Borderless fullscreen with v-sync acts as if it crosses over to second monitor on the right

[PsiGreenEx]

Tested versions

Reproducible in: 4.5.dev1, 4.5.dev3, 4.5.beta4, 4.5.beta5, and 4.5.beta7
Not reproducible in: 4.4.1.stable

System information

Godot v4.5.beta7 - Windows 10 (build 19045) - Multi-window, 2 monitors, Primary 144 Hz and Secondary 60 Hz - Vulkan (Forward+) - dedicated AMD Radeon RX 6800 (Advanced Micro Devices, Inc.; 32.0.21025.1024) - AMD Ryzen 7 5800X 8-Core Processor (16 threads)

Issue description

The vsync'd framerate of the project reflects the same behavior as crossing two monitors with mismatched refresh rates when it is in borderless fullscreen only when the lower refresh rate monitor is on the right. When across two screens (in this case, one at 144 Hz and the other at 60 Hz) and the window's main screen is the highest framerate, the framerate becomes the largest multiple of the lower refresh rate below the higher refreshrate (in this case 120 FPS). This should not occur when in borderless fullscreen because it should be only display on one monitor.

This video was captured using the provided project.

refresh.rate.video.mp4

Steps to reproduce

This may be difficult to reproduce without having the proper monitor setup.

1. (Assuming you are on Windows) Go into your display settings and rearrange your displays as such, where Display 1 has the higher refresh rate and Display 2 has the lower.
   • 
2. Open and run the main scene. Ensure it's not embedded in the game view.
3. Press F11 to enter borderless fullscreen, F12 to enter exclusive fullscreen, and F10 to exit fullscreen. Windowed and exclusive fullscreen should behave as expected.
4. Rearrange your displays so that the left side of Display 2 is no longer touching the right side of Display 1.
5. Repeat steps 2 and 3. The problem in borderless fullscreen goes away.

Minimal reproduction project (MRP)

refresh rate test project 4.5.beta7.zip

[bruvzg]

It is crossing to other screen, and it is exactly how it is supposed to work. WINDOW_MODE_FULLSCREEN exist for a one single purpose, to ensure multiple native windows can be displayed on top of the main full-screen window (e.g, for the Godot editor), and it is deliberately breaking all kind of optimizations.

It this is not something you need, use WINDOW_MODE_EXCLUSIVE_FULLSCREEN for any other purpose, it is normal fullscreen (naming is bad, modes should be WINDOW_MODE_MULTIWINDOW_FULLSCREEN and WINDOW_MODE_FULLSCREEN or something like this).

[SkanerSoft]

WINDOW_MODE_EXCLUSIVE_FULLSCREEN

It's because of the name that I've never used this mode. Damn it))

[PsiGreenEx]

It is crossing to other screen, and it is exactly how it is supposed to work.

If that were the case, then why would it only be crossing over on the right side of the monitor? And why is this not a feature of 4.4.1.stable?

It this is not something you need, use WINDOW_MODE_EXCLUSIVE_FULLSCREEN for any other purpose

And that is what I will be using, though this is problem I have never experienced in a single other game. Godot specifically doesn't have alt-tab and window switching issues with exclusive fullscreen, but most games do, which is why in my experience, people with multi monitor setups default to using borderless.

(naming is bad, modes should be WINDOW_MODE_MULTIWINDOW_FULLSCREEN and WINDOW_MODE_FULLSCREEN or something like this).

Or at the very least WINDOW_MODE_BORDERLESS_FULLSCREEN and WINDOW_MODE_EXCLUSIVE_FULLSCREEN for clarity.

[bruvzg]

If that were the case, then why would it only be crossing over on the right side of the monitor? And why is this not a feature of 4.4.1.stable?

In 4.5 it has an invisible border extending outside (specifically 2 px to the right, it's an arbitrary choice). In 4.4.1 there's visible 1 px border inside the window (in all directions), both added for the same purpose.

Or at the very least WINDOW_MODE_BORDERLESS_FULLSCREEN and WINDOW_MODE_EXCLUSIVE_FULLSCREEN for clarity.

Neither would be precise:

• WINDOW_MODE_EXCLUSIVE_FULLSCREEN is a borderless window with the size of the screen, this allows the GPU driver to disable composition (not render other windows), but not forcing or asking it to do so directly (in most cases it won't).
• WINDOW_MODE_FULLSCREEN is a borderless window that is not matching the size of the screen (by adding a border), to ensure no full-screen optimizations can be applied to it.

[PsiGreenEx]

Then what are the use-cases of "borderless" if the only difference is that it isn't technically even on one screen and it disables the optimizations meant for fullscreen? /genuine

[bruvzg]

Editor (and other non-game UI), since it's using multiple windows, it will break if driver will decide to disable composition (which depends on user configuration). It's the same condition as messy alt-tab, but it case of editor it will make it completely unusable.

[PsiGreenEx]

Ah, I see. I'll let someone else close this issue if they determine that this is behavior is ideal, even if expected. Being 1 of like 7 people who have the combo of high refresh rate monitor and normal refresh rate monitor (using Windows, as terrible as it is) has caused some unique headaches for all sorts reasons, and I suspect this was never a problem anticipated when making the arbitrary descision of adding 2px to the right.