Making a window pop in and out of the edge of the screen

Question

I'm trying to re-write an application I have for Windows in Objective-C for my Mac, and I want to be able to do something like Mac's hot corners. If I move my mouse to the left side of the screen it will make a window visible, if I move it outside of the window location the window will hide again. (window would be pushed up to the left side of screen).

Does anyone know where I can find some demo code (or reference) on how to do this, or at least how to tell where the mouse is at, even if the current application is not on top. (not sure how to word this, too used to Windows world).

Thank you

-Brad

Answer 1

You're going to want to implement an invisible window on the edge of the screen with the window order set so it's always on top. Then, you can listen for mouse-moved events in this window.

To set the window to be invisible and on top, make a window subclass use calls like:

[self setBackgroundColor:[NSColor clearColor]];
[self setExcludedFromWindowsMenu:YES];
[self setCanHide:NO];
[self setLevel:NSScreenSaverWindowLevel];
[self setAlphaValue:0.0f];
[self setOpaque:NO];
[self orderFrontRegardless];

then, to turn on mouse moved events,

[self setAcceptsMouseMovedEvents:YES];

will cause the window to get calls to:

- (void)mouseMoved:(NSEvent *)theEvent
{
   NSLog(@"mouse moved into invisible window.");
}

So hopefully that's enough to give you a start.

-Ken

Answer 2

Here's AutoHidingWindow - a subclass of SlidingWindow which pops up when the mouse hits the edge of the screen. Feedback welcome.

@interface ActivationWindow : NSWindow
{
    AutoHidingWindow *_activationDelegate;
    NSTrackingArea *_trackingArea;
}

- (ActivationWindow*)initWithDelegate:(AutoHidingWindow*)activationDelegate;

@property (assign) AutoHidingWindow *activationDelegate;
@property (retain) NSTrackingArea *trackingArea;

- (void)adjustWindowFrame;
- (void)adjustTrackingArea;

@end

@interface AutoHidingWindow ()

- (void)autoShow;
- (void)autoHide;

@end 


@implementation AutoHidingWindow

- (id)initWithContentRect:(NSRect) contentRect 
                styleMask:(unsigned int) styleMask 
                  backing:(NSBackingStoreType) backingType 
                    defer:(BOOL) flag
{

    if ((self = [super initWithContentRect:contentRect
                                 styleMask:NSBorderlessWindowMask 
                                   backing:backingType
                                     defer:flag])) {
        _activationWindow = [[ActivationWindow alloc] initWithDelegate:self];
    }

    return self;
}

@synthesize activationWindow = _activationWindow;

- (void)dealloc
{
    [_activationWindow release], _activationWindow = nil;

    [super dealloc];
}

- (void)makeKeyAndOrderFront:(id)sender
{
    [super makeKeyAndOrderFront:sender];

}

- (void)autoShow
{
    [self makeKeyAndOrderFront:self];

    [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(autoHide) object:nil];
    [self performSelector:@selector(autoHide) withObject:nil afterDelay:2];
}

- (void)autoHide
{
    NSPoint mouseLocation = [NSEvent mouseLocation];
    NSRect windowFrame = [self frame];

    if (NSPointInRect(mouseLocation, windowFrame)) {
        [self performSelector:@selector(autoHide) withObject:nil afterDelay:2];
    }
    else {
        [self orderOut:self];
    }
}

@end


@implementation ActivationWindow 

- (ActivationWindow*)initWithDelegate:(AutoHidingWindow*)activationDelegate
{   
    if ((self = [super initWithContentRect:[[NSScreen mainScreen] frame]
                                 styleMask:NSBorderlessWindowMask
                                   backing:NSBackingStoreBuffered
                                     defer:NO]) != nil) {
        _activationDelegate = activationDelegate;

        [self setBackgroundColor:[NSColor clearColor]];
        [self setExcludedFromWindowsMenu:YES];
        [self setCanHide:NO];
        [self setHasShadow:NO];
        [self setLevel:NSScreenSaverWindowLevel];
        [self setAlphaValue:0.0];
        [self setIgnoresMouseEvents:YES];
        [self setOpaque:NO];
        [self orderFrontRegardless];

        [self adjustWindowFrame];
        [self.activationDelegate addObserver:self
                                 forKeyPath:@"slidingEdge"
                                    options:0
                                    context:@"slidingEdge"];
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(screenParametersChanged:) 
                                                     name:NSApplicationDidChangeScreenParametersNotification 
                                                   object:nil];     
    }

    return self;
}

@synthesize activationDelegate = _activationDelegate;
@synthesize trackingArea = _trackingArea;

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([@"slidingEdge" isEqual:context]) {
        [self adjustTrackingArea];
    }
    else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}


- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];

    [self.activationDelegate removeObserver:self forKeyPath:@"slidingEdge"];
    _activationDelegate = nil;

    [_trackingArea release], _trackingArea = nil;

    [super dealloc];
}

- (void)screenParametersChanged:(NSNotification *)notification
{
    [self adjustWindowFrame];
}

- (void)adjustWindowFrame
{
    NSScreen *mainScreen = [NSScreen mainScreen];
    CGFloat menuBarHeight = [NSMenuView menuBarHeight];
    NSRect windowFrame = [mainScreen frame];

    windowFrame.size.height -= menuBarHeight;

    [self setFrame:windowFrame display:NO];
    [self adjustTrackingArea];
}

- (void)adjustTrackingArea
{
    NSView *contentView = [self contentView];
    NSRect trackingRect = contentView.bounds;   
    CGRectEdge slidingEdge = self.activationDelegate.slidingEdge;
    CGFloat trackingRectSize = 2.0;

    switch (slidingEdge) {
        case CGRectMaxXEdge:
            trackingRect.origin.x = trackingRect.origin.x + trackingRect.size.width - trackingRectSize;
            trackingRect.size.width = trackingRectSize;
            break;

        case CGRectMaxYEdge:
            trackingRect.origin.y = trackingRect.origin.y + trackingRect.size.height - trackingRectSize;
            trackingRect.size.height = trackingRectSize;
            break;

        case CGRectMinXEdge:
            trackingRect.origin.x = 0;
            trackingRect.size.width = trackingRectSize;
            break;

        case CGRectMinYEdge:
        default:
            trackingRect.origin.y = 0;
            trackingRect.size.height = trackingRectSize;
    }


    NSTrackingAreaOptions options =
    NSTrackingMouseEnteredAndExited | NSTrackingMouseMoved |
    NSTrackingActiveAlways |
    NSTrackingEnabledDuringMouseDrag;

    NSTrackingArea *trackingArea = self.trackingArea;

    if (trackingArea != nil) {
        [contentView removeTrackingArea:trackingArea];
    }

    trackingArea = [[NSTrackingArea alloc] initWithRect:trackingRect
                                                options:options
                                                  owner:self
                                               userInfo:nil];

    [contentView addTrackingArea:trackingArea];

    self.trackingArea = [trackingArea autorelease];
}

- (void)mouseEntered:(NSEvent *)theEvent
{
    [self.activationDelegate autoShow];
}


- (void)mouseMoved:(NSEvent *)theEvent
{
    [self.activationDelegate autoShow];
}

- (void)mouseExited:(NSEvent *)theEvent
{
}

@end