Allow click and dragging a view to drag the window itself?

As of macOS 10.11, the simplest way to do this is to utilize the new -[NSWindow performWindowDragWithEvent:] method:

@interface MyView () {
    BOOL movingWindow;
}
@end

@implementation MyView

...

- (BOOL)mouseDownCanMoveWindow
{
    return NO;
}

- (void)mouseDown:(NSEvent *)event
{
    movingWindow = NO;

    CGPoint point = [self convertPoint:event.locationInWindow
                              fromView:nil];

    // The area in your view where you want the window to move:
    CGRect movableRect = CGRectMake(0, 0, 100, 100);

    if (self.window.movableByWindowBackground &&
        CGRectContainsPoint(movableRect, point)) {

        [self.window performWindowDragWithEvent:event];
        movingWindow = YES;
        return;
    }

    // Handle the -mouseDown: as usual
}

- (void)mouseDragged:(NSEvent *)event
{
    if (movingWindow) return;

    // Handle the -mouseDragged: as usual
}

@end

Here, -performWindowDragWithEvent: will handle the correct behavior of not overlapping the menu bar, and will also snap to edges on macOS 10.12 and later. Be sure to include a BOOL movingWindow instance variable with your view's private interface so you can avoid -mouseDragged: events once you determined you don't want to process them.

Here, we are also checking that -[NSWindow movableByWindowBackground] is set to YES so that this view can be used in non-movable-by-window-background windows, but that is optional.

I found this here:

-(void)mouseDown:(NSEvent *)theEvent {    
    NSRect  windowFrame = [[self window] frame];

    initialLocation = [NSEvent mouseLocation];

    initialLocation.x -= windowFrame.origin.x;
    initialLocation.y -= windowFrame.origin.y;
}

- (void)mouseDragged:(NSEvent *)theEvent {
    NSPoint currentLocation;
    NSPoint newOrigin;

    NSRect  screenFrame = [[NSScreen mainScreen] frame];
    NSRect  windowFrame = [self frame];

    currentLocation = [NSEvent mouseLocation];
    newOrigin.x = currentLocation.x - initialLocation.x;
    newOrigin.y = currentLocation.y - initialLocation.y;

    // Don't let window get dragged up under the menu bar
    if( (newOrigin.y+windowFrame.size.height) > (screenFrame.origin.y+screenFrame.size.height) ){
        newOrigin.y=screenFrame.origin.y + (screenFrame.size.height-windowFrame.size.height);
    }

    //go ahead and move the window to the new location
    [[self window] setFrameOrigin:newOrigin];
}

It works fine, though I'm not 100% sure I'm doing it correctly. There's one bug I've found so far, and that's if the drag begins inside a subview (a tab itself) and then enters the superview (the tab bar). The window jumps around. Some -hitTest: magic, or possibly even just invalidating initialLocation on mouseUp should probably fix that.

I tried the mouseDownCanMoveWindow solution (https://stackoverflow.com/a/4564146/901641) but it didn't work for me. I got rid of that method and instead added this to my window subclass:

- (BOOL)isMovableByWindowBackground {
    return YES;
}

which worked like a charm.