[Bf-blender-cvs] [742119bcb50] master: Fix T68826 Eevee: Multi-Mat not working if switching from Solid shading

[Clément Foucault]

Commit: 742119bcb50a83b7f8bb6ceefb34861ac54d9cc8
Author: Clément Foucault
Date:   Mon Aug 26 15:18:26 2019 +0200
Branches: master
https://developer.blender.org/rB742119bcb50a83b7f8bb6ceefb34861ac54d9cc8

Fix T68826 Eevee: Multi-Mat not working if switching from Solid shading

The correct fix would be to avoid all those hacks but this is needed if
we want to be able to parallelize object vbo extractions.

This is the fixed version of the hack. The issue was that the ibo ranges
were saved before the batch were reset and the IBO was discarded, leading
to a read after free error. All previous reported crash were tested and
are now not reproductible.

===================================================================

M	source/blender/draw/intern/draw_cache_impl_mesh.c

===================================================================

diff --git a/source/blender/draw/intern/draw_cache_impl_mesh.c b/source/blender/draw/intern/draw_cache_impl_mesh.c
index 884d39343c6..336f0a7528a 100644
--- a/source/blender/draw/intern/draw_cache_impl_mesh.c
+++ b/source/blender/draw/intern/draw_cache_impl_mesh.c
@@ -999,6 +999,26 @@ void DRW_mesh_batch_cache_create_requested(
     }
   }
 
+  /* HACK: if MBC_SURF_PER_MAT is requested and ibo.tris is already available, it won't have it's
+   * index ranges initialized. So discard ibo.tris in order to recreate it.
+   * This needs to happen before saved_elem_ranges is populated. */
+  if ((batch_requested & MBC_SURF_PER_MAT) != 0 && (cache->batch_ready & MBC_SURF_PER_MAT) == 0) {
+    FOREACH_MESH_BUFFER_CACHE(cache, mbuffercache)
+    {
+      GPU_INDEXBUF_DISCARD_SAFE(mbuffercache->ibo.tris);
+    }
+    /* Clear all batches that reference ibo.tris. */
+    GPU_BATCH_CLEAR_SAFE(cache->batch.surface);
+    GPU_BATCH_CLEAR_SAFE(cache->batch.surface_weights);
+    GPU_BATCH_CLEAR_SAFE(cache->batch.edit_mesh_analysis);
+    GPU_BATCH_CLEAR_SAFE(cache->batch.edit_triangles);
+    GPU_BATCH_CLEAR_SAFE(cache->batch.edit_lnor);
+    GPU_BATCH_CLEAR_SAFE(cache->batch.edit_selection_faces);
+
+    cache->batch_ready &= ~(MBC_SURFACE | MBC_SURFACE_WEIGHTS | MBC_EDIT_MESH_ANALYSIS |
+                            MBC_EDIT_TRIANGLES | MBC_EDIT_LNOR | MBC_EDIT_SELECTION_FACES);
+  }
+
   if (batch_requested &
       (MBC_SURFACE | MBC_SURF_PER_MAT | MBC_WIRE_LOOPS_UVS | MBC_EDITUV_FACES_STRECH_AREA |
        MBC_EDITUV_FACES_STRECH_ANGLE | MBC_EDITUV_FACES | MBC_EDITUV_EDGES | MBC_EDITUV_VERTS)) {