Cleanup: Use const arguments for volume code

The problem was that you could getting write access to a grid from a
`const Volume *` without breaking const correctness. I encountered this
when working on support for volumes in the bounding box node. For
geometry nodes there is an important distinction between getting data
"for read" and "for write", with the former returning a `const` version
of the data.

Also, for volumes it was necessary to cast away const, since all of
the relevant functions in `volume.cc` didn't have const versions. This
patch adds `const` in these places, distinguising between "for read"
and "for write" versions of functions where necessary.

The downside is that loading and unloading in the global volume cache
needs const write-access to some member variables. I see that as an
inherent problem that comes up with caching that never has a beautiful
solution anyway.

Some of the const-ness could probably be propogated futher in EEVEE
code, but I'll leave that out, since there is another level of caching.

Differential Revision: https://developer.blender.org/D10916

1 files changed, 13 insertions, 3 deletions

diff --git a/source/blender/makesrna/intern/rna_volume.c b/source/blender/makesrna/intern/rna_volume.c
index 1bddd9152db..76db6f3e325 100644
--- a/source/blender/makesrna/intern/rna_volume.c
+++ b/source/blender/makesrna/intern/rna_volume.c
@@ -137,7 +137,7 @@ static void rna_Volume_grids_end(CollectionPropertyIterator *UNUSED(iter))
 static PointerRNA rna_Volume_grids_get(CollectionPropertyIterator *iter)
 {
   Volume *volume = iter->internal.count.ptr;
-  const VolumeGrid *grid = BKE_volume_grid_get(volume, iter->internal.count.item);
+  const VolumeGrid *grid = BKE_volume_grid_get_for_read(volume, iter->internal.count.item);
   return rna_pointer_inherit_refine(&iter->parent, &RNA_VolumeGrid, (void *)grid);
 }
 
@@ -207,6 +207,16 @@ static int rna_VolumeGrids_frame_filepath_length(PointerRNA *ptr)
   return strlen(BKE_volume_grids_frame_filepath(volume));
 }
 
+static bool rna_Volume_load(Volume *volume, Main *bmain)
+{
+  return BKE_volume_load(volume, bmain);
+}
+
+static bool rna_Volume_save(Volume *volume, Main *bmain, ReportList *reports, const char *filepath)
+{
+  return BKE_volume_save(volume, bmain, reports, filepath);
+}
+
 #else
 
 static void rna_def_volume_grid(BlenderRNA *brna)
@@ -335,7 +345,7 @@ static void rna_def_volume_grids(BlenderRNA *brna, PropertyRNA *cprop)
   FunctionRNA *func;
   PropertyRNA *parm;
 
-  func = RNA_def_function(srna, "load", "BKE_volume_load");
+  func = RNA_def_function(srna, "load", "rna_Volume_load");
   RNA_def_function_ui_description(func, "Load list of grids and metadata from file");
   RNA_def_function_flag(func, FUNC_USE_MAIN);
   parm = RNA_def_boolean(func, "success", 0, "", "True if grid list was successfully loaded");
@@ -344,7 +354,7 @@ static void rna_def_volume_grids(BlenderRNA *brna, PropertyRNA *cprop)
   func = RNA_def_function(srna, "unload", "BKE_volume_unload");
   RNA_def_function_ui_description(func, "Unload all grid and voxel data from memory");
 
-  func = RNA_def_function(srna, "save", "BKE_volume_save");
+  func = RNA_def_function(srna, "save", "rna_Volume_save");
   RNA_def_function_ui_description(func, "Save grids and metadata to file");
   RNA_def_function_flag(func, FUNC_USE_MAIN | FUNC_USE_REPORTS);
   parm = RNA_def_string_file_path(func, "filepath", NULL, 0, "", "File path to save to");