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.

1 files changed, 32 insertions, 3 deletions

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+ * bgl makes direct GL calls that makes our state tracking out of date.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;
 }
 
 /** \} */