GPUExtensions: GL backend isolation

This is part of the Vulkan task T68990.

This commits changes a few things:
- Rename extensions to capabilities (but left the file name untouched).
- Cubemap mip render workaround detection is rewritten using gl
  commands to avoid using the GPU API before initialization.
- Put all the capabilities that are only relevant for the GL backend
  inside GLContext as static variables.
- Cleanup the names of the limit variables.
- Separate all GL related workaround search inside the GL module.

1 files changed, 3 insertions, 2 deletions

diff --git a/source/blender/gpu/opengl/gl_uniform_buffer.cc b/source/blender/gpu/opengl/gl_uniform_buffer.cc
index 0e0c64e5c60..82b7341d145 100644
--- a/source/blender/gpu/opengl/gl_uniform_buffer.cc
+++ b/source/blender/gpu/opengl/gl_uniform_buffer.cc
@@ -42,6 +42,7 @@ namespace blender::gpu {
 GLUniformBuf::GLUniformBuf(size_t size, const char *name) : UniformBuf(size, name)
 {
   /* Do not create ubo GL buffer here to allow allocation from any thread. */
+  BLI_assert(size <= GLContext::max_ubo_size);
 }
 
 GLUniformBuf::~GLUniformBuf()
@@ -90,12 +91,12 @@ void GLUniformBuf::update(const void *data)
 
 void GLUniformBuf::bind(int slot)
 {
-  if (slot >= GPU_max_ubo_binds()) {
+  if (slot >= GLContext::max_ubo_binds) {
     fprintf(stderr,
             "Error: Trying to bind \"%s\" ubo to slot %d which is above the reported limit of %d.",
             name_,
             slot,
-            GPU_max_ubo_binds());
+            GLContext::max_ubo_binds);
     return;
   }