KTMar 20

@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.

Show threadaevaMar 20

@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

Show threadaevaMar 20
@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?
Show threadKTMar 20

@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?

Show threadaevaMar 20
@kertinker @landelare if you can, post your GL initialization code
Show threadKTMar 20

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

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

Show threadaevaMar 20
@kertinker @landelare what is the GL major and minor version reported by your program?
Show threadaevaMar 20

@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

Show threadaevaMar 20
@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
Show threadLaura
@aeva @kertinker This crap is why I'm using DirectX.
Mar 20 at 10:20pmWeb
Show threadaevaMar 20
@landelare @kertinker as it happens, Windows is the really weird one for GL
Show threadaevaMar 20
@landelare @kertinker granted they all have quirks, but that's the tradeoff for not being shackled to microslop
Show threadaevaMar 20
@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
Show threadKTMar 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.
Show threadaevaMar 21
@kertinker @landelare these things happen, but we got it working :D
Show threadKTMar 21
@aeva @landelare Now my cludgey pointless geometry shader draws a box *three* times!
Show threadaevaMar 21
@kertinker @landelare woohoo! :D