When triple clicking on text, we should select the entire paragraph, or
entire line in <input>s and <textarea>s. If the mouse button is held
down and the user starts dragging, the selection expands with additional
paragraphs or lines.
This expands on the work of Kai Wildberger (PR #7681) but was adjusted
for the work that happened previously to support double click + drag
moves and includes triple click support for our Qt UI.
Co-authored-by: Kai Wildberger <kiawildberger@gmail.com>
The faux position we created here is adjusted by the device pixel ratio
later on, which would invoke integer overflow on screens with a DPR
greater than 1.
Instead of creating special data for a mouse move event, let's just add
an explicit leave event handler.
Our existing coalescing mechanism for input events didn't prevent
multiple mousemove/mousewheel events from being processed between paint
cycles. Since handling these events can trigger style & layout updates
solely for hit-testing purposes, we might end up doing work that won't
be observable by a user and could be avoided by shceduling input events
processing to happen right before painting the next frame.
