Versions QT5 OK on WIN7, WIN10 and LINUX

My PlanetCNCW64 software accepts G41/42 but gave an error on generated g-code G40 (“Arc without IJK or R is not valid” G40 X85.6 Y62.24 Their bug?). So, I had to fill “Interpolate axes with line segments” in CAM Configuration. A little window QCAD CAM “Regenerating tool path…” opens, shows 50% all the time, and a button “Abort” that closes that window when clicked, but doesn’t stop the process; a lot of messages “regenerating tool paths…” run at the bottom with great speed, as expected.

With QT6 but not QT5, after a while, these messages start slowing more and more, when I believe the arc segments are being generated, but keep a normal speed on lines, till the program freezes. During this process, with both QT6 and QT5, the memory used is growing, but is not released until the program is closed. Garbage collection problem?

Heather theme has QTreeView::item:hover by default → Bug occurs
Dark theme has no QTreeView::item:hover → Normal behavior
Custom CSS with ONLY QTreeView::item:hover {} → Bug occurs

This did NOT occur in Qt5 production versions.

Reproduction Steps:
1. Apply Heather theme (contains QTreeView::item:hover by default)
2. OR: Apply any theme + add ONLY this CSS rule:

 QTreeView::item:hover {
 }

3. Restart QCAD as prompted after theme modification
4. Open layer list panel
5. Hover mouse over any layer item → Active layer immediately switches to hovered layer

Expected Behavior:
- Hover should only affect visual appearance
- Active layer should only change on explicit click selection
- Empty CSS rule "{}" should have no functional effect

Actual Behavior:
- Every layer becomes active as mouse hovers over it
- Affects ALL layers in layer list
- Property editor QTreeView and block list QTreeView are NOT affected

Workaround:
- Remove QTreeView::item:hover rule completely from CSS
- Use themes without QTreeView::item:hover (e.g., Dark theme)

Environment:
- QCAD: 3.32.9.0
- Qt: 6.11.0
- OS: Windows 11 25H2 (Build 26200.8328)
- Trigger: Heather theme OR any theme + QTreeView::item:hover CSS rule

Tested QCAD 3.32.8 on Ubuntu24.04 and MacOS10.10

Attached screenshots were taken using QT5 and QT6 for comparison (both at 125% scaling). Antialiasing was turned off. Note how the grid dots fade in and out like a moiré pattern.

Downloaded 'plano de fundametacion.dxf' from topic 11566 (Spanish forum)

The file opened as:
'1eedfe3098f558d1e0a2e6f515c42ccb8bf2913a.dxf'

Regards,
CVH