[v2, windows] Make sure to open the CommonFileDialogs on the main thread (#2606)

Otherwise it might have some strange side-effects like blocking
the completion of Deferrals in WebView2 when using custom
IStreams.

v2/internal/frontend/desktop/windows/dialog.go

@@ -4,13 +4,14 @@
 package windows
 
 import (
+	"path/filepath"
+	"strings"
+	"syscall"
+
 	"github.com/wailsapp/wails/v2/internal/frontend"
 	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/winc/w32"
 	"github.com/wailsapp/wails/v2/internal/go-common-file-dialog/cfd"
 	"golang.org/x/sys/windows"
-	"path/filepath"
-	"strings"
-	"syscall"
 )
 
 func (f *Frontend) getHandleForDialog() w32.HWND {
@@ -40,27 +41,20 @@ func (f *Frontend) OpenDirectoryDialog(options frontend.OpenDialogOptions) (stri
 		Role:   "PickFolder",
 		Folder: defaultFolder,
 	}
-	thisDialog, err := cfd.NewSelectFolderDialog(config)
-	if err != nil {
-		return "", err
-	}
-	thisDialog.SetParentWindowHandle(f.getHandleForDialog())
-	defer func(thisDialog cfd.SelectFolderDialog) {
-		err := thisDialog.Release()
-		if err != nil {
-			println("ERROR: Unable to release dialog:", err.Error())
-		}
-	}(thisDialog)
-	result, err := thisDialog.ShowAndGetResult()
+
+	result, err := f.showCfdDialog(
+		func() (cfd.Dialog, error) {
+			return cfd.NewSelectFolderDialog(config)
+		}, false)
+
 	if err != nil && err != cfd.ErrorCancelled {
 		return "", err
 	}
-	return result, nil
+	return result.(string), nil
 }
 
 // OpenFileDialog prompts the user to select a file
 func (f *Frontend) OpenFileDialog(options frontend.OpenDialogOptions) (string, error) {
-
 	defaultFolder, err := getDefaultFolder(options.DefaultDirectory)
 	if err != nil {
 		return "", err
@@ -72,22 +66,16 @@ func (f *Frontend) OpenFileDialog(options frontend.OpenDialogOptions) (string, e
 		FileName:    options.DefaultFilename,
 		Title:       options.Title,
 	}
-	thisdialog, err := cfd.NewOpenFileDialog(config)
-	if err != nil {
-		return "", err
-	}
-	thisdialog.SetParentWindowHandle(f.getHandleForDialog())
-	defer func(thisdialog cfd.OpenFileDialog) {
-		err := thisdialog.Release()
-		if err != nil {
-			println("ERROR: Unable to release dialog:", err.Error())
-		}
-	}(thisdialog)
-	result, err := thisdialog.ShowAndGetResult()
+
+	result, err := f.showCfdDialog(
+		func() (cfd.Dialog, error) {
+			return cfd.NewOpenFileDialog(config)
+		}, false)
+
 	if err != nil && err != cfd.ErrorCancelled {
 		return "", err
 	}
-	return result, nil
+	return result.(string), nil
 }
 
 // OpenMultipleFilesDialog prompts the user to select a file
@@ -105,22 +93,16 @@ func (f *Frontend) OpenMultipleFilesDialog(options frontend.OpenDialogOptions) (
 		FileName:    options.DefaultFilename,
 		Folder:      defaultFolder,
 	}
-	thisdialog, err := cfd.NewOpenMultipleFilesDialog(config)
-	if err != nil {
-		return nil, err
-	}
-	thisdialog.SetParentWindowHandle(f.getHandleForDialog())
-	defer func(thisdialog cfd.OpenMultipleFilesDialog) {
-		err := thisdialog.Release()
-		if err != nil {
-			println("ERROR: Unable to release dialog:", err.Error())
-		}
-	}(thisdialog)
-	result, err := thisdialog.ShowAndGetResults()
+
+	result, err := f.showCfdDialog(
+		func() (cfd.Dialog, error) {
+			return cfd.NewOpenMultipleFilesDialog(config)
+		}, true)
+
 	if err != nil && err != cfd.ErrorCancelled {
 		return nil, err
 	}
-	return result, nil
+	return result.([]string), nil
 }
 
 // SaveFileDialog prompts the user to select a file
@@ -131,26 +113,44 @@ func (f *Frontend) SaveFileDialog(options frontend.SaveDialogOptions) (string, e
 		return "", err
 	}
 
-	saveDialog, err := cfd.NewSaveFileDialog(cfd.DialogConfig{
+	config := cfd.DialogConfig{
 		Title:       options.Title,
 		Role:        "SaveFile",
 		FileFilters: convertFilters(options.Filters),
 		FileName:    options.DefaultFilename,
 		Folder:      defaultFolder,
-	})
-	if err != nil {
-		return "", err
 	}
-	saveDialog.SetParentWindowHandle(f.getHandleForDialog())
-	err = saveDialog.Show()
-	if err != nil {
-		return "", err
-	}
-	result, err := saveDialog.GetResult()
+
+	result, err := f.showCfdDialog(
+		func() (cfd.Dialog, error) {
+			return cfd.NewSaveFileDialog(config)
+		}, false)
+
 	if err != nil && err != cfd.ErrorCancelled {
 		return "", err
 	}
-	return result, nil
+	return result.(string), nil
+}
+
+func (f *Frontend) showCfdDialog(newDlg func() (cfd.Dialog, error), isMultiSelect bool) (any, error) {
+	return invokeSync(f.mainWindow, func() (any, error) {
+		dlg, err := newDlg()
+		if err != nil {
+			return nil, err
+		}
+		defer func() {
+			err := dlg.Release()
+			if err != nil {
+				println("ERROR: Unable to release dialog:", err.Error())
+			}
+		}()
+
+		dlg.SetParentWindowHandle(f.getHandleForDialog())
+		if multi, _ := dlg.(cfd.OpenMultipleFilesDialog); multi != nil && isMultiSelect {
+			return multi.ShowAndGetResults()
+		}
+		return dlg.ShowAndGetResult()
+	})
 }
 
 func calculateMessageDialogFlags(options frontend.MessageDialogOptions) uint32 {

v2/internal/frontend/desktop/windows/window.go

@@ -3,6 +3,7 @@
 package windows
 
 import (
+	"sync"
 	"unsafe"
 
 	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/go-webview2/pkg/edge"
@@ -323,3 +324,14 @@ func (w *Window) SetTheme(theme winoptions.Theme) {
 		w.UpdateTheme()
 	})
 }
+
+func invokeSync[T any](cba *Window, fn func() (T, error)) (res T, err error) {
+	var wg sync.WaitGroup
+	wg.Add(1)
+	cba.Invoke(func() {
+		res, err = fn()
+		wg.Done()
+	})
+	wg.Wait()
+	return res, err
+}

website/src/pages/changelog.mdx

@@ -30,6 +30,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed `-skipbindings` flag in `wails dev`. Fixed by @stffabi in [PR](https://github.com/wailsapp/wails/pull/2584)
 - Fixed `runtime.MenuUpdateApplicationMenu` on macOS. Fixed by @stffabi in [PR](https://github.com/wailsapp/wails/pull/2588)
 - Fixed add package name for `libwebkit`/`pkg-config` and use shell.RunCommandWithENV instead of shell.RunCommand in `zypper.go`. Fixed by @wgjtyu in [PR](https://github.com/wailsapp/wails/pull/2593)
+- Make sure to start the CommonFileDialogs on Windows on the Main-Thread. Fixed by @stffabi in [PR](https://github.com/wailsapp/wails/pull/2606)
 
 ## v2.4.1 - 2023-03-20