[macOS] Allow setting status item interactive removal behavior

README.md

@@ -116,6 +116,11 @@ When running as an app bundle, you may want to add one or both of the following
 
 Consult the [Official Apple Documentation here](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFBundles/BundleTypes/BundleTypes.html#//apple_ref/doc/uid/10000123i-CH101-SW1).
 
+On macOS, it's possible to set the underlying
+[`NSStatusItemBehavior`](https://developer.apple.com/documentation/appkit/nsstatusitembehavior?language=objc)
+with `systray.SetRemovalAllowed(true)`. When enabled, the user can cmd-drag the
+icon off the menu bar.
+
 ## Credits
 
 - https://github.com/xilp/systray

example/main.go

@@ -37,6 +37,7 @@ func onReady() {
 		systray.SetTitle("Awesome App")
 		systray.SetTooltip("Pretty awesome棒棒嗒")
 		mChange := systray.AddMenuItem("Change Me", "Change Me")
+		mAllowRemoval := systray.AddMenuItem("Allow removal", "macOS only: allow removal of the icon when cmd is pressed")
 		mChecked := systray.AddMenuItemCheckbox("Unchecked", "Check Me", true)
 		mEnabled := systray.AddMenuItem("Enabled", "Enabled")
 		// Sets the icon of a menu item. Only available on Mac.
@@ -78,6 +79,8 @@ func onReady() {
 			select {
 			case <-mChange.ClickedCh:
 				mChange.SetTitle("I've Changed")
+			case <-mAllowRemoval.ClickedCh:
+				systray.SetRemovalAllowed(true)
 			case <-mChecked.ClickedCh:
 				if mChecked.Checked() {
 					mChecked.Uncheck()

systray.h

@@ -10,6 +10,7 @@ void setIcon(const char* iconBytes, int length, bool template);
 void setMenuItemIcon(const char* iconBytes, int length, int menuId, bool template);
 void setTitle(char* title);
 void setTooltip(char* tooltip);
+void setRemovalAllowed(bool allowed);
 void add_or_update_menu_item(int menuId, int parentMenuId, char* title, char* tooltip, short disabled, short checked, short isCheckable);
 void add_separator(int menuId);
 void hide_menu_item(int menuId);

systray_darwin.go

@@ -36,3 +36,9 @@ func (item *MenuItem) SetTemplateIcon(templateIconBytes []byte, regularIconBytes
 	cstr := (*C.char)(unsafe.Pointer(&templateIconBytes[0]))
 	C.setMenuItemIcon(cstr, (C.int)(len(templateIconBytes)), C.int(item.id), true)
 }
+
+// SetRemovalAllowed sets whether a user can remove the systray icon or not.
+// This is only supported on macOS.
+func SetRemovalAllowed(allowed bool) {
+	C.setRemovalAllowed((C.bool)(allowed))
+}

systray_darwin.m

@@ -71,6 +71,11 @@ - (void)applicationDidFinishLaunching:(NSNotification *)aNotification
   self->menu = [[NSMenu alloc] init];
   [self->menu setAutoenablesItems: FALSE];
   [self->statusItem setMenu:self->menu];
+  // Once the user has removed it, the item needs to be explicitly brought back,
+  // even restarting the application is insufficient.
+  // Since the interface from Go is relatively simple, for now we ensure it's always
+  // visible at application startup.
+  self->statusItem.visible = TRUE;
   systray_ready();
 }
 
@@ -79,6 +84,16 @@ - (void)applicationWillTerminate:(NSNotification *)aNotification
   systray_on_exit();
 }
 
+- (void)setRemovalAllowed:(BOOL)allowed {
+  NSStatusItemBehavior behavior = [self->statusItem behavior];
+  if (allowed) {
+    behavior |= NSStatusItemBehaviorRemovalAllowed;
+  } else {
+    behavior &= ~NSStatusItemBehaviorRemovalAllowed;
+  }
+  self->statusItem.behavior = behavior;
+}
+
 - (void)setIcon:(NSImage *)image {
   statusItem.button.image = image;
   [self updateTitleButtonStyle];
@@ -266,6 +281,12 @@ void setTooltip(char* ctooltip) {
   runInMainThread(@selector(setTooltip:), (id)tooltip);
 }
 
+void setRemovalAllowed(bool allowed) {
+  // must use an object wrapper for the bool, to use with performSelectorOnMainThread:
+  NSNumber *allow = [NSNumber numberWithBool:(BOOL)allowed];
+  runInMainThread(@selector(setRemovalAllowed:), (id)allow);
+}
+
 void add_or_update_menu_item(int menuId, int parentMenuId, char* title, char* tooltip, short disabled, short checked, short isCheckable) {
   MenuItem* item = [[MenuItem alloc] initWithId: menuId withParentMenuId: parentMenuId withTitle: title withTooltip: tooltip withDisabled: disabled withChecked: checked];
   free(title);

systray_linux.go

@@ -8,6 +8,11 @@ func SetTemplateIcon(templateIconBytes []byte, regularIconBytes []byte) {
 	SetIcon(regularIconBytes)
 }
 
+// SetRemovalAllowed sets whether a user can remove the systray icon or not.
+// This is only supported on macOS.
+func SetRemovalAllowed(allowed bool) {
+}
+
 // SetIcon sets the icon of a menu item. Only works on macOS and Windows.
 // iconBytes should be the content of .ico/.jpg/.png
 func (item *MenuItem) SetIcon(iconBytes []byte) {

systray_windows.go

@@ -907,6 +907,11 @@ func SetTooltip(tooltip string) {
 	}
 }
 
+// SetRemovalAllowed sets whether a user can remove the systray icon or not.
+// This is only supported on macOS.
+func SetRemovalAllowed(allowed bool) {
+}
+
 func addOrUpdateMenuItem(item *MenuItem) {
 	err := wt.addOrUpdateMenuItem(uint32(item.id), item.parentId(), item.title, item.disabled, item.checked)
 	if err != nil {