New (non-embedded) window transparency glitching based on focus if window is size is equal to monitor resolution

[KMouratidis]

Godot version

4.0.2 + 4.0.3 + 4.1

System information

Windows 11, Forward+, Intel i7-13700k, Nvidia RTX 4070ti

Also replicated on: Windows 10, Forward+, Intel i7-11850H, Nvidia MX450
Also replicated on: Windows 11, Forward+, AMD Ryzen 7 6800 HS, Nvidia 3060M (both discrete & integrated graphics)
But on: Ubuntu 22.04, AMD Ryzen 7 6800 HS, Nvidia 3060M:

• It works as expected on all renderers for (a) integrated graphics, (b) on dedicated graphics + X11 (nouveau), and (c) on Wayland (all combinations I tried)
• The window gets opened but doesn't show at all (no pink rect) with the proprietary 530 driver if using Forward+ or Mobile but it does show if using Compatibility

Not affected by monitor or number of monitors.

Issue description

When creating a new window with Window.new(), add_child() etc, I'm trying to make it transparent. I've enabled Display > Window > Size > Transparent, Display > Window > Per Pixel Transparency > Allowed and Rendering > Viewport > Transparent Background and I've set all flags that seem relevant:

window.size = DisplayServer.screen_get_size()
window.always_on_top = true
window.transparent = true
window.borderless = true
window.set_transparent_background(true)

But the window turns completely completely black (minus the ColorRect which show fine, as soon as OBS catches up):

Edit: The recording show the transitions as taking some time but they actually happen instantly. Not sure what the issue with the recording is :/

WindowTransparency.mp4

However when I change the size:

window.size = DisplayServer.screen_get_size() - Vector2i(1, 1)

Everything works fine:

WindowTransparency2.mp4

Steps to reproduce

1. Open provided project and run it
2. Double click inside the main window to trigger opening of a new window
3. New window is black despite best efforts to have it transparent
4. Focusing on any other window (e.g. click or alt-tab), be it Godot or otherwise, fixes the transparency
5. Re-focusing on the new window causes it to go black again

Minimal reproduction project

WindowTransparency.zip

[Calinou]

• Related to Godot uses exclusive fullscreen on Windows if window size matches screen size, even if borderless is enabled in the Project Settings (fixed in master) #60665.

This is due to Windows making those windows use exclusive fullscreen if they match the screen size. As a workaround, make their width or height 1 pixel smaller than the screen's width/height.

[KMouratidis]

iirc, I replicated it on Ubuntu 22 + Nvidia (proprietary) + X11 as well, but all other combinations on Ubuntu worked fine.

[bruvzg]

Instead of setting window to borderless and setting window size manually (which is equivalent to WINDOW_MODE_EXCLUSIVE_FULLSCREEN), try using WINDOW_MODE_FULLSCREEN, it should prevent OS from disabling compositor when in full screen and allow transparency to work.

[KMouratidis]

@bruvzg sorry for the late reply. I don't think I understand. I tried various combinations of these but nothing worked:

var window := Window.new()
window.position = Vector2(0.0, 0.0)
# window.size = DisplayServer.screen_get_size()  # <--- commented out, or not
window.always_on_top = true
window.transparent = true
# window.borderless = true  #  <--- commented out, or not
window.mode = Window.MODE_FULLSCREEN # or Window.MODE_EXCLUSIVE_FULLSCREEN, or commented out
window.set_transparent_background(true)

MODE_FULLSCREEN with borderless still has the same issue, and without it, it has borders.