Gamepad: Improve unknown gamepad heuristics and mappings

content/public/android/java/src/org/chromium/content/browser/input/GamepadMappings.java

Index: content/public/android/java/src/org/chromium/content/browser/input/GamepadMappings.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/input/GamepadMappings.java b/content/public/android/java/src/org/chromium/content/browser/input/GamepadMappings.java
index 1ded67f0bddd1465d72c7892f92614398ec34f68..f924b7841e95235fc8c283aaa097716c8467cefb 100644
--- a/content/public/android/java/src/org/chromium/content/browser/input/GamepadMappings.java
+++ b/content/public/android/java/src/org/chromium/content/browser/input/GamepadMappings.java
@@ -77,7 +77,14 @@ class GamepadMappings {
         mappedButtons[CanonicalButtonIndex.RIGHT_THUMBSTICK] = thumbR;
     }
 
-    private static void mapCommonTriggerButtons(float[] mappedButtons, float[] rawButtons) {
+    /**
+     * Method for mapping the L1/R1 buttons to lower shoulder buttons, rather than
+     * upper shoulder as the user would normally expect. Please think twice before
+     * using this, as it can easily confuse the user. It is only really useful if
+     * the controller completely lacks a second set of shoulder buttons
+     */
+    private static void mapUpperTriggerButtonsToBottomShoulder(float[] mappedButtons,
+            float[] rawButtons) {
         float l1 = rawButtons[KeyEvent.KEYCODE_BUTTON_L1];
         float r1 = rawButtons[KeyEvent.KEYCODE_BUTTON_R1];
         mappedButtons[CanonicalButtonIndex.LEFT_TRIGGER] = l1;
@@ -117,13 +124,6 @@ class GamepadMappings {
         mappedAxes[CanonicalAxisIndex.RIGHT_STICK_Y] = rawAxes[MotionEvent.AXIS_RZ];
     }
 
-    private static void mapTriggerAxexToShoulderButtons(float[] mappedButtons, float[] rawAxes) {
-        float lTrigger = rawAxes[MotionEvent.AXIS_LTRIGGER];
-        float rTrigger = rawAxes[MotionEvent.AXIS_RTRIGGER];
-        mappedButtons[CanonicalButtonIndex.LEFT_SHOULDER] = lTrigger;
-        mappedButtons[CanonicalButtonIndex.RIGHT_SHOULDER] = rTrigger;
-    }
-
     private static void mapPedalAxesToBottomShoulder(float[] mappedButtons, float[] rawAxes) {
         float lTrigger = rawAxes[MotionEvent.AXIS_BRAKE];
         float rTrigger = rawAxes[MotionEvent.AXIS_GAS];
@@ -131,6 +131,13 @@ class GamepadMappings {
         mappedButtons[CanonicalButtonIndex.RIGHT_TRIGGER] = rTrigger;
     }
 
+    private static void mapAltPedalAxesToBottomShoulder(float[] mappedButtons, float[] rawAxes) {
+        float lTrigger = rawAxes[MotionEvent.AXIS_BRAKE];
+        float rTrigger = rawAxes[MotionEvent.AXIS_THROTTLE];
+        mappedButtons[CanonicalButtonIndex.LEFT_TRIGGER] = lTrigger;
+        mappedButtons[CanonicalButtonIndex.RIGHT_TRIGGER] = rTrigger;
+    }
+
     private static void mapTriggerAxesToBottomShoulder(float[] mappedButtons, float[] rawAxes) {
         float lTrigger = rawAxes[MotionEvent.AXIS_LTRIGGER];
         float rTrigger = rawAxes[MotionEvent.AXIS_RTRIGGER];
@@ -138,6 +145,31 @@ class GamepadMappings {
         mappedButtons[CanonicalButtonIndex.RIGHT_TRIGGER] = rTrigger;
     }
 
+    private static void mapLowerTriggerButtonsToBottomShoulder(float[] mappedButtons,
+            float[] rawButtons) {
+        float l2 = rawButtons[KeyEvent.KEYCODE_BUTTON_L2];
+        float r2 = rawButtons[KeyEvent.KEYCODE_BUTTON_R2];
+        mappedButtons[CanonicalButtonIndex.LEFT_TRIGGER] = l2;
+        mappedButtons[CanonicalButtonIndex.RIGHT_TRIGGER] = r2;
+    }
+
+    private static boolean triggersPopulated(float[] mappedButtons) {
+        return mappedButtons[CanonicalButtonIndex.LEFT_TRIGGER] != 0
+            || mappedButtons[CanonicalButtonIndex.RIGHT_TRIGGER] != 0;
+    }
+
+    private static boolean dpadPopulated(float[] mappedButtons) {
+        return mappedButtons[CanonicalButtonIndex.DPAD_DOWN] != 0
+            || mappedButtons[CanonicalButtonIndex.DPAD_UP] != 0
+            || mappedButtons[CanonicalButtonIndex.DPAD_LEFT] != 0
+            || mappedButtons[CanonicalButtonIndex.DPAD_RIGHT] != 0;
+    }
+
+    private static boolean rightStickPopulated(float[] mappedAxes) {
+        return mappedAxes[CanonicalAxisIndex.RIGHT_STICK_X] != 0
+            || mappedAxes[CanonicalAxisIndex.RIGHT_STICK_Y] != 0;
+    }
+
     @VisibleForTesting
     static float negativeAxisValueAsButton(float input) {
         return (input < -0.5f) ? 1.f : 0.f;
@@ -213,11 +245,11 @@ class GamepadMappings {
         mappedButtons[CanonicalButtonIndex.TERTIARY] = a;
         mappedButtons[CanonicalButtonIndex.QUATERNARY] = b;
 
-        mapCommonTriggerButtons(mappedButtons, rawButtons);
+        mapTriggerButtonsToTopShoulder(mappedButtons, rawButtons);
         mapCommonThumbstickButtons(mappedButtons, rawButtons);
         mapCommonDpadButtons(mappedButtons, rawButtons);
         mapCommonStartSelectMetaButtons(mappedButtons, rawButtons);
-        mapTriggerAxexToShoulderButtons(mappedButtons, rawAxes);
+        mapTriggerAxesToBottomShoulder(mappedButtons, rawAxes);
 
         mapXYAxes(mappedAxes, rawAxes);
         mapZAndRZAxesToRightStick(mappedAxes, rawAxes);
@@ -226,7 +258,7 @@ class GamepadMappings {
     private static void mapSamsungEIGP20Gamepad(float[] mappedButtons, float[] rawButtons,
             float[] mappedAxes, float[] rawAxes) {
         mapCommonXYABButtons(mappedButtons, rawButtons);
-        mapCommonTriggerButtons(mappedButtons, rawButtons);
+        mapUpperTriggerButtonsToBottomShoulder(mappedButtons, rawButtons);
         mapCommonThumbstickButtons(mappedButtons, rawButtons);
         mapCommonStartSelectMetaButtons(mappedButtons, rawButtons);
         mapHatAxisToDpadButtons(mappedButtons, rawAxes);
@@ -241,14 +273,40 @@ class GamepadMappings {
      */
     private static void mapUnknownGamepad(float[] mappedButtons, float[] rawButtons,
             float[] mappedAxes, float[] rawAxes) {
+        // These are correct on all standard Android gamepads
         mapCommonXYABButtons(mappedButtons, rawButtons);
-        mapCommonTriggerButtons(mappedButtons, rawButtons);
+        mapTriggerButtonsToTopShoulder(mappedButtons, rawButtons);
         mapCommonThumbstickButtons(mappedButtons, rawButtons);
         mapCommonStartSelectMetaButtons(mappedButtons, rawButtons);
-        mapTriggerAxexToShoulderButtons(mappedButtons, rawAxes);
-        mapCommonDpadButtons(mappedButtons, rawButtons);
-
         mapXYAxes(mappedAxes, rawAxes);
-        mapRXAndRYAxesToRightStick(mappedAxes, rawAxes);
+
+        // Some gamepads (like Shield) use AXIS_LTRIGGER and AXIS_RTRIGGER
+        mapTriggerAxesToBottomShoulder(mappedButtons, rawAxes);
+        if (!triggersPopulated(mappedButtons)) {
+            // Moga gamepads use AXIS_BRAKE and AXIS_GAS
+            mapPedalAxesToBottomShoulder(mappedButtons, rawAxes);
+            if (!triggersPopulated(mappedButtons)) {
+                // Xiaomi gamepads use AXIS_BRAKE and AXIS_THROTTLE
+                mapAltPedalAxesToBottomShoulder(mappedButtons, rawAxes);
+                if (!triggersPopulated(mappedButtons)) {
+                    // Devices without analog triggers use digital buttons
+                    mapLowerTriggerButtonsToBottomShoulder(mappedButtons, rawButtons);
+                }
+            }
+        }
+
+        // Some gamepads expose a hat axis for the dpad
+        mapHatAxisToDpadButtons(mappedButtons, rawAxes);
+        if (!dpadPopulated(mappedButtons)) {
+            // Others only generate KEYCODE_DPAD events
+            mapCommonDpadButtons(mappedButtons, rawButtons);
+        }
+
+        // Most gamepads use Z and RZ for right stick
+        mapZAndRZAxesToRightStick(mappedAxes, rawAxes);
+        if (!rightStickPopulated(mappedAxes)) {
+            // Others use RX and RY
+            mapRXAndRYAxesToRightStick(mappedAxes, rawAxes);
+        }
     }
 }