Fix T62941 Subdivision Modifier Showing all face dots

Previously in 2.79 we were using a specialized drawing using derivedMesh.

Now the subsurf modifier tag each center vertex as facedot and let the
DRWManager pick it up.

Some modifiers (deforming ones) do not clear the tag so we can use this
technique even if there is deforming modifiers after subsurf modifiers.

1 files changed, 32 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/modifier.c b/source/blender/blenkernel/intern/modifier.c
index 2254207e545..d547449aa60 100644
--- a/source/blender/blenkernel/intern/modifier.c
+++ b/source/blender/blenkernel/intern/modifier.c
@@ -778,6 +778,38 @@ bool modifiers_usesArmature(Object *ob, bArmature *arm)
   return false;
 }
 
+bool modifiers_usesSubsurfFacedots(struct Scene *scene, Object *ob)
+{
+  /* Search (backward) in the modifier stack to find if we have a subsurf modifier (enabled) before
+   * the last modifier displayed on cage (or if the subsurf is the last). */
+  VirtualModifierData virtualModifierData;
+  ModifierData *md = modifiers_getVirtualModifierList(ob, &virtualModifierData);
+  int cage_index = modifiers_getCageIndex(scene, ob, NULL, 1);
+  /* Find first modifier enabled on cage. */
+  for (int i; md && i < cage_index; i++) {
+    md = md->next;
+  }
+  /* Now from this point, search for subsurf modifier. */
+  for (; md; md = md->prev) {
+    const ModifierTypeInfo *mti = modifierType_getInfo(md->type);
+    if (md->type == eModifierType_Subsurf) {
+      ModifierMode mode = eModifierMode_Realtime | eModifierMode_Editmode;
+      if (modifier_isEnabled(scene, md, mode)) {
+        return true;
+      }
+    }
+    else if (mti->type == eModifierTypeType_OnlyDeform) {
+      /* Theses modifiers do not reset the subdiv flag nor change the topology.
+       * We can still search for a subsurf modifier. */
+    }
+    else {
+      /* Other modifiers may reset the subdiv facedot flag or create. */
+      return false;
+    }
+  }
+  return false;
+}
+
 bool modifier_isCorrectableDeformed(ModifierData *md)
 {
   const ModifierTypeInfo *mti = modifierType_getInfo(md->type);