Cleanup: make functions for setting active/render layer more consistent

The active/render layer is indexed from the first layer of that type. These functions
incorrectly subtracted the layer index of *each* layer, instead of the first one.
If there's only a single layer this doesn't matter, but when there are multiple layers
it will set the wrong active layer for consecutive layers.

I'm not aware of any actual errors caused by this, because the active and render layers are
only ever queried from the first layer of that type, but it was confusing during debugging a
related issue. This patch makes the behavior of CustomData_set_layer_active_index()
consistent with CustomData_set_layer_active() and the same for render.

Differential Revision: https://developer.blender.org/D14955

1 files changed, 8 insertions, 2 deletions

diff --git a/source/blender/blenkernel/intern/customdata.cc b/source/blender/blenkernel/intern/customdata.cc
index 62351a31042..52d2060a1fc 100644
--- a/source/blender/blenkernel/intern/customdata.cc
+++ b/source/blender/blenkernel/intern/customdata.cc
@@ -2575,18 +2575,24 @@ void CustomData_set_layer_stencil(CustomData *data, int type, int n)
 
 void CustomData_set_layer_active_index(CustomData *data, int type, int n)
 {
+  const int layer_index = data->typemap[type];
+  BLI_assert(customdata_typemap_is_valid(data));
+
   for (int i = 0; i < data->totlayer; i++) {
     if (data->layers[i].type == type) {
-      data->layers[i].active = n - i;
+      data->layers[i].active = n - layer_index;
     }
   }
 }
 
 void CustomData_set_layer_render_index(CustomData *data, int type, int n)
 {
+  const int layer_index = data->typemap[type];
+  BLI_assert(customdata_typemap_is_valid(data));
+
   for (int i = 0; i < data->totlayer; i++) {
     if (data->layers[i].type == type) {
-      data->layers[i].active_rnd = n - i;
+      data->layers[i].active_rnd = n - layer_index;
     }
   }
 }