On Mac OS, scrollbars move on mouse press event when there is no mouse movement

Hi,

In Mac OS 12.5.1 "Monterey", with Qt 6.4.0, scrollbars jump slightly when the mouse is pressed down without mouse movement. It is somewhat intermittent. Clicking toward the left side seems to make the scrollbar jump right, and clicking toward the right side seems to make the scrollbar jump left (equivalent for vertical orientation). The amount of jump seems to depend on singleStep (not certain of this).

This makes it feel quite strange and jittery when scrolling from one end of the scroll range, as the scrollbar jumps just before you start dragging it. It is a problem to have a jump on mouse press but before the mouse moves, if the scrollbar is controlling something with high precision.

I've attached a short video of this in Qt Creator, but it is replicated in my own projects so it is a Qt issue rather than a Qt Creator issue. In the video it is a little hard to see as you can't tell when I'm pressing the left mouse button down, but you will see the scroll bar moving in small steps apparently while the mouse stays completely still (here, I am repeatedly pressing the left mouse button but keeping the mouse still), and jumping at the beginning of a scroll movement.

I have tested in Windows and this does not happen, so it is most likely a mac-specific issue. But I haven't checked linux.

Cheers, best wishes,

Mick