Fix T77830: Crash in VR session when opening material preview

Draw-manager mutex has to be set before activating OpenGL/GPU context.
Otherwise, parallel jobs (like preview rendering) may try to activate
the context from another thread.

Also: Use WM wrappers for activating/releasing OpenGL context, which
have an additional assert check.

Suggest to backport this for 2.83.1.

3 files changed, 21 insertions, 4 deletions

diff --git a/source/blender/windowmanager/intern/wm_surface.c b/source/blender/windowmanager/intern/wm_surface.c
index e8850693d69..12e55790259 100644
--- a/source/blender/windowmanager/intern/wm_surface.c
+++ b/source/blender/windowmanager/intern/wm_surface.c
@@ -53,10 +53,17 @@ void wm_surfaces_iter(bContext *C, void (*cb)(bContext *C, wmSurface *))
 void wm_surface_clear_drawable(void)
 {
   if (g_drawable) {
+    WM_opengl_context_release(g_drawable->ghost_ctx);
+    GPU_context_active_set(NULL);
+
     BLF_batch_reset();
     gpu_batch_presets_reset();
     immDeactivate();
 
+    if (g_drawable->deactivate) {
+      g_drawable->deactivate();
+    }
+
     g_drawable = NULL;
   }
 }
@@ -67,7 +74,10 @@ void wm_surface_set_drawable(wmSurface *surface, bool activate)
 
   g_drawable = surface;
   if (activate) {
-    GHOST_ActivateOpenGLContext(surface->ghost_ctx);
+    if (surface->activate) {
+      surface->activate();
+    }
+    WM_opengl_context_activate(surface->ghost_ctx);
   }
 
   GPU_context_active_set(surface->gpu_ctx);
@@ -109,6 +119,8 @@ void wm_surface_remove(wmSurface *surface)
 
 void wm_surfaces_free(void)
 {
+  wm_surface_clear_drawable();
+
   for (wmSurface *surf = global_surface_list.first, *surf_next; surf; surf = surf_next) {
     surf_next = surf->next;
     wm_surface_remove(surf);
diff --git a/source/blender/windowmanager/wm_surface.h b/source/blender/windowmanager/wm_surface.h
index e1b00ae1ade..bc1cc825e4b 100644
--- a/source/blender/windowmanager/wm_surface.h
+++ b/source/blender/windowmanager/wm_surface.h
@@ -38,6 +38,11 @@ typedef struct wmSurface {
   void (*draw)(struct bContext *);
   /** Free customdata, not the surface itself (done by wm_surface API) */
   void (*free_data)(struct wmSurface *);
+
+  /** Called  when surface is activated for drawing (made drawable). */
+  void (*activate)(void);
+  /** Called  when surface is deactivated for drawing (current drawable cleared). */
+  void (*deactivate)(void);
 } wmSurface;
 
 /* Create/Free */
diff --git a/source/blender/windowmanager/xr/intern/wm_xr_session.c b/source/blender/windowmanager/xr/intern/wm_xr_session.c
index e9ff38c5a92..2f72b2b25a5 100644
--- a/source/blender/windowmanager/xr/intern/wm_xr_session.c
+++ b/source/blender/windowmanager/xr/intern/wm_xr_session.c
@@ -315,12 +315,9 @@ static void wm_xr_session_surface_draw(bContext *C)
   wm_xr_session_draw_data_populate(
       &wm->xr, CTX_data_scene(C), CTX_data_ensure_evaluated_depsgraph(C), &draw_data);
 
-  DRW_xr_drawing_begin();
-
   GHOST_XrSessionDrawViews(wm->xr.runtime->context, &draw_data);
 
   GPU_offscreen_unbind(surface_data->offscreen, false);
-  DRW_xr_drawing_end();
 }
 
 bool wm_xr_session_surface_offscreen_ensure(wmXrSurfaceData *surface_data,
@@ -391,6 +388,9 @@ static wmSurface *wm_xr_session_surface_create(void)
 
   surface->draw = wm_xr_session_surface_draw;
   surface->free_data = wm_xr_session_surface_free_data;
+  surface->activate = DRW_xr_drawing_begin;
+  surface->deactivate = DRW_xr_drawing_end;
+
   surface->ghost_ctx = DRW_xr_opengl_context_get();
   surface->gpu_ctx = DRW_xr_gpu_context_get();