Adds how-to-release-the-mouse instructions for Cocoa.

OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift

@@ -154,6 +154,11 @@ class MachineDocument:
 	// a sheet mysteriously floating on its own. For now, use windowDidUpdate as a proxy to know that the window
 	// is visible, though it's a little premature.
 	func windowDidUpdate(_ notification: Notification) {
+		// Grab the regular window title, if it's not already stored.
+		if self.unadornedWindowTitle.count == 0 {
+			self.unadornedWindowTitle = self.windowControllers[0].window!.title
+		}
+
 		// If an interaction mode is not yet in effect, pick the proper one and display the relevant thing.
 		if self.interactionMode == .notStarted {
 			// If a full machine exists, just continue showing it.
@@ -613,7 +618,17 @@ class MachineDocument:
 		try! pngData?.write(to: url)
 	}
 
-	// MARK: Activity display.
+	// MARK: - Window Title Updates.
+	private var unadornedWindowTitle = ""
+	func openGLViewDidCaptureMouse(_ view: CSOpenGLView) {
+		self.windowControllers[0].window?.title = self.unadornedWindowTitle + " (press ⌘+command to release mouse)"
+	}
+
+	func openGLViewDidReleaseMouse(_ view: CSOpenGLView) {
+		self.windowControllers[0].window?.title = self.unadornedWindowTitle
+	}
+
+	// MARK: - Activity Display.
 
 	private class LED {
 		let levelIndicator: NSLevelIndicator

OSBindings/Mac/Clock Signal/Views/CSOpenGLView.h

@@ -37,6 +37,19 @@ typedef NS_ENUM(NSInteger, CSOpenGLViewRedrawEvent) {
 */
 - (void)openGLView:(nonnull CSOpenGLView *)view didReceiveFileAtURL:(nonnull NSURL *)URL;
 
+/*!
+	Announces 'capture' of the mouse — i.e. that the view is now preventing the mouse from exiting
+	the window, in order to forward continuous mouse motion.
+	@param view The view making the announcement.
+*/
+- (void)openGLViewDidCaptureMouse:(nonnull CSOpenGLView *)view;
+
+/*!
+	Announces that the mouse is no longer captured.
+	@param view The view making the announcement.
+*/
+- (void)openGLViewDidReleaseMouse:(nonnull CSOpenGLView *)view;
+
 @end
 
 @protocol CSOpenGLViewResponderDelegate <NSObject>

OSBindings/Mac/Clock Signal/Views/CSOpenGLView.m

@@ -223,6 +223,7 @@ static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeSt
 		_mouseIsCaptured = NO;
 		CGAssociateMouseAndMouseCursorPosition(true);
 		[NSCursor unhide];
+		[self.delegate openGLViewDidReleaseMouse:self];
 	}
 }
 
@@ -281,6 +282,7 @@ static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeSt
 			_mouseIsCaptured = YES;
 			[NSCursor hide];
 			CGAssociateMouseAndMouseCursorPosition(false);
+			[self.delegate openGLViewDidCaptureMouse:self];
 
 			// Don't report the first click to the delegate; treat that as merely
 			// an invitation to capture the cursor.