Fix crash when rendering Eevee/Workbench while VR session runs

We have to set the main draw-manager mutex.

Also some related cleanup.

3 files changed, 42 insertions, 27 deletions

diff --git a/source/blender/draw/DRW_engine.h b/source/blender/draw/DRW_engine.h
index 0aa38de27e5..7ecf9df275d 100644
--- a/source/blender/draw/DRW_engine.h
+++ b/source/blender/draw/DRW_engine.h
@@ -140,10 +140,13 @@ void DRW_opengl_context_destroy(void);
 void DRW_opengl_context_enable(void);
 void DRW_opengl_context_disable(void);
 
-/* Not nice to expose these. Code to render offscreen viewports can save expensive context switches
- * by using this directly however. */
+#ifdef WITH_XR_OPENXR
+/* XXX see comment on DRW_xr_opengl_context_get() */
 void *DRW_xr_opengl_context_get(void);
 void *DRW_xr_gpu_context_get(void);
+void DRW_xr_drawing_begin(void);
+void DRW_xr_drawing_end(void);
+#endif
 
 /* For garbage collection */
 void DRW_cache_free_old_batches(struct Main *bmain);
diff --git a/source/blender/draw/intern/draw_manager.c b/source/blender/draw/intern/draw_manager.c
index ce6d391c481..618922d8544 100644
--- a/source/blender/draw/intern/draw_manager.c
+++ b/source/blender/draw/intern/draw_manager.c
@@ -2795,30 +2795,6 @@ void DRW_opengl_context_disable(void)
   DRW_opengl_context_disable_ex(true);
 }
 
-#ifdef WITH_XR_OPENXR
-
-/* XXX
- * There should really be no such getter, but for VR we currently can't easily avoid it. OpenXR
- * needs some low level info for the OpenGL context that will be used for submitting the
- * final framebuffer. VR could in theory create its own context, but that would mean we have to
- * switch to it just to submit the final frame, which has notable performance impact.
- *
- * We could "inject" a context through DRW_opengl_render_context_enable(), but that would have to
- * work from the main thread, which is tricky to get working too. The preferable solution would be
- * using a separate thread for VR drawing where a single context can stay active. */
-void *DRW_xr_opengl_context_get(void)
-{
-  return DST.gl_context;
-}
-
-/* XXX See comment on DRW_xr_opengl_context_get(). */
-void *DRW_xr_gpu_context_get(void)
-{
-  return DST.gpu_context;
-}
-
-#endif
-
 void DRW_opengl_render_context_enable(void *re_gl_context)
 {
   /* If thread is main you should use DRW_opengl_context_enable(). */
@@ -2854,4 +2830,39 @@ void DRW_gpu_render_context_disable(void *UNUSED(re_gpu_context))
   GPU_context_active_set(NULL);
 }
 
+#ifdef WITH_XR_OPENXR
+
+/* XXX
+ * There should really be no such getter, but for VR we currently can't easily avoid it. OpenXR
+ * needs some low level info for the OpenGL context that will be used for submitting the
+ * final framebuffer. VR could in theory create its own context, but that would mean we have to
+ * switch to it just to submit the final frame, which has notable performance impact.
+ *
+ * We could "inject" a context through DRW_opengl_render_context_enable(), but that would have to
+ * work from the main thread, which is tricky to get working too. The preferable solution would be
+ * using a separate thread for VR drawing where a single context can stay active. */
+void *DRW_xr_opengl_context_get(void)
+{
+  return DST.gl_context;
+}
+
+/* XXX See comment on DRW_xr_opengl_context_get(). */
+void *DRW_xr_gpu_context_get(void)
+{
+  return DST.gpu_context;
+}
+
+/* XXX See comment on DRW_xr_opengl_context_get(). */
+void DRW_xr_drawing_begin(void)
+{
+  BLI_ticket_mutex_lock(DST.gl_context_mutex);
+}
+
+/* XXX See comment on DRW_xr_opengl_context_get(). */
+void DRW_xr_drawing_end(void)
+{
+  BLI_ticket_mutex_unlock(DST.gl_context_mutex);
+}
+
+#endif
 /** \} */
diff --git a/source/blender/windowmanager/intern/wm_xr.c b/source/blender/windowmanager/intern/wm_xr.c
index 19d05826341..bd9fd7cdc3e 100644
--- a/source/blender/windowmanager/intern/wm_xr.c
+++ b/source/blender/windowmanager/intern/wm_xr.c
@@ -516,9 +516,10 @@ static void wm_xr_session_surface_draw(bContext *C)
   if (!GHOST_XrSessionIsRunning(wm->xr.runtime->context)) {
     return;
   }
+  DRW_xr_drawing_begin();
   GHOST_XrSessionDrawViews(wm->xr.runtime->context, C);
-
   GPU_offscreen_unbind(surface_data->offscreen, false);
+  DRW_xr_drawing_end();
 }
 
 static void wm_xr_session_free_data(wmSurface *surface)