Detect multi-touch gestures or drags with mouse in Mac OS X App

Question

How can one detect when a drag is happening or a swipe on the track-pad or magic-mouse is occurring in a Mac OSX app being made in Xcode.

By drag I mean the user has clicked on the left or right edge of the window and the mouse is held down and now moving away from that side-of-the-window horizontally.

I am trying to run code on left drag or right swipe (on magic-mouse or track-pad) and another set of code on right drag or left swipe (on magic-mouse or track-pad).

Here are some definitions of the gestures that I am talking about:

A left drag is when the right side of the window is clicked and held on and the cursor moves to the left.

A right drag is when the left side of the window is clicked and held on and the cursor moves to the right.

A top drag is when the top on the window, under the frame / where the traffic-lights are, is being dragged down.

A top swipe is a swipe that starts on the top of the track-pad or magic-mouse and goes down.

In pseudo-code what I am trying to achieve is like:

if( right-drag || left-swipe ){
    /*run code*/
}
else if( left-drag || right-swipe ){
    /* run different code */
}
else if( top-drag || top-swipe ){
    /* run other code */
}
else{
   /* do nothing */
}

Answer 1

Cocoa Event Handling Guide is the place to start

Especially the part on Handling Gesture Events.

They tell you how to deal with:

• Pinching movements (in or out) are gestures meaning zoom out or zoom in (also called magnification).
• Two fingers moving in opposite semicircles is a gesture meaning rotate.
• Three fingers brushing across the trackpad surface in a common direction is a swipe gesture.
• Two fingers moving vertically or horizontally is a scroll gesture.

and more...

In particular the method:

- (void)swipeWithEvent:(NSEvent *)event

from NSResponder is your best bet. T*his event informs the receiver that the user has begun a swipe gesture. The event will be sent to the view under the touch in the key window.*

Taken from the same document, below is an example on how to Handle s swipe gesture:

- (void)swipeWithEvent:(NSEvent *)event {
    CGFloat x = [event deltaX];
    CGFloat y = [event deltaY];
    if (x != 0) {
        swipeColorValue = (x > 0)  ? SwipeLeftGreen : SwipeRightBlue;
    }
    if (y != 0) {
        swipeColorValue = (y > 0)  ? SwipeUpRed : SwipeDownYellow;
    }
    NSString *direction;
    switch (swipeColorValue) {
        case SwipeLeftGreen:
            direction = @"left";
            break;
        case SwipeRightBlue:
            direction = @"right";
            break;
        case SwipeUpRed:
            direction = @"up";
            break;
        case SwipeDownYellow:
        default:
            direction = @"down";
            break;
    }
    [resultsField setStringValue:[NSString stringWithFormat:@"Swipe %@", direction]];
    [self setNeedsDisplay:YES];
}