all: allow unregister hotkeys (linux, x11)

Updates #5, #7

Author: changkun

hotkey_linux.go

@@ -15,7 +15,11 @@ int displayTest();
 int waitHotkey(unsigned int mod, int key);
 */
 import "C"
-import "context"
+import (
+	"context"
+	"errors"
+	"sync"
+)
 
 const errmsg = `Failed to initialize the X11 display, and the clipboard package
 will not work properly. Install the following dependency may help:
@@ -36,17 +40,46 @@ func init() {
 	}
 }
 
+type platformHotkey struct {
+	mu         sync.Mutex
+	registered bool
+	ctx        context.Context
+	cancel     context.CancelFunc
+	canceled   chan struct{}
+}
+
 // Nothing needs to do for register
-func (hk *Hotkey) register() error { return nil }
+func (hk *Hotkey) register() error {
+	hk.mu.Lock()
+	if hk.registered {
+		hk.mu.Unlock()
+		return errors.New("hotkey already registered.")
+	}
+	hk.registered = true
+	hk.ctx, hk.cancel = context.WithCancel(context.Background())
+	hk.canceled = make(chan struct{})
+	hk.mu.Unlock()
+
+	go hk.handle()
+	return nil
+}
 
 // Nothing needs to do for unregister
-func (hk *Hotkey) unregister() {}
+func (hk *Hotkey) unregister() error {
+	hk.mu.Lock()
+	defer hk.mu.Unlock()
+	if !hk.registered {
+		return errors.New("hotkey is not registered.")
+	}
+	hk.cancel()
+	hk.registered = false
+	<-hk.canceled
+	return nil
+}
 
 // handle registers an application global hotkey to the system,
 // and returns a channel that will signal if the hotkey is triggered.
-//
-// No customization for the hotkey, the hotkey is always: Ctrl+Mod4+s
-func (hk *Hotkey) handle(ctx context.Context) {
+func (hk *Hotkey) handle() {
 	// KNOWN ISSUE: if a hotkey is grabbed by others, C side will crash the program
 
 	var mod Modifier
@@ -55,7 +88,8 @@ func (hk *Hotkey) handle(ctx context.Context) {
 	}
 	for {
 		select {
-		case <-ctx.Done():
+		case <-hk.ctx.Done():
+			close(hk.canceled)
 			return
 		default:
 			ret := C.waitHotkey(C.uint(mod), C.int(hk.key))

hotkey_linux_test.go

@@ -21,24 +21,20 @@ import (
 // This is a test to run and for manually testing, registered combination:
 // Ctrl+Alt+A (Ctrl+Mod2+Mod4+A on Linux)
 func TestHotkey(t *testing.T) {
-	tt := time.Second * 5
-
-	ctx, cancel := context.WithTimeout(context.Background(), tt)
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
 
-	hk, err := hotkey.Register([]hotkey.Modifier{
+	hk := hotkey.New([]hotkey.Modifier{
 		hotkey.ModCtrl, hotkey.Mod2, hotkey.Mod4}, hotkey.KeyA)
-	if err != nil {
+	if err := hk.Register(); err != nil {
 		t.Errorf("failed to register hotkey: %v", err)
 		return
 	}
-
-	trigger := hk.Listen(ctx)
 	for {
 		select {
 		case <-ctx.Done():
 			return
-		case <-trigger:
+		case <-hk.Listen():
 			fmt.Println("triggered")
 		}
 	}

hotkey_nocgo.go

@@ -10,6 +10,8 @@ package hotkey
 
 import "context"
 
+type platformHotkey struct{}
+
 // Modifier represents a modifier
 type Modifier uint32
 
@@ -21,7 +23,7 @@ func (hk *Hotkey) register() error {
 }
 
 // unregister deregisteres a system hotkey.
-func (hk *Hotkey) unregister() {
+func (hk *Hotkey) unregister() error {
 	panic("hotkey: cannot use when CGO_ENABLED=0")
 }
 

hotkey_nocgo_test.go

@@ -25,5 +25,10 @@ func TestHotkey(t *testing.T) {
 		t.Fatalf("expect to fail when CGO_ENABLED=0")
 	}()
 
-	hotkey.Register([]hotkey.Modifier{}, hotkey.Key(0))
+	hk := hotkey.New([]hotkey.Modifier{}, hotkey.Key(0))
+	err := hk.Register()
+	if err != nil {
+		t.Fatal(err)
+	}
+	hk.Unregister()
 }

mainthread/os.go

@@ -4,7 +4,7 @@
 //
 // Written by Changkun Ou <changkun.de>
 
-//go:build !darwin
+//go:build windows || linux || (darwin && !cgo)
 
 package mainthread