More control over menus (#4031)

* Add prepend and clear method to menus

* Document appending and clearing menus

* Add `Destroy()`
Add notes to documentation.

* Remove menu item from map when destroying

* Remove menu items from map when clearing

* Update v3/pkg/application/menu.go

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* Minor updates

* Fix build error

---------

Co-authored-by: Lea Anthony <lea.anthony@gmail.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

docs/src/content/docs/changelog.mdx

@@ -42,6 +42,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - New Menu guide by [@leaanthony](https://github.com/leaanthony)
 - Add doc comments for Service API by [@fbbdev](https://github.com/fbbdev) in [#4024](https://github.com/wailsapp/wails/pull/4024)
 - Add function `application.NewServiceWithOptions` to initialise services with additional configuration by [@leaanthony](https://github.com/leaanthony) in [#4024](https://github.com/wailsapp/wails/pull/4024)
+- Improved menu control by [@FalcoG](https://github.com/FalcoG) and [@leaanthony](https://github.com/leaanthony) in [#4031](https://github.com/wailsapp/wails/pull/4031)
 - More documentation by [@leaanthony](https://github.com/leaanthony)
 - Support cancellation of events in standard event listeners by [@leaanthony](https://github.com/leaanthony)
 - Systray `Hide`, `Show` and `Destroy` support by [@leaanthony](https://github.com/leaanthony)

docs/src/content/docs/guides/menus.mdx

@@ -56,6 +56,65 @@ submenu.Add("Open")
 submenu.Add("Save")
 ```
 
+#### Combining menus
+A menu can be added into another menu by appending or prepending it.
+```go
+menu := application.NewMenu()
+menu.Add("First Menu")
+
+secondaryMenu := application.NewMenu()
+secondaryMenu.Add("Second Menu")
+
+// insert 'secondaryMenu' after 'menu'
+menu.Append(secondaryMenu)
+
+// insert 'secondaryMenu' before 'menu'
+menu.Prepend(secondaryMenu)
+
+// update the menu
+menu.Update()
+```
+
+:::note
+By default, `prepend` and `append` will share state with the original menu. If you want to create a new menu with its own state,
+you can call `.Clone()` on the menu.
+
+E.g: `menu.Append(secondaryMenu.Clone())`
+:::
+
+#### Clearing a menu
+In some cases it'll be better to construct a whole new menu if you are working with a variable amount of menu items.
+
+This will clear all items on an existing menu and allows you to add items again.
+
+```go
+menu := application.NewMenu()
+menu.Add("Waiting for update...")
+
+// after certain logic, the menu has to be updated
+menu.Clear()
+menu.Add("Update complete!")
+menu.Update()
+```
+
+:::note
+Clearing a menu simply clears the menu items at the top level. Whilst Submenus won't be visible, they will still occupy memory
+so be sure to manage your menus carefully.
+:::
+
+#### Destroying a menu
+
+If you want to clear and release a menu, use the `Destroy()` method:
+
+```go
+menu := application.NewMenu()
+menu.Add("Waiting for update...")
+
+// after certain logic, the menu has to be destroyed
+menu.Destroy()
+```
+
+
 ### Menu Item Properties
 
 Menu items have several properties that can be configured:

v3/pkg/application/linux_cgo.go

@@ -587,6 +587,10 @@ func menuItemNew(label string, bitmap []byte) pointer {
 	return menuItemAddProperties(C.gtk_menu_item_new(), label, bitmap)
 }
 
+func menuItemDestroy(widget pointer) {
+	C.gtk_widget_destroy((*C.GtkWidget)(widget))
+}
+
 func menuItemAddProperties(menuItem *C.GtkWidget, label string, bitmap []byte) pointer {
 	/*
 		   // FIXME: Support accelerator configuration

v3/pkg/application/menu.go

@@ -69,6 +69,21 @@ func (m *Menu) Update() {
 	m.impl.update()
 }
 
+// Clear all menu items
+func (m *Menu) Clear() {
+	for _, item := range m.items {
+		removeMenuItemByID(item.id)
+	}
+	m.items = nil
+}
+
+func (m *Menu) Destroy() {
+	for _, item := range m.items {
+		item.Destroy()
+	}
+	m.items = nil
+}
+
 func (m *Menu) AddSubmenu(s string) *Menu {
 	result := NewSubMenuItem(s)
 	m.items = append(m.items, result)
@@ -186,10 +201,19 @@ func (m *Menu) Clone() *Menu {
 	return result
 }
 
+// Append menu to an existing menu
 func (m *Menu) Append(in *Menu) {
+	if in == nil {
+		return
+	}
 	m.items = append(m.items, in.items...)
 }
 
+// Prepend menu before an existing menu
+func (m *Menu) Prepend(in *Menu) {
+	m.items = append(in.items, m.items...)
+}
+
 func (a *App) NewMenu() *Menu {
 	return &Menu{}
 }

v3/pkg/application/menuitem.go

@@ -33,6 +33,12 @@ func getMenuItemByID(id uint) *MenuItem {
 	return menuItemMap[id]
 }
 
+func removeMenuItemByID(id uint) {
+	menuItemMapLock.Lock()
+	defer menuItemMapLock.Unlock()
+	delete(menuItemMap, id)
+}
+
 type menuItemImpl interface {
 	setTooltip(s string)
 	setLabel(s string)
@@ -41,6 +47,7 @@ type menuItemImpl interface {
 	setAccelerator(accelerator *accelerator)
 	setHidden(hidden bool)
 	setBitmap(bitmap []byte)
+	destroy()
 }
 
 type MenuItem struct {
@@ -425,3 +432,29 @@ func (m *MenuItem) Clone() *MenuItem {
 	}
 	return result
 }
+
+func (m *MenuItem) Destroy() {
+
+	removeMenuItemByID(m.id)
+
+	// Clean up resources
+	if m.impl != nil {
+		m.impl.destroy()
+	}
+	if m.submenu != nil {
+		m.submenu.Destroy()
+		m.submenu = nil
+	}
+
+	if m.contextMenuData != nil {
+		m.contextMenuData = nil
+	}
+
+	if m.accelerator != nil {
+		m.accelerator = nil
+	}
+
+	m.callback = nil
+	m.radioGroupMembers = nil
+
+}

v3/pkg/application/menuitem_darwin.go

@@ -295,6 +295,11 @@ void setMenuItemBitmap(void* nsMenuItem, unsigned char *bitmap, int length) {
 	NSImage *image = [[NSImage alloc] initWithData:[NSData dataWithBytes:bitmap length:length]];
 	[menuItem setImage:image];
 }
+
+void destroyMenuItem(void* nsMenuItem) {
+	MenuItem *menuItem = (MenuItem *)nsMenuItem;
+	[menuItem release];
+}
 */
 import "C"
 import (
@@ -344,6 +349,10 @@ func (m macosMenuItem) setAccelerator(accelerator *accelerator) {
 	C.setMenuItemKeyEquivalent(m.nsMenuItem, key, modifier)
 }
 
+func (m macosMenuItem) destroy() {
+	C.destroyMenuItem(m.nsMenuItem)
+}
+
 func newMenuItemImpl(item *MenuItem) *macosMenuItem {
 	result := &macosMenuItem{
 		menuItem: item,

v3/pkg/application/menuitem_linux.go

@@ -21,6 +21,14 @@ func (l linuxMenuItem) setTooltip(tooltip string) {
 	})
 }
 
+func (l linuxMenuItem) destroy() {
+	InvokeSync(func() {
+		l.blockSignal()
+		defer l.unBlockSignal()
+		menuItemDestroy(l.native)
+	})
+}
+
 func (l linuxMenuItem) blockSignal() {
 	if l.handlerId != 0 {
 		menuItemSignalBlock(l.native, l.handlerId, true)

v3/pkg/application/menuitem_windows.go

@@ -96,6 +96,10 @@ func (m *windowsMenuItem) setChecked(checked bool) {
 	m.update()
 }
 
+func (m *windowsMenuItem) destroy() {
+	w32.RemoveMenu(m.hMenu, m.id, w32.MF_BYCOMMAND)
+}
+
 func (m *windowsMenuItem) setAccelerator(accelerator *accelerator) {
 	//// Set the keyboard shortcut of the menu item
 	//var modifier C.int

v3/pkg/application/systemtray_linux.go

@@ -87,6 +87,8 @@ func (s *systrayMenuItem) setDisabled(disabled bool) {
 	}
 }
 
+func (s *systrayMenuItem) destroy() {}
+
 func (s *systrayMenuItem) setChecked(checked bool) {
 	v := dbus.MakeVariant(0)
 	if checked {