app: [macos] don't relay key events handled by the IME

Widgets such as Editor use certain key events such as the backspace key
to implement text editing. On macOS, such key events are sometimes used
by an input method, and in those cases the key effect would be applied
twice: first by the IME and then the Editor.

Report such key events through the doCommandBySelector callback, which
receives key events not handled by the IME.

References: https://todo.sr.ht/~eliasnaur/gio/616
Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/os_macos.go

@@ -39,6 +39,12 @@ import (
 #define MOUSE_DOWN 3
 #define MOUSE_SCROLL 4
 
+#define KEY_DELETE_BACKWARD 0x7f
+#define KEY_RETURN 0xd
+#define KEY_ENTER 0x3
+#define KEY_ESCAPE 0x1b
+#define KEY_TAB 0x09
+
 __attribute__ ((visibility ("hidden"))) void gio_main(void);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_createView(int presentWithTrans);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_createWindow(CFTypeRef viewRef, CGFloat width, CGFloat height, CGFloat minWidth, CGFloat minHeight, CGFloat maxWidth, CGFloat maxHeight);
@@ -343,6 +349,8 @@ type window struct {
 
 	scale  float32
 	config Config
+
+	cmdKeysDown map[key.Name]struct{}
 }
 
 // launched is closed when applicationDidFinishLaunching is called.
@@ -551,7 +559,16 @@ func gio_onKeys(h C.uintptr_t, cstr C.CFTypeRef, ti C.double, mods C.NSUInteger,
 	}
 	w := windowFor(h)
 	for _, k := range str {
-		if n, ok := convertKey(k); ok {
+		n, ok := convertKey(k)
+		if !ok && ks == key.Release {
+			// Key release events are not reported by onCommandBySelector.
+			n, ok = convertCommandKey(k)
+			if ok {
+				_, ok = w.cmdKeysDown[n]
+				delete(w.cmdKeysDown, n)
+			}
+		}
+		if ok {
 			w.ProcessEvent(key.Event{
 				Name:      n,
 				Modifiers: kmods,
@@ -561,6 +578,29 @@ func gio_onKeys(h C.uintptr_t, cstr C.CFTypeRef, ti C.double, mods C.NSUInteger,
 	}
 }
 
+//export gio_onCommandBySelector
+func gio_onCommandBySelector(h C.uintptr_t, k C.int, ti C.double, mods C.NSUInteger) {
+	w := windowFor(h)
+	w.commandKey(rune(k), ti, mods)
+}
+
+func (w *window) commandKey(k rune, ti C.double, mods C.NSUInteger) bool {
+	n, ok := convertCommandKey(k)
+	if !ok {
+		return false
+	}
+	if w.cmdKeysDown == nil {
+		w.cmdKeysDown = make(map[key.Name]struct{})
+	}
+	w.cmdKeysDown[n] = struct{}{}
+	w.ProcessEvent(key.Event{
+		Modifiers: convertMods(mods),
+		Name:      n,
+		State:     key.Press,
+	})
+	return true
+}
+
 //export gio_onText
 func gio_onText(h C.uintptr_t, cstr C.CFTypeRef) {
 	str := nsstringToString(cstr)
@@ -749,8 +789,19 @@ func gio_substringForProposedRange(h C.uintptr_t, crng C.NSRange, actual C.NSRan
 }
 
 //export gio_insertText
-func gio_insertText(h C.uintptr_t, cstr C.CFTypeRef, crng C.NSRange) {
+func gio_insertText(h C.uintptr_t, cstr C.CFTypeRef, crng C.NSRange, ti C.double, mods C.NSUInteger) {
 	w := windowFor(h)
+	str := nsstringToString(cstr)
+	// macOS IME in some cases calls insertText for command keys such as backspace
+	// instead of doCommandBySelector.
+	hadCommands := false
+	for _, r := range str {
+		hadCommands = w.commandKey(r, ti, mods) || hadCommands
+	}
+	if hadCommands {
+		w.w.SetComposingRegion(key.Range{Start: -1, End: -1})
+		return
+	}
 	state := w.w.EditorState()
 	rng := state.compose
 	if rng.Start == -1 {
@@ -762,7 +813,6 @@ func gio_insertText(h C.uintptr_t, cstr C.CFTypeRef, crng C.NSRange) {
 			End:   state.RunesIndex(int(crng.location + crng.length)),
 		}
 	}
-	str := nsstringToString(cstr)
 	w.w.EditorReplace(rng, str)
 	w.w.SetComposingRegion(key.Range{Start: -1, End: -1})
 	start := rng.Start
@@ -957,10 +1007,10 @@ func osMain() {
 	C.gio_main()
 }
 
-func convertKey(k rune) (key.Name, bool) {
+func convertCommandKey(k rune) (key.Name, bool) {
 	var n key.Name
 	switch k {
-	case 0x1b:
+	case C.KEY_ESCAPE:
 		n = key.NameEscape
 	case C.NSLeftArrowFunctionKey:
 		n = key.NameLeftArrow
@@ -970,22 +1020,33 @@ func convertKey(k rune) (key.Name, bool) {
 		n = key.NameUpArrow
 	case C.NSDownArrowFunctionKey:
 		n = key.NameDownArrow
-	case 0xd:
+	case C.KEY_RETURN:
 		n = key.NameReturn
-	case 0x3:
+	case C.KEY_ENTER:
 		n = key.NameEnter
 	case C.NSHomeFunctionKey:
 		n = key.NameHome
 	case C.NSEndFunctionKey:
 		n = key.NameEnd
-	case 0x7f:
+	case C.KEY_DELETE_BACKWARD, 0x08:
 		n = key.NameDeleteBackward
 	case C.NSDeleteFunctionKey:
 		n = key.NameDeleteForward
+	case C.KEY_TAB, 0x19:
+		n = key.NameTab
 	case C.NSPageUpFunctionKey:
 		n = key.NamePageUp
 	case C.NSPageDownFunctionKey:
 		n = key.NamePageDown
+	default:
+		return "", false
+	}
+	return n, true
+}
+
+func convertKey(k rune) (key.Name, bool) {
+	var n key.Name
+	switch k {
 	case C.NSF1FunctionKey:
 		n = key.NameF1
 	case C.NSF2FunctionKey:
@@ -1010,8 +1071,6 @@ func convertKey(k rune) (key.Name, bool) {
 		n = key.NameF11
 	case C.NSF12FunctionKey:
 		n = key.NameF12
-	case 0x09, 0x19:
-		n = key.NameTab
 	case 0x20:
 		n = key.NameSpace
 	default: