LibOverride: Do not store some heavy data from override IDs.

This commit removes geometry from meshes and shapekeys, and embedded
files, from liboverride IDs.

This data is never overrideable, there is no reason to store extra
useless copies of it in production files.

See T78944.

Note that we may add more data to be skipped on write for liboverrides
in the future, but this commit should address all the most important
cases already.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D9810

1 files changed, 40 insertions, 11 deletions

diff --git a/source/blender/blenkernel/intern/mesh.c b/source/blender/blenkernel/intern/mesh.c
index 9ccdf5189d1..53f2a85fdad 100644
--- a/source/blender/blenkernel/intern/mesh.c
+++ b/source/blender/blenkernel/intern/mesh.c
@@ -173,24 +173,53 @@ static void mesh_foreach_id(ID *id, LibraryForeachIDData *data)
 static void mesh_blend_write(BlendWriter *writer, ID *id, const void *id_address)
 {
   Mesh *mesh = (Mesh *)id;
-  if (mesh->id.us > 0 || BLO_write_is_undo(writer)) {
-    /* cache only - don't write */
-    mesh->mface = NULL;
-    mesh->totface = 0;
-    memset(&mesh->fdata, 0, sizeof(mesh->fdata));
-    memset(&mesh->runtime, 0, sizeof(mesh->runtime));
-
+  const bool is_undo = BLO_write_is_undo(writer);
+  if (mesh->id.us > 0 || is_undo) {
     CustomDataLayer *vlayers = NULL, vlayers_buff[CD_TEMP_CHUNK_SIZE];
     CustomDataLayer *elayers = NULL, elayers_buff[CD_TEMP_CHUNK_SIZE];
     CustomDataLayer *flayers = NULL, flayers_buff[CD_TEMP_CHUNK_SIZE];
     CustomDataLayer *llayers = NULL, llayers_buff[CD_TEMP_CHUNK_SIZE];
     CustomDataLayer *players = NULL, players_buff[CD_TEMP_CHUNK_SIZE];
 
-    CustomData_blend_write_prepare(&mesh->vdata, &vlayers, vlayers_buff, ARRAY_SIZE(vlayers_buff));
-    CustomData_blend_write_prepare(&mesh->edata, &elayers, elayers_buff, ARRAY_SIZE(elayers_buff));
+    /* cache only - don't write */
+    mesh->mface = NULL;
+    mesh->totface = 0;
+    memset(&mesh->fdata, 0, sizeof(mesh->fdata));
+    memset(&mesh->runtime, 0, sizeof(mesh->runtime));
     flayers = flayers_buff;
-    CustomData_blend_write_prepare(&mesh->ldata, &llayers, llayers_buff, ARRAY_SIZE(llayers_buff));
-    CustomData_blend_write_prepare(&mesh->pdata, &players, players_buff, ARRAY_SIZE(players_buff));
+
+    /* Do not store actual geometry data in case this is a library override ID. */
+    if (ID_IS_OVERRIDE_LIBRARY(mesh) && !is_undo) {
+      mesh->mvert = NULL;
+      mesh->totvert = 0;
+      memset(&mesh->vdata, 0, sizeof(mesh->vdata));
+      vlayers = vlayers_buff;
+
+      mesh->medge = NULL;
+      mesh->totedge = 0;
+      memset(&mesh->edata, 0, sizeof(mesh->edata));
+      elayers = elayers_buff;
+
+      mesh->mloop = NULL;
+      mesh->totloop = 0;
+      memset(&mesh->ldata, 0, sizeof(mesh->ldata));
+      llayers = llayers_buff;
+
+      mesh->mpoly = NULL;
+      mesh->totpoly = 0;
+      memset(&mesh->pdata, 0, sizeof(mesh->pdata));
+      players = players_buff;
+    }
+    else {
+      CustomData_blend_write_prepare(
+          &mesh->vdata, &vlayers, vlayers_buff, ARRAY_SIZE(vlayers_buff));
+      CustomData_blend_write_prepare(
+          &mesh->edata, &elayers, elayers_buff, ARRAY_SIZE(elayers_buff));
+      CustomData_blend_write_prepare(
+          &mesh->ldata, &llayers, llayers_buff, ARRAY_SIZE(llayers_buff));
+      CustomData_blend_write_prepare(
+          &mesh->pdata, &players, players_buff, ARRAY_SIZE(players_buff));
+    }
 
     BLO_write_id_struct(writer, Mesh, id_address, &mesh->id);
     BKE_id_blend_write(writer, &mesh->id);