Mastodawn

@aeva @landelare Looks interesting! Hm...
printf("%d\n", GLEW_ARB_shader_image_load_store);
0
Looks like not that one either. GL_OES_mapbuffer maybe...? I might be hosed.

Laura Mar 20

@kertinker @aeva You don't printf into these. Use imageStore() if you want to use ARB_shader_image_load_store.

@landelare @aeva I was using printf in a CPU side program, to print the "GLEW_ARB_shader_image_load_store" variable, which I think the OpenGL Extension Wrangler would set to 1, if ARB_shader_image_load_store was supported by my graphics card.

I made sure to call glewInit and have a valid context and all.

@landelare as of version 1.1.0, GLEW signals extension availability with variables containing boolean values, so while the examples KT is posting look like name constants, they're mutable binary values that the initialization code sets up. relevant docs: https://glew.sourceforge.net/basic.html

@kertinker what GL version are you targeting and what platform? for a sanity check, could you post what GLEW_ARB_vertex_program is after init?

GLEW: The OpenGL Extension Wrangler Library

@kertinker @landelare also if you happen to be on linux could you paste the output of glxinfo to a pastebin somewhere and link it here?

@aeva @landelare Oh, sure. I don't have a "glxinfo" command, but visualinfo produces this: https://nopaste.net/l92XzrU5kr which... oddly includes GL_EXT_shader_image_load_store.

I'm clearly doing something wrong. Not sure how I could get a working OpenGL program running, without it saying extensions that are supported, are supported. Maybe you have to set a specific... mode, before they get supported?

@kertinker @landelare if you can, post your GL initialization code

@aeva @landelare https://nopaste.net/aTFTXWDVRU

Other than that just the usual gtk init and creating a GtkGlArea.

@kertinker @landelare what is the GL major and minor version reported by your program?

aeva

@kertinker @landelare I'm not familiar with GtkGlArea, but I spotted this in the docs https://docs.gtk.org/gtk4/method.GLArea.set_required_version.html

You have to call gtk_gl_area_set_required_version before the widget's rendering context is created, but I imagine if you set it to 4.6 (based on your earlier visualinfo paste) then you should be able to see the extensions you are missing. Ideally you'll want to set it to the lowest required version you need, but 4.6 is fine for debugging.

Gtk.GLArea.set_required_version

@kertinker @landelare it occurred to me just now if there's an explicit GL context initialization step needed that is missing entirely, then GLEW might be reporting 0 for most or all extensions depending on the platform you're on

Laura Mar 20

@aeva @kertinker This crap is why I'm using DirectX.

@landelare @kertinker as it happens, Windows is the really weird one for GL

@landelare @kertinker granted they all have quirks, but that's the tradeoff for not being shackled to microslop

@landelare @kertinker not to imply that d3d doesn't also have its own problems, but I don't think it's especially helpful to dunk

KT Mar 21

@landelare Can't blame OpenGL in this case. @aeva pointed out I missed an initialization function, in GTK not OpenGL, so it would have failed even if I used DirectX. Looks like the problem is me not reading the documentation correctly.

aeva Mar 21

@kertinker @landelare these things happen, but we got it working :D

KT Mar 21

@aeva @landelare Now my cludgey pointless geometry shader draws a box *three* times!

aeva Mar 21

@kertinker @landelare woohoo! :D

KT Mar 21

@aeva Huh, it must default to a really low version, which is why so many extensions say they're unsupported. Thanks so much! I'll go try it right away.

...

Yes, all extensions except ARB_vertex_program are now supported!