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
diff --git a/include/input/InputWindow.h b/include/input/InputWindow.h
index 18cca2c..233c7ae 100644
--- a/include/input/InputWindow.h
+++ b/include/input/InputWindow.h
@@ -19,6 +19,7 @@
 
 #include <binder/Parcel.h>
 #include <binder/Parcelable.h>
+#include <input/Flags.h>
 #include <input/Input.h>
 #include <input/InputTransport.h>
 #include <ui/Rect.h>
@@ -38,92 +39,92 @@
     InputWindowInfo() = default;
 
     // Window flags from WindowManager.LayoutParams
-    enum : uint32_t {
-        FLAG_ALLOW_LOCK_WHILE_SCREEN_ON = 0x00000001,
-        FLAG_DIM_BEHIND = 0x00000002,
-        FLAG_BLUR_BEHIND = 0x00000004,
-        FLAG_NOT_FOCUSABLE = 0x00000008,
-        FLAG_NOT_TOUCHABLE = 0x00000010,
-        FLAG_NOT_TOUCH_MODAL = 0x00000020,
-        FLAG_TOUCHABLE_WHEN_WAKING = 0x00000040,
-        FLAG_KEEP_SCREEN_ON = 0x00000080,
-        FLAG_LAYOUT_IN_SCREEN = 0x00000100,
-        FLAG_LAYOUT_NO_LIMITS = 0x00000200,
-        FLAG_FULLSCREEN = 0x00000400,
-        FLAG_FORCE_NOT_FULLSCREEN = 0x00000800,
-        FLAG_DITHER = 0x00001000,
-        FLAG_SECURE = 0x00002000,
-        FLAG_SCALED = 0x00004000,
-        FLAG_IGNORE_CHEEK_PRESSES = 0x00008000,
-        FLAG_LAYOUT_INSET_DECOR = 0x00010000,
-        FLAG_ALT_FOCUSABLE_IM = 0x00020000,
-        FLAG_WATCH_OUTSIDE_TOUCH = 0x00040000,
-        FLAG_SHOW_WHEN_LOCKED = 0x00080000,
-        FLAG_SHOW_WALLPAPER = 0x00100000,
-        FLAG_TURN_SCREEN_ON = 0x00200000,
-        FLAG_DISMISS_KEYGUARD = 0x00400000,
-        FLAG_SPLIT_TOUCH = 0x00800000,
-        FLAG_HARDWARE_ACCELERATED = 0x01000000,
-        FLAG_LAYOUT_IN_OVERSCAN = 0x02000000,
-        FLAG_TRANSLUCENT_STATUS = 0x04000000,
-        FLAG_TRANSLUCENT_NAVIGATION = 0x08000000,
-        FLAG_LOCAL_FOCUS_MODE = 0x10000000,
-        FLAG_SLIPPERY = 0x20000000,
-        FLAG_LAYOUT_ATTACHED_IN_DECOR = 0x40000000,
-        FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS = 0x80000000,
-    };
+    enum class Flag : uint32_t {
+        ALLOW_LOCK_WHILE_SCREEN_ON = 0x00000001,
+        DIM_BEHIND = 0x00000002,
+        BLUR_BEHIND = 0x00000004,
+        NOT_FOCUSABLE = 0x00000008,
+        NOT_TOUCHABLE = 0x00000010,
+        NOT_TOUCH_MODAL = 0x00000020,
+        TOUCHABLE_WHEN_WAKING = 0x00000040,
+        KEEP_SCREEN_ON = 0x00000080,
+        LAYOUT_IN_SCREEN = 0x00000100,
+        LAYOUT_NO_LIMITS = 0x00000200,
+        FULLSCREEN = 0x00000400,
+        FORCE_NOT_FULLSCREEN = 0x00000800,
+        DITHER = 0x00001000,
+        SECURE = 0x00002000,
+        SCALED = 0x00004000,
+        IGNORE_CHEEK_PRESSES = 0x00008000,
+        LAYOUT_INSET_DECOR = 0x00010000,
+        ALT_FOCUSABLE_IM = 0x00020000,
+        WATCH_OUTSIDE_TOUCH = 0x00040000,
+        SHOW_WHEN_LOCKED = 0x00080000,
+        SHOW_WALLPAPER = 0x00100000,
+        TURN_SCREEN_ON = 0x00200000,
+        DISMISS_KEYGUARD = 0x00400000,
+        SPLIT_TOUCH = 0x00800000,
+        HARDWARE_ACCELERATED = 0x01000000,
+        LAYOUT_IN_OVERSCAN = 0x02000000,
+        TRANSLUCENT_STATUS = 0x04000000,
+        TRANSLUCENT_NAVIGATION = 0x08000000,
+        LOCAL_FOCUS_MODE = 0x10000000,
+        SLIPPERY = 0x20000000,
+        LAYOUT_ATTACHED_IN_DECOR = 0x40000000,
+        DRAWS_SYSTEM_BAR_BACKGROUNDS = 0x80000000,
+    }; // Window types from WindowManager.LayoutParams
 
-    // Window types from WindowManager.LayoutParams
-    enum {
+    enum class Type : int32_t {
+        UNKNOWN = 0,
         FIRST_APPLICATION_WINDOW = 1,
-        TYPE_BASE_APPLICATION = 1,
-        TYPE_APPLICATION = 2,
-        TYPE_APPLICATION_STARTING = 3,
+        BASE_APPLICATION = 1,
+        APPLICATION = 2,
+        APPLICATION_STARTING = 3,
         LAST_APPLICATION_WINDOW = 99,
         FIRST_SUB_WINDOW = 1000,
-        TYPE_APPLICATION_PANEL = FIRST_SUB_WINDOW,
-        TYPE_APPLICATION_MEDIA = FIRST_SUB_WINDOW + 1,
-        TYPE_APPLICATION_SUB_PANEL = FIRST_SUB_WINDOW + 2,
-        TYPE_APPLICATION_ATTACHED_DIALOG = FIRST_SUB_WINDOW + 3,
-        TYPE_APPLICATION_MEDIA_OVERLAY = FIRST_SUB_WINDOW + 4,
+        APPLICATION_PANEL = FIRST_SUB_WINDOW,
+        APPLICATION_MEDIA = FIRST_SUB_WINDOW + 1,
+        APPLICATION_SUB_PANEL = FIRST_SUB_WINDOW + 2,
+        APPLICATION_ATTACHED_DIALOG = FIRST_SUB_WINDOW + 3,
+        APPLICATION_MEDIA_OVERLAY = FIRST_SUB_WINDOW + 4,
         LAST_SUB_WINDOW = 1999,
         FIRST_SYSTEM_WINDOW = 2000,
-        TYPE_STATUS_BAR = FIRST_SYSTEM_WINDOW,
-        TYPE_SEARCH_BAR = FIRST_SYSTEM_WINDOW + 1,
-        TYPE_PHONE = FIRST_SYSTEM_WINDOW + 2,
-        TYPE_SYSTEM_ALERT = FIRST_SYSTEM_WINDOW + 3,
-        TYPE_KEYGUARD = FIRST_SYSTEM_WINDOW + 4,
-        TYPE_TOAST = FIRST_SYSTEM_WINDOW + 5,
-        TYPE_SYSTEM_OVERLAY = FIRST_SYSTEM_WINDOW + 6,
-        TYPE_PRIORITY_PHONE = FIRST_SYSTEM_WINDOW + 7,
-        TYPE_SYSTEM_DIALOG = FIRST_SYSTEM_WINDOW + 8,
-        TYPE_KEYGUARD_DIALOG = FIRST_SYSTEM_WINDOW + 9,
-        TYPE_SYSTEM_ERROR = FIRST_SYSTEM_WINDOW + 10,
-        TYPE_INPUT_METHOD = FIRST_SYSTEM_WINDOW + 11,
-        TYPE_INPUT_METHOD_DIALOG = FIRST_SYSTEM_WINDOW + 12,
-        TYPE_WALLPAPER = FIRST_SYSTEM_WINDOW + 13,
-        TYPE_STATUS_BAR_PANEL = FIRST_SYSTEM_WINDOW + 14,
-        TYPE_SECURE_SYSTEM_OVERLAY = FIRST_SYSTEM_WINDOW + 15,
-        TYPE_DRAG = FIRST_SYSTEM_WINDOW + 16,
-        TYPE_STATUS_BAR_SUB_PANEL = FIRST_SYSTEM_WINDOW + 17,
-        TYPE_POINTER = FIRST_SYSTEM_WINDOW + 18,
-        TYPE_NAVIGATION_BAR = FIRST_SYSTEM_WINDOW + 19,
-        TYPE_VOLUME_OVERLAY = FIRST_SYSTEM_WINDOW + 20,
-        TYPE_BOOT_PROGRESS = FIRST_SYSTEM_WINDOW + 21,
-        TYPE_INPUT_CONSUMER = FIRST_SYSTEM_WINDOW + 22,
-        TYPE_NAVIGATION_BAR_PANEL = FIRST_SYSTEM_WINDOW + 24,
-        TYPE_MAGNIFICATION_OVERLAY = FIRST_SYSTEM_WINDOW + 27,
-        TYPE_ACCESSIBILITY_OVERLAY = FIRST_SYSTEM_WINDOW + 32,
-        TYPE_DOCK_DIVIDER = FIRST_SYSTEM_WINDOW + 34,
-        TYPE_ACCESSIBILITY_MAGNIFICATION_OVERLAY = FIRST_SYSTEM_WINDOW + 39,
-        TYPE_NOTIFICATION_SHADE = FIRST_SYSTEM_WINDOW + 40,
+        STATUS_BAR = FIRST_SYSTEM_WINDOW,
+        SEARCH_BAR = FIRST_SYSTEM_WINDOW + 1,
+        PHONE = FIRST_SYSTEM_WINDOW + 2,
+        SYSTEM_ALERT = FIRST_SYSTEM_WINDOW + 3,
+        KEYGUARD = FIRST_SYSTEM_WINDOW + 4,
+        TOAST = FIRST_SYSTEM_WINDOW + 5,
+        SYSTEM_OVERLAY = FIRST_SYSTEM_WINDOW + 6,
+        PRIORITY_PHONE = FIRST_SYSTEM_WINDOW + 7,
+        SYSTEM_DIALOG = FIRST_SYSTEM_WINDOW + 8,
+        KEYGUARD_DIALOG = FIRST_SYSTEM_WINDOW + 9,
+        SYSTEM_ERROR = FIRST_SYSTEM_WINDOW + 10,
+        INPUT_METHOD = FIRST_SYSTEM_WINDOW + 11,
+        INPUT_METHOD_DIALOG = FIRST_SYSTEM_WINDOW + 12,
+        WALLPAPER = FIRST_SYSTEM_WINDOW + 13,
+        STATUS_BAR_PANEL = FIRST_SYSTEM_WINDOW + 14,
+        SECURE_SYSTEM_OVERLAY = FIRST_SYSTEM_WINDOW + 15,
+        DRAG = FIRST_SYSTEM_WINDOW + 16,
+        STATUS_BAR_SUB_PANEL = FIRST_SYSTEM_WINDOW + 17,
+        POINTER = FIRST_SYSTEM_WINDOW + 18,
+        NAVIGATION_BAR = FIRST_SYSTEM_WINDOW + 19,
+        VOLUME_OVERLAY = FIRST_SYSTEM_WINDOW + 20,
+        BOOT_PROGRESS = FIRST_SYSTEM_WINDOW + 21,
+        INPUT_CONSUMER = FIRST_SYSTEM_WINDOW + 22,
+        NAVIGATION_BAR_PANEL = FIRST_SYSTEM_WINDOW + 24,
+        MAGNIFICATION_OVERLAY = FIRST_SYSTEM_WINDOW + 27,
+        ACCESSIBILITY_OVERLAY = FIRST_SYSTEM_WINDOW + 32,
+        DOCK_DIVIDER = FIRST_SYSTEM_WINDOW + 34,
+        ACCESSIBILITY_MAGNIFICATION_OVERLAY = FIRST_SYSTEM_WINDOW + 39,
+        NOTIFICATION_SHADE = FIRST_SYSTEM_WINDOW + 40,
         LAST_SYSTEM_WINDOW = 2999,
     };
 
-    enum {
-        INPUT_FEATURE_DISABLE_TOUCH_PAD_GESTURES = 0x00000001,
-        INPUT_FEATURE_NO_INPUT_CHANNEL = 0x00000002,
-        INPUT_FEATURE_DISABLE_USER_ACTIVITY = 0x00000004,
+    enum class Feature {
+        DISABLE_TOUCH_PAD_GESTURES = 0x00000001,
+        NO_INPUT_CHANNEL = 0x00000002,
+        DISABLE_USER_ACTIVITY = 0x00000004,
     };
 
     /* These values are filled in by the WM and passed through SurfaceFlinger
@@ -135,8 +136,8 @@
     // This uniquely identifies the input window.
     int32_t id = -1;
     std::string name;
-    int32_t layoutParamsFlags = 0;
-    int32_t layoutParamsType = 0;
+    Flags<Flag> flags;
+    Type type = Type::UNKNOWN;
     std::chrono::nanoseconds dispatchingTimeout = std::chrono::seconds(5);
 
     /* These values are filled in by SurfaceFlinger. */
@@ -182,7 +183,7 @@
     bool trustedOverlay = false;
     int32_t ownerPid = -1;
     int32_t ownerUid = -1;
-    int32_t inputFeatures = 0;
+    Flags<Feature> inputFeatures;
     int32_t displayId = ADISPLAY_ID_NONE;
     int32_t portalToDisplayId = ADISPLAY_ID_NONE;
     InputApplicationInfo applicationInfo;
@@ -204,9 +205,9 @@
     status_t writeToParcel(android::Parcel* parcel) const override;
 
     status_t readFromParcel(const android::Parcel* parcel) override;
-};
 
-std::string inputWindowFlagsToString(uint32_t flags);
+    static std::optional<std::string> flagToString(Flag f);
+};
 
 /*
  * Handle for a window that can receive input.
@@ -267,7 +268,6 @@
 
     InputWindowInfo mInfo;
 };
-
 } // namespace android
 
 #endif // _UI_INPUT_WINDOW_H