doc: document the correct usage of X11 hotkey registration

[wsy998]

I can’t use it,is it my problem? (system:ubuntu 22.04)

[changkun]

I guess the support for Linux OS was not well enough. If the registered hotkey conflicts with an existing hotkey, it won't have any effect.

Generally you can run this example and see if it works on your system:

hotkey/examples/fyne/main.go

Lines 15 to 34 in a5dde31

	func main() {
	w := app.New().NewWindow("golang.design/x/hotkey")
	label := widget.NewLabel("Hello golang.design!")
	button := widget.NewButton("Hi!", func() { label.SetText("Welcome :)") })
	w.SetContent(container.NewVBox(label, button))
	go func() {
	// Register a desired hotkey.
	hk := hotkey.New([]hotkey.Modifier{hotkey.ModCtrl, hotkey.ModShift}, hotkey.KeyS)
	if err := hk.Register(); err != nil {
	panic("hotkey registration failed")
	}
	// Start listen hotkey event whenever it is ready.
	for range hk.Keydown() {
	button.Tapped(&fyne.PointEvent{})
	}
	}()
	w.ShowAndRun()
	}

[wsy998]

I checked that my hotkeys (including SYSTEM, INPUT METHOD, IDE) are not conflicting. The sample also failed to run successfully.

[changkun]

It might be useful if you could find a second device to test the environment.

[changkun]

@wsy998 OK. Now I recall the issue on Linux systems.

In general, Ubuntu maps multiple Mod keys to represent a single mod key. To be able to correctly register the key combination, you need figure out what is the correct underlying keycode combination for the platform. For example, a regular Ctrl+Alt+S should be registered as: Ctrl+Mod2+Mod4+S.

This example works on my Ubuntu 20.04 (Ctrl+Alt+S):

package main

import (
	"fmt"

	"golang.design/x/hotkey"
	"golang.design/x/hotkey/mainthread"
)

func main() { mainthread.Init(fn) }
func fn() {
	hk := hotkey.New([]hotkey.Modifier{hotkey.ModCtrl, hotkey.Mod2, hotkey.Mod4}, hotkey.KeyS)
	err := hk.Register()
	if err != nil {
		return
	}
	fmt.Printf("hotkey: %v is registered\n", hk)
	<-hk.Keydown()
	fmt.Printf("hotkey: %v is down\n", hk)
	<-hk.Keyup()
	fmt.Printf("hotkey: %v is up\n", hk)
	hk.Unregister()
	fmt.Printf("hotkey: %v is unregistered\n", hk)
}

[wsy998]

OK，Let me try.

[mwalkerr]

How did you find the other mod keys that are mapped?