cogl-primitive: Add the missing cogl_primitive_new_p2 function

There was a struct defined for CoglP2Vertex but there was no
constructor function to use it.

clutter/cogl/cogl/cogl-primitive.c

@@ -120,6 +120,33 @@ cogl_primitive_new (CoglVerticesMode mode,
                                                    attributes);
 }
 
+CoglPrimitive *
+cogl_primitive_new_p2 (CoglVerticesMode mode,
+                       int n_vertices,
+                       const CoglP2Vertex *data)
+{
+  CoglVertexArray *array =
+    cogl_vertex_array_new (n_vertices * sizeof (CoglP2Vertex));
+  CoglBuffer *buffer = COGL_BUFFER (array);
+  CoglVertexAttribute *attributes[2];
+
+  cogl_buffer_set_data (buffer, 0, (guint8 *)data,
+                        n_vertices * sizeof (CoglP2Vertex));
+  attributes[0] =
+    cogl_vertex_attribute_new (array,
+                               "cogl_position_in",
+                               sizeof (CoglP2Vertex),
+                               offsetof (CoglP2Vertex, x),
+                               2,
+                               COGL_VERTEX_ATTRIBUTE_TYPE_FLOAT);
+  attributes[1] = NULL;
+
+  cogl_object_unref (array);
+
+  return _cogl_primitive_new_with_attributes_array_unref (mode, n_vertices,
+                                                          attributes);
+}
+
 CoglPrimitive *
 cogl_primitive_new_p3 (CoglVerticesMode mode,
                        int n_vertices,

clutter/cogl/cogl/cogl-primitive.h

@@ -237,6 +237,50 @@ cogl_primitive_new_with_attributes_array (CoglVerticesMode mode,
                                           int n_vertices,
                                           CoglVertexAttribute **attributes);
 
+/**
+ * cogl_primitive_new_p2:
+ * @mode: A #CoglVerticesMode defining how to draw the vertices
+ * @n_vertices: The number of vertices to process when drawing
+ * @data: An array of #CoglP2Vertex vertices
+ *
+ * Provides a convenient way to describe a primitive, such as a single
+ * triangle strip or a triangle fan, that will internally allocate the
+ * necessary #CoglVertexArray storage, describe the position
+ * attribute with a #CoglVertexAttribute and upload your data.
+ *
+ * For example to draw a convex polygon you can do:
+ * |[
+ * CoglP2Vertex triangle[] =
+ * {
+ *   { 0,   300 },
+ *   { 150, 0,  },
+ *   { 300, 300 }
+ * };
+ * prim = cogl_primitive_new_p2 (COGL_VERTICES_MODE_TRIANGLE_FAN,
+ *                               3, triangle);
+ * cogl_primitive_draw (prim);
+ * ]|
+ *
+ * <note>The primitive API doesn't support drawing with sliced
+ * textures (since switching between slices implies changing state and
+ * so that implies multiple primitives need to be submitted). You
+ * should pass the %COGL_TEXTURE_NO_SLICING flag to all textures that
+ * might be used while drawing with this API. If your hardware doesn't
+ * support non-power of two textures (For example you are using GLES
+ * 1.1) then you will need to make sure your assets are resized to a
+ * power-of-two size (though they don't have to be square)</note>
+ *
+ * Return value: A newly allocated #CoglPrimitive with a reference of
+ * 1. This can be freed using cogl_object_unref().
+ *
+ * Since: 1.6
+ * Stability: Unstable
+ */
+CoglPrimitive *
+cogl_primitive_new_p2 (CoglVerticesMode mode,
+                       int n_vertices,
+                       const CoglP2Vertex *data);
+
 /**
  * cogl_primitive_new_p3:
  * @mode: A #CoglVerticesMode defining how to draw the vertices