fix cursor visibility in OSX

PanoPainter-OSX/main.cpp

@@ -45,6 +45,14 @@ std::mutex task_mutex;
 {
     [[NSApplication sharedApplication] terminate:nil];
 }
+- (void)show_cursor:(bool)visible
+{
+    if (cursor_visible == visible)
+        return;
+    cursor_visible = visible;
+    if (cursor_inside)
+        visible ? [NSCursor unhide] : [NSCursor hide];
+}
 - (std::string)pick_file:(NSArray<NSString*>*)types
 {
     NSOpenPanel *panel = [NSOpenPanel openPanel];
@@ -107,6 +115,8 @@ std::mutex task_mutex;
     airdrop_service = [NSSharingService  sharingServiceNamed:NSSharingServiceNameSendViaAirDrop];
     airdrop_service.delegate = self;
     gl_ready = false;
+    cursor_visible = CGCursorIsVisible();
+    cursor_inside = false;
     NSOpenGLPixelFormatAttribute attrs[] =
     {
         NSOpenGLPFADoubleBuffer,
@@ -125,7 +135,7 @@ std::mutex task_mutex;
     [self setPixelFormat:pf];
     [self setOpenGLContext:context];
 
-    self->trackingArea = [[NSTrackingArea alloc] initWithRect:frameRect
+    trackingArea = [[NSTrackingArea alloc] initWithRect:frameRect
             options: (NSTrackingMouseEnteredAndExited | NSTrackingMouseMoved | NSTrackingActiveInKeyWindow )
             owner:self userInfo:nil];
     [self addTrackingArea:trackingArea];
@@ -268,9 +278,9 @@ static CVReturn MyDisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTime
 }
 - (void)updateTrackingAreas
 {
-    if(self->trackingArea != nil)
-        [self removeTrackingArea:self->trackingArea];
-    self->trackingArea = [[NSTrackingArea alloc] initWithRect:[self bounds]
+    if(trackingArea != nil)
+        [self removeTrackingArea:trackingArea];
+    trackingArea = [[NSTrackingArea alloc] initWithRect:[self bounds]
             options: (NSTrackingMouseEnteredAndExited | NSTrackingMouseMoved | NSTrackingActiveInKeyWindow)
             owner:self userInfo:nil];
     [self addTrackingArea:trackingArea];
@@ -389,14 +399,15 @@ static CVReturn MyDisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTime
 }
 -(void)mouseExited:(NSEvent *)event
 {
-    self->cursor_visible = CGCursorIsVisible();
-    if (!self->cursor_visible)
+    if (!cursor_visible)
         [NSCursor unhide];
+    cursor_inside = false;
 }
 -(void)mouseEntered:(NSEvent *)event
 {
-    if (!self->cursor_visible)
+    if (!cursor_visible)
         [NSCursor hide];
+    cursor_inside = true;
 }
 - (void)scrollWheel:(NSEvent *)theEvent
 {