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AMD Radeon R9 – Massive text flickering again

Graphics issues like: bad framerates, weird colors, OpenGL errors etc. Bad graphics ar usually the result of bad graphics cards or drivers.
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Re: AMD Radeon R9 – Massive text flickering again

Postby bugman » Fri Dec 18, 2015 2:34 pm

I had the flickering problem on my Linux system with the AMD driver (I can't remember if it was open source or Catalyst). Anyway, Mageia 5 was released with new graphics drivers and I haven't seen the problem since (with the open source driver).

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Re: AMD Radeon R9 – Massive text flickering again

Postby Babbo » Fri Dec 18, 2015 6:57 pm

Teenage nervous breakdown: my oh-so-calm minimal configuration from yesterday is strongly flickering today.

This all is completely frustrating.
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Re: AMD Radeon R9 – Massive text flickering again

Postby Richard » Fri Dec 18, 2015 7:02 pm

Hooray wrote in Fri Dec 18, 2015 5:46 am:So, "minimal startup profile" + standard renderer (no ALS/Rembrandt, all shaders/effects disabled) = no flickering at all when using the legacy PUI style ?
If so, we can check the git logs (or do a bisect) to see if the commits related to supporting PUI styling, look suspicious.

2.12.1 with ALS has the problem. with ALS has the problem.
2.0.0 has the problem with the basic renderer
0.9 has a similar problem with disabled text in menus when looking at the sky.

0.9 works fine with txf; I didn't test this with the interim versions.

I've tried swapping out the fg fonts for those in PUI and it still does the same.

I'm still not totally convinced that I'm right about this. If I can manage to build PUI I'll try to debug it. It might be something related to GLUT.
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Re: AMD Radeon R9 – Massive text flickering again

Postby Richard » Fri Dec 18, 2015 9:35 pm

Been investigating how PUI does this; and I'm wondering if it's related to the way the bitmap font is rendered in fntBitmap ... ap.cxx#L85

which is called by ... t.cxx#L110

What struck me as odd was the glDisable ( GL_TEXTURE_2D ) ; at the end of drawString().

I'm not sure if this is applicable

You should disable GL_TEXTURE_2D before you draw the bitmap font.

Internally, glutBitmapCharacter() uses glBitmap. This function maps the bitmap to a rectangle to the screen and generates a fragment for every framebuffer pixel in that rectangle where the bitmap is 1. Those fragments get the associated data from the values associated with the current raster position.

The generated fragments are processed like every other fragment (i.e. the ones generated by drawing primitives like lines or triangles). So stuff like texturing, lighting, fog, blending and so on will also affect everything drawn by glBitmap. Due to the fact that all fragments generated by a single bitmap get the same associated data, they all will get the same texture coordinate. Since you left texturing on, the GL textures all of these fragments with the very same sample from the texture, so that they all appear in the same color.
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