PR Description

What type of PR is this? (Check one of the boxes below)

• Bug fix (non-breaking change which fixes an issue)

What does this pull request do?

Given that the Qt OpenGL module was deprecated in Qt 5.4.0, removed in Qt 6 and most importantly was not functioning under a Wayland session (e.g. alpha output in KDE KWin or corrupted images in Sway), I've replaced its usage with the newer OpenGL integration from Qt Gui and used both type definitions plus preprocessor conditionals for backwards compatibility with Qt 4.

Show a few screenshots (if this is a visual change)

Have you tested your changes (if applicable)? If so, how?

By building Natron and using the viewer, the dope sheet editor, the curve editor and the histogram.

Futher details of this pull request

Will post support for Wayland offscreen (OSGLContext) soon.