Android: two-finger tilt sensitivity depends on display density

What happened?

Android calculates tilt using 0.1° per physical pixel of vertical finger movement. This makes the same drag distance in dp produce different pitch changes depending on display density.

For example, after gesture recognition, a 100 dp drag produces:

• Density 1: 10° of pitch change.
• Density 3: 30° of pitch change.

Expected: equivalent drag distances in dp should produce equivalent pitch changes.

Source evidence

ShoveGestureDetector calculates the centroid displacement directly from MotionEvent.getY(), in pixels.

MapGestureDetector multiplies this displacement by SHOVE_PIXEL_CHANGE_FACTOR (0.1) without normalizing for display density.

For comparison, iOS uses 0.5° per UIKit point, independent of screen scale.

I personally found 0.5° to be a bit fast, so made MapLibre Compose default to 0.3°/Dp on all targets.

Environment

Source inspection of main at c82c14f9710a861e0a4cef335eff311eea50cd86.

Start with ShoveGestureDetector.java, where centroid displacement comes from MotionEvent.getY(), then trace MapGestureDetector.java and SHOVE_PIXEL_CHANGE_FACTOR. Compare the Android calculation with the iOS point-based behavior and verify that equivalent drag distances in dp produce equivalent pitch changes across display densities.