Add RunWithContext function

form.go

@@ -2,11 +2,13 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build windows
 // +build windows
 
 package walk
 
 import (
+	"context"
 	"fmt"
 	"math"
 	"sync"
@@ -341,6 +343,15 @@ func (fb *FormBase) SetRightToLeftLayout(rtl bool) error {
 }
 
 func (fb *FormBase) Run() int {
+	return fb.run(context.Background())
+}
+
+// RunWithContext does the same as Run, but with the context cancellation respect.
+func (fb *FormBase) RunWithContext(ctx context.Context) int {
+	return fb.run(ctx)
+}
+
+func (fb *FormBase) run(ctx context.Context) int {
 	if fb.owner != nil {
 		win.EnableWindow(fb.owner.Handle(), false)
 
@@ -372,7 +383,7 @@ func (fb *FormBase) Run() int {
 
 	fb.SetSuspended(false)
 
-	return fb.mainLoop()
+	return fb.mainLoop(ctx)
 }
 
 func (fb *FormBase) handleKeyDown(msg *win.MSG) bool {

mainloop_cgo.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build windows && walk_use_cgo
 // +build windows,walk_use_cgo
 
 package walk
@@ -51,6 +52,6 @@ func shimRunSynchronized(fb uintptr) {
 	(*FormBase)(unsafe.Pointer(fb)).group.RunSynchronized()
 }
 
-func (fb *FormBase) mainLoop() int {
+func (fb *FormBase) mainLoop(_ context.Context) int {
 	return int(C.mainloop(C.uintptr_t(uintptr(unsafe.Pointer(&fb.hWnd))), C.uintptr_t(uintptr(unsafe.Pointer(fb)))))
 }

mainloop_default.go

@@ -2,21 +2,27 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build windows && !walk_use_cgo
 // +build windows,!walk_use_cgo
 
 package walk
 
 import (
+	"context"
 	"unsafe"
 
 	"github.com/lxn/win"
 )
 
-func (fb *FormBase) mainLoop() int {
+func (fb *FormBase) mainLoop(ctx context.Context) int {
 	msg := (*win.MSG)(unsafe.Pointer(win.GlobalAlloc(0, unsafe.Sizeof(win.MSG{}))))
 	defer win.GlobalFree(win.HGLOBAL(unsafe.Pointer(msg)))
 
 	for fb.hWnd != 0 {
+		if err := ctx.Err(); err != nil {
+			return 0
+		}
+
 		switch win.GetMessage(msg, 0, 0, 0) {
 		case 0:
 			return int(msg.WParam)