馃崚 applets/pager: fix window/screen size/position when using Qt scaling
On X11, the rect returned from QScreen::virtualGeometry cannot be used as the whole screen rect. Instead, compute the whole screen rect manually, and map all windows/screens to the non-scaled coordinate system on X11 to make windows show in right positions in the pager applet.
BUG: 446627 FIXED-IN: 5.27.8
(cherry picked from commit 18b91601)
Edited by Fushan Wen