GL: Add error checking function

This is to ease the debugging process on Apple GL implementation.

source/blender/gpu/opengl/gl_batch.cc

@@ -327,6 +327,8 @@ void GLBatch::bind(int i_first)
 
 void GLBatch::draw(int v_first, int v_count, int i_first, int i_count)
 {
+  GL_CHECK_ERROR("Batch Pre drawing");
+
   this->bind(i_first);
 
   BLI_assert(v_count > 0 && i_count > 0);
@@ -353,6 +355,7 @@ void GLBatch::draw(int v_first, int v_count, int i_first, int i_count)
       glDrawElementsInstancedBaseVertex(
           gl_type, v_count, index_type, v_first_ofs, i_count, base_index);
     }
+    GL_CHECK_ERROR("Batch Post-drawing Indexed");
   }
   else {
 #ifdef __APPLE__
@@ -367,6 +370,7 @@ void GLBatch::draw(int v_first, int v_count, int i_first, int i_count)
 #ifdef __APPLE__
     glEnable(GL_PRIMITIVE_RESTART);
 #endif
+    GL_CHECK_ERROR("Batch Post-drawing Non-indexed");
   }
 }
 

source/blender/gpu/opengl/gl_context.cc

@@ -22,6 +22,7 @@
  */
 
 #include "BLI_assert.h"
+#include "BLI_system.h"
 #include "BLI_utildefines.h"
 
 #include "GPU_framebuffer.h"
@@ -238,3 +239,37 @@ void GLContext::framebuffer_unregister(struct GPUFrameBuffer *fb)
 }
 
 /** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Error Checking
+ *
+ * This is only useful for implementation that does not support the KHR_debug extension.
+ * \{ */
+
+void GLContext::check_error(const char *info)
+{
+  GLenum error = glGetError();
+
+#define ERROR_CASE(err) \
+  case err: \
+    fprintf(stderr, "GL error: %s : %s\n", #err, info); \
+    BLI_system_backtrace(stderr); \
+    break;
+
+  switch (error) {
+    ERROR_CASE(GL_INVALID_ENUM)
+    ERROR_CASE(GL_INVALID_VALUE)
+    ERROR_CASE(GL_INVALID_OPERATION)
+    ERROR_CASE(GL_INVALID_FRAMEBUFFER_OPERATION)
+    ERROR_CASE(GL_OUT_OF_MEMORY)
+    ERROR_CASE(GL_STACK_UNDERFLOW)
+    ERROR_CASE(GL_STACK_OVERFLOW)
+    case GL_NO_ERROR:
+      break;
+    default:
+      fprintf(stderr, "Unknown GL error: %x : %s", error, info);
+      break;
+  }
+}
+
+/** \} */

source/blender/gpu/opengl/gl_context.hh

@@ -34,6 +34,15 @@
 
 #include <mutex>
 
+#ifdef DEBUG
+/* Enabled on MacOS by default since there is no support for debug callbacks. */
+#  ifdef __APPLE__
+#    define GL_CHECK_ERROR(info) GLContext::check_error(info)
+#  else
+#    define GL_CHECK_ERROR(info)
+#  endif
+#endif
+
 namespace blender {
 namespace gpu {
 
@@ -78,6 +87,8 @@ class GLContext : public GPUContext {
   GLContext(void *ghost_window, GLSharedOrphanLists &shared_orphan_list);
   ~GLContext();
 
+  static void check_error(const char *info);
+
   void activate(void) override;
   void deactivate(void) override;