cogl-material: Add support for point sprites

This adds a new API call to enable point sprite coordinate generation
for a material layer:

void
cogl_material_set_layer_point_sprite_coords_enabled (CoglHandle material,
                                                     int layer_index,
                                                     gboolean enable);

There is also a corresponding get function.

Enabling point sprite coords simply sets the GL_COORD_REPLACE of the
GL_POINT_SPRITE glTexEnv when flusing the material. There is no
separate application control for glEnable(GL_POINT_SPRITE). Instead it
is left permanently enabled under the assumption that it has no affect
unless GL_COORD_REPLACE is enabled for a texture unit.

http://bugzilla.openedhand.com/show_bug.cgi?id=2047

cogl/cogl-context.c

@@ -41,6 +41,11 @@
 #define glActiveTexture _context->drv.pf_glActiveTexture
 #endif
 
+/* This isn't defined in the GLES headers */
+#ifndef GL_POINT_SPRITE
+#define GL_POINT_SPRITE 0x8861
+#endif
+
 extern void
 _cogl_create_context_driver (CoglContext *context);
 extern void
@@ -211,6 +216,15 @@ cogl_create_context (void)
   _context->atlas = NULL;
   _context->atlas_texture = COGL_INVALID_HANDLE;
 
+  /* As far as I can tell, GL_POINT_SPRITE doesn't have any effect
+     unless GL_COORD_REPLACE is enabled for an individual
+     layer. Therefore it seems like it should be ok to just leave it
+     enabled all the time instead of having to have a set property on
+     each material to track whether any layers have point sprite
+     coords enabled */
+  if (cogl_features_available (COGL_FEATURE_POINT_SPRITE))
+    GE (glEnable (GL_POINT_SPRITE));
+
   return TRUE;
 }
 

cogl/cogl-material-private.h

@@ -184,7 +184,9 @@ typedef enum
   COGL_MATERIAL_LAYER_STATE_COMBINE_CONSTANT = 1L<<5,
   COGL_MATERIAL_LAYER_STATE_USER_MATRIX      = 1L<<6,
 
-  /* COGL_MATERIAL_LAYER_STATE_TEXTURE_INTERN   = 1L<<7, */
+  COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS = 1L<<7,
+
+  /* COGL_MATERIAL_LAYER_STATE_TEXTURE_INTERN   = 1L<<8, */
 
   COGL_MATERIAL_LAYER_STATE_ALL_SPARSE =
     COGL_MATERIAL_LAYER_STATE_UNIT |
@@ -193,12 +195,14 @@ typedef enum
     COGL_MATERIAL_LAYER_STATE_WRAP_MODES |
     COGL_MATERIAL_LAYER_STATE_COMBINE |
     COGL_MATERIAL_LAYER_STATE_COMBINE_CONSTANT |
-    COGL_MATERIAL_LAYER_STATE_USER_MATRIX,
+    COGL_MATERIAL_LAYER_STATE_USER_MATRIX |
+    COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS,
 
   COGL_MATERIAL_LAYER_STATE_NEEDS_BIG_STATE =
     COGL_MATERIAL_LAYER_STATE_COMBINE |
     COGL_MATERIAL_LAYER_STATE_COMBINE_CONSTANT |
-    COGL_MATERIAL_LAYER_STATE_USER_MATRIX
+    COGL_MATERIAL_LAYER_STATE_USER_MATRIX |
+    COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS,
 
 } CoglMaterialLayerState;
 
@@ -219,6 +223,8 @@ typedef struct
   /* The texture matrix dscribes how to transform texture coordinates */
   CoglMatrix matrix;
 
+  gboolean point_sprite_coords;
+
 } CoglMaterialLayerBigState;
 
 struct _CoglMaterialLayer

cogl/cogl-material.c

@@ -72,7 +72,13 @@
 #define glUseProgram ctx->drv.pf_glUseProgram
 #endif
 
-/* This isn't defined in the GLES headers */
+/* These aren't defined in the GLES headers */
+#ifndef GL_POINT_SPRITE
+#define GL_POINT_SPRITE 0x8861
+#endif
+#ifndef GL_COORD_REPLACE
+#define GL_COORD_REPLACE 0x8862
+#endif
 #ifndef GL_CLAMP_TO_BORDER
 #define GL_CLAMP_TO_BORDER 0x812d
 #endif
@@ -1549,6 +1555,9 @@ _cogl_material_layer_initialize_state (CoglMaterialLayer *dest,
 
   if (differences & COGL_MATERIAL_LAYER_STATE_USER_MATRIX)
     dest->big_state->matrix = src->big_state->matrix;
+
+  if (differences & COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS)
+    dest->big_state->point_sprite_coords = src->big_state->point_sprite_coords;
 }
 
 /* NB: This function will allocate a new derived layer if you are
@@ -2466,6 +2475,123 @@ _cogl_material_layer_get_wrap_modes (CoglMaterialLayer *layer,
   *wrap_mode_r = authority->wrap_mode_r;
 }
 
+gboolean
+cogl_material_set_layer_point_sprite_coords_enabled (CoglMaterial *material,
+                                                     int layer_index,
+                                                     gboolean enable,
+                                                     GError **error)
+{
+  CoglMaterialLayerState       change =
+    COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS;
+  CoglMaterialLayer           *layer;
+  CoglMaterialLayer           *new;
+  CoglMaterialLayer           *authority;
+
+  g_return_val_if_fail (cogl_is_material (material), FALSE);
+
+  /* Don't allow point sprite coordinates to be enabled if the driver
+     doesn't support it */
+  if (enable && !cogl_features_available (COGL_FEATURE_POINT_SPRITE))
+    {
+      if (error)
+        {
+          g_set_error (error, COGL_ERROR, COGL_ERROR_MISSING_FEATURE,
+                       "Point sprite texture coordinates are enabled "
+                       "for a layer but the GL driver does not support it.");
+        }
+      else
+        {
+          static gboolean warning_seen = FALSE;
+          if (!warning_seen)
+            g_warning ("Point sprite texture coordinates are enabled "
+                       "for a layer but the GL driver does not support it.");
+          warning_seen = TRUE;
+        }
+
+      return FALSE;
+    }
+
+  /* Note: this will ensure that the layer exists, creating one if it
+   * doesn't already.
+   *
+   * Note: If the layer already existed it's possibly owned by another
+   * material. If the layer is created then it will be owned by
+   * material. */
+  layer = _cogl_material_get_layer (material, layer_index);
+
+  /* Now find the ancestor of the layer that is the authority for the
+   * state we want to change */
+  authority = _cogl_material_layer_get_authority (layer, change);
+
+  if (authority->big_state->point_sprite_coords == enable)
+    return TRUE;
+
+  new = _cogl_material_layer_pre_change_notify (material, layer, change);
+  if (new != layer)
+    layer = new;
+  else
+    {
+      /* If the original layer we found is currently the authority on
+       * the state we are changing see if we can revert to one of our
+       * ancestors being the authority. */
+      if (layer == authority && authority->parent != NULL)
+        {
+          CoglMaterialLayer *old_authority =
+            _cogl_material_layer_get_authority (authority->parent, change);
+
+          if (old_authority->big_state->point_sprite_coords == enable)
+            {
+              layer->differences &= ~change;
+
+              g_assert (layer->owner == material);
+              if (layer->differences == 0)
+                _cogl_material_prune_empty_layer_difference (material,
+                                                             layer);
+              return TRUE;
+            }
+        }
+    }
+
+  layer->big_state->point_sprite_coords = enable;
+
+  /* If we weren't previously the authority on this state then we need
+   * to extended our differences mask and so it's possible that some
+   * of our ancestry will now become redundant, so we aim to reparent
+   * ourselves if that's true... */
+  if (layer != authority)
+    {
+      layer->differences |= change;
+      _cogl_material_layer_prune_redundant_ancestry (layer);
+    }
+
+  return TRUE;
+}
+
+gboolean
+cogl_material_get_layer_point_sprite_coords_enabled (CoglMaterial *material,
+                                                     int layer_index)
+{
+  CoglMaterialLayerState       change =
+    COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS;
+  CoglMaterialLayer *layer;
+  CoglMaterialLayer *authority;
+
+  g_return_val_if_fail (cogl_is_material (material), FALSE);
+
+  /* Note: this will ensure that the layer exists, creating one if it
+   * doesn't already.
+   *
+   * Note: If the layer already existed it's possibly owned by another
+   * material. If the layer is created then it will be owned by
+   * material. */
+  layer = _cogl_material_get_layer (material, layer_index);
+  /* FIXME: we shouldn't ever construct a layer in a getter function */
+
+  authority = _cogl_material_layer_get_authority (layer, change);
+
+  return authority->big_state->point_sprite_coords;
+}
+
 typedef struct
 {
   CoglMaterial *material;
@@ -2793,6 +2919,16 @@ _cogl_material_layer_user_matrix_equal (CoglMaterialLayer *authority0,
   return TRUE;
 }
 
+static gboolean
+_cogl_material_layer_point_sprite_coords_equal (CoglMaterialLayer *authority0,
+                                                CoglMaterialLayer *authority1)
+{
+  CoglMaterialLayerBigState *big_state0 = authority0->big_state;
+  CoglMaterialLayerBigState *big_state1 = authority1->big_state;
+
+  return big_state0->point_sprite_coords == big_state1->point_sprite_coords;
+}
+
 typedef gboolean
 (*CoglMaterialLayerStateComparitor) (CoglMaterialLayer *authority0,
                                      CoglMaterialLayer *authority1);
@@ -2859,6 +2995,12 @@ _cogl_material_layer_equal (CoglMaterialLayer *layer0,
                           _cogl_material_layer_user_matrix_equal))
     return FALSE;
 
+  if (layers_difference & COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS &&
+      !layer_state_equal (COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS,
+                          layer0, layer1,
+                          _cogl_material_layer_point_sprite_coords_equal))
+    return FALSE;
+
   return TRUE;
 }
 
@@ -4357,6 +4499,8 @@ _cogl_material_init_default_layers (void)
   big_state->texture_combine_alpha_op[0] = GL_SRC_ALPHA;
   big_state->texture_combine_alpha_op[1] = GL_SRC_ALPHA;
 
+  big_state->point_sprite_coords = FALSE;
+
   cogl_matrix_init_identity (&big_state->matrix);
 
   ctx->default_layer_0 = _cogl_material_layer_object_new (layer);
@@ -5575,9 +5719,23 @@ flush_layers_common_gl_state_cb (CoglMaterialLayer *layer, void *user_data)
       _cogl_matrix_stack_flush_to_gl (unit->matrix_stack, COGL_MATRIX_TEXTURE);
     }
 
-  cogl_object_ref (layer);
+  if (layers_difference & COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS)
-  if (unit->layer != NULL)
+    {
-    cogl_object_unref (unit->layer);
+      CoglMaterialState change = COGL_MATERIAL_LAYER_STATE_POINT_SPRITE_COORDS;
+      CoglMaterialLayer *authority =
+        _cogl_material_layer_get_authority (layer, change);
+      CoglMaterialLayerBigState *big_state = authority->big_state;
+
+      _cogl_set_active_texture_unit (unit_index);
+
+      GE (glTexEnvi (GL_POINT_SPRITE, GL_COORD_REPLACE,
+                     big_state->point_sprite_coords));
+    }
+
+  cogl_handle_ref (layer);
+  if (unit->layer != COGL_INVALID_HANDLE)
+    cogl_handle_unref (unit->layer);
+
   unit->layer = layer;
   unit->layer_changes_since_flush = 0;
 

cogl/cogl-material.h

@@ -921,6 +921,50 @@ cogl_material_set_layer_filters (CoglMaterial      *material,
                                  CoglMaterialFilter min_filter,
                                  CoglMaterialFilter mag_filter);
 
+/**
+ * cogl_material_set_layer_point_sprite_coords_enabled:
+ * @material: a #CoglHandle to a material.
+ * @layer_index: the layer number to change.
+ * @enable: whether to enable point sprite coord generation.
+ * @error: A return location for a GError, or NULL to ignore errors.
+ *
+ * When rendering points, if @enable is %TRUE then the texture
+ * coordinates for this layer will be replaced with coordinates that
+ * vary from 0.0 to 1.0 across the primitive. The top left of the
+ * point will have the coordinates 0.0,0.0 and the bottom right will
+ * have 1.0,1.0. If @enable is %FALSE then the coordinates will be
+ * fixed for the entire point.
+ *
+ * This function will only work if %COGL_FEATURE_POINT_SPRITE is
+ * available. If the feature is not available then the function will
+ * return %FALSE and set @error.
+ *
+ * Return value: %TRUE if the function succeeds, %FALSE otherwise.
+ * Since: 1.4
+ */
+gboolean
+cogl_material_set_layer_point_sprite_coords_enabled (CoglMaterial *material,
+                                                     int           layer_index,
+                                                     gboolean      enable,
+                                                     GError      **error);
+
+/**
+ * cogl_material_get_layer_point_sprite_coords_enabled:
+ * @material: a #CoglHandle to a material.
+ * @layer_index: the layer number to check.
+ *
+ * Gets whether point sprite coordinate generation is enabled for this
+ * texture layer.
+ *
+ * Return value: whether the texture coordinates will be replaced with
+ * point sprite coordinates.
+ *
+ * Since: 1.4
+ */
+gboolean
+cogl_material_get_layer_point_sprite_coords_enabled (CoglMaterial *material,
+                                                     int           layer_index);
+
 /**
  * cogl_material_set_layer_wrap_mode_s:
  * @material: A #CoglMaterial object

cogl/cogl-types.h

@@ -248,6 +248,8 @@ typedef enum { /*< prefix=COGL_PIXEL_FORMAT >*/
  * @COGL_FEATURE_TEXTURE_NPOT_REPEAT: Repeat modes other than
  *     %COGL_MATERIAL_WRAP_MODE_CLAMP_TO_EDGE are supported by the
  *     hardware.
+ * @COGL_FEATURE_POINT_SPRITE: Whether
+ *     cogl_material_set_layer_point_sprite_coords_enabled() is supported.
  *
  * Flags for the supported features.
  *
@@ -271,7 +273,8 @@ typedef enum
   COGL_FEATURE_DEPTH_RANGE            = (1 << 14),
   COGL_FEATURE_TEXTURE_NPOT_BASIC     = (1 << 15),
   COGL_FEATURE_TEXTURE_NPOT_MIPMAP    = (1 << 16),
-  COGL_FEATURE_TEXTURE_NPOT_REPEAT    = (1 << 17)
+  COGL_FEATURE_TEXTURE_NPOT_REPEAT    = (1 << 17),
+  COGL_FEATURE_POINT_SPRITE           = (1 << 18)
 } CoglFeatureFlags;
 
 /**

cogl/driver/gl/cogl-feature-functions.h

@@ -380,3 +380,10 @@ COGL_FEATURE_FUNCTION (void, glBlendEquationSeparate,
                        (GLenum                modeRGB,
                         GLenum                modeAlpha))
 COGL_FEATURE_END ()
+
+COGL_FEATURE_BEGIN (point_sprites, 2, 0,
+                    "ARB\0",
+                    "point_sprite\0",
+                    COGL_FEATURE_POINT_SPRITE,
+                    0)
+COGL_FEATURE_END ()

cogl/driver/gles/cogl-gles2-wrapper.c

@@ -155,6 +155,9 @@ initialize_texture_units (CoglGles2Wrapper *w)
                                 GL_SRC_COLOR) );
       GE( _cogl_wrap_glTexEnvi (GL_TEXTURE_ENV, GL_OPERAND1_ALPHA,
                                 GL_SRC_COLOR) );
+
+      GE( _cogl_wrap_glTexEnvi (GL_POINT_SPRITE, GL_COORD_REPLACE,
+                                GL_FALSE) );
     }
 
   GE( _cogl_wrap_glMatrixMode ((GLenum) prev_mode));
@@ -256,6 +259,10 @@ cogl_gles2_settings_equal (const CoglGles2WrapperSettings *a,
           int arg, n_args;
           GLenum func;
 
+          if (tex_env_a->point_sprite_coords !=
+              tex_env_b->point_sprite_coords)
+            return FALSE;
+
           func = tex_env_a->texture_combine_rgb_func;
 
           if (func != tex_env_b->texture_combine_rgb_func)
@@ -329,7 +336,8 @@ cogl_gles2_get_vertex_shader (const CoglGles2WrapperSettings *settings)
   g_string_append (shader_source, _cogl_fixed_vertex_shader_main_start);
 
   for (i = 0; i < COGL_GLES2_MAX_TEXTURE_UNITS; i++)
-    if (COGL_GLES2_TEXTURE_UNIT_IS_ENABLED (settings->texture_units, i))
+    if (COGL_GLES2_TEXTURE_UNIT_IS_ENABLED (settings->texture_units, i) &&
+        !settings->tex_env[i].point_sprite_coords)
       {
         g_string_append_printf (shader_source,
                                 "transformed_tex_coord = "
@@ -386,6 +394,26 @@ cogl_gles2_get_vertex_shader (const CoglGles2WrapperSettings *settings)
   return shader;
 }
 
+static void
+cogl_gles2_add_texture_lookup (int unit,
+                               const char *swizzle,
+                               GString *shader_source)
+{
+  _COGL_GET_GLES2_WRAPPER (w, NO_RETVAL);
+
+  g_string_append_printf (shader_source, "texture2D (texture_unit[%d], ", unit);
+
+  /* If point sprite coord generation is being used then divert to the
+     built-in varying var for that instead of the texture
+     coordinates */
+  if (w->settings.tex_env[unit].point_sprite_coords)
+    g_string_append (shader_source, "gl_PointCoord");
+  else
+    g_string_append_printf (shader_source, "tex_coord[%d]", unit);
+
+  g_string_append_printf (shader_source, ").%s", swizzle);
+}
+
 static void
 cogl_gles2_add_arg (int unit,
                     GLenum src,
@@ -413,9 +441,7 @@ cogl_gles2_add_arg (int unit,
   switch (src)
     {
     case GL_TEXTURE:
-      g_string_append_printf (shader_source,
+      cogl_gles2_add_texture_lookup (unit, swizzle, shader_source);
-                              "texture2D (texture_unit[%d], tex_coord[%d]).%s",
-                              unit, unit, swizzle);
       break;
 
     case GL_CONSTANT:
@@ -437,12 +463,8 @@ cogl_gles2_add_arg (int unit,
     default:
       if (src >= GL_TEXTURE0 &&
           src < GL_TEXTURE0 + COGL_GLES2_MAX_TEXTURE_UNITS)
-        g_string_append_printf (shader_source,
+        cogl_gles2_add_texture_lookup (src - GL_TEXTURE0,
-                                "texture2D (texture_unit[%d], "
+                                       swizzle, shader_source);
-                                "tex_coord[%d]).%s",
-                                src - GL_TEXTURE0,
-                                src - GL_TEXTURE0,
-                                swizzle);
       break;
     }
 
@@ -1350,14 +1372,14 @@ _cogl_wrap_glDrawElements (GLenum mode, GLsizei count, GLenum type,
 void
 _cogl_wrap_glTexEnvi (GLenum target, GLenum pname, GLint param)
 {
+  CoglGles2WrapperTexEnv *tex_env;
+
+  _COGL_GET_GLES2_WRAPPER (w, NO_RETVAL);
+
+  tex_env = w->settings.tex_env + w->active_texture_unit;
+
   if (target == GL_TEXTURE_ENV)
     {
-      CoglGles2WrapperTexEnv *tex_env;
-
-      _COGL_GET_GLES2_WRAPPER (w, NO_RETVAL);
-
-      tex_env = w->settings.tex_env + w->active_texture_unit;
-
       switch (pname)
         {
         case GL_COMBINE_RGB:
@@ -1388,6 +1410,17 @@ _cogl_wrap_glTexEnvi (GLenum target, GLenum pname, GLint param)
           break;
         }
 
+      w->settings_dirty = TRUE;
+    }
+  else if (target == GL_POINT_SPRITE)
+    {
+      switch (pname)
+        {
+        case GL_COORD_REPLACE:
+          tex_env->point_sprite_coords = param;
+          break;
+        }
+
       w->settings_dirty = TRUE;
     }
 }

cogl/driver/gles/cogl-gles2-wrapper.h

@@ -117,15 +117,17 @@ struct _CoglGles2WrapperUniforms
 
 struct _CoglGles2WrapperTexEnv
 {
-  GLenum texture_combine_rgb_func;
+  GLenum    texture_combine_rgb_func;
-  GLenum texture_combine_rgb_src[3];
+  GLenum    texture_combine_rgb_src[3];
-  GLenum texture_combine_rgb_op[3];
+  GLenum    texture_combine_rgb_op[3];
 
-  GLenum texture_combine_alpha_func;
+  GLenum    texture_combine_alpha_func;
-  GLenum texture_combine_alpha_src[3];
+  GLenum    texture_combine_alpha_src[3];
-  GLenum texture_combine_alpha_op[3];
+  GLenum    texture_combine_alpha_op[3];
 
-  GLfloat texture_combine_constant[4];
+  GLfloat   texture_combine_constant[4];
+
+  GLboolean point_sprite_coords;
 };
 
 /* NB: We get a copy of this for each fragment/vertex
@@ -319,6 +321,9 @@ struct _CoglGles2WrapperShader
 
 #define GL_MAX_TEXTURE_UNITS   0x84e2
 
+#define GL_POINT_SPRITE        0x8861
+#define GL_COORD_REPLACE       0x8862
+
 #endif /* GL_MODELVIEW */
 
 void _cogl_gles2_wrapper_init (CoglGles2Wrapper *wrapper);

cogl/driver/gles/cogl.c

@@ -107,6 +107,9 @@ _cogl_features_init (void)
 
   flags |= COGL_FEATURE_VBOS;
 
+  /* Both GLES 1.1 and GLES 2.0 support point sprites in core */
+  flags |= COGL_FEATURE_POINT_SPRITE;
+
   /* Cache features */
   ctx->feature_flags = flags;
   ctx->features_cached = TRUE;

doc/reference/cogl/cogl-sections.txt

@@ -491,6 +491,8 @@ cogl_material_remove_layer
 cogl_material_set_layer_combine
 cogl_material_set_layer_combine_constant
 cogl_material_set_layer_matrix
+cogl_material_set_layer_point_sprite_coords_enabled
+cogl_material_get_layer_point_sprite_coords_enabled
 cogl_material_get_layers
 cogl_material_get_n_layers
 CoglMaterialFilter