Ebitengine Version and Environment

Oct 13, 2025 by wbrum.org 29 views

Introduction

When working with multiple monitors in a graphical application, it's essential to ensure that the monitor settings are applied correctly and efficiently. However, in some cases, the SetMonitor function in Ebitengine can take a while to be applied, leading to unexpected behavior and affecting subsequent window operations. In this article, we'll explore this issue, provide a reproducible example, and discuss possible solutions.

Ebitengine Version and Environment

The issue was encountered using Ebitengine version v2.8.6 on Linux (Archlinux/KDE) with Go Version (go version) go1.23.2 linux/amd64.

Reproducible Example

The following Go code demonstrates the issue:

package main

import (
	"fmt"

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

type App struct {
	tick int
}

func (app *App) Layout(w, h int) (int, int) {
	return w, h
}

func (app *App) Update() error {
	if ebiten.IsKeyPressed(ebiten.KeyEscape) {
		return ebiten.Termination
	}

	switch app.tick {
	case 0:
		monitor := ebiten.AppendMonitors(nil)[1]
		fmt.Printf("changing monitor to '%s'\n", monitor.Name())
		ebiten.SetMonitor(monitor)
		//time.Sleep(1 * time.Millisecond)
		ebiten.SetFullscreen(true)
		fmt.Printf("current monitor: '%s'\n", ebiten.Monitor().Name())
	}

	app.tick += 1
	return nil
}

func (app *App) Draw(*ebiten.Image) {}

func main() {
	fmt.Printf("primary monitor: '%s'\n", ebiten.Monitor().Name())
	err := ebiten.RunGame(&App{})
	if err != nil {
		panic(err)
	}
}

This code creates an Ebitengine application that changes the monitor to the secondary monitor and sets it to fullscreen. However, the fullscreen operation is applied to the primary monitor instead of the secondary monitor.

Expected Result vs. Actual Result

The expected result is that the fullscreen operation is applied to the newly set monitor (secondary monitor). However, the actual result is that the fullscreen operation is applied to the primary monitor.

Possible Causes

The issue is caused by the monitor change taking a while to be applied. This can be observed by uncommenting the time.Sleep(1 * time.Millisecond) line, which ensures that the monitor change is applied before the fullscreen operation. Sometimes, even just moving the printf statement of the current monitor before the SetFullscreen call can affect the results.

Workarounds

To resolve this issue, you can use the following workarounds:

Add a delay: Uncomment the time.Sleep(1 * time.Millisecond) line to ensure that the monitor change is applied before the fullscreen operation.
Move the printf statement: Move the printf statement of the current monitor before the SetFullscreen call to ensure that the monitor change is applied before the fullscreen operation.
Use a different approach: Consider using a different approach to change the monitor, such as using the ebiten.SetMonitor function with a callback to ensure that the monitor change is applied before the fullscreen operation.

Conclusion

Q&A: SetMonitor Issues in Ebitengine

Q: What is the issue with SetMonitor in Ebitengine?

A: The issue is that the SetMonitor function in Ebitengine can take a while to be applied, leading to unexpected behavior and affecting subsequent window operations.

Q: What are the possible causes of this issue?

A: The possible causes of this issue are:

The monitor change taking a while to be applied.
The SetMonitor function not being called before the fullscreen operation.
The printf statement of the current monitor not being moved before the SetFullscreen call.

Q: How can I resolve this issue?

A: To resolve this issue, you can use the following workarounds:

Add a delay: Uncomment the time.Sleep(1 * time.Millisecond) line to ensure that the monitor change is applied before the fullscreen operation.
Move the printf statement: Move the printf statement of the current monitor before the SetFullscreen call to ensure that the monitor change is applied before the fullscreen operation.
Use a different approach: Consider using a different approach to change the monitor, such as using the ebiten.SetMonitor function with a callback to ensure that the monitor change is applied before the fullscreen operation.

Q: What are the implications of this issue?

A: The implications of this issue are:

Unexpected behavior in the graphical application.
Affecting subsequent window operations.
Potential crashes or freezes of the application.

Q: How can I prevent this issue from occurring?

A: To prevent this issue from occurring, you can:

Use a delay to ensure that the monitor change is applied before the fullscreen operation.
Move the printf statement of the current monitor before the SetFullscreen call.
Use a different approach to change the monitor, such as using the ebiten.SetMonitor function with a callback.

Q: Is this issue specific to Ebitengine?

A: No, this issue is not specific to Ebitengine. It can occur in any graphical application that uses multiple monitors and has fullscreen capabilities.

Q: Can I report this issue to the Ebitengine team?

A: Yes, you can report this issue to the Ebitengine team. They will be able to provide further assistance and potentially fix the issue in future versions of the library.

Q: What are the next steps to resolve this issue?

A: The next steps to resolve this issue are:

Investigate the cause of the issue.
Test the workarounds to ensure that they resolve the issue.
Report the issue to the Ebitengine team and provide further assistance.

By following these steps, you can resolve the SetMonitor issue in Ebitengine and ensure that your graphical application works correctly with multiple monitors.