QCursor::setPos doesn't support float arguments?

FishBoneEK

Hello!
Noticed that QCursor::setPos only accept int coordinates, so I can't perfectly set the mouse pos under high DPI screens?

I'm trying to make a drag zone on QML that prevents the mouse to go outside the window while dragging:

start dragging, record start coordinate
onPositionChanged, calculate mouse coord delta, emit event
QCursor:::setPos move mouse back to start coord
onPositionChanged...
In the end the user is able to move something (like a slider, based on emitted delta events)
while preventing the mouse to go outside the window

On 100% scaled screens it works fine, but on 125% scaled screen the moved "thing" starts drifting, e.g. if you move the mouse in a circle the "thing" starts to drift to the corner of the window.

My guess is QCursor::setPos accepts int arguments so each time it's not perfectly set to the start coordinate, causing a bias to the delta events.

Platform is Windows.

Thanks!

FishBoneEK

This post is deleted!

FishBoneEK

Example codes:

QML drag zone: https://pastebin.com/WjEGTBiV
QML main: https://pastebin.com/0eZJqFVh
C++ helper: https://pastebin.com/1L66xgTh

Christian Ehrlicher

There might be a rounding error somewhere but you can't position on a half pixel in e.g. windows - see SetCursorPos.
So yes, with 125% the logical position 61/62 is mapped to the physical position 76/78 while it should be 76,25/77,5 but SetCursorPos can't handle this.