CGAL: Qt5 -> Qt6

[afabri]

Summary of Changes

We have to make the transition from Qt5 to Qt6.

This PR starts with the files in Installation/cmake/modules, and the demos in GraphicsView/demos.
Locally the Polyhedron demo also works (at least with the 3rd party libraries I have installed on my machine).

There are some commented code sections concerning QRegExp as that has changed a lot, and concerning scripting.

And there is a beginning of scripting with the QJSEngine with this commit.

Release Management

• Affected package(s): All demos and the examples which use the Basic_viewer.
• Fix What are the Qt 6 migration plans? #7004
• License and copyright ownership: unchanged

TODO

• Remove all occurrences of Qt5 from the code base (except in CI, to be compatible with release branches).
• Remove the option "Use OpenGL" from DemoMainWindow.h.
• fix the picking by shift+click, to select an items among others (see CGAL: Qt5 -> Qt6 #7397 (comment))
• Merge master and address the comment from Albert: CGAL: Qt5 -> Qt6 #7397 (comment)

[afabri]

The AABB_tree demo works, but there is a runtime error concerning a destructor when exiting the program.

[afabri]

When editing in the Surface Mesh Selection I get

QOpenGLBuffer::bind: buffer is not valid in the current context

[sloriot]

Remaining link errors:

• https://cgal.geometryfactory.com/CGAL/testsuite/CGAL-6.0-Ic-101/Polyhedron_Demo/TestReport_gimeno_Ubuntu-Latest-NO_DEPRECATED_CODE.gz
• https://cgal.geometryfactory.com/CGAL/testsuite/CGAL-6.0-Ic-101/Polyhedron_Demo/TestReport_lrineau_Ubuntu-GCC_master_CXX20-Release.gz
• https://cgal.geometryfactory.com/CGAL/testsuite/CGAL-6.0-Ic-101/Polyhedron_Demo/TestReport_lrineau_Debian-stable-Release.gz

[afabri]

In a previous commit I added virtual to a destructor as the base class destructor is virtual.
Reading the error message in the third link you give above

/usr/bin/ld: CMakeFiles/scene_c3t3_item.dir/scene_c3t3_item_autogen/mocs_compilation.cpp.o:(.data.rel.ro._ZTV15Scene_c3t3_item[_ZTV15Scene_c3t3_item]+0x260): undefined reference to `non-virtual thunk to Scene_c3t3_item::~Scene_c3t3_item()'
/usr/bin/ld: CMakeFiles/scene_c3t3_item.dir/scene_c3t3_item_autogen/mocs_compilation.cpp.o:(.data.rel.ro._ZTV15Scene_c3t3_item[_ZTV15Scene_c3t3_item]+0x268): undefined reference to `non-virtual thunk to Scene_c3t3_item::copyProperties(CGAL::Three::Scene_item*)'
collect2: error: ld returned 1 exit status

I am wondering if we have to add virtual in many places. @sloriot ?

[afabri]

For the second "link error" I have no idea.

[albert-github]

This change should also be done in the, on November 15 2023, integrated 1.10.0 version (see warnings in the overnight documentation build https://cgal.geometryfactory.com/CGAL/Manual_doxygen_test/CGAL-6.0-Ic-108/logs_master/Documentation.log

[lrineau]

I note this as a TODO (see the top message).

[sloriot]

CGAL-6.0-Ic-113 looks good except some issues that are only present in the testsuite and that are tracked in #7882. We decided to merge the branch so that developer can start testing and report issues.

[gdamiand]

Error when compiling Linear cell complex demo:

/home/gdamiand/sources/cgal/builds/debug/demo/Linear_cell_complex/ui_MainWindow.h:14:10: fatal error: QtWidgets/QAction: Aucun fichier ou dossier de ce type
14 | #include <QtWidgets/QAction>

[afabri]

Why not in the testsuite?

[gdamiand]

No error when compiling from a fresh install; the error comes probably from some cache effect. Sorry for the noise.