Wheel deltas were truncated to int at the platform input boundary,
which dropped the sub-pixel tail of trackpad momentum scrolls. Each
NSEvent's scrollingDeltaY arrived as a CGFloat, got cast to int, and
flowed through IPC, EventHandler, and PaintableBox::scroll_by as int,
losing fractional information that never came back.
Widen Web::MouseEvent::wheel_delta_{x,y} to double and propagate
through Page, EventHandler, Paintable, PaintableBox, and the AppKit,
Qt, and GTK input paths.
Use the snapshot from the previous commit to let CompositorThread apply
experimental viewport wheel deltas when async scrolling is enabled. The
event handler first performs synchronous admission on the main thread,
then enqueues a compositor scroll command instead of mutating live
document scroll state directly.
Rasterize accepted scrolls through the same compositor presentation
path added earlier. The compositor stores the newest async viewport
offset so the next main-thread display-list recording can adopt it
before repainting, preventing older paints from snapping the visible
position backward.
Keep DOM wheel dispatch on the main thread. When the compositor already
performed the default action, dispatch the wheel as non-cancelable and
suppress a second default scroll. Non-viewport targets, nested
scrollers, and pages with blocking wheel listeners stay synchronous.
This moves normal/double/triple click checking into WebContent, the
client only has to send a click count in order to activate a double
or triple click in the content. This means that the AppKit UI will no
longer fire multiple double clicks when clicking in place more than 3
times. This matches the behavior of other browsers on macOS.
We will now also fire the click event regardless of whether a dblclick
event will follow, as the spec requires.
