Simple drawing fails with Qt6 6.7.1

[efifogel]

Issue Details

Issue #8058 is very similar, it reported that simple drawing did not work with 6.8. It also reported on some problems with find_package of CGAL with Qt6. The latter was fixed, and it turned out that 6.8 hasn't been officially published, so it was closed. However, it makes me think that the same reason that caused the segmentation with 6.8 is also the reason for the segmentation with 6.7. (This piece of info may be useless...)

All the example programs that use the simple drawing mechanism end with a segmentation fault, e.g., Polygon/draw_polygon, Arrangement_2/draw_arrangement, Surface_mesh/sm_draw_small_faces. Other programs that are based on Qt6 work fine. This is, of course, not a proof that the problem is in our code, but it's suspicious.

I've experienced the same behavior on two separate machines running Ubuntu 22.04.

Here is the trace of the stack: stack_qt_issue.txt

Source Code

Environment

• Operating system Linux, 64 bits):
• Compiler: g++ 11.4.0
• Release or debug mode: both
• Specific flags used (if any):
• CGAL version: latest
• Boost version: 1.82
• Other libraries versions if used (Eigen, TBB, etc.):

[lrineau]

The stack looks strangely similar to https://github.com/CGAL/cgal/issues/8209.

[lrineau]

Actually, I now have exactly the same issue on my Linux machine (with Qt 6.7.1 as well). For all examples involving the basic viewer, I have a segfault. The issue is that QOpenGLContext::currentContext() returns a null pointer.

[gdamiand]

I have no problem with Qt 6.2 nor 6.4.

[sloriot]

@efifogel you can test https://github.com/CGAL/cgal/pull/8453