cocoa - screen not refreshing after CGEventPost mouse click

Question

I am programatically generating mouse clicks when a user clicks a certain keyboard key (CapsLock). So I do a left mouse down when CapsLock is switched on, then a left mouse up when CapsLock is switched off.

This behaves correctly in that if I for example place the mouse over a window title bar, click CapsLock, then move the mouse, then click CapsLock, the window correctly moves. i.e. I correctly 'drag' the window as if I had held the left mouse button down whilst moving the mouse.

However there is one problem - the window does not move whilst I am moving the mouse, it only moves to the final position after I have clicked CapsLock a second time. i.e. after I have 'released' the mouse button.

What do I need to do to ensure the screen is refreshed during the mouse move?

Interestingly, I also hooked to

[NSEvent addGlobalMonitorForEventsMatchingMask:NSLeftMouseDraggedMask

and found that my NSLog statement only output after I released the left mouse button (the real left mouse button)

Mouse click code is below, I can post all the code if necessary, there isn't much of it..

// simulate mouse down

// get current mouse pos
CGEventRef ourEvent = CGEventCreate(NULL);
CGPoint point = CGEventGetLocation(ourEvent);
NSLog(@"Location? x= %f, y = %f", (float)point.x, (float)point.y);

CGEventSourceRef source = CGEventSourceCreate(kCGEventSourceStateCombinedSessionState);
CGEventRef theEvent = CGEventCreateMouseEvent(source, kCGEventLeftMouseDown, point, kCGMouseButtonLeft);
CGEventSetType(theEvent, kCGEventLeftMouseDown);
CGEventPost(kCGHIDEventTap, theEvent);
CFRelease(theEvent);


// simulate mouse up

// get current mouse pos
CGEventRef ourEvent = CGEventCreate(NULL);
CGPoint point = CGEventGetLocation(ourEvent);
NSLog(@"Location? x= %f, y = %f", (float)point.x, (float)point.y);

CGEventSourceRef source = CGEventSourceCreate(kCGEventSourceStateCombinedSessionState);
CGEventRef theEvent = CGEventCreateMouseEvent(source, kCGEventLeftMouseUp, point, kCGMouseButtonLeft);
CGEventSetType(theEvent, kCGEventLeftMouseUp);
CGEventPost(kCGHIDEventTap, theEvent);
CFRelease(theEvent);

How are you retrieving your key events for the left caps lock key? Where's its event loop? — Huperniketes

Jake Petroules Jake Petroules · Accepted Answer · 2011-06-23T00:39:30

If you want to be able to drag windows, the problem is that you also need to post a LeftMouseDragged event.

Simply call beginEventMonitoring to start listening for caps lock key events and mouse move events. The event handlers will simulate a left mouse press and movement just as you wanted. Here is a link to my blog where you can download a full working example for Xcode 4: http://www.jakepetroules.com/2011/06/25/simulating-mouse-events-in-cocoa

The example is in the public domain, do whatever you like with it. :)

According to Apple (NSEvent documentation), "Enable access for assistive devices" needs to be checked in System Preferences > Universal Access for this to work, but I have it unchecked and it wasn't an issue. Just a heads up.

Please let me know if you have any further issues and I will try my best to help.

// Begin listening for caps lock key presses and mouse movements
- (void)beginEventMonitoring
{
    // Determines whether the caps lock key was initially down before we started listening for events
    wasCapsLockDown = CGEventSourceKeyState(kCGEventSourceStateHIDSystemState, kVK_CapsLock);

    capsLockEventMonitor = [NSEvent addGlobalMonitorForEventsMatchingMask:(NSFlagsChangedMask) handler: ^(NSEvent *event)
    {
        // Determines whether the caps lock key was pressed and posts a mouse down or mouse up event depending on its state
        bool isCapsLockDown = [event modifierFlags] & NSAlphaShiftKeyMask;
        if (isCapsLockDown && !wasCapsLockDown)
        {
            [self simulateMouseEvent: kCGEventLeftMouseDown];
            wasCapsLockDown = true;
        }
        else if (wasCapsLockDown)
        {
            [self simulateMouseEvent: kCGEventLeftMouseUp];
            wasCapsLockDown = false;
        }
    }];

    mouseMovementEventMonitor = [NSEvent addGlobalMonitorForEventsMatchingMask:(NSMouseMovedMask) handler:^(NSEvent *event)
    {
        [self simulateMouseEvent: kCGEventLeftMouseDragged];
    }];
}

// Cease listening for caps lock key presses and mouse movements
- (void)endEventMonitoring
{
    if (capsLockEventMonitor)
    {
        [NSEvent removeMonitor: capsLockEventMonitor];
        capsLockEventMonitor = nil;
    }

    if (mouseMovementEventMonitor)
    {
        [NSEvent removeMonitor: mouseMovementEventMonitor];
        mouseMovementEventMonitor = nil;
    }
}

-(void)simulateMouseEvent:(CGEventType)eventType
{
    // Get the current mouse position
    CGEventRef ourEvent = CGEventCreate(NULL);
    CGPoint mouseLocation = CGEventGetLocation(ourEvent);

    // Create and post the event
    CGEventRef event = CGEventCreateMouseEvent(CGEventSourceCreate(kCGEventSourceStateHIDSystemState), eventType, mouseLocation, kCGMouseButtonLeft);
    CGEventPost(kCGHIDEventTap, event);
    CFRelease(event);
}

cocoa - screen not refreshing after CGEventPost mouse click

1 Answers