this appears to be a windows issue only.

i have an MDI application (each subwindow contains a widget derived from QGLWidget) that has worked fine with Qt4 and Qt5 all the way up to Qt 5.12. recently, i updated to 5.15.0 and now i am running into the following issue:

first of all everything works fine for the first subwindow created. the second and all subsequent subwindows when i call mapToGlobal the resulting QPoint is incorrect . as a test i called mapToGlobal with a QPoint(0,0) to get the location of the origin of the subwindow and it appears to be shifted to the right and down; each subsequent window is further shifted from the one previous.

i have also noticed the following warning on creation of the second and subsequent subwindows (not sure if this is related to the incorrect window origin):

QWindowsWindow::setGeometry: Unable to set geometry 1342x942+0+0 (frame: 1342x942+0+0) on QWidgetWindow/"QGLWidgetClassWindow" on "\.\DISPLAY1". Resulting geometry 1342x942+12+8 (frame: 1342x942) margins: 0, 0, 0, 0)

i tried setMinimumSize and setGeometry on both the QGLWidget and the subwindow but i could not remove this warning.

if anyone knows about this issue and a possible workaround or any ideas i would appreciate any help.