Fix T97235: PBVH draw cache invalidation bug

The PBVH draw cache wasn't being invalidated in
all cases.  It is now invalidated whenever a PBVH
node's draw buffers are freed.

source/blender/blenkernel/BKE_pbvh.h

@@ -584,6 +584,7 @@ void BKE_pbvh_vertex_color_set(PBVH *pbvh, int vertex, const float color[4]);
 void BKE_pbvh_vertex_color_get(const PBVH *pbvh, int vertex, float r_color[4]);
 
 void BKE_pbvh_ensure_node_loops(PBVH *pbvh);
+bool BKE_pbvh_draw_cache_invalid(const PBVH *pbvh);
 
 #ifdef __cplusplus
 }

source/blender/blenkernel/intern/pbvh.c

@@ -656,6 +656,7 @@ PBVH *BKE_pbvh_new(void)
 {
   PBVH *pbvh = MEM_callocN(sizeof(PBVH), "pbvh");
   pbvh->respect_hide = true;
+  pbvh->draw_cache_invalid = true;
   return pbvh;
 }
 
@@ -1368,6 +1369,16 @@ static void pbvh_update_draw_buffer_cb(void *__restrict userdata,
   }
 }
 
+void pbvh_free_draw_buffers(PBVH *pbvh, PBVHNode *node)
+{
+  if (node->draw_buffers) {
+    pbvh->draw_cache_invalid = true;
+
+    GPU_pbvh_buffers_free(node->draw_buffers);
+    node->draw_buffers = NULL;
+  }
+}
+
 static void pbvh_update_draw_buffers(PBVH *pbvh, PBVHNode **nodes, int totnode, int update_flag)
 {
   if ((update_flag & PBVH_RebuildDrawBuffers) || ELEM(pbvh->type, PBVH_GRIDS, PBVH_BMESH)) {
@@ -1375,8 +1386,7 @@ static void pbvh_update_draw_buffers(PBVH *pbvh, PBVHNode **nodes, int totnode,
     for (int n = 0; n < totnode; n++) {
       PBVHNode *node = nodes[n];
       if (node->flag & PBVH_RebuildDrawBuffers) {
-        GPU_pbvh_buffers_free(node->draw_buffers);
-        node->draw_buffers = NULL;
+        pbvh_free_draw_buffers(pbvh, node);
       }
       else if ((node->flag & PBVH_UpdateDrawBuffers) && node->draw_buffers) {
         if (pbvh->type == PBVH_GRIDS) {
@@ -2779,6 +2789,8 @@ void BKE_pbvh_draw_cb(PBVH *pbvh,
   int totnode;
   int update_flag = 0;
 
+  pbvh->draw_cache_invalid = false;
+
   /* Search for nodes that need updates. */
   if (update_only_visible) {
     /* Get visible nodes with draw updates. */
@@ -3217,3 +3229,8 @@ void BKE_pbvh_ensure_node_loops(PBVH *pbvh)
 
   MEM_SAFE_FREE(visit);
 }
+
+bool BKE_pbvh_draw_cache_invalid(const PBVH *pbvh)
+{
+  return pbvh->draw_cache_invalid;
+}

source/blender/blenkernel/intern/pbvh_bmesh.c

@@ -348,8 +348,7 @@ static void pbvh_bmesh_node_split(PBVH *pbvh, const BBC *bbc_array, int node_ind
   n->layer_disp = NULL;
 
   if (n->draw_buffers) {
-    GPU_pbvh_buffers_free(n->draw_buffers);
-    n->draw_buffers = NULL;
+    pbvh_free_draw_buffers(pbvh, n);
   }
   n->flag &= ~PBVH_Leaf;
 

source/blender/blenkernel/intern/pbvh_intern.h

@@ -196,6 +196,9 @@ struct PBVH {
   AttributeDomain color_domain;
 
   bool is_drawing;
+
+  /* Used by DynTopo to invalidate the draw cache. */
+  bool draw_cache_invalid;
 };
 
 /* pbvh.c */
@@ -270,6 +273,7 @@ void pbvh_bmesh_normals_update(PBVHNode **nodes, int totnode);
 
 void pbvh_pixels_free(PBVHNode *node);
 void pbvh_pixels_free_brush_test(PBVHNode *node);
+void pbvh_free_draw_buffers(PBVH *pbvh, PBVHNode *node);
 
 #ifdef __cplusplus
 }

source/blender/draw/intern/draw_cache_impl_mesh.c

@@ -883,6 +883,11 @@ static bool mesh_batch_cache_valid(Object *object, Mesh *me)
     if (cache->pbvh_is_drawing != BKE_pbvh_is_drawing(object->sculpt->pbvh)) {
       return false;
     }
+
+    if (BKE_pbvh_is_drawing(object->sculpt->pbvh) &&
+        BKE_pbvh_draw_cache_invalid(object->sculpt->pbvh)) {
+      return false;
+    }
   }
 
   if (cache->is_editmode != (me->edit_mesh != NULL)) {