ossia / score / 30754433360

15%

Build Type

push

github

Committed by jcelerier

Commit Message

fix(widgets): scale custom cursor hotspots on xcb for HiDPI

score::get_cursor loads the @2x cursor asset once devicePixelRatio() >= 1.5 and
tags the pixmap with devicePixelRatio 2. The hotspots in score::Skin are given in
device-independent pixels, which is what QCursor expects.

Qt's xcb backend however passes QCursor::hotSpot() straight to
xcb_render_create_cursor together with the raw device-pixel image
(QXcbCursor::createBitmapCursor -> qt_xcb_createCursorXRender), so the hotspot of a
64x64 @2x cursor lands at (16,16) instead of its centre (32,32). The cursor is then
drawn 16 device pixels down and to the right of the real pointer, which makes every
item look like its hitbox is misplaced: pointing at a small widget actually hits
whatever is up and to the left of it. It is most visible with the UI Zoom setting
above 100%, since Zoom raises devicePixelRatio and therefore the size of the gap in
screen pixels.

Measured with XFixesGetCursorImage on Qt 6.4.2, cursor_pointing_hand@2x.png:
hotspot (16,16) on a 64x64 image before, (32,32) after. That xcb code is unchanged
from Qt 6.2 through 6.11, so express the hotspot in the image's own pixels there
and leave the other platforms, which honour the pixmap devicePixelRatio, alone.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TTUi76cnUWh7dGZC64LqbZ

Coverage Stats

4 of 4 new or added lines in 1 file covered. (100.0%)

263 existing lines in 1 file now uncovered.

30463 of 199568 relevant lines covered (15.26%)

1075.34 hits per line