Undecorated windows are offset by an invisible margin

[rdnt]

Ebitengine Version

v2.8.4

Operating System

• Windows
• macOS
• Linux
• FreeBSD
• OpenBSD
• Android
• iOS
• Nintendo Switch
• PlayStation 5
• Xbox
• Web Browsers

Go Version (go version)

go version go1.23.0 windows/amd64

What steps will reproduce the problem?

• Configure ebiten with ebiten.SetWindowDecorated(false)
• Start a window having the same resolution as the monitor

What is the expected result?

• The window should cover the entirety of the screen

What happens instead?

• The window is offset by an invisible margin
  • On a 4k screen with 150% scaling, it is 34px high

Anything else you feel useful to add?

I have found that if the isInitWindowDecorated check is added on the last lines of the adjustWindowPosition function, then the window is properly positioned. I am unsure if it is a valid fix or more work is needed to configure it (e.g. if window decorations are enabled/disabled during runtime).

func (u *UserInterface) adjustWindowPosition(x, y int, monitor *Monitor) (int, int) {
    
    ...
    
    //if y < my+int(t) {
    if u.isInitWindowDecorated() && y < my+int(t) { // i.e. if decorated && y above the expected bottom of the title bar
        y = my + int(t)
    }
    return x, y
}

I am aware that if I use SetFullscreen then it can become a true fullscreen, but my usecase is around a transparent, click-pass-through, fullscreen overlay.

[hajimehoshi]

I failed to reproduce this:

package main

import (
	"image/color"

	"github.com/hajimehoshi/ebiten/v2"
)

type Game struct {
}

func (g *Game) Update() error {
	if ebiten.IsKeyPressed(ebiten.KeyEscape) {
		return ebiten.Termination
	}
	return nil
}

func (g *Game) Draw(screen *ebiten.Image) {
	screen.Fill(color.RGBA{0x80, 0x80, 0x80, 0xff})
}

func (g *Game) Layout(width, height int) (int, int) {
	return width, height
}

func main() {
	ebiten.SetWindowDecorated(false)
	ebiten.SetWindowPosition(0, 0)
	ebiten.SetWindowSize(ebiten.Monitor().Size())
	if err := ebiten.RunGame(&Game{}); err != nil {
		panic(err)
	}
}

Could you show me a minimized code to reproduce your issue? Thanks,

[rdnt]

Hi @hajimehoshi thanks for the quick response!

The example code you posted perfectly manages to reproduce the issue on my machine:

It has to be something setup-specific, I assume.

It wouldn't surprise me if this is a GPU thing, even. If I use a floating, transparent overlay at exactly the monitor's resolution, the GPU performs optimizations that remove the transparency, as if it's a full screen game of sorts.

So, for completeness:

Windows version: 11 (x64)
GPU: AMD 6900XT
CPU: AMD Ryzen 9 5900X

[hajimehoshi]

Hmm, that's pretty odd. In your machine, does u.window.GetAttrib(glfw.Decorated) in adjustWindowPosition return glfw.True, even though you call ebiten.SetWindowDecorated(false)?

[rdnt]

u.window.GetAttrib(glfw.Decorated) called within adjustWindowPosition returns 0 <nil>.

[hajimehoshi]

Thanks. In this case, didn't this return at the early return?

	if d == glfw.False {
		return x, y, nil
	}

I have found that if the isInitWindowDecorated check is added on the last lines of the adjustWindowPosition function, then the window is properly positioned.

I'm skeptical about this since this should not be reached.

[rdnt]

Something like this?

func (u *UserInterface) adjustWindowPosition(x, y int, monitor *Monitor) (int, int) {
	if microsoftgdk.IsXbox() {
		return x, y
	}
	
	d, err := u.window.GetAttrib(glfw.Decorated)
	if err != nil {
		panic(err)
	}

	mx := monitor.boundsInGLFWPixels.Min.X
	my := monitor.boundsInGLFWPixels.Min.Y
	// As the video width/height might be wrong,
	// adjust x/y at least to enable to handle the window (#328)
	if x < mx {
		x = mx
	}
	t, err := _GetSystemMetrics(_SM_CYCAPTION)
	if err != nil {
		panic(err)
	}

	if d == glfw.False {
		return x, y
	}

	if y < my+int(t) {
		y = my + int(t)
	}

	return x, y
}

If yes then it properly renders in full screen on my machine.

Edit: I am not sure if the snippet you posted is existing code, if it is can you mention the file:line?

[hajimehoshi]

Ah, I'm sorry but I was looking at the main branch, not the 2.8 branch. This means this was already fixed by 8b0c930

EDIT: What I was looking at was

ebiten/internal/ui/ui_windows.go

Lines 118 to 125 in fab511e

	// If a window is not decorated, the window should be able to reach the top of the screen (#3118).
	d, err := u.window.GetAttrib(glfw.Decorated)
	if err != nil {
	return 0, 0, err
	}
	if d == glfw.False {
	return x, y, nil
	}

[hajimehoshi]

As there are multiple reports for the same issue, I'll cherry-pick the fix to 2.8. Let me close this issue later as a duplication with #3118.

[hajimehoshi]

Please try

go get github.com/hajimehoshi/ebiten/v2@53090f31055ee868f1eb2f0c68860fbc4c6f3a2f

go get github.com/hajimehoshi/ebiten/v2@ec57d482f2d20d125def084d9fd982a2236df2b0

I'll tag v2.8.5 a few days later.

[rdnt]

Can confirm the issue is no longer present on main. Lovely!
Apologies for having missed the original issue. Thanks for looking into it.