BGL: Workaround broken bgl usage caused by GPU refactor

This directly adress the issues caused by rB536c2e0ec916.

Since the state tracking is done at a lower level, using the bgl
functions needs to be safegarded by the state manager.
The current workaround is to bypass `apply_state` when inside a
callback that used a `bgl` function.

Related to T80730.

This fix T81003.

Also this fix the default blend equation for callbacks.
Fixes T80169 T81289.

5 files changed, 46 insertions, 9 deletions

diff --git a/source/blender/gpu/GPU_state.h b/source/blender/gpu/GPU_state.h
index 04cf7bc54ba..471edfb7b8f 100644
--- a/source/blender/gpu/GPU_state.h
+++ b/source/blender/gpu/GPU_state.h
@@ -161,7 +161,10 @@ float GPU_line_width_get(void);
 void GPU_flush(void);
 void GPU_finish(void);
 void GPU_apply_state(void);
-void GPU_force_state(void);
+
+void GPU_bgl_start(void);
+void GPU_bgl_end(void);
+bool GPU_bgl_get(void);
 
 void GPU_memory_barrier(eGPUBarrier barrier);
 
diff --git a/source/blender/gpu/intern/gpu_state.cc b/source/blender/gpu/intern/gpu_state.cc
index 44ad9cc9a84..44cc11155bb 100644
--- a/source/blender/gpu/intern/gpu_state.cc
+++ b/source/blender/gpu/intern/gpu_state.cc
@@ -317,10 +317,39 @@ void GPU_apply_state(void)
   Context::get()->state_manager->apply_state();
 }
 
-/* Will set all the states regardless of the current ones. */
-void GPU_force_state(void)
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name BGL workaround
+ *
+ * bgl makes direct GL calls that makes our state tracking out of date.
+ * This flag make it so that the pyGPU calls will not override the state set by
+ * bgl functions.
+ * \{ */
+
+void GPU_bgl_start(void)
+{
+  StateManager &state_manager = *(Context::get()->state_manager);
+  if (state_manager.use_bgl == false) {
+    /* Expected by many addons (see T80169, T81289).
+     * This will reset the blend function. */
+    GPU_blend(GPU_BLEND_NONE);
+    state_manager.apply_state();
+    state_manager.use_bgl = true;
+  }
+}
+
+void GPU_bgl_end(void)
+{
+  StateManager &state_manager = *(Context::get()->state_manager);
+  state_manager.use_bgl = false;
+  /* Resync state tracking. */
+  state_manager.force_state();
+}
+
+bool GPU_bgl_get(void)
 {
-  Context::get()->state_manager->force_state();
+  return Context::get()->state_manager->use_bgl;
 }
 
 /** \} */
diff --git a/source/blender/gpu/intern/gpu_state_private.hh b/source/blender/gpu/intern/gpu_state_private.hh
index d93556a1058..db1747127d4 100644
--- a/source/blender/gpu/intern/gpu_state_private.hh
+++ b/source/blender/gpu/intern/gpu_state_private.hh
@@ -153,6 +153,7 @@ class StateManager {
  public:
   GPUState state;
   GPUStateMutable mutable_state;
+  bool use_bgl = false;
 
  public:
   StateManager();
diff --git a/source/blender/gpu/opengl/gl_debug.cc b/source/blender/gpu/opengl/gl_debug.cc
index 797f9ff404c..b2b05124463 100644
--- a/source/blender/gpu/opengl/gl_debug.cc
+++ b/source/blender/gpu/opengl/gl_debug.cc
@@ -200,7 +200,7 @@ void check_gl_error(const char *info)
 
 void check_gl_resources(const char *info)
 {
-  if (!(G.debug & G_DEBUG_GPU)) {
+  if (!(G.debug & G_DEBUG_GPU) || GPU_bgl_get()) {
     return;
   }
 
diff --git a/source/blender/gpu/opengl/gl_state.cc b/source/blender/gpu/opengl/gl_state.cc
index cd24fa0e0e4..27c9b501add 100644
--- a/source/blender/gpu/opengl/gl_state.cc
+++ b/source/blender/gpu/opengl/gl_state.cc
@@ -73,13 +73,17 @@ GLStateManager::GLStateManager(void) : StateManager()
 
 void GLStateManager::apply_state(void)
 {
-  this->set_state(this->state);
-  this->set_mutable_state(this->mutable_state);
-  this->texture_bind_apply();
-  this->image_bind_apply();
+  if (!this->use_bgl) {
+    this->set_state(this->state);
+    this->set_mutable_state(this->mutable_state);
+    this->texture_bind_apply();
+    this->image_bind_apply();
+  }
+  /* This is needed by gpu_py_offscreen. */
   active_fb->apply_state();
 };
 
+/* Will set all the states regardless of the current ones. */
 void GLStateManager::force_state(void)
 {
   /* Little exception for clip distances since they need to keep the old count correct. */