[RQt-devel] unable to draw glyphs using OpenGL

[Michael Lawrence]

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
>
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