IntelliJ/CLion using X11 backend renders incorrectly on resize

[tarek-y-ismail]

How to reproduce

1. Open up IntelliJ/CLion
2. Try resizing the window, you'll see two different behaviors:
   If you enlarge or shrink the window, you'll see the UI update, but the rendering will be still confined to the old boundaries

intellij-shenanigans.mp4

[AlanGriffiths]

Hmm. I've not seen this, but I've been using the preview Wayland support for the past few weeks

[AlanGriffiths]

Hmm. I've not seen this, but I've been using the preview Wayland support for the past few weeks

I can confirm the above weirdness. I wonder if it is related to the clipping mentioned in #3560 (comment)

[tarek-y-ismail]

Happens as far back as 2.13 (can't get earlier versions to build)

[tarek-y-ismail]

So I found the cause of the bug. If you watch the video, you'll see it happening with only vertical or horizontal resizing and not corner resizing (although that's broken as well).

The culprit was these few lines:

mir/src/server/frontend_xwayland/xwayland_surface.cpp

Lines 1231 to 1237 in b56aa20

	if (spec.value()->width.is_set() &&
	spec.value()->width.value() == scene_surface->content_size().width)
	spec.value()->width.consume();
	if (spec.value()->height.is_set() &&
	spec.value()->height.value() == scene_surface->content_size().height)
	spec.value()->height.consume();

Which broke this conversion from shell::SurfaceSpecification to miral::WindowSpecification:

mir/src/miral/window_specification.cpp

Lines 88 to 89 in b56aa20

	if (spec.width.is_set() && spec.height.is_set())
	size = Size(spec.width.value(), spec.height.value());

The most apparent solution is to consume both the width and height if they're both equal to the current content size, otherwise, both pass even if one hasn't changed. Another solution would be to modify the logic of miral::WindowSpecification to allow width and height to be set separately, but that'll probably open up another can of worms that is probably better left closed

This also exhibits something similar to #3560 and corner resizing, where resizing stops immediately once the cursor leaves the application window. In #3560, this manifests by not being able to resize at all as the widgets are outside the visible window.