Commit da0f76de6d8e31c610a18933423213c46974388e
2021-12-07T00:38:46
cocoa: Don't round scroll deltas from trackpads Rounding the scroll deltas from trackpads causes jerky scrolling behavior by artificially amplifying the effects of very small scroll movements. We should only round events from devices with discrete scroll wheels, because we know the smallest unit of movement there is a single tick.
diff --git a/src/video/cocoa/SDL_cocoamouse.m b/src/video/cocoa/SDL_cocoamouse.m
index e9d832d..9031c83 100644
--- a/src/video/cocoa/SDL_cocoamouse.m
+++ b/src/video/cocoa/SDL_cocoamouse.m
@@ -473,15 +473,19 @@ Cocoa_HandleMouseWheel(SDL_Window *window, NSEvent *event)
}
}
- if (x > 0) {
- x = SDL_ceil(x);
- } else if (x < 0) {
- x = SDL_floor(x);
- }
- if (y > 0) {
- y = SDL_ceil(y);
- } else if (y < 0) {
- y = SDL_floor(y);
+ /* For discrete scroll events from conventional mice, always send a full tick.
+ For continuous scroll events from trackpads, send fractional deltas for smoother scrolling. */
+ if (![event respondsToSelector:@selector(hasPreciseScrollingDeltas)] || ![event hasPreciseScrollingDeltas]) {
+ if (x > 0) {
+ x = SDL_ceil(x);
+ } else if (x < 0) {
+ x = SDL_floor(x);
+ }
+ if (y > 0) {
+ y = SDL_ceil(y);
+ } else if (y < 0) {
+ y = SDL_floor(y);
+ }
}
SDL_SendMouseWheel(window, mouseID, x, y, direction);