Qt and wx default to bitmap present

[almarklein]

To avoid the many problems users face with presenting to a surface in a qt application, I propose we default to 'bitmap' for qt and wx. I briefly considered detecting cases where problems are more likely to occur, like is it on Wayland, or is the widget in a dockwidget, etc. but I figured we can better keep it simple and consistent.

I feel that with #138 we can now do this. Leaving this open for a bit so ppl can react if they have questions or objections.

Some related issue:

• Problems with creating a surface wgpu-py#688
• [Qt] multiple window/docking support #55
• React to changing winId? #62

[Vipitis]

I was trying my idea from earlier to maybe see a difference in latency etc... one thing I directly noticed is that the screen method is way smoother on resize(bitmap is the left, screen the right):

responsiveness.mp4

My tired eyes also made me believe the gamma was different (like maybe srgb?) but I think that is just view angle thing, I couldn't measure any pixel value differences in screenshots... unless the OS compositor hides that from screenshots somehow.

ref: Vipitis@e4837e2

[almarklein]

I made the texture greener, and it does indeed look different. Looking into it ...

As for the resizing, this is somewhat expected. During a resize, qt does multiple paint events. With 'screen' this results in new draws. With 'bitmap' it simply draws the last texture. A new draw will be scheduled, but it will be delayed compared to the paint event, especially on low fps. I don't think this is a problem. On some systems (glfw?) the image freezes during a resize.

[almarklein]

OMG, ok, the difference seems to be that Qt applies a color transformation when on a P3 display. I created an issue to track this further #176