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

Question

I'm using a textured window that has a tab bar along the top of it, just below the title bar.

I've used -setContentBorderThickness:forEdge: on the window to make the gradient look right, and to make sure sheets slide out from the right position.

What's not working however, is dragging the window around. It works if I click and drag the area that's actually the title bar, but since the title bar gradient spills into a (potentially/often empty) tab bar, it's really easy to click too low and it feels really frustrating when you try to drag and realise the window is not moving.

I notice NSToolbar, while occupying roughly the same amount of space below the title bar, allows the window to be dragged around when the cursor is over it. How does one implement this?

Thanks.

Solution 1

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.

Solution 2

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.

Solution 3

It works for me after TWO steps:

1. Subclass NSView, override the mouseDownCanMoveWindow to return YES.
2. Subclass NSWindow, override the isMovableByWindowBackground to return YES.

Solution 4

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.

Solution 5

Have you tried overriding the NSView method mouseDownCanMoveWindow to return YES?

View more solutions

Comments

[d11wtq]

I hadn't, since I didn't know such a method existed, thanks. However, it doesn't appear to have worked. The tab bar is a subview of a larger (almost entire window) view, if it makes a difference.

[Richard]

My next thought was to override mouseDown: (NSControl method) to pass the mouse event to [self window], and ensure that the window isMovableByWindowBackground, but that still doesn't work for me. Sorry.

[d11wtq]

No dramas. You were on the right track. Thanks for investigating! :)

[d11wtq]

As suspected, invalidating the "initialLocation" variable in the mouseUp: event (just by setting the y position to a negative number), then adding a guard clause to mouseDragged: fixes the bug.

[twe4ked]

In Swift: window.movableByWindowBackground = true.

[ArtOfWarfare]

@Odin - I'd imagine window.movableByWindowBackground = YES; works in Obj-C, but I think I went the method overriding route because I was specifically looking to make a subclass of NSWindow that exhibited this trait always.

[twe4ked]

You're probably right, I just pasted what I ended up with for anyone else that visits this page using Swift. Thanks for the answer :)

[Keith Smiley]

This is often useful but it seems like it's only called a few times when the view is loaded and then never again. Because of this you can't conditionally return based on some logic.

[Sam Soffes]

You can skip step two if you make your window "textured". (There's a checkbox in IB.)

[VinceFior]

You don't need to subclass NSWindow, since you can call [self.view.window setMovableByWindowBackground:YES] in the view controller. It appears NSWindow's isMovableByWindowBackground is mutable while NSView's mouseDownCanMoveWindow is read-only.

[Clifton Labrum]

Swift 3: window.isMovableByWindowBackground = true

[Lax]

This method works for my project. except that any mouse events in movableRect will perform moving, even if there are subviews above the view.

[Dimitri Bouniol]

@Lax You may want to check that your view that appears above the dragging view is hit testing correctly - are both of them getting mouse down events?

[NickSpag]

Are you sure you need the event code? Simply subclassing NSTableView and overriding 'mouseDownCanMoveWindow' works for me, even with selection enabled.

[Paulo Mattos]

Hey @NickSpag, as far as I remember, doing as you suggested would mess up the table selection behaviour (when trying to drag the window by clicking over a given selectable table row).

[ervinbosenbacher]

Thanks for the help, solved my problem but I needed it in Swift 5. Here is what I came up with