app

Overview ¶

Package app provides a platform-independent interface to operating system functionality for running graphical user interfaces.

See https://gioui.org for instructions to set up and run Gio programs.

Windows ¶

Create a new Window by calling NewWindow. On mobile platforms or when Gio is embedded in another project, NewWindow merely connects with a previously created window.

A Window is run by calling NextEvent in a loop. The most important event is FrameEvent that prompts an update of the window contents.

For example:

import "gioui.org/unit"

w := app.NewWindow()
for {
	e := w.NextEvent()
	if e, ok := e.(system.FrameEvent); ok {
		ops.Reset()
		// Add operations to ops.
		...
		// Completely replace the window contents and state.
		e.Frame(ops)
	}
}

A program must keep receiving events from the event channel until DestroyEvent is received.

Main ¶

The Main function must be called from a program's main function, to hand over control of the main thread to operating systems that need it.

Because Main is also blocking on some platforms, the event loop of a Window must run in a goroutine.

For example, to display a blank but otherwise functional window:

package main

import "gioui.org/app"

func main() {
	go func() {
		w := app.NewWindow()
		for {
			w.NextEvent()
		}
	}()
	app.Main()
}

Event queue ¶

A FrameEvent's Queue method returns an event.Queue implementation that distributes incoming events to the event handlers declared in the last frame. See the gioui.org/io/event package for more information about event handlers.

Permissions ¶

The packages under gioui.org/app/permission should be imported by a Gio program or by one of its dependencies to indicate that specific operating-system permissions are required. Please see documentation for package gioui.org/app/permission for more information.