Move things in InputWindowInfo to enum classes
Also introduce a new Flag class to make it possible to deal with flags
while treating the individual flags as part of an enum class in a type
safe manner.
Bug: 160010896
Test: atest inputflinger_tests, atest libinput_tests
Change-Id: I915a1c1e3b31f1c0fd99b83ba5fad7e537cd6f84
diff --git a/include/input/Flags.h b/include/input/Flags.h
new file mode 100644
index 0000000..f3198c9
--- /dev/null
+++ b/include/input/Flags.h
@@ -0,0 +1,179 @@
+/*
+ * Copyright (C) 2020 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 <android-base/stringprintf.h>
+
+#include <cstdint>
+#include <optional>
+#include <string>
+#include <type_traits>
+
+#include "utils/BitSet.h"
+
+#ifndef __UI_INPUT_FLAGS_H
+#define __UI_INPUT_FLAGS_H
+
+namespace android {
+
+// A trait for determining whether a type is specifically an enum class or not.
+template <typename T, bool = std::is_enum_v<T>>
+struct is_enum_class : std::false_type {};
+
+// By definition, an enum class is an enum that is not implicitly convertible to its underlying
+// type.
+template <typename T>
+struct is_enum_class<T, true>
+ : std::bool_constant<!std::is_convertible_v<T, std::underlying_type_t<T>>> {};
+
+template <typename T>
+inline constexpr bool is_enum_class_v = is_enum_class<T>::value;
+
+/* A class for handling flags defined by an enum or enum class in a type-safe way. */
+template <class F, typename = std::enable_if_t<std::is_enum_v<F>>>
+class Flags {
+ // F must be an enum or its underlying type is undefined. Theoretically we could specialize this
+ // further to avoid this restriction but in general we want to encourage the use of enums
+ // anyways.
+ using U = typename std::underlying_type_t<F>;
+
+public:
+ constexpr Flags(F f) : flags(static_cast<U>(f)) {}
+ constexpr Flags() : flags(0) {}
+ constexpr Flags(const Flags<F>& f) : flags(f.flags) {}
+
+ // Provide a non-explicit construct for non-enum classes since they easily convert to their
+ // underlying types (e.g. when used with bitwise operators). For enum classes, however, we
+ // should force them to be explicitly constructed from their underlying types to make full use
+ // of the type checker.
+ template <typename T = U>
+ constexpr Flags(T t, typename std::enable_if_t<!is_enum_class_v<F>, T>* = nullptr) : flags(t) {}
+ template <typename T = U>
+ explicit constexpr Flags(T t, typename std::enable_if_t<is_enum_class_v<F>, T>* = nullptr)
+ : flags(t) {}
+ /*
+ * Tests whether the given flag is set.
+ */
+ bool test(F flag) const {
+ U f = static_cast<U>(flag);
+ return (f & flags) == f;
+ }
+
+ /* Tests whether any of the given flags are set */
+ bool any(Flags<F> f) { return (flags & f.flags) != 0; }
+
+ /* Tests whether all of the given flags are set */
+ bool all(Flags<F> f) { return (flags & f.flags) == f.flags; }
+
+ Flags<F> operator|(Flags<F> rhs) const { return static_cast<F>(flags | rhs.flags); }
+ Flags<F>& operator|=(Flags<F> rhs) {
+ flags = flags | rhs.flags;
+ return *this;
+ }
+
+ Flags<F> operator&(Flags<F> rhs) const { return static_cast<F>(flags & rhs.flags); }
+ Flags<F>& operator&=(Flags<F> rhs) {
+ flags = flags & rhs.flags;
+ return *this;
+ }
+
+ Flags<F> operator^(Flags<F> rhs) const { return static_cast<F>(flags ^ rhs.flags); }
+ Flags<F>& operator^=(Flags<F> rhs) {
+ flags = flags ^ rhs.flags;
+ return *this;
+ }
+
+ Flags<F> operator~() { return static_cast<F>(~flags); }
+
+ bool operator==(Flags<F> rhs) const { return flags == rhs.flags; }
+ bool operator!=(Flags<F> rhs) const { return !operator==(rhs); }
+
+ Flags<F>& operator=(const Flags<F>& rhs) {
+ flags = rhs.flags;
+ return *this;
+ }
+
+ /*
+ * Returns the stored set of flags.
+ *
+ * Note that this returns the underlying type rather than the base enum class. This is because
+ * the value is no longer necessarily a strict member of the enum since the returned value could
+ * be multiple enum variants OR'd together.
+ */
+ U get() const { return flags; }
+
+ std::string string() const { return string(defaultStringify); }
+
+ std::string string(std::function<std::optional<std::string>(F)> stringify) const {
+ // The type can't be larger than 64-bits otherwise it won't fit in BitSet64.
+ static_assert(sizeof(U) <= sizeof(uint64_t));
+ std::string result;
+ bool first = true;
+ U unstringified = 0;
+ for (BitSet64 bits(flags); !bits.isEmpty();) {
+ uint64_t bit = bits.clearLastMarkedBit(); // counts from left
+ const U flag = 1 << (64 - bit - 1);
+ std::optional<std::string> flagString = stringify(static_cast<F>(flag));
+ if (flagString) {
+ appendFlag(result, flagString.value(), first);
+ } else {
+ unstringified |= flag;
+ }
+ }
+
+ if (unstringified != 0) {
+ appendFlag(result, base::StringPrintf("0x%08x", unstringified), first);
+ }
+
+ if (first) {
+ result += "0x0";
+ }
+
+ return result;
+ }
+
+private:
+ U flags;
+
+ static std::optional<std::string> defaultStringify(F) { return std::nullopt; }
+ static void appendFlag(std::string& str, const std::string& flag, bool& first) {
+ if (first) {
+ first = false;
+ } else {
+ str += " | ";
+ }
+ str += flag;
+ }
+};
+
+// This namespace provides operator overloads for enum classes to make it easier to work with them
+// as flags. In order to use these, add them via a `using namespace` declaration.
+namespace flag_operators {
+
+template <typename F, typename = std::enable_if_t<is_enum_class_v<F>>>
+inline Flags<F> operator~(F f) {
+ using U = typename std::underlying_type_t<F>;
+ return static_cast<F>(~static_cast<U>(f));
+}
+template <typename F, typename = std::enable_if_t<is_enum_class_v<F>>>
+Flags<F> operator|(F lhs, F rhs) {
+ using U = typename std::underlying_type_t<F>;
+ return static_cast<F>(static_cast<U>(lhs) | static_cast<U>(rhs));
+}
+
+} // namespace flag_operators
+} // namespace android
+
+#endif // __UI_INPUT_FLAGS_H
\ No newline at end of file