Re: -mouseDragged: invoked when it should not (and without mouseDown)
Re: -mouseDragged: invoked when it should not (and without mouseDown)
- Subject: Re: -mouseDragged: invoked when it should not (and without mouseDown)
- From: Graham Cox <email@hidden>
- Date: Mon, 04 Feb 2013 11:21:33 +1100
On 25/01/2013, at 6:30 AM, Tae Won Ha <email@hidden> wrote:
> Hi, guys. I need some help in event handling. I have a custom view embedded in a scroll view which is embedded in a split view. The window has got a toolbar. When I move the window down by dragging the toolbar, very often the -mouseDragged: of my custom view gets invoked. Curiously enough, it does not seem to happen when I drag the window up. My questions:
>
> - Why?
> - When I NSLog() things, I see that -mouseDown: of the custom view is not invoked. What's going on?
>
> It's the following file
>
> https://github.com/qvacua/qmind/blob/master/Qmind/QMMindmapView.m
>
> from line 706.
>
> I created a dummy project which has got a dummy -mouseDragged: implementation inside a window with a toolbar. In the dummy project it does not happen at all.
>
> I'm clueless. Am I missing something quite simple here? Anybody had similar problems?
Yes, I've seen this happen sometimes - I believe it's a bug.
You can mitigate it by examining the event that you get in the mouseDragged: method - if I recall correctly there is something different about the event that allows you to detect that it's the "wrong" one and ignore it, but I can't pinpoint the exact necessaries in my code, sorry.
Another option is to forget about using mouseDragged: in your custom view and do everything from mouseDown:, including keeping control and fetching and handling events in a loop and do your dragging there. I'm finding that approach often simplifies things a lot and it means you can only fetch the events you need.
--Graham
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