[Octave-bug-tracker] [bug #50298] Zoomming causes lines to be "dashed" until next redraw

[Pantxo Diribarne]

URL:
  <http://savannah.gnu.org/bugs/?50298>

                 Summary: Zoomming causes lines to be "dashed" until next
redraw
                 Project: GNU Octave
            Submitted by: pantxo
            Submitted on: Mon 13 Feb 2017 09:59:04 PM UTC
                Category: Plotting with OpenGL
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Regression
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.2.0
        Operating System: GNU/Linux

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Details:

On my system (Linux mint 17.3, integrated Intel graphics controller, Mesa DRI
driver), trying to zoom in a simple plot as "plot (1:10)", leads to some lines
not being drawn (horizontal or vertical), or "dashed" (oblique lines). With qt
toolkit, simply changing the focus to another window is enough to have the
figure redrawn correctly while with fltk one needs to use "drawnow".
This used to work well on the same machine in Octave 4.0.

Setting "linewidth" to some value greater than one, fixes the issue. So I
tried to set the figure "graphicssmoothing" to "off" prior to plotting and it
"fixes" the issue but then I get a bunch of warnings when drawing the
zoombox:


warning: opengl_renderer: Error 'invalid operation' (1282) occurred in
init_gl_context
...


or sometimes


warning: opengl_renderer: Error 'stack overflow' (1283) occurred in
init_gl_context
...


and the zoom box is drawn opaque blue instead of transparent.




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