 'y')('c', 'z');
+    EXPECT_EQ(map.get('c', [](char c) { return std::toupper(c); }), 'Z');
   }
   {
     // Mutable unary operation.
-    ftl::SmallMap map = ftl::init::map('a', 'x')('b', 'y')('c', 'z');
-    EXPECT_TRUE(map.find('c', [](char& c) { c = std::toupper(c); }));
+    SmallMap map = ftl::init::map('a', 'x')('b', 'y')('c', 'z');
+    EXPECT_TRUE(map.get('c', [](char& c) { c = std::toupper(c); }));
 
     EXPECT_EQ(map, SmallMap(ftl::init::map('c', 'Z')('b', 'y')('a', 'x')));
   }
 }
 
+TEST(SmallMap, TryEmplace) {
+  SmallMap<int, std::string, 3> map;
+  using Pair = decltype(map)::value_type;
+
+  {
+    const auto [it, ok] = map.try_emplace(123, "abc");
+    ASSERT_TRUE(ok);
+    EXPECT_EQ(*it, Pair(123, "abc"s));
+  }
+  {
+    const auto [it, ok] = map.try_emplace(42, 3u, '?');
+    ASSERT_TRUE(ok);
+    EXPECT_EQ(*it, Pair(42, "???"s));
+  }
+  {
+    const auto [it, ok] = map.try_emplace(-1);
+    ASSERT_TRUE(ok);
+    EXPECT_EQ(*it, Pair(-1, std::string()));
+    EXPECT_FALSE(map.dynamic());
+  }
+  {
+    // Insertion fails if mapping exists.
+    const auto [it, ok] = map.try_emplace(42, "!!!");
+    EXPECT_FALSE(ok);
+    EXPECT_EQ(*it, Pair(42, "???"));
+    EXPECT_FALSE(map.dynamic());
+  }
+  {
+    // Insertion at capacity promotes the map.
+    const auto [it, ok] = map.try_emplace(999, "xyz");
+    ASSERT_TRUE(ok);
+    EXPECT_EQ(*it, Pair(999, "xyz"));
+    EXPECT_TRUE(map.dynamic());
+  }
+
+  EXPECT_EQ(map, SmallMap(ftl::init::map(-1, ""s)(42, "???"s)(123, "abc"s)(999, "xyz"s)));
+}
+
+namespace {
+
+// The mapped type does not require a copy/move assignment operator.
+struct String {
+  template <typename... Args>
+  String(Args... args) : str(args...) {}
+  const std::string str;
+
+  bool operator==(const String& other) const { return other.str == str; }
+};
+
+}  // namespace
+
+TEST(SmallMap, TryReplace) {
+  SmallMap<int, String, 3> map = ftl::init::map(1, "a")(2, "B");
+  using Pair = decltype(map)::value_type;
+
+  {
+    // Replacing fails unless mapping exists.
+    const auto it = map.try_replace(3, "c");
+    EXPECT_EQ(it, map.end());
+  }
+  {
+    // Replacement arguments can refer to the replaced mapping.
+    const auto ref = map.get(2, [](const auto& s) { return s.str[0]; });
+    ASSERT_TRUE(ref);
+
+    // Construct std::string from one character.
+    const auto it = map.try_replace(2, 1u, static_cast<char>(std::tolower(*ref)));
+    ASSERT_NE(it, map.end());
+    EXPECT_EQ(*it, Pair(2, "b"));
+  }
+
+  EXPECT_FALSE(map.dynamic());
+  EXPECT_TRUE(map.try_emplace(3, "abc").second);
+  EXPECT_TRUE(map.try_emplace(4, "d").second);
+  EXPECT_TRUE(map.dynamic());
+
+  {
+    // Replacing fails unless mapping exists.
+    const auto it = map.try_replace(5, "e");
+    EXPECT_EQ(it, map.end());
+  }
+  {
+    // Replacement arguments can refer to the replaced mapping.
+    const auto ref = map.get(3);
+    ASSERT_TRUE(ref);
+
+    // Construct std::string from substring.
+    const auto it = map.try_replace(3, ref->get().str, 2u, 1u);
+    ASSERT_NE(it, map.end());
+    EXPECT_EQ(*it, Pair(3, "c"));
+  }
+
+  EXPECT_EQ(map, SmallMap(ftl::init::map(4, "d"s)(3, "c"s)(2, "b"s)(1, "a"s)));
+}
+
+TEST(SmallMap, EmplaceOrReplace) {
+  SmallMap<int, String, 3> map = ftl::init::map(1, "a")(2, "B");
+  using Pair = decltype(map)::value_type;
+
+  {
+    // New mapping is emplaced.
+    const auto [it, emplace] = map.emplace_or_replace(3, "c");
+    EXPECT_TRUE(emplace);
+    EXPECT_EQ(*it, Pair(3, "c"));
+  }
+  {
+    // Replacement arguments can refer to the replaced mapping.
+    const auto ref = map.get(2, [](const auto& s) { return s.str[0]; });
+    ASSERT_TRUE(ref);
+
+    // Construct std::string from one character.
+    const auto [it, emplace] = map.emplace_or_replace(2, 1u, static_cast<char>(std::tolower(*ref)));
+    EXPECT_FALSE(emplace);
+    EXPECT_EQ(*it, Pair(2, "b"));
+  }
+
+  EXPECT_FALSE(map.dynamic());
+  EXPECT_FALSE(map.emplace_or_replace(3, "abc").second);  // Replace.
+  EXPECT_TRUE(map.emplace_or_replace(4, "d").second);     // Emplace.
+  EXPECT_TRUE(map.dynamic());
+
+  {
+    // New mapping is emplaced.
+    const auto [it, emplace] = map.emplace_or_replace(5, "e");
+    EXPECT_TRUE(emplace);
+    EXPECT_EQ(*it, Pair(5, "e"));
+  }
+  {
+    // Replacement arguments can refer to the replaced mapping.
+    const auto ref = map.get(3);
+    ASSERT_TRUE(ref);
+
+    // Construct std::string from substring.
+    const auto [it, emplace] = map.emplace_or_replace(3, ref->get().str, 2u, 1u);
+    EXPECT_FALSE(emplace);
+    EXPECT_EQ(*it, Pair(3, "c"));
+  }
+
+  EXPECT_EQ(map, SmallMap(ftl::init::map(5, "e"s)(4, "d"s)(3, "c"s)(2, "b"s)(1, "a"s)));
+}
+
+TEST(SmallMap, Erase) {
+  {
+    SmallMap map = ftl::init::map(1, '1')(2, '2')(3, '3')(4, '4');
+    EXPECT_FALSE(map.dynamic());
+
+    EXPECT_FALSE(map.erase(0));  // Key not found.
+
+    EXPECT_TRUE(map.erase(2));
+    EXPECT_EQ(map, SmallMap(ftl::init::map(1, '1')(3, '3')(4, '4')));
+
+    EXPECT_TRUE(map.erase(1));
+    EXPECT_EQ(map, SmallMap(ftl::init::map(3, '3')(4, '4')));
+
+    EXPECT_TRUE(map.erase(4));
+    EXPECT_EQ(map, SmallMap(ftl::init::map(3, '3')));
+
+    EXPECT_TRUE(map.erase(3));
+    EXPECT_FALSE(map.erase(3));  // Key not found.
+
+    EXPECT_TRUE(map.empty());
+    EXPECT_FALSE(map.dynamic());
+  }
+  {
+    SmallMap map = ftl::init::map(1, '1')(2, '2')(3, '3');
+    map.try_emplace(4, '4');
+    EXPECT_TRUE(map.dynamic());
+
+    EXPECT_FALSE(map.erase(0));  // Key not found.
+
+    EXPECT_TRUE(map.erase(2));
+    EXPECT_EQ(map, SmallMap(ftl::init::map(1, '1')(3, '3')(4, '4')));
+
+    EXPECT_TRUE(map.erase(1));
+    EXPECT_EQ(map, SmallMap(ftl::init::map(3, '3')(4, '4')));
+
+    EXPECT_TRUE(map.erase(4));
+    EXPECT_EQ(map, SmallMap(ftl::init::map(3, '3')));
+
+    EXPECT_TRUE(map.erase(3));
+    EXPECT_FALSE(map.erase(3));  // Key not found.
+
+    EXPECT_TRUE(map.empty());
+    EXPECT_TRUE(map.dynamic());
+  }
+}
+
 }  // namespace android::test
diff --git a/libs/ftl/string_test.cpp b/libs/ftl/string_test.cpp
new file mode 100644
index 0000000..f3d85c8
--- /dev/null
+++ b/libs/ftl/string_test.cpp
@@ -0,0 +1,187 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <ftl/string.h>
+#include <gtest/gtest.h>
+
+#include <algorithm>
+#include <cstdint>
+#include <iterator>
+#include <limits>
+#include <sstream>
+#include <type_traits>
+
+namespace android::test {
+
+// Keep in sync with example usage in header file.
+TEST(String, ToChars) {
+  ftl::to_chars_buffer_t<> buffer;
+
+  EXPECT_EQ(ftl::to_chars(buffer, 123u), "123");
+  EXPECT_EQ(ftl::to_chars(buffer, -42, ftl::Radix::kBin), "-0b101010");
+  EXPECT_EQ(ftl::to_chars(buffer, 0xcafe, ftl::Radix::kHex), "0xcafe");
+  EXPECT_EQ(ftl::to_chars(buffer, '*', ftl::Radix::kHex), "0x2a");
+}
+
+namespace {
+
+template <typename F, typename T>
+void ToCharsTest() {
+  constexpr auto kRadix = F::kRadix;
+
+  using Limits = std::numeric_limits<T>;
+  constexpr auto kMin = Limits::min();
+  constexpr auto kMax = Limits::max();
+  constexpr auto kNeg = static_cast<T>(-42);
+  constexpr auto kPos = static_cast<T>(123);
+
+  ftl::to_chars_buffer_t<T> buffer;
+
+  EXPECT_EQ(ftl::to_chars(buffer, kMin, kRadix), F{}(kMin));
+  EXPECT_EQ(ftl::to_chars(buffer, kMax, kRadix), F{}(kMax));
+  EXPECT_EQ(ftl::to_chars(buffer, kNeg, kRadix), F{}(kNeg));
+  EXPECT_EQ(ftl::to_chars(buffer, kPos, kRadix), F{}(kPos));
+}
+
+template <typename...>
+struct Types {};
+
+template <typename F, typename Types>
+struct ToCharsTests;
+
+template <typename F, typename T, typename... Ts>
+struct ToCharsTests<F, Types<T, Ts...>> {
+  static void test() {
+    ToCharsTest<F, T>();
+    ToCharsTests<F, Types<Ts...>>::test();
+  }
+};
+
+template <typename F>
+struct ToCharsTests<F, Types<>> {
+  static void test() {}
+};
+
+template <typename T, typename U = std::make_unsigned_t<T>>
+U to_unsigned(std::ostream& stream, T v) {
+  if (std::is_same_v<T, U>) return v;
+
+  if (v < 0) {
+    stream << '-';
+    return std::numeric_limits<U>::max() - static_cast<U>(v) + 1;
+  } else {
+    return static_cast<U>(v);
+  }
+}
+
+struct Bin {
+  static constexpr auto kRadix = ftl::Radix::kBin;
+
+  template <typename T>
+  std::string operator()(T v) const {
+    std::ostringstream stream;
+    auto u = to_unsigned(stream, v);
+    stream << "0b";
+
+    if (u == 0) {
+      stream << 0;
+    } else {
+      std::ostringstream digits;
+      do {
+        digits << (u & 1);
+      } while (u >>= 1);
+
+      const auto str = digits.str();
+      std::copy(str.rbegin(), str.rend(), std::ostream_iterator<char>(stream));
+    }
+
+    return stream.str();
+  }
+};
+
+struct Dec {
+  static constexpr auto kRadix = ftl::Radix::kDec;
+
+  template <typename T>
+  std::string operator()(T v) const {
+    return std::to_string(v);
+  }
+};
+
+struct Hex {
+  static constexpr auto kRadix = ftl::Radix::kHex;
+
+  template <typename T>
+  std::string operator()(T v) const {
+    std::ostringstream stream;
+    const auto u = to_unsigned(stream, v);
+    stream << "0x" << std::hex << std::nouppercase;
+    stream << (sizeof(T) == 1 ? static_cast<unsigned>(u) : u);
+    return stream.str();
+  }
+};
+
+using IntegerTypes =
+    Types<char, unsigned char, signed char, std::uint8_t, std::uint16_t, std::uint32_t,
+          std::uint64_t, std::int8_t, std::int16_t, std::int32_t, std::int64_t>;
+
+}  // namespace
+
+TEST(String, ToCharsBin) {
+  ToCharsTests<Bin, IntegerTypes>::test();
+
+  {
+    const std::uint8_t x = 0b1111'1111;
+    ftl::to_chars_buffer_t<decltype(x)> buffer;
+    EXPECT_EQ(ftl::to_chars(buffer, x, ftl::Radix::kBin), "0b11111111");
+  }
+  {
+    const std::int16_t x = -0b1000'0000'0000'0000;
+    ftl::to_chars_buffer_t<decltype(x)> buffer;
+    EXPECT_EQ(ftl::to_chars(buffer, x, ftl::Radix::kBin), "-0b1000000000000000");
+  }
+}
+
+TEST(String, ToCharsDec) {
+  ToCharsTests<Dec, IntegerTypes>::test();
+
+  {
+    const std::uint32_t x = UINT32_MAX;
+    ftl::to_chars_buffer_t<decltype(x)> buffer;
+    EXPECT_EQ(ftl::to_chars(buffer, x), "4294967295");
+  }
+  {
+    const std::int32_t x = INT32_MIN;
+    ftl::to_chars_buffer_t<decltype(x)> buffer;
+    EXPECT_EQ(ftl::to_chars(buffer, x), "-2147483648");
+  }
+}
+
+TEST(String, ToCharsHex) {
+  ToCharsTests<Hex, IntegerTypes>::test();
+
+  {
+    const std::uint16_t x = 0xfade;
+    ftl::to_chars_buffer_t<decltype(x)> buffer;
+    EXPECT_EQ(ftl::to_chars(buffer, x, ftl::Radix::kHex), "0xfade");
+  }
+  {
+    ftl::to_chars_buffer_t<> buffer;
+    EXPECT_EQ(ftl::to_chars(buffer, INT64_MIN, ftl::Radix::kHex), "-0x8000000000000000");
+  }
+}
+
+}  // namespace android::test
diff --git a/libs/gui/ISurfaceComposer.cpp b/libs/gui/ISurfaceComposer.cpp
index 71e18a9..f6a48d7 100644
--- a/libs/gui/ISurfaceComposer.cpp
+++ b/libs/gui/ISurfaceComposer.cpp
@@ -123,11 +123,11 @@
         return remote()->transact(BnSurfaceComposer::CAPTURE_DISPLAY, data, &reply);
     }
 
-    status_t captureDisplay(uint64_t displayOrLayerStack,
+    status_t captureDisplay(DisplayId displayId,
                             const sp<IScreenCaptureListener>& captureListener) override {
         Parcel data, reply;
         data.writeInterfaceToken(ISurfaceComposer::getInterfaceDescriptor());
-        SAFE_PARCEL(data.writeUint64, displayOrLayerStack);
+        SAFE_PARCEL(data.writeUint64, displayId.value);
         SAFE_PARCEL(data.writeStrongBinder, IInterface::asBinder(captureListener));
 
         return remote()->transact(BnSurfaceComposer::CAPTURE_DISPLAY_BY_ID, data, &reply);
@@ -281,9 +281,14 @@
             NO_ERROR) {
             std::vector<uint64_t> rawIds;
             if (reply.readUint64Vector(&rawIds) == NO_ERROR) {
-                std::vector<PhysicalDisplayId> displayIds(rawIds.size());
-                std::transform(rawIds.begin(), rawIds.end(), displayIds.begin(),
-                               [](uint64_t rawId) { return PhysicalDisplayId(rawId); });
+                std::vector<PhysicalDisplayId> displayIds;
+                displayIds.reserve(rawIds.size());
+
+                for (const uint64_t rawId : rawIds) {
+                    if (const auto id = DisplayId::fromValue<PhysicalDisplayId>(rawId)) {
+                        displayIds.push_back(*id);
+                    }
+                }
                 return displayIds;
             }
         }
@@ -1326,12 +1331,15 @@
         }
         case CAPTURE_DISPLAY_BY_ID: {
             CHECK_INTERFACE(ISurfaceComposer, data, reply);
-            uint64_t displayOrLayerStack = 0;
+            uint64_t value;
+            SAFE_PARCEL(data.readUint64, &value);
+            const auto id = DisplayId::fromValue(value);
+            if (!id) return BAD_VALUE;
+
             sp<IScreenCaptureListener> captureListener;
-            SAFE_PARCEL(data.readUint64, &displayOrLayerStack);
             SAFE_PARCEL(data.readStrongBinder, &captureListener);
 
-            return captureDisplay(displayOrLayerStack, captureListener);
+            return captureDisplay(*id, captureListener);
         }
         case CAPTURE_LAYERS: {
             CHECK_INTERFACE(ISurfaceComposer, data, reply);
@@ -1398,9 +1406,9 @@
         }
         case GET_PHYSICAL_DISPLAY_TOKEN: {
             CHECK_INTERFACE(ISurfaceComposer, data, reply);
-            PhysicalDisplayId displayId(data.readUint64());
-            sp<IBinder> display = getPhysicalDisplayToken(displayId);
-            reply->writeStrongBinder(display);
+            const auto id = DisplayId::fromValue<PhysicalDisplayId>(data.readUint64());
+            if (!id) return BAD_VALUE;
+            reply->writeStrongBinder(getPhysicalDisplayToken(*id));
             return NO_ERROR;
         }
         case GET_DISPLAY_STATE: {
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index b9bc117..a4ff4c8 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -2151,12 +2151,12 @@
     return s->captureDisplay(captureArgs, captureListener);
 }
 
-status_t ScreenshotClient::captureDisplay(uint64_t displayOrLayerStack,
+status_t ScreenshotClient::captureDisplay(DisplayId displayId,
                                           const sp<IScreenCaptureListener>& captureListener) {
     sp<ISurfaceComposer> s(ComposerService::getComposerService());
     if (s == nullptr) return NO_INIT;
 
-    return s->captureDisplay(displayOrLayerStack, captureListener);
+    return s->captureDisplay(displayId, captureListener);
 }
 
 status_t ScreenshotClient::captureLayers(const LayerCaptureArgs& captureArgs,
diff --git a/libs/gui/include/gui/ISurfaceComposer.h b/libs/gui/include/gui/ISurfaceComposer.h
index 439d90a..6b1e6c1 100644
--- a/libs/gui/include/gui/ISurfaceComposer.h
+++ b/libs/gui/include/gui/ISurfaceComposer.h
@@ -115,6 +115,11 @@
 
     using EventRegistrationFlags = Flags<EventRegistration>;
 
+    template <typename T>
+    struct SpHash {
+        size_t operator()(const sp<T>& k) const { return std::hash<T*>()(k.get()); }
+    };
+
     /*
      * Create a connection with SurfaceFlinger.
      */
@@ -238,24 +243,17 @@
      * The subregion can be optionally rotated.  It will also be scaled to
      * match the size of the output buffer.
      */
-    virtual status_t captureDisplay(const DisplayCaptureArgs& args,
-                                    const sp<IScreenCaptureListener>& captureListener) = 0;
+    virtual status_t captureDisplay(const DisplayCaptureArgs&,
+                                    const sp<IScreenCaptureListener>&) = 0;
 
-    virtual status_t captureDisplay(uint64_t displayOrLayerStack,
-                                    const sp<IScreenCaptureListener>& captureListener) = 0;
-
-    template <class AA>
-    struct SpHash {
-        size_t operator()(const sp<AA>& k) const { return std::hash<AA*>()(k.get()); }
-    };
+    virtual status_t captureDisplay(DisplayId, const sp<IScreenCaptureListener>&) = 0;
 
     /**
      * Capture a subtree of the layer hierarchy, potentially ignoring the root node.
      * This requires READ_FRAME_BUFFER permission. This function will fail if there
      * is a secure window on screen
      */
-    virtual status_t captureLayers(const LayerCaptureArgs& args,
-                                   const sp<IScreenCaptureListener>& captureListener) = 0;
+    virtual status_t captureLayers(const LayerCaptureArgs&, const sp<IScreenCaptureListener>&) = 0;
 
     /* Clears the frame statistics for animations.
      *
diff --git a/libs/gui/include/gui/SurfaceComposerClient.h b/libs/gui/include/gui/SurfaceComposerClient.h
index 153bcda..8019238 100644
--- a/libs/gui/include/gui/SurfaceComposerClient.h
+++ b/libs/gui/include/gui/SurfaceComposerClient.h
@@ -631,12 +631,9 @@
 
 class ScreenshotClient {
 public:
-    static status_t captureDisplay(const DisplayCaptureArgs& captureArgs,
-                                   const sp<IScreenCaptureListener>& captureListener);
-    static status_t captureDisplay(uint64_t displayOrLayerStack,
-                                   const sp<IScreenCaptureListener>& captureListener);
-    static status_t captureLayers(const LayerCaptureArgs& captureArgs,
-                                  const sp<IScreenCaptureListener>& captureListener);
+    static status_t captureDisplay(const DisplayCaptureArgs&, const sp<IScreenCaptureListener>&);
+    static status_t captureDisplay(DisplayId, const sp<IScreenCaptureListener>&);
+    static status_t captureLayers(const LayerCaptureArgs&, const sp<IScreenCaptureListener>&);
 };
 
 // ---------------------------------------------------------------------------
diff --git a/libs/gui/tests/Surface_test.cpp b/libs/gui/tests/Surface_test.cpp
index b8d34c3..42c2c10 100644
--- a/libs/gui/tests/Surface_test.cpp
+++ b/libs/gui/tests/Surface_test.cpp
@@ -752,21 +752,19 @@
     }
     status_t setActiveColorMode(const sp<IBinder>& /*display*/,
         ColorMode /*colorMode*/) override { return NO_ERROR; }
-    status_t captureDisplay(const DisplayCaptureArgs& /* captureArgs */,
-                            const sp<IScreenCaptureListener>& /* captureListener */) override {
-        return NO_ERROR;
-    }
     void setAutoLowLatencyMode(const sp<IBinder>& /*display*/, bool /*on*/) override {}
     void setGameContentType(const sp<IBinder>& /*display*/, bool /*on*/) override {}
-    status_t captureDisplay(uint64_t /*displayOrLayerStack*/,
-                            const sp<IScreenCaptureListener>& /* captureListener */) override {
+
+    status_t captureDisplay(const DisplayCaptureArgs&, const sp<IScreenCaptureListener>&) override {
         return NO_ERROR;
     }
-    virtual status_t captureLayers(
-            const LayerCaptureArgs& /* captureArgs */,
-            const sp<IScreenCaptureListener>& /* captureListener */) override {
+    status_t captureDisplay(DisplayId, const sp<IScreenCaptureListener>&) override {
         return NO_ERROR;
     }
+    status_t captureLayers(const LayerCaptureArgs&, const sp<IScreenCaptureListener>&) override {
+        return NO_ERROR;
+    }
+
     status_t clearAnimationFrameStats() override { return NO_ERROR; }
     status_t getAnimationFrameStats(FrameStats* /*outStats*/) const override {
         return NO_ERROR;
diff --git a/libs/input/Input.cpp b/libs/input/Input.cpp
index 70ed438..124331f 100644
--- a/libs/input/Input.cpp
+++ b/libs/input/Input.cpp
@@ -307,10 +307,6 @@
     scaleAxisValue(*this, AMOTION_EVENT_AXIS_TOOL_MINOR, globalScaleFactor);
 }
 
-void PointerCoords::scale(float globalScaleFactor) {
-    scale(globalScaleFactor, globalScaleFactor, globalScaleFactor);
-}
-
 void PointerCoords::applyOffset(float xOffset, float yOffset) {
     setAxisValue(AMOTION_EVENT_AXIS_X, getX() + xOffset);
     setAxisValue(AMOTION_EVENT_AXIS_Y, getY() + yOffset);
diff --git a/libs/nativedisplay/AChoreographer.cpp b/libs/nativedisplay/AChoreographer.cpp
index 0edb213..e7bd977 100644
--- a/libs/nativedisplay/AChoreographer.cpp
+++ b/libs/nativedisplay/AChoreographer.cpp
@@ -306,8 +306,9 @@
         // Fortunately, these events are small so sending packets across the
         // socket should be atomic across processes.
         DisplayEventReceiver::Event event;
-        event.header = DisplayEventReceiver::Event::Header{DisplayEventReceiver::DISPLAY_EVENT_NULL,
-                                                           PhysicalDisplayId(0), systemTime()};
+        event.header =
+                DisplayEventReceiver::Event::Header{DisplayEventReceiver::DISPLAY_EVENT_NULL,
+                                                    PhysicalDisplayId::fromPort(0), systemTime()};
         injectEvent(event);
     }
 }
diff --git a/libs/nativewindow/include/android/hardware_buffer.h b/libs/nativewindow/include/android/hardware_buffer.h
index d93a84c..d5e7cb2 100644
--- a/libs/nativewindow/include/android/hardware_buffer.h
+++ b/libs/nativewindow/include/android/hardware_buffer.h
@@ -556,6 +556,7 @@
                                    int32_t* _Nonnull outBytesPerPixel,
                                    int32_t* _Nonnull outBytesPerStride) __INTRODUCED_IN(29);
 
+
 /**
  * Get the system wide unique id for an AHardwareBuffer.
  *
diff --git a/libs/ui/Android.bp b/libs/ui/Android.bp
index 74d17ce..5a118ec 100644
--- a/libs/ui/Android.bp
+++ b/libs/ui/Android.bp
@@ -137,7 +137,6 @@
         "HdrCapabilities.cpp",
         "PixelFormat.cpp",
         "PublicFormat.cpp",
-        "Size.cpp",
         "StaticDisplayInfo.cpp",
     ],
 
diff --git a/libs/ui/Size.cpp b/libs/ui/Size.cpp
deleted file mode 100644
index d2996d1..0000000
--- a/libs/ui/Size.cpp
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Copyright 2019 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <ui/Size.h>
-
-namespace android::ui {
-
-const Size Size::INVALID{-1, -1};
-const Size Size::EMPTY{0, 0};
-
-} // namespace android::ui
diff --git a/libs/ui/include/ui/DisplayId.h b/libs/ui/include/ui/DisplayId.h
index f196ab9..9120972 100644
--- a/libs/ui/include/ui/DisplayId.h
+++ b/libs/ui/include/ui/DisplayId.h
@@ -38,12 +38,22 @@
 
     uint64_t value;
 
+    // For deserialization.
+    static constexpr std::optional<DisplayId> fromValue(uint64_t);
+
+    // As above, but also upcast to Id.
+    template <typename Id>
+    static constexpr std::optional<Id> fromValue(uint64_t value) {
+        if (const auto id = Id::tryCast(DisplayId(value))) {
+            return id;
+        }
+        return {};
+    }
+
 protected:
     explicit constexpr DisplayId(uint64_t id) : value(id) {}
 };
 
-static_assert(sizeof(DisplayId) == sizeof(uint64_t));
-
 inline bool operator==(DisplayId lhs, DisplayId rhs) {
     return lhs.value == rhs.value;
 }
@@ -80,11 +90,8 @@
 
     // TODO(b/162612135) Remove default constructor
     PhysicalDisplayId() = default;
-    // TODO(b/162612135) Remove constructor
-    explicit constexpr PhysicalDisplayId(uint64_t id) : DisplayId(id) {}
 
     constexpr uint16_t getManufacturerId() const { return static_cast<uint16_t>(value >> 40); }
-
     constexpr uint8_t getPort() const { return static_cast<uint8_t>(value); }
 
 private:
@@ -96,10 +103,9 @@
     explicit constexpr PhysicalDisplayId(DisplayId other) : DisplayId(other) {}
 };
 
-static_assert(sizeof(PhysicalDisplayId) == sizeof(uint64_t));
-
 struct VirtualDisplayId : DisplayId {
     using BaseId = uint32_t;
+
     // Flag indicating that this virtual display is backed by the GPU.
     static constexpr uint64_t FLAG_GPU = 1ULL << 61;
 
@@ -163,10 +169,23 @@
     explicit constexpr HalDisplayId(DisplayId other) : DisplayId(other) {}
 };
 
+constexpr std::optional<DisplayId> DisplayId::fromValue(uint64_t value) {
+    if (const auto id = fromValue<PhysicalDisplayId>(value)) {
+        return id;
+    }
+    if (const auto id = fromValue<VirtualDisplayId>(value)) {
+        return id;
+    }
+    return {};
+}
+
+static_assert(sizeof(DisplayId) == sizeof(uint64_t));
+static_assert(sizeof(HalDisplayId) == sizeof(uint64_t));
 static_assert(sizeof(VirtualDisplayId) == sizeof(uint64_t));
+
+static_assert(sizeof(PhysicalDisplayId) == sizeof(uint64_t));
 static_assert(sizeof(HalVirtualDisplayId) == sizeof(uint64_t));
 static_assert(sizeof(GpuVirtualDisplayId) == sizeof(uint64_t));
-static_assert(sizeof(HalDisplayId) == sizeof(uint64_t));
 
 } // namespace android
 
diff --git a/libs/ui/include/ui/Size.h b/libs/ui/include/ui/Size.h
index f1e8252..ecc192d 100644
--- a/libs/ui/include/ui/Size.h
+++ b/libs/ui/include/ui/Size.h
@@ -23,103 +23,70 @@
 #include <type_traits>
 #include <utility>
 
-namespace android {
-namespace ui {
+namespace android::ui {
 
-// Forward declare a few things.
-struct Size;
-bool operator==(const Size& lhs, const Size& rhs);
-
-/**
- * A simple value type representing a two-dimensional size
- */
+// A simple value type representing a two-dimensional size.
 struct Size {
-    int32_t width;
-    int32_t height;
+    int32_t width = -1;
+    int32_t height = -1;
 
-    // Special values
-    static const Size INVALID;
-    static const Size EMPTY;
+    constexpr Size() = default;
 
-    // ------------------------------------------------------------------------
-    // Construction
-    // ------------------------------------------------------------------------
-
-    Size() : Size(INVALID) {}
     template <typename T>
-    Size(T&& w, T&& h)
-          : width(Size::clamp<int32_t, T>(std::forward<T>(w))),
-            height(Size::clamp<int32_t, T>(std::forward<T>(h))) {}
-
-    // ------------------------------------------------------------------------
-    // Accessors
-    // ------------------------------------------------------------------------
+    constexpr Size(T w, T h) : width(clamp<int32_t>(w)), height(clamp<int32_t>(h)) {}
 
     int32_t getWidth() const { return width; }
     int32_t getHeight() const { return height; }
 
-    template <typename T>
-    void setWidth(T&& v) {
-        width = Size::clamp<int32_t, T>(std::forward<T>(v));
-    }
-    template <typename T>
-    void setHeight(T&& v) {
-        height = Size::clamp<int32_t, T>(std::forward<T>(v));
-    }
-
-    // ------------------------------------------------------------------------
-    // Assignment
-    // ------------------------------------------------------------------------
-
-    void set(const Size& size) { *this = size; }
-    template <typename T>
-    void set(T&& w, T&& h) {
-        set(Size(std::forward<T>(w), std::forward<T>(h)));
-    }
-
-    // Sets the value to INVALID
-    void makeInvalid() { set(INVALID); }
-
-    // Sets the value to EMPTY
-    void clear() { set(EMPTY); }
-
-    // ------------------------------------------------------------------------
-    // Semantic checks
-    // ------------------------------------------------------------------------
-
     // Valid means non-negative width and height
     bool isValid() const { return width >= 0 && height >= 0; }
 
     // Empty means zero width and height
-    bool isEmpty() const { return *this == EMPTY; }
+    bool isEmpty() const;
 
-    // ------------------------------------------------------------------------
-    // Clamp Helpers
-    // ------------------------------------------------------------------------
-
-    // Note: We use only features available in C++11 here for compatibility with
-    // external targets which include this file directly or indirectly and which
-    // themselves use C++11.
-
-    // C++11 compatible replacement for std::remove_cv_reference_t [C++20]
     template <typename T>
-    using remove_cv_reference_t =
-            typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+    void setWidth(T v) {
+        width = clamp<int32_t>(v);
+    }
+
+    template <typename T>
+    void setHeight(T v) {
+        height = clamp<int32_t>(v);
+    }
+
+    void set(Size size) { *this = size; }
+
+    template <typename T>
+    void set(T w, T h) {
+        set(Size(w, h));
+    }
+
+    // Sets the value to kInvalidSize
+    void makeInvalid();
+
+    // Sets the value to kEmptySize
+    void clear();
+
+    // TODO: Replace with std::remove_cvref_t in C++20.
+    template <typename T>
+    using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<T>>;
 
     // Takes a value of type FromType, and ensures it can be represented as a value of type ToType,
     // clamping the input value to the output range if necessary.
     template <typename ToType, typename FromType>
-    static Size::remove_cv_reference_t<ToType>
-    clamp(typename std::enable_if<
-            std::numeric_limits<Size::remove_cv_reference_t<ToType>>::is_specialized &&
-                    std::numeric_limits<Size::remove_cv_reference_t<FromType>>::is_specialized,
-            FromType>::type v) {
-        using BareToType = remove_cv_reference_t<ToType>;
-        using BareFromType = remove_cv_reference_t<FromType>;
-        static constexpr auto toHighest = std::numeric_limits<BareToType>::max();
-        static constexpr auto toLowest = std::numeric_limits<BareToType>::lowest();
-        static constexpr auto fromHighest = std::numeric_limits<BareFromType>::max();
-        static constexpr auto fromLowest = std::numeric_limits<BareFromType>::lowest();
+    static constexpr remove_cvref_t<ToType> clamp(FromType v) {
+        using BareToType = remove_cvref_t<ToType>;
+        using ToLimits = std::numeric_limits<BareToType>;
+
+        using BareFromType = remove_cvref_t<FromType>;
+        using FromLimits = std::numeric_limits<BareFromType>;
+
+        static_assert(ToLimits::is_specialized && FromLimits::is_specialized);
+
+        constexpr auto toHighest = ToLimits::max();
+        constexpr auto toLowest = ToLimits::lowest();
+        constexpr auto fromHighest = FromLimits::max();
+        constexpr auto fromLowest = FromLimits::lowest();
 
         // Get the closest representation of [toLowest, toHighest] in type
         // FromType to use to clamp the input value before conversion.
@@ -127,37 +94,35 @@
         // std::common_type<...> is used to get a value-preserving type for the
         // top end of the range.
         using CommonHighestType = std::common_type_t<BareToType, BareFromType>;
+        using CommonLimits = std::numeric_limits<CommonHighestType>;
 
         // std::make_signed<std::common_type<...>> is used to get a
         // value-preserving type for the bottom end of the range, except this is
         // a bit trickier for non-integer types like float.
-        using CommonLowestType =
-                std::conditional_t<std::numeric_limits<CommonHighestType>::is_integer,
-                                   std::make_signed_t<std::conditional_t<
-                                           std::numeric_limits<CommonHighestType>::is_integer,
-                                           CommonHighestType, int /* not used */>>,
-                                   CommonHighestType>;
+        using CommonLowestType = std::conditional_t<
+                CommonLimits::is_integer,
+                std::make_signed_t<std::conditional_t<CommonLimits::is_integer, CommonHighestType,
+                                                      int /* not used */>>,
+                CommonHighestType>;
 
         // We can then compute the clamp range in a way that can be later
         // trivially converted to either the 'from' or 'to' types, and be
-        // representabile in either.
-        static constexpr auto commonClampHighest =
-                std::min(static_cast<CommonHighestType>(fromHighest),
-                         static_cast<CommonHighestType>(toHighest));
-        static constexpr auto commonClampLowest =
-                std::max(static_cast<CommonLowestType>(fromLowest),
-                         static_cast<CommonLowestType>(toLowest));
+        // representable in either.
+        constexpr auto commonClampHighest = std::min(static_cast<CommonHighestType>(fromHighest),
+                                                     static_cast<CommonHighestType>(toHighest));
+        constexpr auto commonClampLowest = std::max(static_cast<CommonLowestType>(fromLowest),
+                                                    static_cast<CommonLowestType>(toLowest));
 
-        static constexpr auto fromClampHighest = static_cast<BareFromType>(commonClampHighest);
-        static constexpr auto fromClampLowest = static_cast<BareFromType>(commonClampLowest);
+        constexpr auto fromClampHighest = static_cast<BareFromType>(commonClampHighest);
+        constexpr auto fromClampLowest = static_cast<BareFromType>(commonClampLowest);
 
         // A clamp is needed only if the range we are clamping to is not the
         // same as the range of the input.
-        static constexpr bool isClampNeeded =
+        constexpr bool isClampNeeded =
                 (fromLowest != fromClampLowest) || (fromHighest != fromClampHighest);
 
         // If a clamp is not needed, the conversion is just a trivial cast.
-        if (!isClampNeeded) {
+        if constexpr (!isClampNeeded) {
             return static_cast<BareToType>(v);
         }
 
@@ -170,34 +135,46 @@
 
         // Otherwise clamping is done by using the already computed endpoints
         // for each type.
-        return (v <= fromClampLowest)
-                ? toClampLowest
-                : ((v >= fromClampHighest) ? toClampHighest : static_cast<BareToType>(v));
+        if (v <= fromClampLowest) {
+            return toClampLowest;
+        }
+
+        return v >= fromClampHighest ? toClampHighest : static_cast<BareToType>(v);
     }
 };
 
-// ------------------------------------------------------------------------
-// Comparisons
-// ------------------------------------------------------------------------
+constexpr Size kInvalidSize;
+constexpr Size kEmptySize{0, 0};
 
-inline bool operator==(const Size& lhs, const Size& rhs) {
+inline void Size::makeInvalid() {
+    set(kInvalidSize);
+}
+
+inline void Size::clear() {
+    set(kEmptySize);
+}
+
+inline bool operator==(Size lhs, Size rhs) {
     return lhs.width == rhs.width && lhs.height == rhs.height;
 }
 
-inline bool operator!=(const Size& lhs, const Size& rhs) {
-    return !operator==(lhs, rhs);
+inline bool Size::isEmpty() const {
+    return *this == kEmptySize;
 }
 
-inline bool operator<(const Size& lhs, const Size& rhs) {
+inline bool operator!=(Size lhs, Size rhs) {
+    return !(lhs == rhs);
+}
+
+inline bool operator<(Size lhs, Size rhs) {
     // Orders by increasing width, then height.
     if (lhs.width != rhs.width) return lhs.width < rhs.width;
     return lhs.height < rhs.height;
 }
 
 // Defining PrintTo helps with Google Tests.
-static inline void PrintTo(const Size& size, ::std::ostream* os) {
-    *os << "Size(" << size.width << ", " << size.height << ")";
+inline void PrintTo(Size size, std::ostream* stream) {
+    *stream << "Size(" << size.width << ", " << size.height << ')';
 }
 
-} // namespace ui
-} // namespace android
+} // namespace android::ui
diff --git a/libs/ui/tests/DisplayId_test.cpp b/libs/ui/tests/DisplayId_test.cpp
index 1d908b8..8ddee7e 100644
--- a/libs/ui/tests/DisplayId_test.cpp
+++ b/libs/ui/tests/DisplayId_test.cpp
@@ -32,6 +32,9 @@
     EXPECT_FALSE(GpuVirtualDisplayId::tryCast(id));
     EXPECT_TRUE(PhysicalDisplayId::tryCast(id));
     EXPECT_TRUE(HalDisplayId::tryCast(id));
+
+    EXPECT_EQ(id, DisplayId::fromValue(id.value));
+    EXPECT_EQ(id, DisplayId::fromValue<PhysicalDisplayId>(id.value));
 }
 
 TEST(DisplayIdTest, createPhysicalIdFromPort) {
@@ -43,6 +46,9 @@
     EXPECT_FALSE(GpuVirtualDisplayId::tryCast(id));
     EXPECT_TRUE(PhysicalDisplayId::tryCast(id));
     EXPECT_TRUE(HalDisplayId::tryCast(id));
+
+    EXPECT_EQ(id, DisplayId::fromValue(id.value));
+    EXPECT_EQ(id, DisplayId::fromValue<PhysicalDisplayId>(id.value));
 }
 
 TEST(DisplayIdTest, createGpuVirtualId) {
@@ -52,6 +58,9 @@
     EXPECT_FALSE(HalVirtualDisplayId::tryCast(id));
     EXPECT_FALSE(PhysicalDisplayId::tryCast(id));
     EXPECT_FALSE(HalDisplayId::tryCast(id));
+
+    EXPECT_EQ(id, DisplayId::fromValue(id.value));
+    EXPECT_EQ(id, DisplayId::fromValue<GpuVirtualDisplayId>(id.value));
 }
 
 TEST(DisplayIdTest, createHalVirtualId) {
@@ -61,6 +70,9 @@
     EXPECT_FALSE(GpuVirtualDisplayId::tryCast(id));
     EXPECT_FALSE(PhysicalDisplayId::tryCast(id));
     EXPECT_TRUE(HalDisplayId::tryCast(id));
+
+    EXPECT_EQ(id, DisplayId::fromValue(id.value));
+    EXPECT_EQ(id, DisplayId::fromValue<HalVirtualDisplayId>(id.value));
 }
 
 } // namespace android::ui
diff --git a/libs/ui/tests/Size_test.cpp b/libs/ui/tests/Size_test.cpp
index 5f75aea..acef47f 100644
--- a/libs/ui/tests/Size_test.cpp
+++ b/libs/ui/tests/Size_test.cpp
@@ -93,9 +93,8 @@
     }
 
     {
-        const auto& s = Size::INVALID;
-        EXPECT_FALSE(s.isValid());
-        EXPECT_FALSE(s.isEmpty());
+        EXPECT_FALSE(kInvalidSize.isValid());
+        EXPECT_FALSE(kInvalidSize.isEmpty());
     }
 
     {
@@ -112,9 +111,8 @@
     }
 
     {
-        const auto& s = Size::EMPTY;
-        EXPECT_TRUE(s.isValid());
-        EXPECT_TRUE(s.isEmpty());
+        EXPECT_TRUE(kEmptySize.isValid());
+        EXPECT_TRUE(kEmptySize.isEmpty());
     }
 
     {
diff --git a/services/automotive/display/AutomotiveDisplayProxyService.cpp b/services/automotive/display/AutomotiveDisplayProxyService.cpp
index d6fc695..d205231 100644
--- a/services/automotive/display/AutomotiveDisplayProxyService.cpp
+++ b/services/automotive/display/AutomotiveDisplayProxyService.cpp
@@ -34,7 +34,10 @@
     sp<IBinder> displayToken = nullptr;
     sp<SurfaceControl> surfaceControl = nullptr;
     if (it == mDisplays.end()) {
-        displayToken = SurfaceComposerClient::getPhysicalDisplayToken(PhysicalDisplayId(id));
+        if (const auto displayId = DisplayId::fromValue<PhysicalDisplayId>(id)) {
+            displayToken = SurfaceComposerClient::getPhysicalDisplayToken(*displayId);
+        }
+
         if (displayToken == nullptr) {
             ALOGE("Given display id, 0x%lX, is invalid.", (unsigned long)id);
             return nullptr;
@@ -157,7 +160,11 @@
     HwDisplayConfig activeConfig;
     HwDisplayState  activeState;
 
-    auto displayToken = SurfaceComposerClient::getPhysicalDisplayToken(PhysicalDisplayId(id));
+    sp<IBinder> displayToken;
+    if (const auto displayId = DisplayId::fromValue<PhysicalDisplayId>(id)) {
+        displayToken = SurfaceComposerClient::getPhysicalDisplayToken(*displayId);
+    }
+
     if (displayToken == nullptr) {
         ALOGE("Given display id, 0x%lX, is invalid.", (unsigned long)id);
     } else {
diff --git a/services/inputflinger/dispatcher/Entry.cpp b/services/inputflinger/dispatcher/Entry.cpp
index 881024f..8d6bd8a 100644
--- a/services/inputflinger/dispatcher/Entry.cpp
+++ b/services/inputflinger/dispatcher/Entry.cpp
@@ -176,10 +176,11 @@
     }
     return StringPrintf("KeyEvent(deviceId=%d, eventTime=%" PRIu64
                         ", source=0x%08x, displayId=%" PRId32 ", action=%s, "
-                        "flags=0x%08x, keyCode=%d, scanCode=%d, metaState=0x%08x, "
+                        "flags=0x%08x, keyCode=%s(%d), scanCode=%d, metaState=0x%08x, "
                         "repeatCount=%d), policyFlags=0x%08x",
                         deviceId, eventTime, source, displayId, KeyEvent::actionToString(action),
-                        flags, keyCode, scanCode, metaState, repeatCount, policyFlags);
+                        flags, KeyEvent::getLabel(keyCode), keyCode, scanCode, metaState,
+                        repeatCount, policyFlags);
 }
 
 void KeyEntry::recycle() {
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/DisplayCreationArgs.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/DisplayCreationArgs.h
index 14eddb1..526e7da 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/DisplayCreationArgs.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/DisplayCreationArgs.h
@@ -40,7 +40,7 @@
     std::optional<ui::DisplayConnectionType> connectionType;
 
     // Size of the display in pixels
-    ui::Size pixels = ui::Size::INVALID;
+    ui::Size pixels = ui::kInvalidSize;
 
     // True if this display should be considered secure
     bool isSecure = false;
diff --git a/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp b/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp
index db9437b..f4a5835 100644
--- a/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp
@@ -60,7 +60,7 @@
 constexpr HalVirtualDisplayId HAL_VIRTUAL_DISPLAY_ID{456u};
 constexpr GpuVirtualDisplayId GPU_VIRTUAL_DISPLAY_ID{789u};
 
-const ui::Size DEFAULT_RESOLUTION{1920, 1080};
+constexpr ui::Size DEFAULT_RESOLUTION{1920, 1080};
 constexpr uint32_t DEFAULT_LAYER_STACK = 42;
 
 struct Layer {
diff --git a/services/surfaceflinger/CompositionEngine/tests/MockHWComposer.h b/services/surfaceflinger/CompositionEngine/tests/MockHWComposer.h
index 64cbea9..72de0b1 100644
--- a/services/surfaceflinger/CompositionEngine/tests/MockHWComposer.h
+++ b/services/surfaceflinger/CompositionEngine/tests/MockHWComposer.h
@@ -51,6 +51,7 @@
                  bool(HalVirtualDisplayId, ui::Size, ui::PixelFormat*,
                       std::optional<PhysicalDisplayId>));
     MOCK_METHOD2(allocatePhysicalDisplay, void(hal::HWDisplayId, PhysicalDisplayId));
+
     MOCK_METHOD1(createLayer, std::shared_ptr<HWC2::Layer>(HalDisplayId));
     MOCK_METHOD4(getDeviceCompositionChanges,
                  status_t(HalDisplayId, bool, std::chrono::steady_clock::time_point,
diff --git a/services/surfaceflinger/CompositionEngine/tests/RenderSurfaceTest.cpp b/services/surfaceflinger/CompositionEngine/tests/RenderSurfaceTest.cpp
index 5090bb2..431cc93 100644
--- a/services/surfaceflinger/CompositionEngine/tests/RenderSurfaceTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/RenderSurfaceTest.cpp
@@ -35,7 +35,7 @@
 
 constexpr int32_t DEFAULT_DISPLAY_WIDTH = 1920;
 constexpr int32_t DEFAULT_DISPLAY_HEIGHT = 1080;
-constexpr DisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId(123u);
+constexpr DisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId::fromPort(123u);
 const std::string DEFAULT_DISPLAY_NAME = "Mock Display";
 
 using testing::_;
diff --git a/services/surfaceflinger/DisplayDevice.h b/services/surfaceflinger/DisplayDevice.h
index 70dcc1e..b068daf 100644
--- a/services/surfaceflinger/DisplayDevice.h
+++ b/services/surfaceflinger/DisplayDevice.h
@@ -297,16 +297,4 @@
     DisplayModes supportedModes;
 };
 
-// Predicates for display lookup.
-
-struct WithLayerStack {
-    explicit WithLayerStack(ui::LayerStack layerStack) : layerStack(layerStack) {}
-
-    bool operator()(const DisplayDevice& display) const {
-        return display.getLayerStack() == layerStack;
-    }
-
-    ui::LayerStack layerStack;
-};
-
 } // namespace android
diff --git a/services/surfaceflinger/RefreshRateOverlay.cpp b/services/surfaceflinger/RefreshRateOverlay.cpp
index a9fd16c..075d0eb 100644
--- a/services/surfaceflinger/RefreshRateOverlay.cpp
+++ b/services/surfaceflinger/RefreshRateOverlay.cpp
@@ -25,6 +25,10 @@
 #include "Client.h"
 #include "Layer.h"
 
+#include <SkBlendMode.h>
+#include <SkPaint.h>
+#include <SkRect.h>
+#include <SkSurface.h>
 #include <gui/IProducerListener.h>
 
 #undef LOG_TAG
@@ -32,85 +36,64 @@
 
 namespace android {
 
-void RefreshRateOverlay::SevenSegmentDrawer::drawRect(const Rect& r, const half4& color,
-                                                      const sp<GraphicBuffer>& buffer,
-                                                      uint8_t* pixels) {
-    for (int32_t j = r.top; j < r.bottom; j++) {
-        if (j >= buffer->getHeight()) {
-            break;
-        }
-
-        for (int32_t i = r.left; i < r.right; i++) {
-            if (i >= buffer->getWidth()) {
-                break;
-            }
-
-            uint8_t* iter = pixels + 4 * (i + (buffer->getStride() * j));
-            iter[0] = uint8_t(color.r * 255);
-            iter[1] = uint8_t(color.g * 255);
-            iter[2] = uint8_t(color.b * 255);
-            iter[3] = uint8_t(color.a * 255);
-        }
-    }
-}
-
-void RefreshRateOverlay::SevenSegmentDrawer::drawSegment(Segment segment, int left,
-                                                         const half4& color,
-                                                         const sp<GraphicBuffer>& buffer,
-                                                         uint8_t* pixels) {
-    const Rect rect = [&]() {
+void RefreshRateOverlay::SevenSegmentDrawer::drawSegment(Segment segment, int left, SkColor& color,
+                                                         SkCanvas& canvas) {
+    const SkRect rect = [&]() {
         switch (segment) {
             case Segment::Upper:
-                return Rect(left, 0, left + DIGIT_WIDTH, DIGIT_SPACE);
+                return SkRect::MakeLTRB(left, 0, left + DIGIT_WIDTH, DIGIT_SPACE);
             case Segment::UpperLeft:
-                return Rect(left, 0, left + DIGIT_SPACE, DIGIT_HEIGHT / 2);
+                return SkRect::MakeLTRB(left, 0, left + DIGIT_SPACE, DIGIT_HEIGHT / 2);
             case Segment::UpperRight:
-                return Rect(left + DIGIT_WIDTH - DIGIT_SPACE, 0, left + DIGIT_WIDTH,
-                            DIGIT_HEIGHT / 2);
+                return SkRect::MakeLTRB(left + DIGIT_WIDTH - DIGIT_SPACE, 0, left + DIGIT_WIDTH,
+                                        DIGIT_HEIGHT / 2);
             case Segment::Middle:
-                return Rect(left, DIGIT_HEIGHT / 2 - DIGIT_SPACE / 2, left + DIGIT_WIDTH,
-                            DIGIT_HEIGHT / 2 + DIGIT_SPACE / 2);
+                return SkRect::MakeLTRB(left, DIGIT_HEIGHT / 2 - DIGIT_SPACE / 2,
+                                        left + DIGIT_WIDTH, DIGIT_HEIGHT / 2 + DIGIT_SPACE / 2);
             case Segment::LowerLeft:
-                return Rect(left, DIGIT_HEIGHT / 2, left + DIGIT_SPACE, DIGIT_HEIGHT);
+                return SkRect::MakeLTRB(left, DIGIT_HEIGHT / 2, left + DIGIT_SPACE, DIGIT_HEIGHT);
             case Segment::LowerRight:
-                return Rect(left + DIGIT_WIDTH - DIGIT_SPACE, DIGIT_HEIGHT / 2, left + DIGIT_WIDTH,
-                            DIGIT_HEIGHT);
-            case Segment::Buttom:
-                return Rect(left, DIGIT_HEIGHT - DIGIT_SPACE, left + DIGIT_WIDTH, DIGIT_HEIGHT);
+                return SkRect::MakeLTRB(left + DIGIT_WIDTH - DIGIT_SPACE, DIGIT_HEIGHT / 2,
+                                        left + DIGIT_WIDTH, DIGIT_HEIGHT);
+            case Segment::Bottom:
+                return SkRect::MakeLTRB(left, DIGIT_HEIGHT - DIGIT_SPACE, left + DIGIT_WIDTH,
+                                        DIGIT_HEIGHT);
         }
     }();
 
-    drawRect(rect, color, buffer, pixels);
+    SkPaint paint;
+    paint.setColor(color);
+    paint.setBlendMode(SkBlendMode::kSrc);
+    canvas.drawRect(rect, paint);
 }
 
-void RefreshRateOverlay::SevenSegmentDrawer::drawDigit(int digit, int left, const half4& color,
-                                                       const sp<GraphicBuffer>& buffer,
-                                                       uint8_t* pixels) {
+void RefreshRateOverlay::SevenSegmentDrawer::drawDigit(int digit, int left, SkColor& color,
+                                                       SkCanvas& canvas) {
     if (digit < 0 || digit > 9) return;
 
     if (digit == 0 || digit == 2 || digit == 3 || digit == 5 || digit == 6 || digit == 7 ||
         digit == 8 || digit == 9)
-        drawSegment(Segment::Upper, left, color, buffer, pixels);
+        drawSegment(Segment::Upper, left, color, canvas);
     if (digit == 0 || digit == 4 || digit == 5 || digit == 6 || digit == 8 || digit == 9)
-        drawSegment(Segment::UpperLeft, left, color, buffer, pixels);
+        drawSegment(Segment::UpperLeft, left, color, canvas);
     if (digit == 0 || digit == 1 || digit == 2 || digit == 3 || digit == 4 || digit == 7 ||
         digit == 8 || digit == 9)
-        drawSegment(Segment::UpperRight, left, color, buffer, pixels);
+        drawSegment(Segment::UpperRight, left, color, canvas);
     if (digit == 2 || digit == 3 || digit == 4 || digit == 5 || digit == 6 || digit == 8 ||
         digit == 9)
-        drawSegment(Segment::Middle, left, color, buffer, pixels);
+        drawSegment(Segment::Middle, left, color, canvas);
     if (digit == 0 || digit == 2 || digit == 6 || digit == 8)
-        drawSegment(Segment::LowerLeft, left, color, buffer, pixels);
+        drawSegment(Segment::LowerLeft, left, color, canvas);
     if (digit == 0 || digit == 1 || digit == 3 || digit == 4 || digit == 5 || digit == 6 ||
         digit == 7 || digit == 8 || digit == 9)
-        drawSegment(Segment::LowerRight, left, color, buffer, pixels);
+        drawSegment(Segment::LowerRight, left, color, canvas);
     if (digit == 0 || digit == 2 || digit == 3 || digit == 5 || digit == 6 || digit == 8 ||
         digit == 9)
-        drawSegment(Segment::Buttom, left, color, buffer, pixels);
+        drawSegment(Segment::Bottom, left, color, canvas);
 }
 
-std::vector<sp<GraphicBuffer>> RefreshRateOverlay::SevenSegmentDrawer::drawNumber(
-        int number, const half4& color, bool showSpinner) {
+std::vector<sp<GraphicBuffer>> RefreshRateOverlay::SevenSegmentDrawer::draw(
+        int number, SkColor& color, ui::Transform::RotationFlags rotation, bool showSpinner) {
     if (number < 0 || number > 1000) return {};
 
     const auto hundreds = number / 100;
@@ -120,55 +103,76 @@
     std::vector<sp<GraphicBuffer>> buffers;
     const auto loopCount = showSpinner ? 6 : 1;
     for (int i = 0; i < loopCount; i++) {
+        // Pre-rotate the buffer before it reaches SurfaceFlinger.
+        SkMatrix canvasTransform = SkMatrix();
+        auto [bufferWidth, bufferHeight] = [&] {
+            switch (rotation) {
+                case ui::Transform::ROT_90:
+                    canvasTransform.setTranslate(BUFFER_HEIGHT, 0);
+                    canvasTransform.preRotate(90);
+                    return std::make_tuple(BUFFER_HEIGHT, BUFFER_WIDTH);
+                case ui::Transform::ROT_270:
+                    canvasTransform.setRotate(270, BUFFER_WIDTH / 2.0, BUFFER_WIDTH / 2.0);
+                    return std::make_tuple(BUFFER_HEIGHT, BUFFER_WIDTH);
+                default:
+                    return std::make_tuple(BUFFER_WIDTH, BUFFER_HEIGHT);
+            }
+        }();
         sp<GraphicBuffer> buffer =
-                new GraphicBuffer(BUFFER_WIDTH, BUFFER_HEIGHT, HAL_PIXEL_FORMAT_RGBA_8888, 1,
+                new GraphicBuffer(bufferWidth, bufferHeight, HAL_PIXEL_FORMAT_RGBA_8888, 1,
                                   GRALLOC_USAGE_SW_WRITE_RARELY | GRALLOC_USAGE_HW_COMPOSER |
                                           GRALLOC_USAGE_HW_TEXTURE,
                                   "RefreshRateOverlayBuffer");
         const status_t bufferStatus = buffer->initCheck();
         LOG_ALWAYS_FATAL_IF(bufferStatus != OK, "RefreshRateOverlay: Buffer failed to allocate: %d",
                             bufferStatus);
-        uint8_t* pixels;
-        buffer->lock(GRALLOC_USAGE_SW_WRITE_RARELY, reinterpret_cast<void**>(&pixels));
-        // Clear buffer content
-        drawRect(Rect(BUFFER_WIDTH, BUFFER_HEIGHT), half4(0), buffer, pixels);
+
+        sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(bufferWidth, bufferHeight);
+        SkCanvas* canvas = surface->getCanvas();
+        canvas->setMatrix(canvasTransform);
+
         int left = 0;
         if (hundreds != 0) {
-            drawDigit(hundreds, left, color, buffer, pixels);
+            drawDigit(hundreds, left, color, *canvas);
         }
         left += DIGIT_WIDTH + DIGIT_SPACE;
 
         if (tens != 0) {
-            drawDigit(tens, left, color, buffer, pixels);
+            drawDigit(tens, left, color, *canvas);
         }
         left += DIGIT_WIDTH + DIGIT_SPACE;
 
-        drawDigit(ones, left, color, buffer, pixels);
+        drawDigit(ones, left, color, *canvas);
         left += DIGIT_WIDTH + DIGIT_SPACE;
 
         if (showSpinner) {
             switch (i) {
                 case 0:
-                    drawSegment(Segment::Upper, left, color, buffer, pixels);
+                    drawSegment(Segment::Upper, left, color, *canvas);
                     break;
                 case 1:
-                    drawSegment(Segment::UpperRight, left, color, buffer, pixels);
+                    drawSegment(Segment::UpperRight, left, color, *canvas);
                     break;
                 case 2:
-                    drawSegment(Segment::LowerRight, left, color, buffer, pixels);
+                    drawSegment(Segment::LowerRight, left, color, *canvas);
                     break;
                 case 3:
-                    drawSegment(Segment::Buttom, left, color, buffer, pixels);
+                    drawSegment(Segment::Bottom, left, color, *canvas);
                     break;
                 case 4:
-                    drawSegment(Segment::LowerLeft, left, color, buffer, pixels);
+                    drawSegment(Segment::LowerLeft, left, color, *canvas);
                     break;
                 case 5:
-                    drawSegment(Segment::UpperLeft, left, color, buffer, pixels);
+                    drawSegment(Segment::UpperLeft, left, color, *canvas);
                     break;
             }
         }
 
+        void* pixels = nullptr;
+        buffer->lock(GRALLOC_USAGE_SW_WRITE_RARELY, reinterpret_cast<void**>(&pixels));
+        const SkImageInfo& imageInfo = surface->imageInfo();
+        size_t dstRowBytes = buffer->getStride() * imageInfo.bytesPerPixel();
+        canvas->readPixels(imageInfo, pixels, dstRowBytes, 0, 0);
         buffer->unlock();
         buffers.emplace_back(buffer);
     }
@@ -210,7 +214,22 @@
 
 const std::vector<std::shared_ptr<renderengine::ExternalTexture>>&
 RefreshRateOverlay::getOrCreateBuffers(uint32_t fps) {
-    if (mBufferCache.find(fps) == mBufferCache.end()) {
+    ui::Transform::RotationFlags transformHint = mLayer->getTransformHint();
+    // Tell SurfaceFlinger about the pre-rotation on the buffer.
+    const auto transform = [&] {
+        switch (transformHint) {
+            case ui::Transform::ROT_90:
+                return ui::Transform::ROT_270;
+            case ui::Transform::ROT_270:
+                return ui::Transform::ROT_90;
+            default:
+                return ui::Transform::ROT_0;
+        }
+    }();
+    mLayer->setTransform(transform);
+
+    if (mBufferCache.find(transformHint) == mBufferCache.end() ||
+        mBufferCache.at(transformHint).find(fps) == mBufferCache.at(transformHint).end()) {
         // Ensure the range is > 0, so we don't divide by 0.
         const auto rangeLength = std::max(1u, mHighFps - mLowFps);
         // Clip values outside the range [mLowFps, mHighFps]. The current fps may be outside
@@ -218,12 +237,14 @@
         fps = std::max(fps, mLowFps);
         fps = std::min(fps, mHighFps);
         const auto fpsScale = static_cast<float>(fps - mLowFps) / rangeLength;
-        half4 color;
-        color.r = HIGH_FPS_COLOR.r * fpsScale + LOW_FPS_COLOR.r * (1 - fpsScale);
-        color.g = HIGH_FPS_COLOR.g * fpsScale + LOW_FPS_COLOR.g * (1 - fpsScale);
-        color.b = HIGH_FPS_COLOR.b * fpsScale + LOW_FPS_COLOR.b * (1 - fpsScale);
-        color.a = ALPHA;
-        auto buffers = SevenSegmentDrawer::drawNumber(fps, color, mShowSpinner);
+        SkColor4f colorBase = SkColor4f::FromColor(HIGH_FPS_COLOR) * fpsScale;
+        SkColor4f lowFpsColor = SkColor4f::FromColor(LOW_FPS_COLOR) * (1 - fpsScale);
+        colorBase.fR = colorBase.fR + lowFpsColor.fR;
+        colorBase.fG = colorBase.fG + lowFpsColor.fG;
+        colorBase.fB = colorBase.fB + lowFpsColor.fB;
+        colorBase.fA = ALPHA;
+        SkColor color = colorBase.toSkColor();
+        auto buffers = SevenSegmentDrawer::draw(fps, color, transformHint, mShowSpinner);
         std::vector<std::shared_ptr<renderengine::ExternalTexture>> textures;
         std::transform(buffers.begin(), buffers.end(), std::back_inserter(textures),
                        [&](const auto& buffer) -> std::shared_ptr<renderengine::ExternalTexture> {
@@ -233,10 +254,10 @@
                                                                   renderengine::ExternalTexture::
                                                                           Usage::READABLE);
                        });
-        mBufferCache.emplace(fps, textures);
+        mBufferCache[transformHint].emplace(fps, textures);
     }
 
-    return mBufferCache[fps];
+    return mBufferCache[transformHint][fps];
 }
 
 void RefreshRateOverlay::setViewport(ui::Size viewport) {
diff --git a/services/surfaceflinger/RefreshRateOverlay.h b/services/surfaceflinger/RefreshRateOverlay.h
index aa8329c..cb8b227 100644
--- a/services/surfaceflinger/RefreshRateOverlay.h
+++ b/services/surfaceflinger/RefreshRateOverlay.h
@@ -22,6 +22,8 @@
 #include <ui/Size.h>
 #include <utils/StrongPointer.h>
 
+#include <SkCanvas.h>
+#include <SkColor.h>
 #include <unordered_map>
 
 #include "Fps.h"
@@ -47,20 +49,16 @@
 private:
     class SevenSegmentDrawer {
     public:
-        static std::vector<sp<GraphicBuffer>> drawNumber(int number, const half4& color,
-                                                         bool showSpinner);
+        static std::vector<sp<GraphicBuffer>> draw(int number, SkColor& color,
+                                                   ui::Transform::RotationFlags, bool showSpinner);
         static uint32_t getHeight() { return BUFFER_HEIGHT; }
         static uint32_t getWidth() { return BUFFER_WIDTH; }
 
     private:
-        enum class Segment { Upper, UpperLeft, UpperRight, Middle, LowerLeft, LowerRight, Buttom };
+        enum class Segment { Upper, UpperLeft, UpperRight, Middle, LowerLeft, LowerRight, Bottom };
 
-        static void drawRect(const Rect& r, const half4& color, const sp<GraphicBuffer>& buffer,
-                             uint8_t* pixels);
-        static void drawSegment(Segment segment, int left, const half4& color,
-                                const sp<GraphicBuffer>& buffer, uint8_t* pixels);
-        static void drawDigit(int digit, int left, const half4& color,
-                              const sp<GraphicBuffer>& buffer, uint8_t* pixels);
+        static void drawSegment(Segment segment, int left, SkColor& color, SkCanvas& canvas);
+        static void drawDigit(int digit, int left, SkColor& color, SkCanvas& canvas);
 
         static constexpr uint32_t DIGIT_HEIGHT = 100;
         static constexpr uint32_t DIGIT_WIDTH = 64;
@@ -80,13 +78,15 @@
     sp<IBinder> mIBinder;
     sp<IGraphicBufferProducer> mGbp;
 
-    std::unordered_map<int, std::vector<std::shared_ptr<renderengine::ExternalTexture>>>
+    std::unordered_map<
+            ui::Transform::RotationFlags,
+            std::unordered_map<int, std::vector<std::shared_ptr<renderengine::ExternalTexture>>>>
             mBufferCache;
     std::optional<int> mCurrentFps;
     int mFrame = 0;
     static constexpr float ALPHA = 0.8f;
-    const half3 LOW_FPS_COLOR = half3(1.0f, 0.0f, 0.0f);
-    const half3 HIGH_FPS_COLOR = half3(0.0f, 1.0f, 0.0f);
+    const SkColor LOW_FPS_COLOR = SK_ColorRED;
+    const SkColor HIGH_FPS_COLOR = SK_ColorGREEN;
 
     const bool mShowSpinner;
 
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 13a27d0..46893bd 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -5642,37 +5642,24 @@
             }
             case 1035: {
                 const int modeId = data.readInt32();
-                mDebugDisplayModeSetByBackdoor = false;
 
-                const auto displayId = [&]() -> std::optional<PhysicalDisplayId> {
-                    uint64_t inputDisplayId = 0;
-                    if (data.readUint64(&inputDisplayId) == NO_ERROR) {
-                        const auto token = getPhysicalDisplayToken(
-                                static_cast<PhysicalDisplayId>(inputDisplayId));
-                        if (!token) {
-                            ALOGE("No display with id: %" PRIu64, inputDisplayId);
-                            return std::nullopt;
-                        }
-
-                        return std::make_optional<PhysicalDisplayId>(inputDisplayId);
+                const auto display = [&]() -> sp<IBinder> {
+                    uint64_t value;
+                    if (data.readUint64(&value) != NO_ERROR) {
+                        return getInternalDisplayToken();
                     }
 
-                    return getInternalDisplayId();
+                    if (const auto id = DisplayId::fromValue<PhysicalDisplayId>(value)) {
+                        return getPhysicalDisplayToken(*id);
+                    }
+
+                    ALOGE("Invalid physical display ID");
+                    return nullptr;
                 }();
 
-                if (!displayId) {
-                    ALOGE("No display found");
-                    return NO_ERROR;
-                }
-
-                status_t result = setActiveMode(getPhysicalDisplayToken(*displayId), modeId);
-                if (result != NO_ERROR) {
-                    return result;
-                }
-
-                mDebugDisplayModeSetByBackdoor = true;
-
-                return NO_ERROR;
+                const status_t result = setActiveMode(display, modeId);
+                mDebugDisplayModeSetByBackdoor = result == NO_ERROR;
+                return result;
             }
             case 1036: {
                 if (data.readInt32() > 0) {
@@ -5735,14 +5722,11 @@
                             std::optional<PhysicalDisplayId> inputId = std::nullopt;
                             if (uint64_t inputDisplayId;
                                 data.readUint64(&inputDisplayId) == NO_ERROR) {
-                                const auto token = getPhysicalDisplayToken(
-                                        static_cast<PhysicalDisplayId>(inputDisplayId));
-                                if (!token) {
+                                inputId = DisplayId::fromValue<PhysicalDisplayId>(inputDisplayId);
+                                if (!inputId || getPhysicalDisplayToken(*inputId)) {
                                     ALOGE("No display with id: %" PRIu64, inputDisplayId);
                                     return NAME_NOT_FOUND;
                                 }
-
-                                inputId = std::make_optional<PhysicalDisplayId>(inputDisplayId);
                             }
                             {
                                 Mutex::Autolock lock(mStateLock);
@@ -5994,7 +5978,7 @@
                                captureListener);
 }
 
-status_t SurfaceFlinger::captureDisplay(uint64_t displayIdOrLayerStack,
+status_t SurfaceFlinger::captureDisplay(DisplayId displayId,
                                         const sp<IScreenCaptureListener>& captureListener) {
     ui::LayerStack layerStack;
     wp<const DisplayDevice> displayWeak;
@@ -6002,21 +5986,14 @@
     ui::Dataspace dataspace;
     {
         Mutex::Autolock lock(mStateLock);
-        auto display = getDisplayDeviceLocked(PhysicalDisplayId{displayIdOrLayerStack});
 
-        // Fall back to first display whose layer stack matches.
-        if (!display) {
-            const auto layerStack = static_cast<ui::LayerStack>(displayIdOrLayerStack);
-            display = findDisplay(WithLayerStack(layerStack));
-        }
-
+        const auto display = getDisplayDeviceLocked(displayId);
         if (!display) {
             return NAME_NOT_FOUND;
         }
 
-        layerStack = display->getLayerStack();
         displayWeak = display;
-
+        layerStack = display->getLayerStack();
         size = display->getLayerStackSpaceRect().getSize();
 
         dataspace =
@@ -6101,7 +6078,11 @@
             }
         }
 
-        const auto display = findDisplay(WithLayerStack(parent->getLayerStack()));
+        const auto display =
+                findDisplay([layerStack = parent->getLayerStack()](const auto& display) {
+                    return display.getLayerStack() == layerStack;
+                });
+
         if (!display) {
             return NAME_NOT_FOUND;
         }
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 8656778..dd951be 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -620,12 +620,10 @@
     sp<IDisplayEventConnection> createDisplayEventConnection(
             ISurfaceComposer::VsyncSource vsyncSource = eVsyncSourceApp,
             ISurfaceComposer::EventRegistrationFlags eventRegistration = {}) override;
-    status_t captureDisplay(const DisplayCaptureArgs& args,
-                            const sp<IScreenCaptureListener>& captureListener) override;
-    status_t captureDisplay(uint64_t displayOrLayerStack,
-                            const sp<IScreenCaptureListener>& captureListener) override;
-    status_t captureLayers(const LayerCaptureArgs& args,
-                           const sp<IScreenCaptureListener>& captureListener) override;
+
+    status_t captureDisplay(const DisplayCaptureArgs&, const sp<IScreenCaptureListener>&) override;
+    status_t captureDisplay(DisplayId, const sp<IScreenCaptureListener>&) override;
+    status_t captureLayers(const LayerCaptureArgs&, const sp<IScreenCaptureListener>&) override;
 
     status_t getDisplayStats(const sp<IBinder>& displayToken, DisplayStatInfo* stats) override;
     status_t getDisplayState(const sp<IBinder>& displayToken, ui::DisplayState*)
@@ -939,14 +937,6 @@
         return it == mDisplays.end() ? nullptr : it->second;
     }
 
-    sp<const DisplayDevice> getDisplayDeviceLocked(PhysicalDisplayId id) const
-            REQUIRES(mStateLock) {
-        if (const auto token = getPhysicalDisplayTokenLocked(id)) {
-            return getDisplayDeviceLocked(token);
-        }
-        return nullptr;
-    }
-
     sp<const DisplayDevice> getDefaultDisplayDeviceLocked() const REQUIRES(mStateLock) {
         return const_cast<SurfaceFlinger*>(this)->getDefaultDisplayDeviceLocked();
     }
diff --git a/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp b/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp
index 162711d..a9e935d 100644
--- a/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp
+++ b/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp
@@ -279,7 +279,7 @@
     }
 
     bool waitForHotplugEvent(Display displayId, bool connected) {
-        return waitForHotplugEvent(PhysicalDisplayId(displayId), connected);
+        return waitForHotplugEvent(physicalIdFromHwcDisplayId(displayId), connected);
     }
 
     bool waitForHotplugEvent(PhysicalDisplayId displayId, bool connected) {
@@ -305,7 +305,7 @@
     }
 
     bool waitForModeChangedEvent(Display display, int32_t modeId) {
-        PhysicalDisplayId displayId(display);
+        PhysicalDisplayId displayId = physicalIdFromHwcDisplayId(display);
         int waitCount = 20;
         while (waitCount--) {
             while (!mReceivedDisplayEvents.empty()) {
diff --git a/services/surfaceflinger/tests/unittests/Android.bp b/services/surfaceflinger/tests/unittests/Android.bp
index b5086fa..bd6fe1d 100644
--- a/services/surfaceflinger/tests/unittests/Android.bp
+++ b/services/surfaceflinger/tests/unittests/Android.bp
@@ -23,7 +23,10 @@
 
 cc_test {
     name: "libsurfaceflinger_unittest",
-    defaults: ["surfaceflinger_defaults"],
+    defaults: [
+        "skia_renderengine_deps",
+        "surfaceflinger_defaults",
+    ],
     test_suites: ["device-tests"],
     sanitize: {
         // Using the address sanitizer not only helps uncover issues in the code
diff --git a/services/surfaceflinger/tests/unittests/CompositionTest.cpp b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
index 560f139..fca3bfc 100644
--- a/services/surfaceflinger/tests/unittests/CompositionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
@@ -77,7 +77,7 @@
 constexpr hal::HWLayerId HWC_LAYER = 5000;
 constexpr Transform DEFAULT_TRANSFORM = static_cast<Transform>(0);
 
-constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID(42);
+constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId::fromPort(42u);
 constexpr int DEFAULT_DISPLAY_WIDTH = 1920;
 constexpr int DEFAULT_DISPLAY_HEIGHT = 1024;
 
diff --git a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
index cc24323..60b0f53 100644
--- a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
@@ -122,7 +122,7 @@
 
 sp<DisplayDevice> DisplayTransactionTest::injectDefaultInternalDisplay(
         std::function<void(FakeDisplayDeviceInjector&)> injectExtra) {
-    constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID(777);
+    constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId::fromPort(255u);
     constexpr int DEFAULT_DISPLAY_WIDTH = 1080;
     constexpr int DEFAULT_DISPLAY_HEIGHT = 1920;
     constexpr HWDisplayId DEFAULT_DISPLAY_HWC_DISPLAY_ID = 0;
diff --git a/services/surfaceflinger/tests/unittests/EventThreadTest.cpp b/services/surfaceflinger/tests/unittests/EventThreadTest.cpp
index b4a1481..62acc6b 100644
--- a/services/surfaceflinger/tests/unittests/EventThreadTest.cpp
+++ b/services/surfaceflinger/tests/unittests/EventThreadTest.cpp
@@ -41,10 +41,13 @@
 
 namespace {
 
-constexpr PhysicalDisplayId INTERNAL_DISPLAY_ID(111);
-constexpr PhysicalDisplayId EXTERNAL_DISPLAY_ID(222);
-constexpr PhysicalDisplayId DISPLAY_ID_64BIT(0xabcd12349876fedcULL);
+constexpr PhysicalDisplayId INTERNAL_DISPLAY_ID = PhysicalDisplayId::fromPort(111u);
+constexpr PhysicalDisplayId EXTERNAL_DISPLAY_ID = PhysicalDisplayId::fromPort(222u);
+constexpr PhysicalDisplayId DISPLAY_ID_64BIT =
+        PhysicalDisplayId::fromEdid(0xffu, 0xffffu, 0xffff'ffffu);
+
 constexpr std::chrono::duration VSYNC_PERIOD(16ms);
+
 class MockVSyncSource : public VSyncSource {
 public:
     const char* getName() const override { return "test"; }
diff --git a/services/surfaceflinger/tests/unittests/OneShotTimerTest.cpp b/services/surfaceflinger/tests/unittests/OneShotTimerTest.cpp
index 6916764..597e5e7 100644
--- a/services/surfaceflinger/tests/unittests/OneShotTimerTest.cpp
+++ b/services/surfaceflinger/tests/unittests/OneShotTimerTest.cpp
@@ -72,7 +72,8 @@
     mIdleTimer->stop();
 }
 
-TEST_F(OneShotTimerTest, resetTest) {
+// TODO(b/186417847) This test is flaky. Reenable once fixed.
+TEST_F(OneShotTimerTest, DISABLED_resetTest) {
     fake::FakeClock* clock = new fake::FakeClock();
     mIdleTimer = std::make_unique<scheduler::OneShotTimer>("TestTimer", 1ms,
                                                            mResetTimerCallback.getInvocable(),
@@ -94,7 +95,8 @@
     EXPECT_FALSE(mResetTimerCallback.waitForUnexpectedCall().has_value());
 }
 
-TEST_F(OneShotTimerTest, resetBackToBackTest) {
+// TODO(b/186417847) This test is flaky. Reenable once fixed.
+TEST_F(OneShotTimerTest, DISABLED_resetBackToBackTest) {
     fake::FakeClock* clock = new fake::FakeClock();
     mIdleTimer = std::make_unique<scheduler::OneShotTimer>("TestTimer", 1ms,
                                                            mResetTimerCallback.getInvocable(),
@@ -144,7 +146,8 @@
     EXPECT_FALSE(mResetTimerCallback.waitForUnexpectedCall().has_value());
 }
 
-TEST_F(OneShotTimerTest, idleTimerIdlesTest) {
+// TODO(b/186417847) This test is flaky. Reenable once fixed.
+TEST_F(OneShotTimerTest, DISABLED_idleTimerIdlesTest) {
     fake::FakeClock* clock = new fake::FakeClock();
     mIdleTimer = std::make_unique<scheduler::OneShotTimer>("TestTimer", 1ms,
                                                            mResetTimerCallback.getInvocable(),
@@ -169,7 +172,8 @@
     EXPECT_FALSE(mResetTimerCallback.waitForUnexpectedCall().has_value());
 }
 
-TEST_F(OneShotTimerTest, timeoutCallbackExecutionTest) {
+// TODO(b/186417847) This test is flaky. Reenable once fixed.
+TEST_F(OneShotTimerTest, DISABLED_timeoutCallbackExecutionTest) {
     fake::FakeClock* clock = new fake::FakeClock();
     mIdleTimer = std::make_unique<scheduler::OneShotTimer>("TestTimer", 1ms,
                                                            mResetTimerCallback.getInvocable(),
diff --git a/services/surfaceflinger/tests/unittests/SchedulerTest.cpp b/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
index 423d0cc..e23c20e 100644
--- a/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
+++ b/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
@@ -34,7 +34,7 @@
 namespace android {
 namespace {
 
-constexpr PhysicalDisplayId PHYSICAL_DISPLAY_ID(999);
+constexpr PhysicalDisplayId PHYSICAL_DISPLAY_ID = PhysicalDisplayId::fromPort(255u);
 
 class SchedulerTest : public testing::Test {
 protected:
diff --git a/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.cpp b/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.cpp
index 7de1872..20d41e6 100644
--- a/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.cpp
+++ b/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.cpp
@@ -18,6 +18,7 @@
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wconversion"
 
+#undef LOG_TAG
 #define LOG_TAG "MockComposer"
 #include "mock/DisplayHardware/MockComposer.h"