[Windows] Try to use "borderless fullscreen" is "borderless" flag is set.

[bruvzg]

Partially addresses #63500, by allowing to set both WINDOW_FLAG_BORDERLESS and WINDOW_MODE_EXCLUSIVE_FULLSCREEN.

• Test on NVIDIA GPU (works as expected, tested on Windows 11 with RTX 2070 SUPER).
• Test on AMD GPU (most likely WINDOW_FLAG_BORDERLESS will have no effect and still enter exclusive mode).
• Test on Intel GPU.

[Maran23]

If needed, I can test this on my AMD GPU. :)
Should I execute the code linked in the issue?

get_tree().root.mode = Window.MODE_FULLSCREEN # or WINDOW_MODE_EXCLUSIVE_FULLSCREEN
get_tree().root.borderless = true

[bruvzg]

Tested on AMD APU as well (as expected there's no difference, but unlike NVidia multiwindow support is not completely broken even in exclusive fs, it's just switched to non-exclusive mode when another window is open).

[bruvzg]

Should I execute the code linked in the issue?

Yes, but set the borderless flag first.

For the reference behavior on NVidia is:

• FS mode - with single pixel border, non exclusive (screen is not going black, other windows can be used).
• EX_FS with borderless - no border, non exclusive
• EX_FS w/o borderless - no border, exclusive

[bruvzg]

It's not a perfect solution, but I did not find any issues, and should not be compatibility breaking.

[Calinou]

• EX_FS w/o borderless - no border, non exclusive
• EX_FS with borderless - no border, exclusive

Shouldn't it be the other way around? I thought WINDOW_MODE_EXCLUSIVE_FULLSCREEN would keep its current behavior in most projects where borderless is disabled in the Project Settings.

In other words, I'd expect this instead:

• EX_FS w/o borderless - no border, exclusive (forced exclusive fullscreen)
• EX_FS with borderless - no border, non exclusive ("best effort" borderless fullscreen, may be converted to exclusive by the driver)

[bruvzg]

Shouldn't it be the other way around?

It is the other way.

[Calinou]

Tested locally (rebased on top of master 23191b8), I can't see any difference on Windows 11 22H2 with a GeForce RTX 4090 (NVIDIA 551.61). Alt-tabbing doesn't cause flickering when in exclusive fullscreen mode, but that's also the case on master without this PR.

I'd typically use Special K to diagnose the actual window mode seen by the OS but I can't get it to work with Godot (pressing Ctrl + Shift + Backspace to show its overlay does nothing).

[RedMser]

@Calinou You could try FrameView, its overlay also includes into about fullscreen mode.

[alvinhochun]

I tested this locally on Windows 10, Intel + NVIDIA (Optimus, Intel as primary GPU), no noticeable differences between both modes on either GPU with OpenGL, Vulkan or D3D12.

[alvinhochun]

Oh no, you probably should only swap WS_POPUP with WS_OVERLAPPED for fullscreen windows, not all borderless windows. (It breaks rendering of menus and dropdowns on Intel + OpenGL.)