It's a bit jarring, but ensures volume control shows and hides according to mouse cursor.

OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme

@@ -67,7 +67,7 @@
       </Testables>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Release"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       enableASanStackUseAfterReturn = "YES"

OSBindings/Mac/Clock Signal/Base.lproj/MachineDocument.xib

@@ -29,7 +29,7 @@
                     <openGLView hidden="YES" wantsLayer="YES" useAuxiliaryDepthBufferStencil="NO" allowOffline="YES" wantsBestResolutionOpenGLSurface="YES" translatesAutoresizingMaskIntoConstraints="NO" id="DEG-fq-cjd" customClass="CSOpenGLView">
                         <rect key="frame" x="0.0" y="0.0" width="600" height="450"/>
                     </openGLView>
-                    <box boxType="custom" cornerRadius="4" title="Box" titlePosition="noTitle" translatesAutoresizingMaskIntoConstraints="NO" id="4ap-Gi-2AO">
+                    <box hidden="YES" boxType="custom" cornerRadius="4" title="Box" titlePosition="noTitle" translatesAutoresizingMaskIntoConstraints="NO" id="4ap-Gi-2AO">
                         <rect key="frame" x="150" y="20" width="300" height="48"/>
                         <view key="contentView" id="gwO-Ty-LCX">
                             <rect key="frame" x="1" y="1" width="298" height="46"/>

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

@@ -722,4 +722,14 @@ class MachineDocument:
 			machine.setVolume(sender.floatValue);
 		}
 	}
+
+	func openGLViewDidShowOSMouseCursor(_ view: CSOpenGLView) {
+		// The OS mouse cursor became visible, so show the volume controls.
+		volumeView.isHidden = false
+	}
+
+	func openGLViewWillHideOSMouseCursor(_ view: CSOpenGLView) {
+		// The OS mouse cursor will be hidden, so hide the volume controls.
+		volumeView.isHidden = true
+	}
 }

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

@@ -50,6 +50,18 @@ typedef NS_ENUM(NSInteger, CSOpenGLViewRedrawEvent) {
 */
 - (void)openGLViewDidReleaseMouse:(nonnull CSOpenGLView *)view;
 
+/*!
+	Announces that the OS mouse cursor is now being displayed again, after having been invisible.
+	@param view The view making the announcement.
+*/
+- (void)openGLViewDidShowOSMouseCursor:(nonnull CSOpenGLView *)view;
+
+/*!
+	Announces that the OS mouse cursor will now be hidden.
+	@param view The view making the announcement.
+*/
+- (void)openGLViewWillHideOSMouseCursor:(nonnull CSOpenGLView *)view;
+
 @end
 
 @protocol CSOpenGLViewResponderDelegate <NSObject>

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

@@ -288,10 +288,12 @@ static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeSt
 
 - (void)scheduleMouseHide {
 	if(!self.shouldCaptureMouse) {
+		[self.delegate openGLViewDidShowOSMouseCursor:self];
 		[_mouseHideTimer invalidate];
 
 		_mouseHideTimer = [NSTimer scheduledTimerWithTimeInterval:3.0 repeats:NO block:^(NSTimer * _Nonnull timer) {
 			[NSCursor setHiddenUntilMouseMoves:YES];
+			[self.delegate openGLViewWillHideOSMouseCursor:self];
 		}];
 	}
 }