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, 13 insertions, 0 deletions

diff --git a/source/blender/gpu/opengl/gl_context.hh b/source/blender/gpu/opengl/gl_context.hh
index 9e6359fabad..e2ae8bf24b2 100644
--- a/source/blender/gpu/opengl/gl_context.hh
+++ b/source/blender/gpu/opengl/gl_context.hh
@@ -55,6 +55,19 @@ class GLSharedOrphanLists {
 
 class GLContext : public GPUContext {
  public:
+  /** Capabilities. */
+  static GLint max_texture_3d_size;
+  static GLint max_cubemap_size;
+  static GLint max_ubo_size;
+  static GLint max_ubo_binds;
+  /** Extensions. */
+  static bool base_instance_support;
+  static bool texture_cube_map_array_support;
+  /** Workarounds. */
+  static bool texture_copy_workaround;
+  static bool unused_fb_slot_workaround;
+  static float derivative_signs[2];
+
   /** Used for debugging purpose. Bitflags of all bound slots. */
   uint16_t bound_ubo_slots;