mutter/cogl/cogl-primitives.c

/*
 * Cogl
 *
 * An object oriented GL/GLES Abstraction/Utility Layer
 *
 * Copyright (C) 2007,2008,2009 Intel Corporation.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "cogl.h"
#include "cogl-internal.h"
#include "cogl-context.h"
#include "cogl-journal-private.h"
#include "cogl-texture-private.h"
#include "cogl-material-private.h"
#include "cogl-vertex-buffer-private.h"
#include "cogl-draw-buffer-private.h"

#include <string.h>
#include <math.h>

#define _COGL_MAX_BEZ_RECURSE_DEPTH 16


typedef struct _TextureSlicedQuadState
{
  CoglHandle material;
  float tex_virtual_origin_x;
  float tex_virtual_origin_y;
  float quad_origin_x;
  float quad_origin_y;
  float v_to_q_scale_x;
  float v_to_q_scale_y;
  float quad_len_x;
  float quad_len_y;
  gboolean flipped_x;
  gboolean flipped_y;
} TextureSlicedQuadState;

typedef struct _TextureSlicedPolygonState
{
  CoglTextureVertex *vertices;
  int n_vertices;
  int stride;
} TextureSlicedPolygonState;

/* these are defined in the particular backend */
void _cogl_path_add_node    (gboolean new_sub_path,
			     float x,
                             float y);
void _cogl_path_fill_nodes    ();
void _cogl_path_stroke_nodes  ();

static void
log_quad_sub_textures_cb (CoglHandle texture_handle,
                          GLuint gl_handle,
                          GLenum gl_target,
                          float *subtexture_coords,
                          float *virtual_coords,
                          void *user_data)
{
  TextureSlicedQuadState *state = user_data;
  float quad_coords[4];

#define TEX_VIRTUAL_TO_QUAD(V, Q, AXIS) \
    do { \
	Q = V - state->tex_virtual_origin_##AXIS; \
	Q *= state->v_to_q_scale_##AXIS; \
	if (state->flipped_##AXIS) \
	    Q = state->quad_len_##AXIS - Q; \
	Q += state->quad_origin_##AXIS; \
    } while (0);

  TEX_VIRTUAL_TO_QUAD (virtual_coords[0], quad_coords[0], x);
  TEX_VIRTUAL_TO_QUAD (virtual_coords[1], quad_coords[1], y);

  TEX_VIRTUAL_TO_QUAD (virtual_coords[2], quad_coords[2], x);
  TEX_VIRTUAL_TO_QUAD (virtual_coords[3], quad_coords[3], y);

#undef TEX_VIRTUAL_TO_QUAD

  COGL_NOTE (DRAW,
             "~~~~~ slice\n"
             "qx1: %f\t"
             "qy1: %f\n"
             "qx2: %f\t"
             "qy2: %f\n"
             "tx1: %f\t"
             "ty1: %f\n"
             "tx2: %f\t"
             "ty2: %f\n",
             quad_coords[0], quad_coords[1],
             quad_coords[2], quad_coords[3],
             subtexture_coords[0], subtexture_coords[1],
             subtexture_coords[2], subtexture_coords[3]);

  /* FIXME: when the wrap mode becomes part of the material we need to
   * be able to override the wrap mode when logging a quad. */
  _cogl_journal_log_quad (quad_coords[0],
                          quad_coords[1],
                          quad_coords[2],
                          quad_coords[3],
                          state->material,
                          1, /* one layer */
                          0, /* don't need to use fallbacks */
                          gl_handle, /* replace the layer0 texture */
                          subtexture_coords,
                          4);
}

/* This path doesn't currently support multitexturing but is used for
 * CoglTextures that don't support repeating using the GPU so we need to
 * manually emit extra geometry to fake the repeating. This includes:
 *
 * - CoglTexture2DSliced: when made of > 1 slice or if the users given
 *   texture coordinates require repeating,
 * - CoglTexture2DAtlas: if the users given texture coordinates require
 *   repeating,
 * - CoglTextureRectangle: if the users given texture coordinates require
 *   repeating,
 * - CoglTexturePixmap: if the users given texture coordinates require
 *   repeating
 */
/* TODO: support multitexturing */
static void
_cogl_texture_quad_multiple_primitives (CoglHandle   tex_handle,
                                        CoglHandle   material,
                                        float        x_1,
                                        float        y_1,
                                        float        x_2,
                                        float        y_2,
                                        float        tx_1,
                                        float        ty_1,
                                        float        tx_2,
                                        float        ty_2)
{
  TextureSlicedQuadState state;
  gboolean tex_virtual_flipped_x;
  gboolean tex_virtual_flipped_y;
  gboolean quad_flipped_x;
  gboolean quad_flipped_y;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  COGL_NOTE (DRAW, "Drawing Tex Quad (Multi-Prim Mode)");

  /* We can't use hardware repeat so we need to set clamp to edge
     otherwise it might pull in edge pixels from the other side */
  /* FIXME: wrap modes should be part of the material! */
  _cogl_texture_set_wrap_mode_parameter (tex_handle, GL_CLAMP_TO_EDGE);

  state.material = material;

  /* Get together the data we need to transform the virtual texture
   * coordinates of each slice into quad coordinates...
   *
   * NB: We need to consider that the quad coordinates and the texture
   * coordinates may be inverted along the x or y axis, and must preserve the
   * inversions when we emit the final geometry.
   */

  tex_virtual_flipped_x = (tx_1 > tx_2) ? TRUE : FALSE;
  tex_virtual_flipped_y = (ty_1 > ty_2) ? TRUE : FALSE;
  state.tex_virtual_origin_x = tex_virtual_flipped_x ? tx_2 : tx_1;
  state.tex_virtual_origin_y = tex_virtual_flipped_y ? ty_2 : ty_1;

  quad_flipped_x = (x_1 > x_2) ? TRUE : FALSE;
  quad_flipped_y = (y_1 > y_2) ? TRUE : FALSE;
  state.quad_origin_x = quad_flipped_x ? x_2 : x_1;
  state.quad_origin_y = quad_flipped_y ? y_2 : y_1;

  /* flatten the two forms of coordinate inversion into one... */
  state.flipped_x = tex_virtual_flipped_x ^ quad_flipped_x;
  state.flipped_y = tex_virtual_flipped_y ^ quad_flipped_y;

  /* We use the _len_AXIS naming here instead of _width and _height because
   * log_quad_slice_cb uses a macro with symbol concatenation to handle both
   * axis, so this is more convenient... */
  state.quad_len_x = fabs (x_2 - x_1);
  state.quad_len_y = fabs (y_2 - y_1);

  state.v_to_q_scale_x = fabs (state.quad_len_x / (tx_2 - tx_1));
  state.v_to_q_scale_y = fabs (state.quad_len_y / (ty_2 - ty_1));

  _cogl_texture_foreach_sub_texture_in_region (tex_handle,
                                               tx_1, ty_1, tx_2, ty_2,
                                               log_quad_sub_textures_cb,
                                               &state);
}

/* This path supports multitexturing but only when each of the layers is
 * handled with a single GL texture. Also if repeating is necessary then
 * _cogl_texture_can_hardware_repeat() must return TRUE.
 * This includes layers made from:
 *
 * - CoglTexture2DSliced: if only comprised of a single slice with optional
 *   waste, assuming the users given texture coordinates don't require
 *   repeating.
 * - CoglTexture{1D,2D,3D}: always.
 * - CoglTexture2DAtlas: assuming the users given texture coordinates don't
 *   require repeating.
 * - CoglTextureRectangle: assuming the users given texture coordinates don't
 *   require repeating.
 * - CoglTexturePixmap: assuming the users given texture coordinates don't
 *   require repeating.
 */
static gboolean
_cogl_multitexture_quad_single_primitive (float        x_1,
                                          float        y_1,
                                          float        x_2,
                                          float        y_2,
                                          CoglHandle   material,
                                          guint32      fallback_layers,
                                          const float *user_tex_coords,
                                          int          user_tex_coords_len)
{
  int          n_layers = cogl_material_get_n_layers (material);
  float       *final_tex_coords = alloca (sizeof (float) * 4 * n_layers);
  const GList *layers;
  GList       *tmp;
  int          i;

  _COGL_GET_CONTEXT (ctx, FALSE);

  /*
   * Validate the texture coordinates for this rectangle.
   */
  layers = cogl_material_get_layers (material);
  for (tmp = (GList *)layers, i = 0; tmp != NULL; tmp = tmp->next, i++)
    {
      CoglHandle         layer = (CoglHandle)tmp->data;
      CoglHandle         tex_handle;
      const float       *in_tex_coords;
      float             *out_tex_coords;
      float              default_tex_coords[4] = {0.0, 0.0, 1.0, 1.0};

      tex_handle = cogl_material_layer_get_texture (layer);

      /* COGL_INVALID_HANDLE textures are handled by
       * _cogl_material_flush_gl_state */
      if (tex_handle == COGL_INVALID_HANDLE)
        continue;

      in_tex_coords = &user_tex_coords[i * 4];
      out_tex_coords = &final_tex_coords[i * 4];


      /* If the texture has waste or we are using GL_TEXTURE_RECT we
       * can't handle texture repeating so we check that the texture
       * coords lie in the range [0,1].
       *
       * NB: We already know that the texture isn't sliced so we can assume
       * that the default coords (0,0) and (1,1) would only reference a single
       * GL texture.
       *
       * NB: We already know that no texture matrix is being used if the
       * texture doesn't support hardware repeat.
       */
      if (!_cogl_texture_can_hardware_repeat (tex_handle)
           && i < user_tex_coords_len / 4
           && (in_tex_coords[0] < 0 || in_tex_coords[0] > 1.0
               || in_tex_coords[1] < 0 || in_tex_coords[1] > 1.0
               || in_tex_coords[2] < 0 || in_tex_coords[2] > 1.0
               || in_tex_coords[3] < 0 || in_tex_coords[3] > 1.0))
        {
          if (i == 0)
            {
              if (n_layers > 1)
                {
                  static gboolean warning_seen = FALSE;
                  if (!warning_seen)
                    g_warning ("Skipping layers 1..n of your material since "
                               "the first layer doesn't support hardware "
                               "repeat (e.g. because of waste or use of "
                               "GL_TEXTURE_RECTANGLE_ARB) and you supplied "
                               "texture coordinates outside the range [0,1]."
                               "Falling back to software repeat assuming "
                               "layer 0 is the most important one keep");
                  warning_seen = TRUE;
                }
              return FALSE;
            }
          else
            {
              static gboolean warning_seen = FALSE;
              if (!warning_seen)
                g_warning ("Skipping layer %d of your material "
                           "since you have supplied texture coords "
                           "outside the range [0,1] but the texture "
                           "doesn't support hardware repeat (e.g. "
                           "because of waste or use of "
                           "GL_TEXTURE_RECTANGLE_ARB). This isn't "
                           "supported with multi-texturing.", i);
              warning_seen = TRUE;

              /* NB: marking for fallback will replace the layer with
               * a default transparent texture */
              fallback_layers |= (1 << i);
            }
        }


      /*
       * Setup the texture unit...
       */

      /* NB: The user might not have supplied texture coordinates for all
       * layers... */
      if (i < (user_tex_coords_len / 4))
        {
          GLenum wrap_mode;

          /* If the texture coords are all in the range [0,1] then we want to
             clamp the coords to the edge otherwise it can pull in edge pixels
             from the wrong side when scaled */
          if (in_tex_coords[0] >= 0 && in_tex_coords[0] <= 1.0
              && in_tex_coords[1] >= 0 && in_tex_coords[1] <= 1.0
              && in_tex_coords[2] >= 0 && in_tex_coords[2] <= 1.0
              && in_tex_coords[3] >= 0 && in_tex_coords[3] <= 1.0)
            wrap_mode = GL_CLAMP_TO_EDGE;
          else
            wrap_mode = GL_REPEAT;

          memcpy (out_tex_coords, in_tex_coords, sizeof (GLfloat) * 4);

          _cogl_texture_set_wrap_mode_parameter (tex_handle, wrap_mode);
        }
      else
        {
          memcpy (out_tex_coords, default_tex_coords, sizeof (GLfloat) * 4);

          _cogl_texture_set_wrap_mode_parameter (tex_handle, GL_CLAMP_TO_EDGE);
        }

      _cogl_texture_transform_coords_to_gl (tex_handle,
                                            &out_tex_coords[0],
                                            &out_tex_coords[1]);
      _cogl_texture_transform_coords_to_gl (tex_handle,
                                            &out_tex_coords[2],
                                            &out_tex_coords[3]);
    }

  _cogl_journal_log_quad (x_1,
                          y_1,
                          x_2,
                          y_2,
                          material,
                          n_layers,
                          fallback_layers,
                          0, /* don't replace the layer0 texture */
                          final_tex_coords,
                          n_layers * 4);

  return TRUE;
}

struct _CoglMutiTexturedRect
{
  float        x_1;
  float        y_1;
  float        x_2;
  float        y_2;
  const float *tex_coords;
  gint             tex_coords_len;
};

static void
_cogl_rectangles_with_multitexture_coords (
                                        struct _CoglMutiTexturedRect *rects,
                                        gint                          n_rects)
{
  CoglHandle	 material;
  const GList	*layers;
  int		 n_layers;
  const GList	*tmp;
  guint32        fallback_layers = 0;
  gboolean	 all_use_sliced_quad_fallback = FALSE;
  int		 i;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  material = ctx->source_material;

  layers = cogl_material_get_layers (material);
  n_layers = cogl_material_get_n_layers (material);

  /*
   * Validate all the layers of the current source material...
   */

  for (tmp = layers, i = 0; tmp != NULL; tmp = tmp->next, i++)
    {
      CoglHandle     layer = tmp->data;
      CoglHandle     tex_handle;
      gulong         flags;

      if (cogl_material_layer_get_type (layer)
	  != COGL_MATERIAL_LAYER_TYPE_TEXTURE)
	continue;

      tex_handle = cogl_material_layer_get_texture (layer);

      /* COGL_INVALID_HANDLE textures are handled by
       * _cogl_material_flush_gl_state */
      if (tex_handle == COGL_INVALID_HANDLE)
        continue;

      /* XXX:
       * For now, if the first layer is sliced then all other layers are
       * ignored since we currently don't support multi-texturing with
       * sliced textures. If the first layer is not sliced then any other
       * layers found to be sliced will be skipped. (with a warning)
       *
       * TODO: Add support for multi-texturing rectangles with sliced
       * textures if no texture matrices are in use.
       */
      if (cogl_texture_is_sliced (tex_handle))
	{
	  if (i == 0)
	    {
              fallback_layers = ~1; /* fallback all except the first layer */
	      all_use_sliced_quad_fallback = TRUE;
              if (tmp->next)
                {
                  static gboolean warning_seen = FALSE;
                  if (!warning_seen)
                    g_warning ("Skipping layers 1..n of your material since "
                               "the first layer is sliced. We don't currently "
                               "support any multi-texturing with sliced "
                               "textures but assume layer 0 is the most "
                               "important to keep");
                  warning_seen = TRUE;
                }
	      break;
	    }
          else
            {
              static gboolean warning_seen = FALSE;
              if (!warning_seen)
                g_warning ("Skipping layer %d of your material consisting of "
                           "a sliced texture (unsuported for multi texturing)",
                           i);
              warning_seen = TRUE;

              /* NB: marking for fallback will replace the layer with
               * a default transparent texture */
              fallback_layers |= (1 << i);
	      continue;
            }
	}

      /* If the texture can't be repeated with the GPU (e.g. because it has
       * waste or if using GL_TEXTURE_RECTANGLE_ARB) then we don't support
       * multi texturing since we don't know if the result will end up trying
       * to texture from the waste area. */
      flags = _cogl_material_layer_get_flags (layer);
      if (flags & COGL_MATERIAL_LAYER_FLAG_HAS_USER_MATRIX
          && !_cogl_texture_can_hardware_repeat (tex_handle))
        {
          static gboolean warning_seen = FALSE;
          if (!warning_seen)
            g_warning ("Skipping layer %d of your material since a custom "
                       "texture matrix was given for a texture that can't be "
                       "repeated using the GPU and the result may try to "
                       "sample beyond the bounds of the texture ",
                       i);
          warning_seen = TRUE;

          /* NB: marking for fallback will replace the layer with
           * a default transparent texture */
          fallback_layers |= (1 << i);
          continue;
        }
    }

  /*
   * Emit geometry for each of the rectangles...
   */

  for (i = 0; i < n_rects; i++)
    {
      CoglHandle   first_layer, tex_handle;
      const float  default_tex_coords[4] = {0.0, 0.0, 1.0, 1.0};
      const float *tex_coords;

      if (!all_use_sliced_quad_fallback)
        {
          gboolean success =
            _cogl_multitexture_quad_single_primitive (rects[i].x_1,
                                                      rects[i].y_1,
                                                      rects[i].x_2,
                                                      rects[i].y_2,
                                                      material,
                                                      fallback_layers,
                                                      rects[i].tex_coords,
                                                      rects[i].tex_coords_len);

          /* NB: If _cogl_multitexture_quad_single_primitive fails then it
           * means the user tried to use texture repeat with a texture that
           * can't be repeated by the GPU (e.g. due to waste or use of
           * GL_TEXTURE_RECTANGLE_ARB) */
          if (success)
            continue;
        }

      /* If multitexturing failed or we are drawing with a sliced texture
       * then we only support a single layer so we pluck out the texture
       * from the first material layer... */
      first_layer = layers->data;
      tex_handle = cogl_material_layer_get_texture (first_layer);

      if (rects[i].tex_coords)
        tex_coords = rects[i].tex_coords;
      else
        tex_coords = default_tex_coords;

      _cogl_texture_quad_multiple_primitives (tex_handle,
                                              material,
                                              rects[i].x_1, rects[i].y_1,
                                              rects[i].x_2, rects[i].y_2,
                                              tex_coords[0],
                                              tex_coords[1],
                                              tex_coords[2],
                                              tex_coords[3]);
    }

#if 0
  /* XXX: The current journal doesn't handle changes to the model view matrix
   * so for now we force a flush at the end of every primitive. */
  _cogl_journal_flush ();
#endif
}

void
cogl_rectangles (const float *verts,
                 guint        n_rects)
{
  struct _CoglMutiTexturedRect *rects;
  int i;

  rects = g_alloca (n_rects * sizeof (struct _CoglMutiTexturedRect));

  for (i = 0; i < n_rects; i++)
    {
      rects[i].x_1 = verts[i * 4];
      rects[i].y_1 = verts[i * 4 + 1];
      rects[i].x_2 = verts[i * 4 + 2];
      rects[i].y_2 = verts[i * 4 + 3];
      rects[i].tex_coords = NULL;
      rects[i].tex_coords_len = 0;
    }

  _cogl_rectangles_with_multitexture_coords (rects, n_rects);
}

void
cogl_rectangles_with_texture_coords (const float *verts,
                                     guint        n_rects)
{
  struct _CoglMutiTexturedRect *rects;
  int i;

  rects = g_alloca (n_rects * sizeof (struct _CoglMutiTexturedRect));

  for (i = 0; i < n_rects; i++)
    {
      rects[i].x_1 = verts[i * 8];
      rects[i].y_1 = verts[i * 8 + 1];
      rects[i].x_2 = verts[i * 8 + 2];
      rects[i].y_2 = verts[i * 8 + 3];
      /* FIXME: rect should be defined to have a const float *geom;
       * instead, to avoid this copy
       * rect[i].geom = &verts[n_rects * 8]; */
      rects[i].tex_coords = &verts[i * 8 + 4];
      rects[i].tex_coords_len = 4;
    }

  _cogl_rectangles_with_multitexture_coords (rects, n_rects);
}

void
cogl_rectangle_with_texture_coords (float x_1,
			            float y_1,
			            float x_2,
			            float y_2,
			            float tx_1,
			            float ty_1,
			            float tx_2,
			            float ty_2)
{
  float verts[8];

  verts[0] = x_1;
  verts[1] = y_1;
  verts[2] = x_2;
  verts[3] = y_2;
  verts[4] = tx_1;
  verts[5] = ty_1;
  verts[6] = tx_2;
  verts[7] = ty_2;

  cogl_rectangles_with_texture_coords (verts, 1);
}

void
cogl_rectangle_with_multitexture_coords (float        x_1,
			                 float        y_1,
			                 float        x_2,
			                 float        y_2,
			                 const float *user_tex_coords,
                                         gint         user_tex_coords_len)
{
  struct _CoglMutiTexturedRect rect;

  rect.x_1 = x_1;
  rect.y_1 = y_1;
  rect.x_2 = x_2;
  rect.y_2 = y_2;
  rect.tex_coords = user_tex_coords;
  rect.tex_coords_len = user_tex_coords_len;

  _cogl_rectangles_with_multitexture_coords (&rect, 1);
}

void
cogl_rectangle (float x_1,
                float y_1,
                float x_2,
                float y_2)
{
  cogl_rectangle_with_multitexture_coords (x_1, y_1,
                                           x_2, y_2,
                                           NULL, 0);
}

void
draw_polygon_sub_texture_cb (CoglHandle tex_handle,
                       GLuint gl_handle,
                       GLenum gl_target,
                       float *subtexture_coords,
                       float *virtual_coords,
                       void *user_data)
{
  TextureSlicedPolygonState *state = user_data;
  GLfloat *v;
  int i;
  CoglMaterialFlushOptions options;
  float slice_origin_x;
  float slice_origin_y;
  float virtual_origin_x;
  float virtual_origin_y;
  float v_to_s_scale_x;
  float v_to_s_scale_y;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  slice_origin_x = subtexture_coords[0];
  slice_origin_y = subtexture_coords[1];
  virtual_origin_x = virtual_coords[0];
  virtual_origin_y = virtual_coords[1];
  v_to_s_scale_x = ((virtual_coords[2] - virtual_coords[0]) /
                    (subtexture_coords[2] - subtexture_coords[0]));
  v_to_s_scale_y = ((virtual_coords[3] - virtual_coords[1]) /
                    (subtexture_coords[3] - subtexture_coords[1]));

  /* Convert the vertices into an array of GLfloats ready to pass to
   * OpenGL */
  v = (GLfloat *)ctx->logged_vertices->data;
  for (i = 0; i < state->n_vertices; i++)
    {
      /* NB: layout = [X,Y,Z,TX,TY,R,G,B,A,...] */
      GLfloat *t = v + 3;

      t[0] = ((state->vertices[i].tx - virtual_origin_x) * v_to_s_scale_x
              + slice_origin_x);
      t[1] = ((state->vertices[i].ty - virtual_origin_y) * v_to_s_scale_y
              + slice_origin_y);

      v += state->stride;
    }

  options.flags =
    COGL_MATERIAL_FLUSH_DISABLE_MASK |
    COGL_MATERIAL_FLUSH_LAYER0_OVERRIDE;
  /* disable all except the first layer */
  options.disable_layers = (guint32)~1;
  options.layer0_override_texture = gl_handle;

  _cogl_material_flush_gl_state (ctx->source_material, &options);

  GE (glDrawArrays (GL_TRIANGLE_FAN, 0, state->n_vertices));
}

/* handles 2d-sliced textures with > 1 slice */
static void
_cogl_texture_polygon_multiple_primitives (CoglTextureVertex *vertices,
                                           unsigned int n_vertices,
                                           unsigned int stride,
                                           gboolean use_color)
{
  const GList               *layers;
  CoglHandle                 layer0;
  CoglHandle                 tex_handle;
  GLfloat                   *v;
  int                        i;
  TextureSlicedPolygonState  state;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  /* We can assume in this case that we have at least one layer in the
   * material that corresponds to a sliced cogl texture */
  layers = cogl_material_get_layers (ctx->source_material);
  layer0 = (CoglHandle)layers->data;
  tex_handle = cogl_material_layer_get_texture (layer0);

  v = (GLfloat *)ctx->logged_vertices->data;
  for (i = 0; i < n_vertices; i++)
    {
      guint8 *c;

      v[0] = vertices[i].x;
      v[1] = vertices[i].y;
      v[2] = vertices[i].z;

      if (use_color)
        {
          /* NB: [X,Y,Z,TX,TY,R,G,B,A,...] */
          c = (guint8 *) (v + 5);
          c[0] = cogl_color_get_red_byte (&vertices[i].color);
          c[1] = cogl_color_get_green_byte (&vertices[i].color);
          c[2] = cogl_color_get_blue_byte (&vertices[i].color);
          c[3] = cogl_color_get_alpha_byte (&vertices[i].color);
        }

      v += stride;
    }

  state.stride = stride;
  state.vertices = vertices;
  state.n_vertices = n_vertices;

  _cogl_texture_foreach_sub_texture_in_region (tex_handle,
                                               0, 0, 1, 1,
                                               draw_polygon_sub_texture_cb,
                                               &state);
}

static void
_cogl_multitexture_polygon_single_primitive (CoglTextureVertex *vertices,
                                             guint n_vertices,
                                             guint n_layers,
                                             guint stride,
                                             gboolean use_color,
                                             guint32 fallback_layers)
{
  CoglHandle           material;
  const GList         *layers;
  int                  i;
  GList               *tmp;
  GLfloat             *v;
  CoglMaterialFlushOptions options;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  material = ctx->source_material;
  layers = cogl_material_get_layers (material);

  /* Convert the vertices into an array of GLfloats ready to pass to
     OpenGL */
  for (v = (GLfloat *)ctx->logged_vertices->data, i = 0;
       i < n_vertices;
       v += stride, i++)
    {
      guint8 *c;
      int     j;

      /* NB: [X,Y,Z,TX,TY...,R,G,B,A,...] */
      v[0] = vertices[i].x;
      v[1] = vertices[i].y;
      v[2] = vertices[i].z;

      for (tmp = (GList *)layers, j = 0; tmp != NULL; tmp = tmp->next, j++)
        {
          CoglHandle   layer = (CoglHandle)tmp->data;
          CoglHandle   tex_handle;
          GLfloat     *t;
          float        tx, ty;

          tex_handle = cogl_material_layer_get_texture (layer);

          /* COGL_INVALID_HANDLE textures will be handled in
           * _cogl_material_flush_layers_gl_state but there is no need to worry
           * about scaling texture coordinates in this case */
          if (tex_handle == COGL_INVALID_HANDLE)
            continue;

          tx = vertices[i].tx;
          ty = vertices[i].ty;
          _cogl_texture_transform_coords_to_gl (tex_handle, &tx, &ty);

          /* NB: [X,Y,Z,TX,TY...,R,G,B,A,...] */
          t = v + 3 + 2 * j;
          t[0] = tx;
          t[1] = ty;
        }

      if (use_color)
        {
          /* NB: [X,Y,Z,TX,TY...,R,G,B,A,...] */
          c = (guint8 *) (v + 3 + 2 * n_layers);
          c[0] = cogl_color_get_red_byte (&vertices[i].color);
          c[1] = cogl_color_get_green_byte (&vertices[i].color);
          c[2] = cogl_color_get_blue_byte (&vertices[i].color);
          c[3] = cogl_color_get_alpha_byte (&vertices[i].color);
        }
    }

  options.flags = COGL_MATERIAL_FLUSH_FALLBACK_MASK;
  if (use_color)
    options.flags |= COGL_MATERIAL_FLUSH_SKIP_GL_COLOR;
  options.fallback_layers = fallback_layers;
  _cogl_material_flush_gl_state (ctx->source_material, &options);

  GE (glDrawArrays (GL_TRIANGLE_FAN, 0, n_vertices));
}

void
cogl_polygon (CoglTextureVertex *vertices,
              guint              n_vertices,
	      gboolean           use_color)
{
  CoglHandle           material;
  const GList         *layers;
  int                  n_layers;
  GList               *tmp;
  gboolean	       use_sliced_polygon_fallback = FALSE;
  guint32              fallback_layers = 0;
  int                  i;
  gulong               enable_flags;
  guint                stride;
  gsize                stride_bytes;
  GLfloat             *v;
  int                  prev_n_texcoord_arrays_enabled;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  _cogl_journal_flush ();

  /* NB: _cogl_draw_buffer_flush_state may disrupt various state (such
   * as the material state) when flushing the clip stack, so should
   * always be done first when preparing to draw. */
  _cogl_draw_buffer_flush_state (_cogl_get_draw_buffer (), 0);

  material = ctx->source_material;
  layers = cogl_material_get_layers (ctx->source_material);
  n_layers = g_list_length ((GList *)layers);

  for (tmp = (GList *)layers, i = 0; tmp != NULL; tmp = tmp->next, i++)
    {
      CoglHandle   layer = (CoglHandle)tmp->data;
      CoglHandle   tex_handle = cogl_material_layer_get_texture (layer);

      /* COGL_INVALID_HANDLE textures will be handled in
       * _cogl_material_flush_layers_gl_state */
      if (tex_handle == COGL_INVALID_HANDLE)
        continue;

      if (i == 0 && cogl_texture_is_sliced (tex_handle))
        {
#if defined (HAVE_COGL_GLES) || defined (HAVE_COGL_GLES2)
          {
            static gboolean warning_seen = FALSE;
            if (!warning_seen)
              g_warning ("cogl_polygon does not work for sliced textures "
                         "on GL ES");
            warning_seen = TRUE;
            return;
          }
#endif
          if (n_layers > 1)
            {
              static gboolean warning_seen = FALSE;
              if (!warning_seen)
                {
                  g_warning ("Disabling layers 1..n since multi-texturing with "
                             "cogl_polygon isn't supported when using sliced "
                             "textures\n");
                  warning_seen = TRUE;
                }
            }
          use_sliced_polygon_fallback = TRUE;
          n_layers = 1;

          if (cogl_material_layer_get_min_filter (layer) != GL_NEAREST
              || cogl_material_layer_get_mag_filter (layer) != GL_NEAREST)
            {
              static gboolean warning_seen = FALSE;
              if (!warning_seen)
                {
                  g_warning ("cogl_texture_polygon does not work for sliced textures "
                             "when the minification and magnification filters are not "
                             "CGL_NEAREST");
                  warning_seen = TRUE;
                }
              return;
            }

#ifdef HAVE_COGL_GL
          {
            /* Temporarily change the wrapping mode on all of the slices to use
             * a transparent border
             * XXX: it's doesn't look like we save/restore this, like
             * the comment implies? */
            _cogl_texture_set_wrap_mode_parameter (tex_handle,
                                                   GL_CLAMP_TO_BORDER);
          }
#endif
          break;
        }

      if (cogl_texture_is_sliced (tex_handle))
        {
          static gboolean warning_seen = FALSE;
          if (!warning_seen)
            g_warning ("Disabling layer %d of the current source material, "
                       "because texturing with the vertex buffer API is not "
                       "currently supported using sliced textures, or "
                       "textures with waste\n", i);
          warning_seen = TRUE;

          fallback_layers |= (1 << i);
          continue;
        }
    }

  /* Our data is arranged like:
   * [X, Y, Z, TX0, TY0, TX1, TY1..., R, G, B, A,...] */
  stride = 3 + (2 * n_layers) + (use_color ? 1 : 0);
  stride_bytes = stride * sizeof (GLfloat);

  /* Make sure there is enough space in the global vertex
     array. This is used so we can render the polygon with a single
     call to OpenGL but still support any number of vertices */
  g_array_set_size (ctx->logged_vertices, n_vertices * stride);
  v = (GLfloat *)ctx->logged_vertices->data;

  /* Prepare GL state */
  enable_flags = COGL_ENABLE_VERTEX_ARRAY;
  enable_flags |= _cogl_material_get_cogl_enable_flags (ctx->source_material);

  if (ctx->enable_backface_culling)
    enable_flags |= COGL_ENABLE_BACKFACE_CULLING;

  if (use_color)
    {
      enable_flags |= COGL_ENABLE_COLOR_ARRAY | COGL_ENABLE_BLEND;
      GE( glColorPointer (4, GL_UNSIGNED_BYTE,
                          stride_bytes,
                          /* NB: [X,Y,Z,TX,TY...,R,G,B,A,...] */
                          v + 3 + 2 * n_layers) );
    }

  cogl_enable (enable_flags);

  GE (glVertexPointer (3, GL_FLOAT, stride_bytes, v));

  for (i = 0; i < n_layers; i++)
    {
      GE (glClientActiveTexture (GL_TEXTURE0 + i));
      GE (glEnableClientState (GL_TEXTURE_COORD_ARRAY));
      GE (glTexCoordPointer (2, GL_FLOAT,
                             stride_bytes,
                             /* NB: [X,Y,Z,TX,TY...,R,G,B,A,...] */
                             v + 3 + 2 * i));
    }
  prev_n_texcoord_arrays_enabled =
    ctx->n_texcoord_arrays_enabled;
  ctx->n_texcoord_arrays_enabled = n_layers;
  for (; i < prev_n_texcoord_arrays_enabled; i++)
    {
      GE (glClientActiveTexture (GL_TEXTURE0 + i));
      GE (glDisableClientState (GL_TEXTURE_COORD_ARRAY));
    }

  if (use_sliced_polygon_fallback)
    _cogl_texture_polygon_multiple_primitives (vertices,
                                               n_vertices,
                                               stride,
                                               use_color);
  else
    _cogl_multitexture_polygon_single_primitive (vertices,
                                                 n_vertices,
                                                 n_layers,
                                                 stride,
                                                 use_color,
                                                 fallback_layers);

  /* Reset the size of the logged vertex array because rendering
     rectangles expects it to start at 0 */
  g_array_set_size (ctx->logged_vertices, 0);
}

void
cogl_path_fill (void)
{
  cogl_path_fill_preserve ();

  cogl_path_new ();
}

void
cogl_path_fill_preserve (void)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  if (ctx->path_nodes->len == 0)
    return;

  _cogl_path_fill_nodes ();
}

void
cogl_path_stroke (void)
{
  cogl_path_stroke_preserve ();

  cogl_path_new ();
}

void
cogl_path_stroke_preserve (void)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  if (ctx->path_nodes->len == 0)
    return;

  _cogl_path_stroke_nodes ();
}

void
cogl_path_move_to (float x,
                   float y)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  /* FIXME: handle multiple contours maybe? */

  _cogl_path_add_node (TRUE, x, y);

  ctx->path_start.x = x;
  ctx->path_start.y = y;

  ctx->path_pen = ctx->path_start;
}

void
cogl_path_rel_move_to (float x,
                       float y)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  cogl_path_move_to (ctx->path_pen.x + x,
                     ctx->path_pen.y + y);
}

void
cogl_path_line_to (float x,
                   float y)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  _cogl_path_add_node (FALSE, x, y);

  ctx->path_pen.x = x;
  ctx->path_pen.y = y;
}

void
cogl_path_rel_line_to (float x,
                       float y)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  cogl_path_line_to (ctx->path_pen.x + x,
                     ctx->path_pen.y + y);
}

void
cogl_path_close (void)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  _cogl_path_add_node (FALSE, ctx->path_start.x, ctx->path_start.y);
  ctx->path_pen = ctx->path_start;
}

void
cogl_path_new (void)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  g_array_set_size (ctx->path_nodes, 0);
}

void
cogl_path_line (float x_1,
	        float y_1,
	        float x_2,
	        float y_2)
{
  cogl_path_move_to (x_1, y_1);
  cogl_path_line_to (x_2, y_2);
}

void
cogl_path_polyline (float *coords,
	            gint num_points)
{
  gint c = 0;

  cogl_path_move_to (coords[0], coords[1]);

  for (c = 1; c < num_points; ++c)
    cogl_path_line_to (coords[2*c], coords[2*c+1]);
}

void
cogl_path_polygon (float *coords,
	           gint          num_points)
{
  cogl_path_polyline (coords, num_points);
  cogl_path_close ();
}

void
cogl_path_rectangle (float x_1,
                     float y_1,
                     float x_2,
                     float y_2)
{
  cogl_path_move_to (x_1, y_1);
  cogl_path_line_to (x_2, y_1);
  cogl_path_line_to (x_2, y_2);
  cogl_path_line_to (x_1, y_2);
  cogl_path_close   ();
}

static void
_cogl_path_arc (float center_x,
	        float center_y,
                float radius_x,
                float radius_y,
                float angle_1,
                float angle_2,
                float angle_step,
                guint        move_first)
{
  float a     = 0x0;
  float cosa  = 0x0;
  float sina  = 0x0;
  float px    = 0x0;
  float py    = 0x0;

  /* Fix invalid angles */

  if (angle_1 == angle_2 || angle_step == 0x0)
    return;

  if (angle_step < 0x0)
    angle_step = -angle_step;

  /* Walk the arc by given step */

  a = angle_1;
  while (a != angle_2)
    {
      cosa = cosf (a * (G_PI/180.0));
      sina = sinf (a * (G_PI/180.0));

      px = center_x + (cosa * radius_x);
      py = center_y + (sina * radius_y);

      if (a == angle_1 && move_first)
	cogl_path_move_to (px, py);
      else
	cogl_path_line_to (px, py);

      if (G_LIKELY (angle_2 > angle_1))
        {
          a += angle_step;
          if (a > angle_2)
            a = angle_2;
        }
      else
        {
          a -= angle_step;
          if (a < angle_2)
            a = angle_2;
        }
    }

  /* Make sure the final point is drawn */

  cosa = cosf (angle_2 * (G_PI/180.0));
  sina = sinf (angle_2 * (G_PI/180.0));

  px = center_x + (cosa * radius_x);
  py = center_y + (sina * radius_y);

  cogl_path_line_to (px, py);
}

void
cogl_path_arc (float center_x,
               float center_y,
               float radius_x,
               float radius_y,
               float angle_1,
               float angle_2)
{
  float angle_step = 10;
  /* it is documented that a move to is needed to create a freestanding
   * arc
   */
  _cogl_path_arc (center_x,   center_y,
	          radius_x,   radius_y,
	          angle_1,    angle_2,
	          angle_step, 0 /* no move */);
}


void
cogl_path_arc_rel (float center_x,
		   float center_y,
		   float radius_x,
		   float radius_y,
		   float angle_1,
		   float angle_2,
		   float angle_step)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  _cogl_path_arc (ctx->path_pen.x + center_x,
	          ctx->path_pen.y + center_y,
	          radius_x,   radius_y,
	          angle_1,    angle_2,
	          angle_step, 0 /* no move */);
}

void
cogl_path_ellipse (float center_x,
                   float center_y,
                   float radius_x,
                   float radius_y)
{
  float angle_step = 10;

  /* FIXME: if shows to be slow might be optimized
   * by mirroring just a quarter of it */

  _cogl_path_arc (center_x, center_y,
	          radius_x, radius_y,
	          0, 360,
	          angle_step, 1 /* move first */);

  cogl_path_close();
}

void
cogl_path_round_rectangle (float x_1,
                           float y_1,
                           float x_2,
                           float y_2,
                           float radius,
                           float arc_step)
{
  float inner_width = x_2 - x_1 - radius * 2;
  float inner_height = y_2 - y_1 - radius * 2;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  cogl_path_move_to (x_1, y_1 + radius);
  cogl_path_arc_rel (radius, 0,
		     radius, radius,
		     180,
		     270,
		     arc_step);

  cogl_path_line_to       (ctx->path_pen.x + inner_width,
                           ctx->path_pen.y);
  cogl_path_arc_rel       (0, radius,
			   radius, radius,
			   -90,
			   0,
			   arc_step);

  cogl_path_line_to       (ctx->path_pen.x,
                           ctx->path_pen.y + inner_height);

  cogl_path_arc_rel       (-radius, 0,
			   radius, radius,
			   0,
			   90,
			   arc_step);

  cogl_path_line_to       (ctx->path_pen.x - inner_width,
                           ctx->path_pen.y);
  cogl_path_arc_rel       (0, -radius,
			   radius, radius,
			   90,
			   180,
			   arc_step);

  cogl_path_close ();
}


static void
_cogl_path_bezier3_sub (CoglBezCubic *cubic)
{
  CoglBezCubic   cubics[_COGL_MAX_BEZ_RECURSE_DEPTH];
  CoglBezCubic  *cleft;
  CoglBezCubic  *cright;
  CoglBezCubic  *c;
  floatVec2  dif1;
  floatVec2  dif2;
  floatVec2  mm;
  floatVec2  c1;
  floatVec2  c2;
  floatVec2  c3;
  floatVec2  c4;
  floatVec2  c5;
  gint           cindex;

  /* Put first curve on stack */
  cubics[0] = *cubic;
  cindex    =  0;

  while (cindex >= 0)
    {
      c = &cubics[cindex];


      /* Calculate distance of control points from their
       * counterparts on the line between end points */
      dif1.x = (c->p2.x * 3) - (c->p1.x * 2) - c->p4.x;
      dif1.y = (c->p2.y * 3) - (c->p1.y * 2) - c->p4.y;
      dif2.x = (c->p3.x * 3) - (c->p4.x * 2) - c->p1.x;
      dif2.y = (c->p3.y * 3) - (c->p4.y * 2) - c->p1.y;

      if (dif1.x < 0)
        dif1.x = -dif1.x;
      if (dif1.y < 0)
        dif1.y = -dif1.y;
      if (dif2.x < 0)
        dif2.x = -dif2.x;
      if (dif2.y < 0)
        dif2.y = -dif2.y;


      /* Pick the greatest of two distances */
      if (dif1.x < dif2.x) dif1.x = dif2.x;
      if (dif1.y < dif2.y) dif1.y = dif2.y;

      /* Cancel if the curve is flat enough */
      if (dif1.x + dif1.y <= 1.0 ||
	  cindex == _COGL_MAX_BEZ_RECURSE_DEPTH-1)
	{
	  /* Add subdivision point (skip last) */
	  if (cindex == 0)
            return;

	  _cogl_path_add_node (FALSE, c->p4.x, c->p4.y);

	  --cindex;

          continue;
	}

      /* Left recursion goes on top of stack! */
      cright = c; cleft = &cubics[++cindex];

      /* Subdivide into 2 sub-curves */
      c1.x = ((c->p1.x + c->p2.x) / 2);
      c1.y = ((c->p1.y + c->p2.y) / 2);
      mm.x = ((c->p2.x + c->p3.x) / 2);
      mm.y = ((c->p2.y + c->p3.y) / 2);
      c5.x = ((c->p3.x + c->p4.x) / 2);
      c5.y = ((c->p3.y + c->p4.y) / 2);

      c2.x = ((c1.x + mm.x) / 2);
      c2.y = ((c1.y + mm.y) / 2);
      c4.x = ((mm.x + c5.x) / 2);
      c4.y = ((mm.y + c5.y) / 2);

      c3.x = ((c2.x + c4.x) / 2);
      c3.y = ((c2.y + c4.y) / 2);

      /* Add left recursion to stack */
      cleft->p1 = c->p1;
      cleft->p2 = c1;
      cleft->p3 = c2;
      cleft->p4 = c3;

      /* Add right recursion to stack */
      cright->p1 = c3;
      cright->p2 = c4;
      cright->p3 = c5;
      cright->p4 = c->p4;
    }
}

void
cogl_path_curve_to (float x_1,
                    float y_1,
                    float x_2,
                    float y_2,
                    float x_3,
                    float y_3)
{
  CoglBezCubic cubic;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  /* Prepare cubic curve */
  cubic.p1 = ctx->path_pen;
  cubic.p2.x = x_1;
  cubic.p2.y = y_1;
  cubic.p3.x = x_2;
  cubic.p3.y = y_2;
  cubic.p4.x = x_3;
  cubic.p4.y = y_3;

  /* Run subdivision */
  _cogl_path_bezier3_sub (&cubic);

  /* Add last point */
  _cogl_path_add_node (FALSE, cubic.p4.x, cubic.p4.y);
  ctx->path_pen = cubic.p4;
}

void
cogl_path_rel_curve_to (float x_1,
                        float y_1,
                        float x_2,
                        float y_2,
                        float x_3,
                        float y_3)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  cogl_path_curve_to (ctx->path_pen.x + x_1,
                      ctx->path_pen.y + y_1,
                      ctx->path_pen.x + x_2,
                      ctx->path_pen.y + y_2,
                      ctx->path_pen.x + x_3,
                      ctx->path_pen.y + y_3);
}


/* If second order beziers were needed the following code could
 * be re-enabled:
 */
#if 0

static void
_cogl_path_bezier2_sub (CoglBezQuad *quad)
{
  CoglBezQuad     quads[_COGL_MAX_BEZ_RECURSE_DEPTH];
  CoglBezQuad    *qleft;
  CoglBezQuad    *qright;
  CoglBezQuad    *q;
  floatVec2   mid;
  floatVec2   dif;
  floatVec2   c1;
  floatVec2   c2;
  floatVec2   c3;
  gint            qindex;

  /* Put first curve on stack */
  quads[0] = *quad;
  qindex   =  0;

  /* While stack is not empty */
  while (qindex >= 0)
    {

      q = &quads[qindex];

      /* Calculate distance of control point from its
       * counterpart on the line between end points */
      mid.x = ((q->p1.x + q->p3.x) / 2);
      mid.y = ((q->p1.y + q->p3.y) / 2);
      dif.x = (q->p2.x - mid.x);
      dif.y = (q->p2.y - mid.y);
      if (dif.x < 0) dif.x = -dif.x;
      if (dif.y < 0) dif.y = -dif.y;

      /* Cancel if the curve is flat enough */
      if (dif.x + dif.y <= 1.0 ||
          qindex == _COGL_MAX_BEZ_RECURSE_DEPTH - 1)
	{
	  /* Add subdivision point (skip last) */
	  if (qindex == 0) return;
	  _cogl_path_add_node (FALSE, q->p3.x, q->p3.y);
	  --qindex; continue;
	}

      /* Left recursion goes on top of stack! */
      qright = q; qleft = &quads[++qindex];

      /* Subdivide into 2 sub-curves */
      c1.x = ((q->p1.x + q->p2.x) / 2);
      c1.y = ((q->p1.y + q->p2.y) / 2);
      c3.x = ((q->p2.x + q->p3.x) / 2);
      c3.y = ((q->p2.y + q->p3.y) / 2);
      c2.x = ((c1.x + c3.x) / 2);
      c2.y = ((c1.y + c3.y) / 2);

      /* Add left recursion onto stack */
      qleft->p1 = q->p1;
      qleft->p2 = c1;
      qleft->p3 = c2;

      /* Add right recursion onto stack */
      qright->p1 = c2;
      qright->p2 = c3;
      qright->p3 = q->p3;
    }
}

void
cogl_path_curve2_to (float x_1,
                     float y_1,
                     float x_2,
                     float y_2)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  CoglBezQuad quad;

  /* Prepare quadratic curve */
  quad.p1 = ctx->path_pen;
  quad.p2.x = x_1;
  quad.p2.y = y_1;
  quad.p3.x = x_2;
  quad.p3.y = y_2;

  /* Run subdivision */
  _cogl_path_bezier2_sub (&quad);

  /* Add last point */
  _cogl_path_add_node (FALSE, quad.p3.x, quad.p3.y);
  ctx->path_pen = quad.p3;
}

void
cogl_rel_curve2_to (float x_1,
                    float y_1,
                    float x_2,
                    float y_2)
{
  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  cogl_path_curve2_to (ctx->path_pen.x + x_1,
                       ctx->path_pen.y + y_1,
                       ctx->path_pen.x + x_2,
                       ctx->path_pen.y + y_2);
}
#endif