[RQt-devel] unable to draw glyphs using OpenGL

[Tomas Sieger]

Thanks for clarifying this.
I've tried to find a newer OpenGL driver for my (rather old) linux
system, but with no luck.
I will stick to hacking the stack in some way.
thanks again
 Tomas

On Fri, Oct 26, 2012 at 3:20 PM, Michael Lawrence
<lawrence.michael at gene.com> wrote:
> The only difference then is that the multi-color path sets the texture mode
> to GL_MODULATE (and passes an array of colors), while the other uses the
> GL_REPLACE mode.  Point sprites are an obscure feature in OpenGL, so it's
> not surprising that a linux driver would fail in certain cases. Not sure how
> we can work around this. Have you tried updating your driver?
>
> Michael
>
>
> On Thu, Oct 25, 2012 at 12:58 PM, Tomas Sieger <tomas.sieger at seznam.cz>
> wrote:
>>
>> On Thu, Oct 25, 2012 at 12:36 AM, Michael Lawrence
>> <lawrence.michael at gene.com> wrote:
>> >
>> >
>> > On Wed, Oct 24, 2012 at 1:18 PM, Tomas Sieger <tomas.sieger at seznam.cz>
>> > wrote:
>> >>
>> >> I've tracked the problem down a little bit deeper.
>> >>
>> >> I wanted to add some "use opengl" option to cranvas, but realized that
>> >> some cranvas plots using glyphs *do* work even if using opengl. I
>> >> found out that glyphs that specify stroke color as a vector of length
>> >> at least two (!) work:
>> >>      qdrawGlyph(painter,
>> >> qglyphCircle(r=5),5,5,stroke=rep('#FF0000FF',2)) # works
>> >> while those that specify stroke color as a single value do not:
>> >>      qdrawGlyph(painter,
>> >> qglyphCircle(r=5),5,5,stroke=rep('#FF0000FF',1)) # does not work
>> >> as well as those without an explicit stroke color:
>> >>      qdrawGlyph(painter, qglyphCircle(r=5),5,5) # does not work
>> >>
>> >> The length of the stroke color argument really makes a difference. If
>> >> it is a vector of length >=2, stroke colors get passed to painters
>> >> explicitly. If it is a single value, it sets the default color in the
>> >> painter. In the first case, OpenGLPainter draws glyphs explicitly (and
>> >> the glyph gets rendered correctly). In the latter case, the
>> >> OpenGLPainter delegates the call to QtBasePainter::drawGlyphs (and the
>> >> glyph gets not rendered).
>> >>
>> >> It makes me feel this might be a SW issue, not necessarily a HW one.
>> >>
>> >
>> > Thanks a lot for looking into this in depth. Yes, there are two code
>> > paths
>> > that use the hardware differently. The multi-color case is actually the
>> > more
>> > complicated one, using modulation to color the same texture many times,
>> > so
>> > it's surprising that it works, while the simpler case is broken. One
>> > possible test is to use white, so that the glyph image is exactly the
>> > same
>> > in both cases. That would eliminate one difference at least.
>>
>> The problem persists even for white glyphs.
>> (I'm setting red background using
>> scene$setBackgroundBrush(Qt$QBrush(Qt$QColor('red'))) and drawing
>> white glyphs. "qdrawGlyph(painter,
>> qglyphCircle(r=5),5:7,5:7,stroke=rep('#FFFFFFFF',1))" get not
>> rendered.)
>>
>> Tomas
>
>