[babl] babl: do not use model.data for storing original model backpointer

[Øyvind Kolås <ok src gnome org>]

commit eb4d8943a6c8077c4f5858e5385aa795fb461f09
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Oct 4 16:16:45 2017 +0200

    babl: do not use model.data for storing original model backpointer
    
    Fixing bug #788471

 babl/babl-conversion.c |    2 +-
 babl/babl-fish-path.c  |    4 +++-
 babl/babl-fish.c       |    4 ++--
 babl/babl-model.c      |   14 ++++++++++----
 babl/babl-model.h      |    5 ++---
 5 files changed, 18 insertions(+), 11 deletions(-)
---
diff --git a/babl/babl-conversion.c b/babl/babl-conversion.c
index b08f835..75e5c93 100644
--- a/babl/babl-conversion.c
+++ b/babl/babl-conversion.c
@@ -29,7 +29,7 @@
 static int model_is_rgba (const Babl *model)
 {
   const Babl *RGBA = babl_model_from_id (BABL_RGBA);
-  if (model == RGBA || model->model.data == RGBA)
+  if (model == RGBA || model->model.model == RGBA)
     return 1;
   return 0;
 }
diff --git a/babl/babl-fish-path.c b/babl/babl-fish-path.c
index 2a71464..6a1e194 100644
--- a/babl/babl-fish-path.c
+++ b/babl/babl-fish-path.c
@@ -330,7 +330,9 @@ alias_conversion (Babl *babl,
   BablSpace *space = user_data;
 
   if ((conv->source->class_type == BABL_FORMAT) &&
-      (conv->destination->class_type == BABL_FORMAT))
+      (conv->destination->class_type == BABL_FORMAT) &&
+      (!babl_format_is_palette (conv->source)) &&
+      (!babl_format_is_palette (conv->destination)))
   {
     if ((conv->source->format.space == (void*)babl_space ("sRGB")) &&
         (conv->destination->format.space == babl_space ("sRGB")))
diff --git a/babl/babl-fish.c b/babl/babl-fish.c
index 6e22f89..749b075 100644
--- a/babl/babl-fish.c
+++ b/babl/babl-fish.c
@@ -126,8 +126,8 @@ babl_conversion_find (const void *source,
 
   if (BABL (source)->class_type == BABL_MODEL)
   {
-     const Babl *srgb_source = BABL (source)->model.data ? BABL (source)->model.data:source;
-     const Babl *srgb_destination = BABL (destination)->model.data ? BABL 
(destination)->model.data:destination;
+     const Babl *srgb_source = BABL (source)->model.model ? BABL (source)->model.model:source;
+     const Babl *srgb_destination = BABL (destination)->model.model ? BABL 
(destination)->model.model:destination;
      Babl *reference = babl_conversion_find (srgb_source, srgb_destination);
 
   /* when conversions are sought between models, with non-sRGB chromaticities,
diff --git a/babl/babl-model.c b/babl/babl-model.c
index 0e28a17..d553aca 100644
--- a/babl/babl-model.c
+++ b/babl/babl-model.c
@@ -72,6 +72,7 @@ model_new (const char     *name,
   babl->model.components = components;
   babl->model.space      = space;
   babl->model.data       = NULL;
+  babl->model.model      = NULL;
   strcpy (babl->instance.name, name);
   memcpy (babl->model.component, component, sizeof (BablComponent *) * components);
 
@@ -373,17 +374,22 @@ babl_remodel_with_space (const Babl *model, const Babl *space)
 {
   Babl *ret;
   int i;
+  assert (BABL_IS_BABL (model));
 
   if (model->model.space == space)
     return (void*)model;
 
+  assert (BABL_IS_BABL (model));
+
   /* get back to the sRGB model if we are in a COW clone of it  */
-  if (model->model.data)
-    model = (void*)model->model.data;
+  if (model->model.model)
+    model = (void*)model->model.model;
+
+  assert (BABL_IS_BABL (model));
 
   for (i = 0; i < babl_n_remodels; i++)
   {
-    if (babl_remodels[i]->model.data == model &&
+    if (babl_remodels[i]->model.model == model &&
         babl_remodels[i]->model.space == space)
           return babl_remodels[i];
   }
@@ -391,7 +397,7 @@ babl_remodel_with_space (const Babl *model, const Babl *space)
   ret = babl_calloc (sizeof (BablModel), 1);
   memcpy (ret, model, sizeof (BablModel));
   ret->model.space = space;
-  ret->model.data = (void*)model; /* use the data as a backpointer to original model */
+  ret->model.model = (void*)model; /* use the data as a backpointer to original model */
   return babl_remodels[babl_n_remodels++] = ret;
   return (Babl*)ret;
 }
diff --git a/babl/babl-model.h b/babl/babl-model.h
index 2395005..96ff903 100644
--- a/babl/babl-model.h
+++ b/babl/babl-model.h
@@ -29,9 +29,8 @@ typedef struct
   BablComponent   **component;
   BablType        **type; /*< must be doubles,
                               used here for convenience in code */
-  void             *data; /*  used for palette - and maybe back pointer
-                              to actual model?
-                           */
+  void             *data;    /* user-data, used for palette */
+  void             *model;   /* back pointer to model with sRGB space */
   const Babl       *space;
 } BablModel;