Re: fltk / gl rendering problem

[Jon TURNEY <jon dot turney at dronecode dot org dot uk>]

On 17/06/2013 07:48, marco atzeri wrote:
> Il 6/16/2013 4:51 PM, marco atzeri ha scritto:
>> testing a octave/fltk graphics issue, I noticed that also the
>> demo of fltk with GL interface has a similar issue.

Thanks for reporting this and thanks for providing the test binaries.

>> On http://matzeri.altervista.org/works/fltk_gl/
>> I uploaded the before and after apperance of "gl_overlay" demo.
>>
>> It is enough to move the window to loose the geometrical
>> image while the bars are correctly re-drawn.
>>
>> Running Xwin with -wgl does not show such defect, but it is
>> terribly slow. So I assume it is not a fltk defect but of
>> GL or XServer.

I guess this should read "with -nowgl", in which case, this is a limitation of
the current implementation of -wgl mode, which will require lots of work to fix.

I wrote a bit about these limitations at [1]

[1] http://www.cygwin.com/ml/cygwin-xfree/2012-10/msg00009.html

> further experiment showed that the defect is present when the integrate
> windows manager is used. With external window manager (fvwm, openbox,.. ) that
> defect does not apper.
> 
> With external window manager another defect appears, the upper
> bar effect is not shown at all; while it is present on the integrated
> window manager.

When I tested this, it looks like the solid area controlled by the "sides"
slider didn't get rendered into a separate layer when using software rendering
(either -nowgl or X server in windowed mode), so this is possibly some bug or
limitation in the software renderer, or possibly in a bug in the demo not
recognizing the lack of capabilities of the software renderer.

-- 
Jon TURNEY
Volunteer Cygwin/X X Server maintainer

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