material: Support sparse ARBfp program generation

We don't need to generate a new ARBfp program for every material created
if we can find an ancestor whos state will result in the same program
being generated.

The more code we can have adopt the coding pattern of deriving their
materials from other similar materials using cogl_material_copy() the
more likely this metric will be good enough on its own to minimize the
set of arbfp programs necessary to support a given application.

cogl/cogl-material-private.h

@@ -468,9 +468,9 @@ struct _CoglMaterial
    * material in comparison to its parent. */
   unsigned long    differences;
 
-  /* The fragment processing backend identified by the ->backend
+  /* The fragment processing backends can associate private data with a
-   * bitfield can associate private data with a material. */
+   * material. */
-  void		  *backend_priv;
+  void		  *backend_privs[COGL_MATERIAL_N_BACKENDS];
 
   /* Whenever a material is modified we increment the age. There's no
    * guarantee that it won't wrap but it can nevertheless be a
@@ -523,6 +523,17 @@ struct _CoglMaterial
 
   /* bitfields */
 
+  /* A material can have private data associated with it for multiple
+   * fragment processing backends. Although only one backend is
+   * associated with a material the backends may want to cache private
+   * state with the ancestors of other materials and those ancestors
+   * could currently be associated with different backends.
+   *
+   * Each set bit indicates if the correspondong ->backend_privs[]
+   * entry is valid.
+   */
+  unsigned int          backend_priv_set_mask:COGL_MATERIAL_N_BACKENDS;
+
   /* Weak materials don't count as dependants on their parents which
    * means that the parent material can be modified without
    * considering how the modifications may affect the weak material.
@@ -560,9 +571,6 @@ struct _CoglMaterial
    * the material and any private state the backend has associated
    * with the material. */
   unsigned int          backend:3;
-
-  /* Determines if ->backend_priv has been initialized */
-  unsigned int          backend_priv_set:1;
 };
 
 typedef struct _CoglMaterialBackend
@@ -582,6 +590,7 @@ typedef struct _CoglMaterialBackend
   void (*material_pre_change_notify) (CoglMaterial *material,
                                       CoglMaterialState change,
                                       const CoglColor *new_color);
+  void (*material_set_parent_notify) (CoglMaterial *material);
   void (*layer_pre_change_notify) (CoglMaterialLayer *layer,
                                    CoglMaterialLayerState change);
 

cogl/cogl-material.c

@@ -82,6 +82,9 @@
 
 typedef struct _CoglMaterialBackendARBfpPrivate
 {
+  CoglMaterial *authority_cache;
+  unsigned long authority_cache_age;
+
   GString *source;
   GLuint gl_program;
   gboolean *sampled;
@@ -115,8 +118,11 @@ static const CoglMaterialBackend *backends[] =
 };
 /* NB: material->backend is currently a 3bit unsigned int bitfield */
 #define COGL_MATERIAL_BACKEND_GLSL       0
+#define COGL_MATERIAL_BACKEND_GLSL_MASK  (1L<<0)
 #define COGL_MATERIAL_BACKEND_ARBFP      1
+#define COGL_MATERIAL_BACKEND_ARBFP_MASK (1L<<1)
 #define COGL_MATERIAL_BACKEND_FIXED      2
+#define COGL_MATERIAL_BACKEND_FIXED_MASK (1L<<2)
 
 #elif defined (HAVE_COGL_GLES2)
 
@@ -452,6 +458,35 @@ _cogl_material_unparent (CoglMaterial *material)
   material->parent = NULL;
 }
 
+/* This recursively frees the layers_cache of a material and all of
+ * its descendants.
+ *
+ * For instance if we change a materials ->layer_differences list
+ * then that material and all of its descendants may now have
+ * incorrect layer caches. */
+static void
+recursively_free_layer_caches (CoglMaterial *material)
+{
+  GList *l;
+
+  /* Note: we maintain the invariable that if a material already has a
+   * dirty layers_cache then so do all of its descendants. */
+  if (material->layers_cache_dirty)
+    return;
+
+  if (G_UNLIKELY (material->layers_cache != material->short_layers_cache))
+    g_slice_free1 (sizeof (CoglMaterialLayer *) * material->n_layers,
+                   material->layers_cache);
+  material->layers_cache_dirty = TRUE;
+
+  if (material->has_children)
+    {
+      recursively_free_layer_caches (material->first_child);
+      for (l = material->children; l; l = l->next)
+        recursively_free_layer_caches (l->data);
+    }
+}
+
 static void
 _cogl_material_set_parent (CoglMaterial *material, CoglMaterial *parent)
 {
@@ -476,6 +511,14 @@ _cogl_material_set_parent (CoglMaterial *material, CoglMaterial *parent)
    * layers could now be invalid so free it... */
   if (material->differences & COGL_MATERIAL_STATE_LAYERS)
     recursively_free_layer_caches (material);
+
+  /* If the fragment processing backend is also caching state along
+   * with the material that depends on the materials ancestry then it
+   * may be notified here...
+   */
+  if (material->backend != COGL_MATERIAL_BACKEND_UNDEFINED &&
+      backends[material->backend]->material_set_parent_notify)
+    backends[material->backend]->material_set_parent_notify (material);
 }
 
 /* XXX: Always have an eye out for opportunities to lower the cost of
@@ -495,7 +538,6 @@ cogl_material_copy (CoglHandle handle)
   material->journal_ref_count = 0;
 
   material->parent = NULL;
-  _cogl_material_set_parent (material, src);
 
   material->has_children = FALSE;
 
@@ -518,12 +560,14 @@ cogl_material_copy (CoglHandle handle)
   material->deprecated_get_layers_list_dirty = TRUE;
 
   material->backend = src->backend;
-  material->backend_priv_set = FALSE;
+  material->backend_priv_set_mask = 0;
 
   material->has_static_breadcrumb = FALSE;
 
   material->age = 0;
 
+  _cogl_material_set_parent (material, src);
+
   return _cogl_material_handle_new (material);
 }
 
@@ -706,35 +750,6 @@ _cogl_material_update_layers_cache (CoglMaterial *material)
   g_warn_if_reached ();
 }
 
-/* This recursively frees the layers_cache of a material and all of
- * its descendants.
- *
- * For instance if we change a materials ->layer_differences list
- * then that material and all of its descendants may now have
- * incorrect layer caches. */
-static void
-recursively_free_layer_caches (CoglMaterial *material)
-{
-  GList *l;
-
-  /* Note: we maintain the invariable that if a material already has a
-   * dirty layers_cache then so do all of its descendants. */
-  if (material->layers_cache_dirty)
-    return;
-
-  if (G_UNLIKELY (material->layers_cache != material->short_layers_cache))
-    g_slice_free1 (sizeof (CoglMaterialLayer *) * material->n_layers,
-                   material->layers_cache);
-  material->layers_cache_dirty = TRUE;
-
-  if (material->has_children)
-    {
-      recursively_free_layer_caches (material->first_child);
-      for (l = material->children; l; l = l->next)
-        recursively_free_layer_caches (l->data);
-    }
-}
-
 typedef gboolean (*CoglMaterialLayerCallback) (CoglMaterialLayer *layer,
                                                void *user_data);
 
@@ -5230,6 +5245,7 @@ static const CoglMaterialBackend _cogl_material_glsl_backend =
   _cogl_material_backend_glsl_passthrough,
   _cogl_material_backend_glsl_end,
   NULL, /* material_state_change_notify */
+  NULL, /* material_set_parent_notify */
   NULL, /* layer_state_change_notify */
   NULL, /* free_priv */
 };
@@ -5244,12 +5260,164 @@ _cogl_material_backend_arbfp_get_max_texture_units (void)
   return get_max_texture_image_units ();
 }
 
+typedef struct
+{
+  int i;
+  CoglMaterialLayer **layers;
+} AddLayersToArrayState;
+
+static gboolean
+add_layer_to_array_cb (CoglMaterialLayer *layer,
+                       void *user_data)
+{
+  AddLayersToArrayState *state = user_data;
+  state->layers[state->i++] = layer;
+  return TRUE;
+}
+
+static gboolean
+layers_arbfp_would_differ (CoglMaterialLayer **material0_layers,
+                           CoglMaterialLayer **material1_layers,
+                           int n_layers)
+{
+  int i;
+  /* The layer state that affects arbfp codegen... */
+  unsigned long arbfp_codegen_modifiers =
+    COGL_MATERIAL_LAYER_STATE_COMBINE |
+    COGL_MATERIAL_LAYER_STATE_COMBINE_CONSTANT |
+    COGL_MATERIAL_LAYER_STATE_UNIT |
+    COGL_MATERIAL_LAYER_STATE_TEXTURE;
+
+  for (i = 0; i < n_layers; i++)
+    {
+      CoglMaterialLayer *layer0 = material0_layers[i];
+      CoglMaterialLayer *layer1 = material1_layers[i];
+      unsigned long layer_differences;
+
+      if (layer0 == layer1)
+        continue;
+
+      layer_differences =
+        _cogl_material_layer_compare_differences (layer0, layer1);
+
+      if (layer_differences & arbfp_codegen_modifiers)
+        {
+          /* When it comes to texture differences the only thing that
+           * affects the arbfp is the target enum... */
+          if (layer_differences == COGL_MATERIAL_LAYER_STATE_TEXTURE)
+            {
+              CoglHandle tex0 = _cogl_material_layer_get_texture (layer0);
+              CoglHandle tex1 = _cogl_material_layer_get_texture (layer1);
+              GLenum gl_target0;
+              GLenum gl_target1;
+
+              cogl_texture_get_gl_texture (tex0, NULL, &gl_target0);
+              cogl_texture_get_gl_texture (tex1, NULL, &gl_target1);
+              if (gl_target0 == gl_target1)
+                continue;
+            }
+          return TRUE;
+        }
+    }
+
+  return FALSE;
+}
+
+/* This tries to find the oldest ancestor whos state would generate
+ * the same arbfp program as the current material. This is a simple
+ * mechanism for reducing the number of arbfp programs we have to
+ * generate.
+ */
+static CoglMaterial *
+find_arbfp_authority (CoglMaterial *material)
+{
+  CoglMaterial *authority0;
+  CoglMaterial *authority1;
+  int n_layers;
+  CoglMaterialLayer **authority0_layers;
+  CoglMaterialLayer **authority1_layers;
+
+  /* XXX: we'll need to update this when we add fog support to the
+   * arbfp codegen */
+
+  /* Find the first material that modifies state that affects the
+   * arbfp codegen... */
+  authority0 = _cogl_material_get_authority (material,
+                                             COGL_MATERIAL_STATE_LAYERS);
+
+  /* Find the next ancestor after that, that also modifies state
+   * affecting arbfp codegen... */
+  if (authority0->parent)
+    authority1 = _cogl_material_get_authority (authority0->parent,
+                                               COGL_MATERIAL_STATE_LAYERS);
+  else
+    return authority0;
+
+  n_layers = authority0->n_layers;
+
+  for (;;)
+    {
+      AddLayersToArrayState state;
+
+      if (authority0->n_layers != authority1->n_layers)
+        return authority0;
+
+      authority0_layers =
+        g_alloca (sizeof (CoglMaterialLayer *) * n_layers);
+      state.i = 0;
+      state.layers = authority0_layers;
+      _cogl_material_foreach_layer (authority0,
+                                    add_layer_to_array_cb,
+                                    &state);
+
+      authority1_layers =
+        g_alloca (sizeof (CoglMaterialLayer *) * n_layers);
+      state.i = 0;
+      state.layers = authority1_layers;
+      _cogl_material_foreach_layer (authority1,
+                                    add_layer_to_array_cb,
+                                    &state);
+
+      if (layers_arbfp_would_differ (authority0_layers, authority1_layers,
+                                     n_layers))
+        return authority0;
+
+      /* Find the next ancestor after that, that also modifies state
+       * affecting arbfp codegen... */
+
+      if (!authority1->parent)
+        break;
+
+      authority0 = authority1;
+      authority1 = _cogl_material_get_authority (authority1->parent,
+                                                 COGL_MATERIAL_STATE_LAYERS);
+      if (authority1 == authority0)
+        break;
+    }
+
+  return authority1;
+}
+
+static void
+invalidate_arbfp_authority_cache (CoglMaterial *material)
+{
+  if (material->backend_priv_set_mask  & COGL_MATERIAL_BACKEND_ARBFP_MASK)
+    {
+      CoglMaterialBackendARBfpPrivate *priv =
+        material->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
+      priv->authority_cache = NULL;
+      priv->authority_cache_age = 0;
+    }
+}
+
 static gboolean
 _cogl_material_backend_arbfp_start (CoglMaterial *material,
                                     int n_layers,
                                     unsigned long materials_difference)
 {
+  CoglMaterial *authority;
   CoglMaterialBackendARBfpPrivate *priv;
+  CoglMaterialBackendARBfpPrivate *authority_priv;
 
   _COGL_GET_CONTEXT (ctx, FALSE);
 
@@ -5260,19 +5428,53 @@ _cogl_material_backend_arbfp_start (CoglMaterial *material,
   if (ctx->fog_enabled)
     return FALSE;
 
-  if (!material->backend_priv_set)
+  /* Note: we allocate ARBfp private state for both the given material
-    {
+   * and the authority. (The oldest ancestor whos state will result in
-      material->backend_priv = g_slice_new0 (CoglMaterialBackendARBfpPrivate);
+   * the same program being generated) The former will simply cache a
-      material->backend_priv_set = TRUE;
+   * pointer to the authority and the later will track the arbfp
-    }
+   * program that we will generate.
-  priv = material->backend_priv;
+   */
 
-  if (priv->gl_program == 0)
+  if (!(material->backend_priv_set_mask & COGL_MATERIAL_BACKEND_ARBFP_MASK))
+    {
+      material->backend_privs[COGL_MATERIAL_BACKEND_ARBFP] =
+        g_slice_new0 (CoglMaterialBackendARBfpPrivate);
+      material->backend_priv_set_mask |= COGL_MATERIAL_BACKEND_ARBFP_MASK;
+    }
+  priv = material->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
+
+  /* XXX: We are making assumptions that we don't yet support
+   * modification of ancestors to optimize the sharing of state in the
+   * material graph. When we start to support this then the arbfp
+   * backend will somehow need to be notified of graph changes that
+   * may invalidate authority_cache pointers.
+   */
+
+  if (priv->authority_cache &&
+      priv->authority_cache_age != _cogl_material_get_age (material))
+    invalidate_arbfp_authority_cache (material);
+
+  if (!priv->authority_cache)
+    {
+      priv->authority_cache = find_arbfp_authority (material);
+      priv->authority_cache_age = _cogl_material_get_age (material);
+    }
+
+  authority = priv->authority_cache;
+  if (!(authority->backend_priv_set_mask & COGL_MATERIAL_BACKEND_ARBFP_MASK))
+    {
+      authority->backend_privs[COGL_MATERIAL_BACKEND_ARBFP] =
+        g_slice_new0 (CoglMaterialBackendARBfpPrivate);
+      authority->backend_priv_set_mask |= COGL_MATERIAL_BACKEND_ARBFP_MASK;
+    }
+  authority_priv = authority->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
+
+  if (authority_priv->gl_program == 0)
     {
       /* We reuse a single grow-only GString for ARBfp code-gen */
       g_string_set_size (ctx->arbfp_source_buffer, 0);
-      priv->source = ctx->arbfp_source_buffer;
+      authority_priv->source = ctx->arbfp_source_buffer;
-      g_string_append (priv->source,
+      g_string_append (authority_priv->source,
                        "!!ARBfp1.0\n"
                        "TEMP output;\n"
                        "TEMP tmp0, tmp1, tmp2, tmp3, tmp4;\n"
@@ -5280,12 +5482,23 @@ _cogl_material_backend_arbfp_start (CoglMaterial *material,
                        "PARAM one = {1, 1, 1, 1};\n"
                        "PARAM two = {2, 2, 2, 2};\n"
                        "PARAM minus_one = {-1, -1, -1, -1};\n");
-      priv->sampled = g_new0 (gboolean, n_layers);
+      authority_priv->sampled = g_new0 (gboolean, n_layers);
     }
 
   return TRUE;
 }
 
+static CoglMaterial *
+get_arbfp_authority (CoglMaterial *material)
+{
+  CoglMaterialBackendARBfpPrivate *priv =
+    material->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
+
+  g_return_val_if_fail (priv != NULL, NULL);
+
+  return priv->authority_cache;
+}
+
 /* Determines if we need to handle the RGB and A texture combining
  * separately or is the same function used for both channel masks and
  * with the same arguments...
@@ -5453,7 +5666,9 @@ setup_arg (CoglMaterial *material,
            GLint op,
            CoglMaterialBackendARBfpArg *arg)
 {
-  CoglMaterialBackendARBfpPrivate *priv = material->backend_priv;
+  CoglMaterial *arbfp_authority = get_arbfp_authority (material);
+  CoglMaterialBackendARBfpPrivate *priv =
+    arbfp_authority->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
   static const char *tmp_name[3] = { "tmp0", "tmp1", "tmp2" };
   GLenum gl_target;
   CoglHandle texture;
@@ -5585,7 +5800,9 @@ append_function (CoglMaterial *material,
                  CoglMaterialBackendARBfpArg *args,
                  int n_args)
 {
-  CoglMaterialBackendARBfpPrivate *priv = material->backend_priv;
+  CoglMaterial *arbfp_authority = get_arbfp_authority (material);
+  CoglMaterialBackendARBfpPrivate *priv =
+    arbfp_authority->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
   const char *mask_name;
 
   switch (mask)
@@ -5714,7 +5931,7 @@ append_function (CoglMaterial *material,
 }
 
 static void
-append_masked_combine (CoglMaterial *material,
+append_masked_combine (CoglMaterial *arbfp_authority,
                        CoglMaterialLayer *layer,
                        CoglBlendStringChannelMask mask,
                        GLint function,
@@ -5729,7 +5946,7 @@ append_masked_combine (CoglMaterial *material,
 
   for (i = 0; i < n_args; i++)
     {
-      setup_arg (material,
+      setup_arg (arbfp_authority,
                  layer,
                  mask,
                  i,
@@ -5738,7 +5955,7 @@ append_masked_combine (CoglMaterial *material,
                  &args[i]);
     }
 
-  append_function (material,
+  append_function (arbfp_authority,
                    mask,
                    function,
                    args,
@@ -5750,7 +5967,9 @@ _cogl_material_backend_arbfp_add_layer (CoglMaterial *material,
                                         CoglMaterialLayer *layer,
                                         unsigned long layers_difference)
 {
-  CoglMaterialBackendARBfpPrivate *priv = material->backend_priv;
+  CoglMaterial *arbfp_authority = get_arbfp_authority (material);
+  CoglMaterialBackendARBfpPrivate *priv =
+    arbfp_authority->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
   CoglMaterialLayer *combine_authority =
     _cogl_material_layer_get_authority (layer,
                                         COGL_MATERIAL_LAYER_STATE_COMBINE);
@@ -5831,7 +6050,9 @@ _cogl_material_backend_arbfp_add_layer (CoglMaterial *material,
 gboolean
 _cogl_material_backend_arbfp_passthrough (CoglMaterial *material)
 {
-  CoglMaterialBackendARBfpPrivate *priv = material->backend_priv;
+  CoglMaterial *arbfp_authority = get_arbfp_authority (material);
+  CoglMaterialBackendARBfpPrivate *priv =
+    arbfp_authority->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
 
   if (!priv->source)
     return TRUE;
@@ -5844,7 +6065,9 @@ static gboolean
 _cogl_material_backend_arbfp_end (CoglMaterial *material,
                                   unsigned long materials_difference)
 {
-  CoglMaterialBackendARBfpPrivate *priv = material->backend_priv;
+  CoglMaterial *arbfp_authority = get_arbfp_authority (material);
+  CoglMaterialBackendARBfpPrivate *priv =
+    arbfp_authority->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
 
   _COGL_GET_CONTEXT (ctx, FALSE);
 
@@ -5894,24 +6117,44 @@ _cogl_material_backend_arbfp_material_pre_change_notify (
                                                    CoglMaterialState change,
                                                    const CoglColor *new_color)
 {
-  CoglMaterialBackendARBfpPrivate *priv = material->backend_priv;
+  CoglMaterialBackendARBfpPrivate *priv =
+    material->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
   static const unsigned long fragment_op_changes =
     COGL_MATERIAL_STATE_LAYERS;
     /* TODO: COGL_MATERIAL_STATE_FOG */
 
   _COGL_GET_CONTEXT (ctx, NO_RETVAL);
 
-  if (material->backend_priv_set &&
+  if (material->backend_priv_set_mask & COGL_MATERIAL_BACKEND_ARBFP_MASK &&
       priv->gl_program &&
       change & fragment_op_changes)
     {
-      /* XXX: what if this is the currently bound program? we need to
-       * dirty our cache. */
       GE (glDeletePrograms (1, &priv->gl_program));
       priv->gl_program = 0;
     }
 }
 
+static gboolean
+invalidate_arbfp_authority_cache_cb (CoglMaterial *material,
+                                     void *user_data)
+{
+  invalidate_arbfp_authority_cache (material);
+  return TRUE;
+}
+
+static void
+_cogl_material_backend_arbfp_material_set_parent_notify (
+                                                CoglMaterial *material)
+{
+  /* Any arbfp authority cache associated with this material or
+   * any of its descendants will now be invalid. */
+  invalidate_arbfp_authority_cache (material);
+
+  _cogl_material_foreach_child (material,
+                                invalidate_arbfp_authority_cache_cb,
+                                NULL);
+}
+
 static void
 _cogl_material_backend_arbfp_layer_pre_change_notify (
                                                 CoglMaterialLayer *layer,
@@ -5928,15 +6171,16 @@ _cogl_material_backend_arbfp_free_priv (CoglMaterial *material)
 {
   _COGL_GET_CONTEXT (ctx, NO_RETVAL);
 
-  if (material->backend_priv_set)
+  if (material->backend_priv_set_mask & COGL_MATERIAL_BACKEND_ARBFP_MASK)
     {
-      CoglMaterialBackendARBfpPrivate *priv = material->backend_priv;
+      CoglMaterialBackendARBfpPrivate *priv =
+        material->backend_privs[COGL_MATERIAL_BACKEND_ARBFP];
 
       glDeletePrograms (1, &priv->gl_program);
       if (priv->sampled)
         g_free (priv->sampled);
-      g_slice_free (CoglMaterialBackendARBfpPrivate, material->backend_priv);
+      g_slice_free (CoglMaterialBackendARBfpPrivate, priv);
-      material->backend_priv_set = FALSE;
+      material->backend_priv_set_mask &= ~COGL_MATERIAL_BACKEND_ARBFP_MASK;
     }
 }
 
@@ -5948,6 +6192,7 @@ static const CoglMaterialBackend _cogl_material_arbfp_backend =
   _cogl_material_backend_arbfp_passthrough,
   _cogl_material_backend_arbfp_end,
   _cogl_material_backend_arbfp_material_pre_change_notify,
+  _cogl_material_backend_arbfp_material_set_parent_notify,
   _cogl_material_backend_arbfp_layer_pre_change_notify,
   _cogl_material_backend_arbfp_free_priv,
   NULL
@@ -6099,6 +6344,7 @@ static const CoglMaterialBackend _cogl_material_fixed_backend =
   NULL, /* passthrough */
   _cogl_material_backend_fixed_end,
   NULL, /* material_change_notify */
+  NULL, /* material_set_parent_notify */
   NULL, /* layer_change_notify */
   NULL /* free_priv */
 };