[vtkusers] VTK Cocoa mouse problem

[Drew McCormack]

On Sunday, February 9, 2003, at 07:20  am, Chris Scharver wrote:

> Hello,
>
> I just noticed that mouse events aren't occurring in the correct place 
> on Cocoa windows.  The easiest way to see this is to move a 
> vtkRenderWindow to the right side of the screen. Clicking the mouse on 
> the left side of the window generates a mouse event  with a value 
> which makes the interactor spin to the right. The behavior is 
> obviously incorrect.
>
> Adding some output to the source code, I found that the initial mouse 
> down is properly read in the relative position in the window. However, 
> beyond that (the internal do..while loop within [vtlCocoaGLView 
> mouseDown]) the positions are read in absolute screen coordinates. 
> This conversion should be handled by calling convertPoint:fromView:, 
> which the code does. The window id of the event is 0, so somehow the 
> screen is sending the event rather than the vtkCocoaGLView.
>
> I've copied the code into a stand-alone sample and it works fine, so 
> there's something screwy somewhere in the VTK code. I've tried to copy 
> application initialization and basic capabilities into a nib-less 
> example, and everything runs fine there. I'm not sure what could be 
> causing the problem since the same mouseDown code copied into another 
> snippet runs fine. Any vtkCocoa developers know what may be happening?
>
> I've been trying to track through the code to create a fix, but I 
> haven't had any luck. It's easy to see what's happening, but not why.
>
> Chris

Hello Chris,

I came across the same problem several months ago, but haven't had a 
shot at tracking it down. I just implemented a hack, by creating a 
category, copying the mouse event code, and adding the following line 
to each mouse-event method:

NSPoint mouseLoc = [self convertPoint:[[self window] 
convertScreenToBase:[theEvent locationInWindow]] fromView:nil];

I think you probably have done the same, right? Just like you, I do not 
understand why this would be necessary. As you say, events are being 
interpreted relative to the screen instead of the view. Why, I don't 
know.

If you find the problem, I would love to hear it.

Regards,
Drew

======================================
  Dr. Drew McCormack (Kmr. R153)
  Afd. Theoretische Chemie
  Faculteit Exacte Wetenschappen
  Vrije Universiteit Amsterdam
  De Boelelaan 1083
  1081 HV Amsterdam
  The Netherlands

  Email		cormack at chem.vu.nl
  Telephone  	+31 20 44 47623
  Mobile		+31 6 483 21307
  Fax   		+31 20 44 47629