[Octave-bug-tracker] [bug #57385] Starting Pan/Zoom mouse interaction is slow with large figures

[Pantxo Diribarne]

URL:
  <https://savannah.gnu.org/bugs/?57385>

                 Summary: Starting Pan/Zoom mouse interaction is slow with
large figures
                 Project: GNU Octave
            Submitted by: pantxo
            Submitted on: Mon 09 Dec 2019 10:54:10 AM UTC
                Category: Plotting with OpenGL
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Performance
                  Status: Confirmed
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

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Details:

With the Qt toolkit, and especially when the size of the figure window is
large, starting drawing a zoom box or panning an axes is slow. Steps to
reproduce


hf = figure (); clf;
sombrero;
pan on
## Resize the figure window so that it is as large as the screen
## Try to start panning 
## -> It takes 1-2 seconds before mouse movements lead to the desired effect 


This time lag is not observed with the fltk toolkit.
The problem is that when clicking inside a Qt figure we determine what object
was under the mouse. This "full" selection operation takes much time, even
more for large figures, and I think it is unnecessary since I don't expect the
currentobject to be modified while we are using Pan, Zoom, Text or Rotate
mouse modes.

If you agree with the above, I'll provide a patch that fixes the issue by
avoiding the full selection step.




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