Cannot configure projections properly on Apple Silicon

[Cuperino]

Bug Description
Screen projections can't be configured for more than a single screen nor can the screen be properly specified on modern versions of MacOS.

Bug found initially through conversation with user Nicolas D in our community's Telegram chat, on June 21, 2022.

Steps to Reproduce

1. Run macOS Catalina or newer. Older versions of macOS may also be affected.
2. Prepare a setup with extended displays
3. Launch QPrompt and configure to project to one of the extended displays.
4. QPrompt will configure a screen based on unknown factors. That screen's configuration will be displayed on each screens' settings, but it will only take effect on the screen selected using unknown factors.

Expected behavior
Each screen can be configured individually.

Detailed description of display configuration
There's an extended display to the right of a MacBook Pro's primary display.

Device information

• QPrompt Version: v1.0 and v1.1 betas
• Operating System: macOS Catalina and later. Mojave may be affected. High Sierra is not affected.

Additional context
Happens with Qt 5.15.2 with KDE's Patch collection
Also with Qt 5.15.5 without KDE's Patch collection

Potential fix lies in upgrading to Qt 6, but this is not an option at the time due to KF5 library's reliance on Qt 5.

[Cuperino]

This bug is caused by macOS not providing QPrompt any information about displays, beyond the amount of displays connected, on versions of macOS newer than High Sierra, which was used to test initial development. This bug can likely be fixed by upgrading to Qt 6.

[Cuperino]

I've copied QPrompt's display management code over to a test project that's using Qt 6 and no KDE frameworks. There I found that the issue continues to happen on Big Sur while using the latest version of Qt, 6.3. This is worrying news, as it means that it will take some time until we're able to fix this issue upstream as it is likely broken in all versions of Qt.

[Cuperino]

Issue may be limited to Apple Silicon machines, unable to replicate on Intel machine running macOS Big Sur.

[Cuperino]

Issue fixed by in Qt 6.7 or an earlier version. Projections configuration has nonetheless been removed for different, already documented, reasons that prevent it from working.