gameactivity: don't discard stylus touchscreen inputs

I noticed touch inputs weren't working on my Galaxy S9 tab device which
includes a stylus. The value was 0xD002 for source, which seems to be:

SOURCE_CLASS_POINTER     0b0000 0000 0000 0010
SOURCE_STYLUS            0b0100 0000 0000 0000
SOURCE_BLUETOOTH_STYLUS  0b1000 0000 0000 0000
SOURCE_TOUCHSCREEN       0b0001 0000 0000 0000
----------------------------------------------
                0xD002 = 0b1101 0000 0000 0010

Let's modify default_motion_filter to use bitwise AND (&) instead of
equality (==) when checking SOURCE_TOUCHSCREEN. This ensures stylus
inputs (which combine touchscreen and stylus flags) are not discarded,
while still filtering non-touch events.

Changelog-Fixed: Fix touch inputs on tablets with a stylus
Signed-off-by: William Casarin <[email protected]>

Author: jb55

android-activity/game-activity-csrc/game-activity/native_app_glue/android_native_app_glue.c

@@ -264,7 +264,7 @@ static bool default_key_filter(const GameActivityKeyEvent* event) {
 
 static bool default_motion_filter(const GameActivityMotionEvent* event) {
     // Ignore any non-touch events.
-    return event->source == SOURCE_TOUCHSCREEN;
+    return event->source & SOURCE_TOUCHSCREEN;
 }
 
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