Qt on macOS Graphics/integration update

Topics

Core Animation layer-backed QWindow QTBUG-49856
Make QCocoaWindow work well when embedded in NSView hierarchies where Core Animation compositing is enabled.

Externally driven/unified animations and updates (via CVDisplayLink) QTBUG-49859
An unified invalidate/update API for raster and OpenGL QtWidgets, and Qt Quick.

QWindow embedding API QTBUG-49977
Improve API and implementation for Qt-as-plugin use cases.

Color Space support QTBUG-47660
Basic color space support: Give Qt Apps some options to get correct color management.

NSWindow-backed QWindow
Child QWindows backed by a NSWindow, giving each an independent OpenGL context.

Manual and Auto Testing
Unit tests for the Cocoa platform plugin: QTBUG-50552

OS X Raster Child Window Update Optimizations
QTBUG-54933

Code

qtbase-remac
qt-osx-testbench

Transition Planning

Initial development is in a separate branch. Initial integration will be mainly as opt-in modes, to ease the transition and avoid regressing for current users. (The modes are to some degree already present: environment variables
QT_MAC_WANTS_LAYER and QT_MAC_USE_NSWINDOW). Removing old code paths and selecting default configurations can be done once the new code paths are stable.

General Implementation plan

Build from the ground up:

1. Implement cases in native code only (No Qt)
2. Simple use cases: QOpenGLWindow, QRasterWindow
3. QWidgetWindow, QQuickWindow(gui-thread rendering)
4. QGLWidget
5. Multithreaded OpenGL