10 iii and ii touchscreen events? Difficult to click URL's, v-hard to click-n-hold/double-tap for new-tab/copy-text operations

rainemak · 9 September 2022 11:08

@flypig 's answer is very much correct. If you leave apz.touch_start_tolerance to 0.25 actual touch start will resist more.

Here’s the source line and only place where the apz.touch_start_tolerance is used.

github.com/sailfishos-mirror/gecko-dev

gfx/layers/apz/src/AsyncPanZoomController.cpp

600df6aa6


      
            if (APZCTreeManager* localPtr = mTreeManager) {
              return localPtr->GetDPI();
            }
            // If this APZC has been destroyed then this value is not going to be
            // used for anything that the user will end up seeing, so we can just
            // return 0.
            return 0.0;
          }
          
          ScreenCoord AsyncPanZoomController::GetTouchStartTolerance() const {
            return (StaticPrefs::apz_touch_start_tolerance() * GetDPI());
          }
          
          ScreenCoord AsyncPanZoomController::GetTouchMoveTolerance() const {
            return (StaticPrefs::apz_touch_move_tolerance() * GetDPI());
          }
          
          ScreenCoord AsyncPanZoomController::GetSecondTapTolerance() const {
            return (StaticPrefs::apz_second_tap_tolerance() * GetDPI());
          }

There was a bug in the DPI value that was set down to the ASyncPanZoomContoller. So, the math regarding the touch start tolerance on Xperia 10 III goes as follows :

Before with 0.25

96 * 0.25 = 24 (screen coordinates)

After with 0.0762785 <= calculated value

457 * 0.0762785 = 35 (screen coordinates)

Above 457 is rounded value. So, the new value after the fix is 11px higher when comparing 0.25 apz.touch_start_tolerance. You can simulate the fix by adding 0.364583333 to the apz.touch_start_tolerance. It could well be that for some users even higher return value from GetTouchStartTolerance would work better.