Chapter 2 - Title and size

Updated to Gio 0.8.0 as of April 4th 2025

Goals

The intent of this section is to set a custom title and the size of the window.

Outline

This code is very similar to that of chapter 1. We add:

• two more imports
• two parameters when calling app.NewWindow()

Code

package main

import (
  "gioui.org/app"
  "gioui.org/unit"
)

func main() {
  go func() {
    // create new window
		w := new(app.Window)
		w.Option(app.Title("Egg timer"))
		w.Option(app.Size(unit.Dp(400), unit.Dp(600)))

    // listen for events in the window
    for {
        w.Event()
    }
  }()
  app.Main()
}

Comments

Where chapter 1 was the absolute bare minimum to open a window, we want to make some improvements here.

gioui.org/unit implements device independent units and values. The docs describe a handful of alternatives:

Type	Description
dp	Device independent pixel - independent of the underlying device
sp	Scaled pixel - used for text sizes
px	Pixels - used for precision for the actual device

In general, dp is the most widely used; we like to keep device independency when we can. Hence that’s what we use when we define the window size inside app.NewWindow().

The options of app are fairly self-explanatory, but take note of a few things:

• The size is set using app.Size(x, y).
• The window can be freely resized. Try it! If you want to limit the size you can add:
  • MaxSize
  • MinSize
  • Or use both, effectively locking the window size
• A fullscreen option is available in WindowMode if needed
• If you’re building for Android, Status and Navigation colors can be set here.

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