Add support for per-vertex point sizes

This adds a new function to enable per-vertex point size on a
pipeline. This can be set with
cogl_pipeline_set_per_vertex_point_size(). Once enabled the point size
can be set either by drawing with an attribute named
'cogl_point_size_in' or by writing to the 'cogl_point_size_out'
builtin from a snippet.

There is a feature flag which must be checked for before using
per-vertex point sizes. This will only be set on GL >= 2.0 or on GLES
2.0. GL will only let you set a per-vertex point size from GLSL by
writing to gl_PointSize. This is only available in GL2 and not in the
older GLSL extensions.

The per-vertex point size has its own pipeline state flag so that it
can be part of the state that affects vertex shader generation.

Having to enable the per vertex point size with a separate function is
a bit awkward. Ideally it would work like the color attribute where
you can just set it for every vertex in your primitive with
cogl_pipeline_set_color or set it per-vertex by just using the
attribute. This is harder to get working with the point size because
we need to generate a different vertex shader depending on what
attributes are bound. I think if we wanted to make this work
transparently we would still want to internally have a pipeline
property describing whether the shader was generated with per-vertex
support so that it would work with the shader cache correctly.
Potentially we could make the per-vertex property internal and
automatically make a weak pipeline whenever the attribute is bound.
However we would then also need to automatically detect when an
application is writing to cogl_point_size_out from a snippet.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

(cherry picked from commit 8495d9c1c15ce389885a9356d965eabd97758115)

Conflicts:
	cogl/cogl-context.c
	cogl/cogl-pipeline-private.h
	cogl/cogl-pipeline.c
	cogl/cogl-private.h
	cogl/driver/gl/cogl-pipeline-progend-fixed.c
	cogl/driver/gl/gl/cogl-pipeline-progend-fixed-arbfp.c

cogl/cogl-attribute-private.h

@@ -40,6 +40,7 @@ typedef enum
   COGL_ATTRIBUTE_NAME_ID_COLOR_ARRAY,
   COGL_ATTRIBUTE_NAME_ID_TEXTURE_COORD_ARRAY,
   COGL_ATTRIBUTE_NAME_ID_NORMAL_ARRAY,
+  COGL_ATTRIBUTE_NAME_ID_POINT_SIZE_ARRAY,
   COGL_ATTRIBUTE_NAME_ID_CUSTOM_ARRAY
 } CoglAttributeNameID;
 

cogl/cogl-attribute.c

@@ -101,6 +101,8 @@ validate_cogl_attribute_name (const char *name,
       *name_id = COGL_ATTRIBUTE_NAME_ID_NORMAL_ARRAY;
       *normalized = TRUE;
     }
+  else if (strcmp (name, "point_size_in") == 0)
+    *name_id = COGL_ATTRIBUTE_NAME_ID_POINT_SIZE_ARRAY;
   else
     {
       g_warning ("Unknown cogl_* attribute name cogl_%s\n", name);
@@ -193,6 +195,14 @@ validate_n_components (const CoglAttributeNameState *name_state,
           return FALSE;
         }
       break;
+    case COGL_ATTRIBUTE_NAME_ID_POINT_SIZE_ARRAY:
+      if (G_UNLIKELY (n_components != 1))
+        {
+          g_critical ("The point size attribute can only have one "
+                      "component");
+          return FALSE;
+        }
+      break;
     case COGL_ATTRIBUTE_NAME_ID_CUSTOM_ARRAY:
       return TRUE;
     }

cogl/cogl-attribute.h

@@ -76,6 +76,11 @@ COGL_BEGIN_DECLS
  *    <listitem>"cogl_tex_coord0_in", "cogl_tex_coord1", ...
  * (used for vertex texture coordinates)</listitem>
  *    <listitem>"cogl_normal_in" (used for vertex normals)</listitem>
+ *    <listitem>"cogl_point_size_in" (used to set the size of points
+ *    per-vertex. Note this can only be used if
+ *    %COGL_FEATURE_ID_POINT_SIZE_ATTRIBUTE is advertised and
+ *    cogl_pipeline_set_per_vertex_point_size() is called on the pipeline.
+ *    </listitem>
  *  </itemizedlist>
  *
  * The attribute values corresponding to different vertices can either

cogl/cogl-context.c

@@ -95,6 +95,9 @@ _cogl_init_feature_overrides (CoglContext *ctx)
     {
       ctx->feature_flags &= ~COGL_FEATURE_SHADERS_GLSL;
       COGL_FLAGS_SET (ctx->features, COGL_FEATURE_ID_GLSL, FALSE);
+      COGL_FLAGS_SET (ctx->features,
+                      COGL_FEATURE_ID_PER_VERTEX_POINT_SIZE,
+                      FALSE);
     }
 
   if (G_UNLIKELY (COGL_DEBUG_ENABLED (COGL_DEBUG_DISABLE_NPOT_TEXTURES)))

cogl/cogl-context.h

@@ -214,6 +214,8 @@ cogl_is_context (void *object);
  * @COGL_FEATURE_ID_DEPTH_RANGE: cogl_pipeline_set_depth_range() support
  * @COGL_FEATURE_ID_POINT_SPRITE: Whether
  *     cogl_pipeline_set_layer_point_sprite_coords_enabled() is supported.
+ * @COGL_FEATURE_ID_PER_VERTEX_POINT_SIZE: Whether cogl_point_size_in
+ *     can be used as an attribute to set a per-vertex point size.
  * @COGL_FEATURE_ID_MAP_BUFFER_FOR_READ: Whether cogl_buffer_map() is
  *     supported with CoglBufferAccess including read support.
  * @COGL_FEATURE_ID_MAP_BUFFER_FOR_WRITE: Whether cogl_buffer_map() is
@@ -260,6 +262,7 @@ typedef enum _CoglFeatureID
   COGL_FEATURE_ID_DEPTH_TEXTURE,
   COGL_FEATURE_ID_PRESENTATION_TIME,
   COGL_FEATURE_ID_FENCE,
+  COGL_FEATURE_ID_PER_VERTEX_POINT_SIZE,
 
   /*< private >*/
   _COGL_N_FEATURE_IDS   /*< skip >*/

cogl/cogl-glsl-shader-boilerplate.h

@@ -32,8 +32,7 @@
   "\n" \
   "uniform mat4 cogl_modelview_matrix;\n" \
   "uniform mat4 cogl_modelview_projection_matrix;\n"  \
-  "uniform mat4 cogl_projection_matrix;\n" \
+  "uniform mat4 cogl_projection_matrix;\n"
-  "uniform float cogl_point_size_in;\n"
 
 /* This declares all of the variables that we might need. This is
  * working on the assumption that the compiler will optimise them out

cogl/cogl-pipeline-private.h

@@ -118,6 +118,7 @@ typedef enum
   COGL_PIPELINE_STATE_DEPTH_INDEX,
   COGL_PIPELINE_STATE_FOG_INDEX,
   COGL_PIPELINE_STATE_POINT_SIZE_INDEX,
+  COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE_INDEX,
   COGL_PIPELINE_STATE_LOGIC_OPS_INDEX,
   COGL_PIPELINE_STATE_CULL_FACE_INDEX,
   COGL_PIPELINE_STATE_UNIFORMS_INDEX,
@@ -167,6 +168,8 @@ typedef enum _CoglPipelineState
     1L<<COGL_PIPELINE_STATE_FOG_INDEX,
   COGL_PIPELINE_STATE_POINT_SIZE =
     1L<<COGL_PIPELINE_STATE_POINT_SIZE_INDEX,
+  COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE =
+    1L<<COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE_INDEX,
   COGL_PIPELINE_STATE_LOGIC_OPS =
     1L<<COGL_PIPELINE_STATE_LOGIC_OPS_INDEX,
   COGL_PIPELINE_STATE_CULL_FACE =
@@ -213,6 +216,7 @@ typedef enum _CoglPipelineState
    COGL_PIPELINE_STATE_DEPTH | \
    COGL_PIPELINE_STATE_FOG | \
    COGL_PIPELINE_STATE_POINT_SIZE | \
+   COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE | \
    COGL_PIPELINE_STATE_LOGIC_OPS | \
    COGL_PIPELINE_STATE_CULL_FACE | \
    COGL_PIPELINE_STATE_UNIFORMS | \
@@ -234,6 +238,7 @@ typedef enum _CoglPipelineState
 #define COGL_PIPELINE_STATE_AFFECTS_VERTEX_CODEGEN \
   (COGL_PIPELINE_STATE_LAYERS | \
    COGL_PIPELINE_STATE_USER_SHADER | \
+   COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE |  \
    COGL_PIPELINE_STATE_VERTEX_SNIPPETS)
 
 typedef enum
@@ -329,6 +334,7 @@ typedef struct
   CoglDepthState depth_state;
   CoglPipelineFogState fog_state;
   float point_size;
+  CoglBool per_vertex_point_size;
   CoglPipelineLogicOpsState logic_ops_state;
   CoglPipelineCullFaceState cull_face_state;
   CoglPipelineUniformsState uniforms_state;

cogl/cogl-pipeline-state-private.h

@@ -78,6 +78,9 @@ _cogl_pipeline_fog_state_equal (CoglPipeline *authority0,
 CoglBool
 _cogl_pipeline_point_size_equal (CoglPipeline *authority0,
                                  CoglPipeline *authority1);
+CoglBool
+_cogl_pipeline_per_vertex_point_size_equal (CoglPipeline *authority0,
+                                            CoglPipeline *authority1);
 
 CoglBool
 _cogl_pipeline_logic_ops_state_equal (CoglPipeline *authority0,
@@ -147,6 +150,10 @@ void
 _cogl_pipeline_hash_point_size_state (CoglPipeline *authority,
                                       CoglPipelineHashState *state);
 
+void
+_cogl_pipeline_hash_per_vertex_point_size_state (CoglPipeline *authority,
+                                                 CoglPipelineHashState *state);
+
 void
 _cogl_pipeline_hash_logic_ops_state (CoglPipeline *authority,
                                      CoglPipelineHashState *state);

cogl/cogl-pipeline-state.c

@@ -196,6 +196,14 @@ _cogl_pipeline_point_size_equal (CoglPipeline *authority0,
   return authority0->big_state->point_size == authority1->big_state->point_size;
 }
 
+CoglBool
+_cogl_pipeline_per_vertex_point_size_equal (CoglPipeline *authority0,
+                                            CoglPipeline *authority1)
+{
+  return (authority0->big_state->per_vertex_point_size ==
+          authority1->big_state->per_vertex_point_size);
+}
+
 CoglBool
 _cogl_pipeline_logic_ops_state_equal (CoglPipeline *authority0,
                                       CoglPipeline *authority1)
@@ -1398,6 +1406,63 @@ cogl_pipeline_set_point_size (CoglPipeline *pipeline,
                                    _cogl_pipeline_point_size_equal);
 }
 
+CoglBool
+cogl_pipeline_set_per_vertex_point_size (CoglPipeline *pipeline,
+                                         CoglBool enable,
+                                         CoglError **error)
+{
+  CoglPipelineState state = COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE;
+  CoglPipeline *authority;
+
+  _COGL_GET_CONTEXT (ctx, FALSE);
+  _COGL_RETURN_VAL_IF_FAIL (cogl_is_pipeline (pipeline), FALSE);
+
+  authority = _cogl_pipeline_get_authority (pipeline, state);
+
+  enable = !!enable;
+
+  if (authority->big_state->per_vertex_point_size == enable)
+    return TRUE;
+
+  if (enable && !cogl_has_feature (ctx, COGL_FEATURE_ID_PER_VERTEX_POINT_SIZE))
+    {
+      _cogl_set_error (error,
+                       COGL_SYSTEM_ERROR,
+                       COGL_SYSTEM_ERROR_UNSUPPORTED,
+                       "Per-vertex point size is not supported");
+
+      return FALSE;
+    }
+
+  /* - Flush journal primitives referencing the current state.
+   * - Make sure the pipeline has no dependants so it may be modified.
+   * - If the pipeline isn't currently an authority for the state being
+   *   changed, then initialize that state from the current authority.
+   */
+  _cogl_pipeline_pre_change_notify (pipeline, state, NULL, FALSE);
+
+  pipeline->big_state->per_vertex_point_size = enable;
+
+  _cogl_pipeline_update_authority (pipeline, authority, state,
+                                   _cogl_pipeline_point_size_equal);
+
+  return TRUE;
+}
+
+CoglBool
+cogl_pipeline_get_per_vertex_point_size (CoglPipeline *pipeline)
+{
+  CoglPipeline *authority;
+
+  _COGL_RETURN_VAL_IF_FAIL (cogl_is_pipeline (pipeline), FALSE);
+
+  authority =
+    _cogl_pipeline_get_authority (pipeline,
+                                  COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE);
+
+  return authority->big_state->per_vertex_point_size;
+}
+
 static CoglBoxedValue *
 _cogl_pipeline_override_uniform (CoglPipeline *pipeline,
                                  int location)
@@ -1832,6 +1897,16 @@ _cogl_pipeline_hash_point_size_state (CoglPipeline *authority,
                                                sizeof (point_size));
 }
 
+void
+_cogl_pipeline_hash_per_vertex_point_size_state (CoglPipeline *authority,
+                                                 CoglPipelineHashState *state)
+{
+  CoglBool per_vertex_point_size = authority->big_state->per_vertex_point_size;
+  state->hash = _cogl_util_one_at_a_time_hash (state->hash,
+                                               &per_vertex_point_size,
+                                               sizeof (per_vertex_point_size));
+}
+
 void
 _cogl_pipeline_hash_logic_ops_state (CoglPipeline *authority,
                                      CoglPipelineHashState *state)

cogl/cogl-pipeline-state.h

@@ -516,6 +516,50 @@ cogl_pipeline_set_point_size (CoglPipeline *pipeline,
 float
 cogl_pipeline_get_point_size (CoglPipeline *pipeline);
 
+/**
+ * cogl_pipeline_set_per_vertex_point_size:
+ * @pipeline: a #CoglPipeline pointer
+ * @enable: whether to enable per-vertex point size
+ * @error: a location to store a #CoglError if the change failed
+ *
+ * Sets whether to use a per-vertex point size or to use the value set
+ * by cogl_pipeline_set_point_size(). If per-vertex point size is
+ * enabled then the point size can be set for an individual point
+ * either by drawing with a #CoglAttribute with the name
+ * ‘cogl_point_size_in’ or by writing to the GLSL builtin
+ * ‘cogl_point_size_out’ from a vertex shader snippet.
+ *
+ * If per-vertex point size is enabled and this attribute is not used
+ * and cogl_point_size_out is not written to then the results are
+ * undefined.
+ *
+ * Note that enabling this will only work if the
+ * %COGL_FEATURE_ID_PER_VERTEX_POINT_SIZE feature is available. If
+ * this is not available then the function will return %FALSE and set
+ * a #CoglError.
+ *
+ * Since: 2.0
+ * Stability: Unstable
+ * Return value: %TRUE if the change suceeded or %FALSE otherwise
+ */
+CoglBool
+cogl_pipeline_set_per_vertex_point_size (CoglPipeline *pipeline,
+                                         CoglBool enable,
+                                         CoglError **error);
+
+/**
+ * cogl_pipeline_get_per_vertex_point_size:
+ * @pipeline: a #CoglPipeline pointer
+ *
+ * Since: 2.0
+ * Stability: Unstable
+ * Return value: %TRUE if the pipeline has per-vertex point size
+ *   enabled or %FALSE otherwise. The per-vertex point size can be
+ *   enabled with cogl_pipeline_set_per_vertex_point_size().
+ */
+CoglBool
+cogl_pipeline_get_per_vertex_point_size (CoglPipeline *pipeline);
+
 /**
  * cogl_pipeline_get_color_mask:
  * @pipeline: a #CoglPipeline object.

cogl/cogl-pipeline.c

@@ -1051,6 +1051,9 @@ _cogl_pipeline_copy_differences (CoglPipeline *dest,
   if (differences & COGL_PIPELINE_STATE_POINT_SIZE)
     big_state->point_size = src->big_state->point_size;
 
+  if (differences & COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE)
+    big_state->per_vertex_point_size = src->big_state->per_vertex_point_size;
+
   if (differences & COGL_PIPELINE_STATE_LOGIC_OPS)
     {
       memcpy (&big_state->logic_ops_state,
@@ -1134,6 +1137,7 @@ _cogl_pipeline_init_multi_property_sparse_state (CoglPipeline *pipeline,
     case COGL_PIPELINE_STATE_ALPHA_FUNC_REFERENCE:
     case COGL_PIPELINE_STATE_POINT_SIZE:
     case COGL_PIPELINE_STATE_USER_SHADER:
+    case COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE:
     case COGL_PIPELINE_STATE_REAL_BLEND_ENABLE:
       g_return_if_reached ();
 
@@ -2319,6 +2323,11 @@ _cogl_pipeline_equal (CoglPipeline *pipeline0,
                                                 authorities1[bit]))
             goto done;
           break;
+        case COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE_INDEX:
+          if (!_cogl_pipeline_per_vertex_point_size_equal (authorities0[bit],
+                                                           authorities1[bit]))
+            goto done;
+          break;
         case COGL_PIPELINE_STATE_LOGIC_OPS_INDEX:
           if (!_cogl_pipeline_logic_ops_state_equal (authorities0[bit],
                                                      authorities1[bit]))
@@ -2768,6 +2777,8 @@ _cogl_pipeline_init_state_hash_functions (void)
     _cogl_pipeline_hash_cull_face_state;
   state_hash_functions[COGL_PIPELINE_STATE_POINT_SIZE_INDEX] =
     _cogl_pipeline_hash_point_size_state;
+  state_hash_functions[COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE_INDEX] =
+    _cogl_pipeline_hash_per_vertex_point_size_state;
   state_hash_functions[COGL_PIPELINE_STATE_LOGIC_OPS_INDEX] =
     _cogl_pipeline_hash_logic_ops_state;
   state_hash_functions[COGL_PIPELINE_STATE_UNIFORMS_INDEX] =
@@ -2779,7 +2790,7 @@ _cogl_pipeline_init_state_hash_functions (void)
 
   {
   /* So we get a big error if we forget to update this code! */
-  _COGL_STATIC_ASSERT (COGL_PIPELINE_STATE_SPARSE_COUNT == 16,
+  _COGL_STATIC_ASSERT (COGL_PIPELINE_STATE_SPARSE_COUNT == 17,
                        "Make sure to install a hash function for "
                        "newly added pipeline state and update assert "
                        "in _cogl_pipeline_init_state_hash_functions");

cogl/cogl-private.h

@@ -61,7 +61,8 @@ typedef enum
   /* If this is set then the winsys is responsible for queueing dirty
    * events. Otherwise a dirty event will be queued when the onscreen
    * is first allocated or when it is shown or resized */
-  COGL_PRIVATE_FEATURE_DIRTY_EVENTS = 1L<<25
+  COGL_PRIVATE_FEATURE_DIRTY_EVENTS = 1L<<25,
+  COGL_PRIVATE_FEATURE_ENABLE_PROGRAM_POINT_SIZE = 1L<<26
 } CoglPrivateFeatureFlags;
 
 /* Sometimes when evaluating pipelines, either during comparisons or

cogl/cogl-snippet.h

@@ -203,6 +203,16 @@ COGL_BEGIN_DECLS
  *  </glossentry>
  *  <glossentry>
  *   <glossterm>float
+ *         <emphasis>cogl_point_size_in</emphasis></glossterm>
+ *   <glossdef><para>
+ *    The incoming point size from the cogl_point_size_in attribute.
+ *    This is only available if
+ *    cogl_pipeline_set_per_vertex_point_size() is set on the
+ *    pipeline.
+ *   </para></glossdef>
+ *  </glossentry>
+ *  <glossentry>
+ *   <glossterm>float
  *         <emphasis>cogl_point_size_out</emphasis></glossterm>
  *   <glossdef><para>
  *    The calculated size of a point. This is equivalent to #gl_PointSize.
@@ -321,6 +331,10 @@ typedef struct _CoglSnippet CoglSnippet;
  * @COGL_SNIPPET_HOOK_VERTEX: A hook for the entire vertex processing
  *   stage of the pipeline.
  * @COGL_SNIPPET_HOOK_VERTEX_TRANSFORM: A hook for the vertex transformation.
+ * @COGL_SNIPPET_HOOK_POINT_SIZE: A hook for manipulating the point
+ *   size of a vertex. This is only used if
+ *   cogl_pipeline_set_per_vertex_point_size() is enabled on the
+ *   pipeline.
  * @COGL_SNIPPET_HOOK_FRAGMENT: A hook for the entire fragment
  *   processing stage of the pipeline.
  * @COGL_SNIPPET_HOOK_TEXTURE_COORD_TRANSFORM: A hook for applying the
@@ -422,6 +436,39 @@ typedef struct _CoglSnippet CoglSnippet;
  *   </glossdef>
  *  </glossentry>
  *  <glossentry>
+ *   <glossterm>%COGL_SNIPPET_HOOK_POINT_SIZE</glossterm>
+ *   <glossdef>
+ * <para>
+ * Adds a shader snippet that will hook on to the point size
+ * calculation step within the vertex shader stage. The snippet should
+ * write to the builtin cogl_point_size_out with the new point size.
+ * The snippet can either read cogl_point_size_in directly and write a
+ * new value or first read an existing value in cogl_point_size_out
+ * that would be set by a previous snippet. Note that this hook is
+ * only used if cogl_pipeline_set_per_vertex_point_size() is enabled
+ * on the pipeline.
+ * </para>
+ * <para>
+ * The ‘declarations’ string in @snippet will be inserted in the
+ * global scope of the shader. Use this to declare any uniforms,
+ * attributes or functions that the snippet requires.
+ * </para>
+ * <para>
+ * The ‘pre’ string in @snippet will be inserted just before
+ * calculating the point size.
+ * </para>
+ * <para>
+ * The ‘replace’ string in @snippet will be used instead of the
+ * generated point size calculation if it is present.
+ * </para>
+ * <para>
+ * The ‘post’ string in @snippet will be inserted after the
+ * standard point size calculation is done. This can be used to modify
+ * cogl_point_size_out in addition to the default processing.
+ * </para>
+ *   </glossdef>
+ *  </glossentry>
+ *  <glossentry>
  *   <glossterm>%COGL_SNIPPET_HOOK_FRAGMENT</glossterm>
  *   <glossdef>
  * <para>
@@ -583,6 +630,7 @@ typedef enum {
   COGL_SNIPPET_HOOK_VERTEX = 0,
   COGL_SNIPPET_HOOK_VERTEX_TRANSFORM,
   COGL_SNIPPET_HOOK_VERTEX_GLOBALS,
+  COGL_SNIPPET_HOOK_POINT_SIZE,
 
   /* Per pipeline fragment hooks */
   COGL_SNIPPET_HOOK_FRAGMENT = 2048,

cogl/driver/gl/cogl-pipeline-opengl.c

@@ -58,7 +58,9 @@
 #ifndef GL_CLAMP_TO_BORDER
 #define GL_CLAMP_TO_BORDER 0x812d
 #endif
-
+#ifndef GL_PROGRAM_POINT_SIZE
+#define GL_PROGRAM_POINT_SIZE 0x8642
+#endif
 
 static void
 texture_unit_init (CoglContext *ctx,
@@ -684,6 +686,21 @@ _cogl_pipeline_flush_color_blend_alpha_depth_state (
         }
     }
 
+#ifdef HAVE_COGL_GL
+  if ((ctx->private_feature_flags &
+       COGL_PRIVATE_FEATURE_ENABLE_PROGRAM_POINT_SIZE) &&
+      (pipelines_difference & COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE))
+    {
+      unsigned long state = COGL_PIPELINE_STATE_PER_VERTEX_POINT_SIZE;
+      CoglPipeline *authority = _cogl_pipeline_get_authority (pipeline, state);
+
+      if (authority->big_state->per_vertex_point_size)
+        GE( ctx, glEnable (GL_PROGRAM_POINT_SIZE) );
+      else
+        GE( ctx, glDisable (GL_PROGRAM_POINT_SIZE) );
+    }
+#endif
+
   if (pipeline->real_blend_enable != ctx->gl_blend_enable_cache)
     {
       if (pipeline->real_blend_enable)

cogl/driver/gl/cogl-pipeline-progend-fixed.c

@@ -64,6 +64,11 @@ _cogl_pipeline_progend_fixed_start (CoglPipeline *pipeline)
   if (cogl_pipeline_get_user_program (pipeline))
     return FALSE;
 
+  /* The fixed progend can't handle the per-vertex point size
+   * attribute */
+  if (cogl_pipeline_get_per_vertex_point_size (pipeline))
+    return FALSE;
+
   return TRUE;
 }
 

cogl/driver/gl/cogl-pipeline-vertend-glsl.c

@@ -290,13 +290,21 @@ _cogl_pipeline_vertend_glsl_start (CoglPipeline *pipeline,
                    "cogl_generated_source ()\n"
                    "{\n");
 
-  if (!(ctx->private_feature_flags &
+  if (cogl_pipeline_get_per_vertex_point_size (pipeline))
+    g_string_append (shader_state->header,
+                     "attribute float cogl_point_size_in;\n");
+  else if (!(ctx->private_feature_flags &
             COGL_PRIVATE_FEATURE_BUILTIN_POINT_SIZE_UNIFORM))
-    /* There is no builtin uniform for the pointsize on GLES2 so we need
+    {
-       to copy it from the custom uniform in the vertex shader */
+      /* There is no builtin uniform for the point size on GLES2 so we
+         need to copy it from the custom uniform in the vertex shader if
+         we're not using per-vertex point sizes */
+      g_string_append (shader_state->header,
+                       "uniform float cogl_point_size_in;\n");
       g_string_append (shader_state->source,
                        "  cogl_point_size_out = cogl_point_size_in;\n");
     }
+}
 
 static CoglBool
 _cogl_pipeline_vertend_glsl_add_layer (CoglPipeline *pipeline,
@@ -389,6 +397,8 @@ _cogl_pipeline_vertend_glsl_end (CoglPipeline *pipeline,
       GLuint shader;
       CoglPipelineSnippetData snippet_data;
       CoglPipelineSnippetList *vertex_snippets;
+      CoglBool has_per_vertex_point_size =
+        cogl_pipeline_get_per_vertex_point_size (pipeline);
 
       COGL_STATIC_COUNTER (vertend_glsl_compile_counter,
                            "glsl vertex compile counter",
@@ -407,7 +417,21 @@ _cogl_pipeline_vertend_glsl_end (CoglPipeline *pipeline,
                        "}\n");
 
       g_string_append (shader_state->source,
-                       "  cogl_vertex_transform ();\n"
+                       "  cogl_vertex_transform ();\n");
+
+      if (has_per_vertex_point_size)
+        {
+          g_string_append (shader_state->header,
+                           "void\n"
+                           "cogl_real_point_size_calculation ()\n"
+                           "{\n"
+                           "  cogl_point_size_out = cogl_point_size_in;\n"
+                           "}\n");
+          g_string_append (shader_state->source,
+                           "  cogl_point_size_calculation ();\n");
+        }
+
+      g_string_append (shader_state->source,
                        "  cogl_color_out = cogl_color_in;\n"
                        "}\n");
 
@@ -423,6 +447,19 @@ _cogl_pipeline_vertend_glsl_end (CoglPipeline *pipeline,
       snippet_data.source_buf = shader_state->header;
       _cogl_pipeline_snippet_generate_code (&snippet_data);
 
+      /* Add hooks for the point size calculation part */
+      if (has_per_vertex_point_size)
+        {
+          memset (&snippet_data, 0, sizeof (snippet_data));
+          snippet_data.snippets = vertex_snippets;
+          snippet_data.hook = COGL_SNIPPET_HOOK_POINT_SIZE;
+          snippet_data.chain_function = "cogl_real_point_size_calculation";
+          snippet_data.final_name = "cogl_point_size_calculation";
+          snippet_data.function_prefix = "cogl_point_size_calculation";
+          snippet_data.source_buf = shader_state->header;
+          _cogl_pipeline_snippet_generate_code (&snippet_data);
+        }
+
       /* Add all of the hooks for vertex processing */
       memset (&snippet_data, 0, sizeof (snippet_data));
       snippet_data.snippets = vertex_snippets;
@@ -487,6 +524,7 @@ _cogl_pipeline_vertend_glsl_end (CoglPipeline *pipeline,
       shader_state->gl_shader = shader;
     }
 
+#ifdef HAVE_COGL_GL
   if ((ctx->private_feature_flags &
        COGL_PRIVATE_FEATURE_BUILTIN_POINT_SIZE_UNIFORM) &&
       (pipelines_difference & COGL_PIPELINE_STATE_POINT_SIZE))
@@ -496,6 +534,7 @@ _cogl_pipeline_vertend_glsl_end (CoglPipeline *pipeline,
 
       GE( ctx, glPointSize (authority->big_state->point_size) );
     }
+#endif /* HAVE_COGL_GL */
 
   return TRUE;
 }

cogl/driver/gl/gl/cogl-driver-gl.c

@@ -569,11 +569,23 @@ _cogl_driver_update_features (CoglContext *ctx,
   if (ctx->glGenSamplers)
     private_flags |= COGL_PRIVATE_FEATURE_SAMPLER_OBJECTS;
 
+
   if (COGL_CHECK_GL_VERSION (gl_major, gl_minor, 3, 3) ||
       _cogl_check_extension ("GL_ARB_texture_swizzle", gl_extensions) ||
       _cogl_check_extension ("GL_EXT_texture_swizzle", gl_extensions))
     private_flags |= COGL_PRIVATE_FEATURE_TEXTURE_SWIZZLE;
 
+  /* The per-vertex point size is only available via GLSL with the
+   * gl_PointSize builtin. This is only available in GL 2.0 (not the
+   * GLSL extensions) */
+  if (COGL_CHECK_GL_VERSION (gl_major, gl_minor, 2, 0))
+    {
+      COGL_FLAGS_SET (ctx->features,
+                      COGL_FEATURE_ID_PER_VERTEX_POINT_SIZE,
+                      TRUE);
+      private_flags |= COGL_PRIVATE_FEATURE_ENABLE_PROGRAM_POINT_SIZE;
+    }
+
   if (ctx->driver == COGL_DRIVER_GL)
     {
       int max_clip_planes = 0;

cogl/driver/gl/gl/cogl-pipeline-progend-fixed-arbfp.c

@@ -73,6 +73,11 @@ _cogl_pipeline_progend_fixed_arbfp_start (CoglPipeline *pipeline)
       _cogl_program_get_language (user_program) != COGL_SHADER_LANGUAGE_ARBFP)
     return FALSE;
 
+  /* The ARBfp progend can't handle the per-vertex point size
+   * attribute */
+  if (cogl_pipeline_get_per_vertex_point_size (pipeline))
+    return FALSE;
+
   return TRUE;
 }
 

cogl/driver/gl/gles/cogl-driver-gles.c

@@ -256,6 +256,8 @@ _cogl_driver_update_features (CoglContext *context,
       COGL_FLAGS_SET (context->features, COGL_FEATURE_ID_DEPTH_RANGE, TRUE);
       COGL_FLAGS_SET (context->features,
                       COGL_FEATURE_ID_MIRRORED_REPEAT, TRUE);
+      COGL_FLAGS_SET (context->features,
+                      COGL_FEATURE_ID_PER_VERTEX_POINT_SIZE, TRUE);
 
       private_flags |= COGL_PRIVATE_FEATURE_BLEND_CONSTANT;
     }

doc/reference/cogl-2.0-experimental/cogl-2.0-experimental-sections.txt

@@ -834,6 +834,8 @@ cogl_pipeline_set_blend
 cogl_pipeline_set_blend_constant
 cogl_pipeline_set_point_size
 cogl_pipeline_get_point_size
+cogl_pipeline_set_per_vertex_point_size
+cogl_pipeline_get_per_vertex_point_size
 
 cogl_pipeline_get_color_mask
 cogl_pipeline_set_color_mask

examples/cogl-info.c

@@ -115,6 +115,12 @@ struct {
     "Depth Textures",
     "CoglFramebuffers can be configured to render their depth buffer into "
     "a texture"
+  },
+  {
+    COGL_FEATURE_ID_PER_VERTEX_POINT_SIZE,
+    "Per-vertex point size",
+    "cogl_point_size_in can be used as an attribute to specify a per-vertex "
+    "point size"
   }
 };
 

test-fixtures/test-utils.c

@@ -49,6 +49,12 @@ check_flags (TestFlags flags,
       return FALSE;
     }
 
+  if (flags & TEST_REQUIREMENT_PER_VERTEX_POINT_SIZE &&
+      !cogl_has_feature (test_ctx, COGL_FEATURE_ID_PER_VERTEX_POINT_SIZE))
+    {
+      return FALSE;
+    }
+
   if (flags & TEST_REQUIREMENT_GLES2_CONTEXT &&
       !cogl_has_feature (test_ctx, COGL_FEATURE_ID_GLES2_CONTEXT))
     {

test-fixtures/test-utils.h

@@ -22,7 +22,8 @@ typedef enum _TestFlags
   TEST_REQUIREMENT_MAP_WRITE = 1<<7,
   TEST_REQUIREMENT_GLSL = 1<<8,
   TEST_REQUIREMENT_OFFSCREEN = 1<<9,
-  TEST_REQUIREMENT_FENCE = 1<<10
+  TEST_REQUIREMENT_FENCE = 1<<10,
+  TEST_REQUIREMENT_PER_VERTEX_POINT_SIZE = 1<<11
 } TestFlags;
 
 extern CoglContext *test_ctx;

tests/conform/Makefile.am

@@ -48,6 +48,7 @@ test_sources = \
 	test-read-texture-formats.c \
 	test-write-texture-formats.c \
 	test-point-size.c \
+	test-point-size-attribute.c \
 	test-point-sprite.c \
 	test-no-gl-header.c \
 	test-version.c \

tests/conform/test-conform-main.c

@@ -102,6 +102,11 @@ main (int argc, char **argv)
             0);
 
   ADD_TEST (test_point_size, 0, 0);
+  ADD_TEST (test_point_size_attribute,
+            TEST_REQUIREMENT_PER_VERTEX_POINT_SIZE, 0);
+  ADD_TEST (test_point_size_attribute_snippet,
+            TEST_REQUIREMENT_PER_VERTEX_POINT_SIZE |
+            TEST_REQUIREMENT_GLSL, 0);
   ADD_TEST (test_point_sprite,
             TEST_REQUIREMENT_POINT_SPRITE,
             0);

tests/conform/test-point-size-attribute.c

@@ -0,0 +1,166 @@
+#include <cogl/cogl.h>
+
+#include "test-utils.h"
+
+/* This test assumes the GL driver supports point sizes up to 16
+   pixels. Cogl should probably have some way of querying the size so
+   we start from that instead */
+#define MAX_POINT_SIZE 16
+#define MIN_POINT_SIZE 4
+#define N_POINTS (MAX_POINT_SIZE - MIN_POINT_SIZE + 1)
+/* The size of the area that we'll paint each point in */
+#define POINT_BOX_SIZE (MAX_POINT_SIZE * 2)
+
+typedef struct
+{
+  float x, y;
+  float point_size;
+} PointVertex;
+
+static int
+calc_coord_offset (int pos, int pos_index, int point_size)
+{
+  switch (pos_index)
+    {
+    case 0: return pos - point_size / 2 - 2;
+    case 1: return pos - point_size / 2 + 2;
+    case 2: return pos + point_size / 2 - 2;
+    case 3: return pos + point_size / 2 + 2;
+    }
+
+  g_assert_not_reached ();
+}
+
+static void
+verify_point_size (CoglFramebuffer *test_fb,
+                   int x_pos,
+                   int y_pos,
+                   int point_size)
+{
+  int y, x;
+
+  for (y = 0; y < 4; y++)
+    for (x = 0; x < 4; x++)
+      {
+        CoglBool in_point = x >= 1 && x <= 2 && y >= 1 && y <= 2;
+        uint32_t expected_pixel = in_point ? 0x00ff00ff : 0xff0000ff;
+
+        test_utils_check_pixel (test_fb,
+                                calc_coord_offset (x_pos, x, point_size),
+                                calc_coord_offset (y_pos, y, point_size),
+                                expected_pixel);
+      }
+}
+
+static CoglPrimitive *
+create_primitive (const char *attribute_name)
+{
+  PointVertex vertices[N_POINTS];
+  CoglAttributeBuffer *buffer;
+  CoglAttribute *attributes[2];
+  CoglPrimitive *prim;
+  int i;
+
+  for (i = 0; i < N_POINTS; i++)
+    {
+      vertices[i].x = i * POINT_BOX_SIZE + POINT_BOX_SIZE / 2;
+      vertices[i].y = POINT_BOX_SIZE / 2;
+      vertices[i].point_size = MAX_POINT_SIZE - i;
+    }
+
+  buffer = cogl_attribute_buffer_new (test_ctx,
+                                      sizeof (vertices),
+                                      vertices);
+
+  attributes[0] = cogl_attribute_new (buffer,
+                                      "cogl_position_in",
+                                      sizeof (PointVertex),
+                                      G_STRUCT_OFFSET (PointVertex, x),
+                                      2, /* n_components */
+                                      COGL_ATTRIBUTE_TYPE_FLOAT);
+  attributes[1] = cogl_attribute_new (buffer,
+                                      attribute_name,
+                                      sizeof (PointVertex),
+                                      G_STRUCT_OFFSET (PointVertex, point_size),
+                                      1, /* n_components */
+                                      COGL_ATTRIBUTE_TYPE_FLOAT);
+
+  prim = cogl_primitive_new_with_attributes (COGL_VERTICES_MODE_POINTS,
+                                             N_POINTS,
+                                             attributes,
+                                             2 /* n_attributes */);
+
+  for (i = 0; i < 2; i++)
+    cogl_object_unref (attributes[i]);
+
+  return prim;
+}
+
+static void
+do_test (const char *attribute_name,
+         void (* pipeline_setup_func) (CoglPipeline *pipeline))
+{
+  int fb_width = cogl_framebuffer_get_width (test_fb);
+  int fb_height = cogl_framebuffer_get_height (test_fb);
+  CoglPrimitive *primitive;
+  CoglPipeline *pipeline;
+  int i;
+
+  cogl_framebuffer_orthographic (test_fb,
+                                 0, 0, /* x_1, y_1 */
+                                 fb_width, /* x_2 */
+                                 fb_height /* y_2 */,
+                                 -1, 100 /* near/far */);
+
+  cogl_framebuffer_clear4f (test_fb,
+                            COGL_BUFFER_BIT_COLOR,
+                            1.0f, 0.0f, 0.0f, 1.0f);
+
+  primitive = create_primitive (attribute_name);
+  pipeline = cogl_pipeline_new (test_ctx);
+  cogl_pipeline_set_color4ub (pipeline, 0x00, 0xff, 0x00, 0xff);
+  cogl_pipeline_set_per_vertex_point_size (pipeline, TRUE, NULL);
+  if (pipeline_setup_func)
+    pipeline_setup_func (pipeline);
+  cogl_framebuffer_draw_primitive (test_fb, pipeline, primitive);
+  cogl_object_unref (pipeline);
+  cogl_object_unref (primitive);
+
+  /* Verify all of the points where drawn at the right size */
+  for (i = 0; i < N_POINTS; i++)
+    verify_point_size (test_fb,
+                       i * POINT_BOX_SIZE + POINT_BOX_SIZE / 2, /* x */
+                       POINT_BOX_SIZE / 2, /* y */
+                       MAX_POINT_SIZE - i /* point size */);
+
+  if (cogl_test_verbose ())
+    g_print ("OK\n");
+}
+
+void
+test_point_size_attribute (void)
+{
+  do_test ("cogl_point_size_in", NULL);
+}
+
+static void
+setup_snippet (CoglPipeline *pipeline)
+{
+  CoglSnippet *snippet;
+
+  snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_POINT_SIZE,
+                              "attribute float "
+                              "my_super_duper_point_size_attrib;\n",
+                              NULL);
+  cogl_snippet_set_replace (snippet,
+                            "cogl_point_size_out = "
+                            "my_super_duper_point_size_attrib;\n");
+  cogl_pipeline_add_snippet (pipeline, snippet);
+  cogl_object_unref (snippet);
+}
+
+void
+test_point_size_attribute_snippet (void)
+{
+  do_test ("my_super_duper_point_size_attrib", setup_snippet);
+}