mutter/cogl/cogl-journal.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-framebuffer-private.h"
#include "cogl-profile.h"

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

#define _COGL_MAX_BEZ_RECURSE_DEPTH 16

#ifdef HAVE_COGL_GL

#define glGenBuffers ctx->drv.pf_glGenBuffers
#define glBindBuffer ctx->drv.pf_glBindBuffer
#define glBufferData ctx->drv.pf_glBufferData
#define glBufferSubData ctx->drv.pf_glBufferSubData
#define glDeleteBuffers ctx->drv.pf_glDeleteBuffers
#define glClientActiveTexture ctx->drv.pf_glClientActiveTexture

#elif defined (HAVE_COGL_GLES2)

#include "../gles/cogl-gles2-wrapper.h"

#endif

/* XXX NB:
 * Our journal's vertex data is arranged as follows:
 * 4 vertices per quad:
 *    2 or 3 GLfloats per position (3 when doing software transforms)
 *    4 RGBA GLubytes,
 *    2 GLfloats per tex coord * n_layers
 *
 * Where n_layers corresponds to the number of material layers enabled
 *
 * To avoid frequent changes in the stride of our vertex data we always pad
 * n_layers to be >= 2
 *
 * When we are transforming quads in software we need to also track the z
 * coordinate of transformed vertices.
 *
 * So for a given number of layers this gets the stride in 32bit words:
 */
#define SW_TRANSFORM      (!(cogl_debug_flags & \
                             COGL_DEBUG_DISABLE_SOFTWARE_TRANSFORM))
#define POS_STRIDE        (SW_TRANSFORM ? 3 : 2) /* number of 32bit words */
#define N_POS_COMPONENTS  POS_STRIDE
#define COLOR_STRIDE      1 /* number of 32bit words */
#define TEX_STRIDE        2 /* number of 32bit words */
#define MIN_LAYER_PADING  2
#define GET_JOURNAL_VB_STRIDE_FOR_N_LAYERS(N_LAYERS) \
  (POS_STRIDE + COLOR_STRIDE + \
   TEX_STRIDE * (N_LAYERS < MIN_LAYER_PADING ? MIN_LAYER_PADING : N_LAYERS))

typedef CoglVertexBufferIndices  CoglJournalIndices;

typedef struct _CoglJournalFlushState
{
  size_t              stride;
  /* Note: this is a pointer to handle fallbacks. It normally holds a VBO
   * offset, but when the driver doesn't support VBOs then this points into
   * our GArray of logged vertices. */
  char *              vbo_offset;
  GLuint              vertex_offset;
#ifndef HAVE_COGL_GL
  CoglJournalIndices *indices;
  size_t              indices_type_size;
#endif
  CoglMatrixStack    *modelview_stack;
} CoglJournalFlushState;

typedef void (*CoglJournalBatchCallback) (CoglJournalEntry *start,
                                          int n_entries,
                                          void *data);
typedef gboolean (*CoglJournalBatchTest) (CoglJournalEntry *entry0,
                                          CoglJournalEntry *entry1);

void
_cogl_journal_dump_quad_vertices (guint8 *data, int n_layers)
{
  size_t stride = GET_JOURNAL_VB_STRIDE_FOR_N_LAYERS (n_layers);
  int i;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  g_print ("n_layers = %d; stride = %d; pos stride = %d; color stride = %d; "
           "tex stride = %d; stride in bytes = %d\n",
           n_layers, (int)stride, POS_STRIDE, COLOR_STRIDE,
           TEX_STRIDE, (int)stride * 4);

  for (i = 0; i < 4; i++)
    {
      float *v = (float *)data + (i * stride);
      guint8 *c = data + (POS_STRIDE * 4) + (i * stride * 4);
      int j;

      if (cogl_debug_flags & COGL_DEBUG_DISABLE_SOFTWARE_TRANSFORM)
        g_print ("v%d: x = %f, y = %f, rgba=0x%02X%02X%02X%02X",
                 i, v[0], v[1], c[0], c[1], c[2], c[3]);
      else
        g_print ("v%d: x = %f, y = %f, z = %f, rgba=0x%02X%02X%02X%02X",
                 i, v[0], v[1], v[2], c[0], c[1], c[2], c[3]);
      for (j = 0; j < n_layers; j++)
        {
          float *t = v + POS_STRIDE + COLOR_STRIDE + TEX_STRIDE * j;
          g_print (", tx%d = %f, ty%d = %f", j, t[0], j, t[1]);
        }
      g_print ("\n");
    }
}

void
_cogl_journal_dump_quad_batch (guint8 *data, int n_layers, int n_quads)
{
  size_t byte_stride = GET_JOURNAL_VB_STRIDE_FOR_N_LAYERS (n_layers) * 4;
  int i;

  g_print ("_cogl_journal_dump_quad_batch: n_layers = %d, n_quads = %d\n",
           n_layers, n_quads);
  for (i = 0; i < n_quads; i++)
    _cogl_journal_dump_quad_vertices (data + byte_stride * 4 * i, n_layers);
}

static void
batch_and_call (CoglJournalEntry *entries,
                int n_entries,
                CoglJournalBatchTest can_batch_callback,
                CoglJournalBatchCallback batch_callback,
                void *data)
{
  int i;
  int batch_len = 1;
  CoglJournalEntry *batch_start = entries;

  for (i = 1; i < n_entries; i++)
    {
      CoglJournalEntry *entry0 = &entries[i - 1];
      CoglJournalEntry *entry1 = entry0 + 1;

      if (can_batch_callback (entry0, entry1))
        {
          batch_len++;
          continue;
        }

      batch_callback (batch_start, batch_len, data);

      batch_start = entry1;
      batch_len = 1;
    }

  /* The last batch... */
  batch_callback (batch_start, batch_len, data);
}

static void
_cogl_journal_flush_modelview_and_entries (CoglJournalEntry *batch_start,
                                           int               batch_len,
                                           void             *data)
{
  CoglJournalFlushState *state = data;

  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_BATCHING))
    g_print ("BATCHING:    modelview batch len = %d\n", batch_len);

  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_DISABLE_SOFTWARE_TRANSFORM))
    {
      _cogl_matrix_stack_set (state->modelview_stack,
                              &batch_start->model_view);
      _cogl_matrix_stack_flush_to_gl (state->modelview_stack,
                                      COGL_MATRIX_MODELVIEW);
    }

#ifdef HAVE_COGL_GL

  GE (glDrawArrays (GL_QUADS, state->vertex_offset, batch_len * 4));

#else /* HAVE_COGL_GL */

  if (batch_len > 1)
    {
      int indices_offset = (state->vertex_offset / 4) * 6;
      GE (glDrawElements (GL_TRIANGLES,
                          6 * batch_len,
                          state->indices->type,
                          (GLvoid*)(indices_offset * state->indices_type_size)));
    }
  else
    {
      GE (glDrawArrays (GL_TRIANGLE_FAN,
                        state->vertex_offset, /* first */
                        4)); /* n vertices */
    }
#endif

  /* DEBUGGING CODE XXX:
   * This path will cause all rectangles to be drawn with a red, green
   * or blue outline with no blending. This may e.g. help with debugging
   * texture slicing issues or blending issues, plus it looks quite cool.
   */
  if (cogl_debug_flags & COGL_DEBUG_RECTANGLES)
    {
      static CoglHandle outline = COGL_INVALID_HANDLE;
      static int color = 0;
      int i;
      if (outline == COGL_INVALID_HANDLE)
        outline = cogl_material_new ();

      cogl_enable (COGL_ENABLE_VERTEX_ARRAY);
      for (i = 0; i < batch_len; i++, color = (color + 1) % 3)
        {
          cogl_material_set_color4ub (outline,
                                      color == 0 ? 0xff : 0x00,
                                      color == 1 ? 0xff : 0x00,
                                      color == 2 ? 0xff : 0x00,
                                      0xff);
          _cogl_material_flush_gl_state (outline, NULL);
          GE( glDrawArrays (GL_LINE_LOOP, 4 * i, 4) );
        }
    }

  state->vertex_offset += (4 * batch_len);
}

static gboolean
compare_entry_modelviews (CoglJournalEntry *entry0,
                          CoglJournalEntry *entry1)
{
  /* Batch together quads with the same model view matrix */

  /* FIXME: this is nasty, there are much nicer ways to track this
   * (at the add_quad_vertices level) without resorting to a memcmp!
   *
   * E.g. If the cogl-current-matrix code maintained an "age" for
   * the modelview matrix we could simply check in add_quad_vertices
   * if the age has increased, and if so record the change as a
   * boolean in the journal.
   */

  if (memcmp (&entry0->model_view, &entry1->model_view,
              sizeof (GLfloat) * 16) == 0)
    return TRUE;
  else
    return FALSE;
}

/* At this point we have a run of quads that we know have compatible
 * materials, but they may not all have the same modelview matrix */
static void
_cogl_journal_flush_material_and_entries (CoglJournalEntry *batch_start,
                                          gint              batch_len,
                                          void             *data)
{
  gulong                 enable_flags = 0;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_BATCHING))
    g_print ("BATCHING:   material batch len = %d\n", batch_len);

  _cogl_material_flush_gl_state (batch_start->material,
                                 &batch_start->flush_options);

  /* FIXME: This api is a bit yukky, ideally it will be removed if we
   * re-work the cogl_enable mechanism */
  enable_flags |= _cogl_material_get_cogl_enable_flags (batch_start->material);

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

  enable_flags |= COGL_ENABLE_VERTEX_ARRAY;
  enable_flags |= COGL_ENABLE_COLOR_ARRAY;
  cogl_enable (enable_flags);
  _cogl_flush_face_winding ();

  /* If we haven't transformed the quads in software then we need to also break
   * up batches according to changes in the modelview matrix... */
  if (cogl_debug_flags & COGL_DEBUG_DISABLE_SOFTWARE_TRANSFORM)
    {
      batch_and_call (batch_start,
                      batch_len,
                      compare_entry_modelviews,
                      _cogl_journal_flush_modelview_and_entries,
                      data);
    }
  else
    _cogl_journal_flush_modelview_and_entries (batch_start, batch_len, data);
}

static gboolean
compare_entry_materials (CoglJournalEntry *entry0, CoglJournalEntry *entry1)
{
  /* batch rectangles using compatible materials */

  /* XXX: _cogl_material_equal may give false negatives since it avoids
   * deep comparisons as an optimization. It aims to compare enough so
   * that we that we are able to batch the 90% common cases, but may not
   * look at less common differences. */
  if (_cogl_material_equal (entry0->material,
                            &entry0->flush_options,
                            entry1->material,
                            &entry1->flush_options))
    return TRUE;
  else
    return FALSE;
}

/* Since the stride may not reflect the number of texture layers in use
 * (due to padding) we deal with texture coordinate offsets separately
 * from vertex and color offsets... */
static void
_cogl_journal_flush_texcoord_vbo_offsets_and_entries (
                                          CoglJournalEntry *batch_start,
                                          gint              batch_len,
                                          void             *data)
{
  CoglJournalFlushState *state = data;
  int                    prev_n_texcoord_arrays_enabled;
  int                    i;

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  for (i = 0; i < batch_start->n_layers; i++)
    {
      GE (glClientActiveTexture (GL_TEXTURE0 + i));
      GE (glEnableClientState (GL_TEXTURE_COORD_ARRAY));
      /* XXX NB:
       * Our journal's vertex data is arranged as follows:
       * 4 vertices per quad:
       *    2 or 3 GLfloats per position (3 when doing software transforms)
       *    4 RGBA GLubytes,
       *    2 GLfloats per tex coord * n_layers
       * (though n_layers may be padded; see definition of
       *  GET_JOURNAL_VB_STRIDE_FOR_N_LAYERS for details)
       */
      GE (glTexCoordPointer (2, GL_FLOAT, state->stride,
                             (void *)(state->vbo_offset +
                                      (POS_STRIDE + COLOR_STRIDE) * 4 +
                                      TEX_STRIDE * 4 * i)));
    }
  prev_n_texcoord_arrays_enabled =
    ctx->n_texcoord_arrays_enabled;
  ctx->n_texcoord_arrays_enabled = batch_start->n_layers;
  for (; i < prev_n_texcoord_arrays_enabled; i++)
    {
      GE (glClientActiveTexture (GL_TEXTURE0 + i));
      GE (glDisableClientState (GL_TEXTURE_COORD_ARRAY));
    }

  batch_and_call (batch_start,
                  batch_len,
                  compare_entry_materials,
                  _cogl_journal_flush_material_and_entries,
                  data);
}

static gboolean
compare_entry_n_layers (CoglJournalEntry *entry0, CoglJournalEntry *entry1)
{
  if (entry0->n_layers == entry1->n_layers)
    return TRUE;
  else
    return FALSE;
}

/* At this point we know the stride has changed from the previous batch
 * of journal entries */
static void
_cogl_journal_flush_vbo_offsets_and_entries (CoglJournalEntry *batch_start,
                                             gint              batch_len,
                                             void             *data)
{
  CoglJournalFlushState   *state = data;
  size_t                   stride;
#ifndef HAVE_COGL_GL
  int                      needed_indices = batch_len * 6;
  CoglHandle               indices_handle;
  CoglVertexBufferIndices *indices;
#endif

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_BATCHING))
    g_print ("BATCHING:  vbo offset batch len = %d\n", batch_len);

  /* XXX NB:
   * Our journal's vertex data is arranged as follows:
   * 4 vertices per quad:
   *    2 or 3 GLfloats per position (3 when doing software transforms)
   *    4 RGBA GLubytes,
   *    2 GLfloats per tex coord * n_layers
   * (though n_layers may be padded; see definition of
   *  GET_JOURNAL_VB_STRIDE_FOR_N_LAYERS for details)
   */
  stride = GET_JOURNAL_VB_STRIDE_FOR_N_LAYERS (batch_start->n_layers);
  stride *= sizeof (GLfloat);
  state->stride = stride;

  GE (glVertexPointer (N_POS_COMPONENTS, GL_FLOAT, stride,
                       (void *)state->vbo_offset));
  GE (glColorPointer (4, GL_UNSIGNED_BYTE, stride,
                      (void *)(state->vbo_offset + (POS_STRIDE * 4))));

#ifndef HAVE_COGL_GL
  indices_handle = cogl_vertex_buffer_indices_get_for_quads (needed_indices);
  indices = _cogl_vertex_buffer_indices_pointer_from_handle (indices_handle);
  state->indices = indices;

  if (indices->type == GL_UNSIGNED_BYTE)
    state->indices_type_size = 1;
  else if (indices->type == GL_UNSIGNED_SHORT)
    state->indices_type_size = 2;
  else
    g_critical ("unknown indices type %d", indices->type);

  GE (glBindBuffer (GL_ELEMENT_ARRAY_BUFFER,
                    GPOINTER_TO_UINT (indices->vbo_name)));
#endif

  /* We only call gl{Vertex,Color,Texture}Pointer when the stride within
   * the VBO changes. (due to a change in the number of material layers)
   * While the stride remains constant we walk forward through the above
   * VBO using a vertex offset passed to glDraw{Arrays,Elements} */
  state->vertex_offset = 0;

  if (cogl_debug_flags & COGL_DEBUG_JOURNAL)
    {
      guint8 *verts;

      if (cogl_get_features () & COGL_FEATURE_VBOS)
        verts = ((guint8 *)ctx->logged_vertices->data) +
          (size_t)state->vbo_offset;
      else
        verts = (guint8 *)state->vbo_offset;
      _cogl_journal_dump_quad_batch (verts,
                                     batch_start->n_layers,
                                     batch_len);
    }

  batch_and_call (batch_start,
                  batch_len,
                  compare_entry_n_layers,
                  _cogl_journal_flush_texcoord_vbo_offsets_and_entries,
                  data);

  /* progress forward through the VBO containing all our vertices */
  state->vbo_offset += (stride * 4 * batch_len);
  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_JOURNAL))
    g_print ("new vbo offset = %lu\n", (gulong)state->vbo_offset);
}

static gboolean
compare_entry_strides (CoglJournalEntry *entry0, CoglJournalEntry *entry1)
{
  /* Currently the only thing that affects the stride for our vertex arrays
   * is the number of material layers. We need to update our VBO offsets
   * whenever the stride changes. */
  /* TODO: We should be padding the n_layers == 1 case as if it were
   * n_layers == 2 so we can reduce the need to split batches. */
  if (entry0->n_layers == entry1->n_layers ||
      (entry0->n_layers <= MIN_LAYER_PADING &&
       entry1->n_layers <= MIN_LAYER_PADING))
    return TRUE;
  else
    return FALSE;
}

static GLuint
upload_vertices_to_vbo (GArray *vertices, CoglJournalFlushState *state)
{
  size_t needed_vbo_len;
  GLuint journal_vbo;

  _COGL_GET_CONTEXT (ctx, 0);

  needed_vbo_len = vertices->len * sizeof (GLfloat);

  g_assert (needed_vbo_len);
  GE (glGenBuffers (1, &journal_vbo));
  GE (glBindBuffer (GL_ARRAY_BUFFER, journal_vbo));
  GE (glBufferData (GL_ARRAY_BUFFER,
                    needed_vbo_len,
                    vertices->data,
                    GL_STATIC_DRAW));

  /* As we flush the journal entries in batches we walk forward through the
   * above VBO starting at offset 0... */
  state->vbo_offset = 0;

  return journal_vbo;
}

/* XXX NB: When _cogl_journal_flush() returns all state relating
 * to materials, all glEnable flags and current matrix state
 * is undefined.
 */
void
_cogl_journal_flush (void)
{
  CoglJournalFlushState state;
  int                   i;
  GLuint                journal_vbo;
  gboolean              vbo_fallback =
    (cogl_get_features () & COGL_FEATURE_VBOS) ? FALSE : TRUE;
  CoglHandle            framebuffer;
  CoglMatrixStack      *modelview_stack;
  COGL_STATIC_TIMER (flush_timer,
                     "Mainloop", /* parent */
                     "Journal Flush",
                     "The time spent flushing the Cogl journal",
                     0 /* no application private data */);

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

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

  COGL_TIMER_START (_cogl_uprof_context, flush_timer);

  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_BATCHING))
    g_print ("BATCHING: journal len = %d\n", ctx->journal->len);

  /* Load all the vertex data we have accumulated so far into a single VBO
   * to minimize memory management costs within the GL driver. */
  if (!vbo_fallback)
    journal_vbo = upload_vertices_to_vbo (ctx->logged_vertices, &state);
  else
    state.vbo_offset = (char *)ctx->logged_vertices->data;

  framebuffer = _cogl_get_framebuffer ();
  modelview_stack = _cogl_framebuffer_get_modelview_stack (framebuffer);
  state.modelview_stack = modelview_stack;

  _cogl_matrix_stack_push (modelview_stack);

  /* If we have transformed all our quads at log time then we ensure no
   * further model transform is applied by loading the identity matrix
   * here... */
  if (G_LIKELY (!(cogl_debug_flags & COGL_DEBUG_DISABLE_SOFTWARE_TRANSFORM)))
    {
      _cogl_matrix_stack_load_identity (modelview_stack);
      _cogl_matrix_stack_flush_to_gl (modelview_stack, COGL_MATRIX_MODELVIEW);
    }

  /* batch_and_call() batches a list of journal entries according to some
   * given criteria and calls a callback once for each determined batch.
   *
   * The process of flushing the journal is staggered to reduce the amount
   * of driver/GPU state changes necessary:
   * 1) We split the entries according to the stride of the vertices:
   *      Each time the stride of our vertex data changes we need to call
   *      gl{Vertex,Color}Pointer to inform GL of new VBO offsets.
   *      Currently the only thing that affects the stride of our vertex data
   *      is the number of material layers.
   * 2) We split the entries explicitly by the number of material layers:
   *      We pad our vertex data when the number of layers is < 2 so that we
   *      can minimize changes in stride. Each time the number of layers
   *      changes we need to call glTexCoordPointer to inform GL of new VBO
   *      offsets.
   * 3) We then split according to compatible Cogl materials:
   *      This is where we flush material state
   * 4) Finally we split according to modelview matrix changes:
   *      This is when we finally tell GL to draw something.
   *      Note: Splitting by modelview changes is skipped when are doing the
   *      vertex transformation in software at log time.
   */
  batch_and_call ((CoglJournalEntry *)ctx->journal->data, /* first entry */
                  ctx->journal->len, /* max number of entries to consider */
                  compare_entry_strides,
                  _cogl_journal_flush_vbo_offsets_and_entries, /* callback */
                  &state); /* data */

  _cogl_matrix_stack_pop (modelview_stack);

  for (i = 0; i < ctx->journal->len; i++)
    {
      CoglJournalEntry *entry =
        &g_array_index (ctx->journal, CoglJournalEntry, i);
      _cogl_material_journal_unref (entry->material);
    }

  if (!vbo_fallback)
    GE (glDeleteBuffers (1, &journal_vbo));

  g_array_set_size (ctx->journal, 0);
  g_array_set_size (ctx->logged_vertices, 0);

  COGL_TIMER_STOP (_cogl_uprof_context, flush_timer);
}

static void
_cogl_journal_init (void)
{
  /* Here we flush anything that we know must remain constant until the
   * next the the journal is flushed. Note: This lets up flush things
   * that themselves depend on the journal, such as clip state. */

  /* NB: the journal deals with flushing the modelview stack manually */
  _cogl_framebuffer_flush_state (_cogl_get_framebuffer (),
                                 COGL_FRAMEBUFFER_FLUSH_SKIP_MODELVIEW);
}

void
_cogl_journal_log_quad (float         x_1,
                        float         y_1,
                        float         x_2,
                        float         y_2,
                        CoglHandle    material,
                        int           n_layers,
                        guint32       fallback_layers,
                        GLuint        layer0_override_texture,
                        float        *tex_coords,
                        unsigned int  tex_coords_len)
{
  size_t            stride;
  size_t            byte_stride;
  int               next_vert;
  GLfloat          *v;
  GLubyte          *c;
  GLubyte          *src_c;
  int               i;
  int               next_entry;
  guint32           disable_layers;
  CoglJournalEntry *entry;
  COGL_STATIC_TIMER (log_timer,
                     "Mainloop", /* parent */
                     "Journal Log",
                     "The time spent logging in the Cogl journal",
                     0 /* no application private data */);

  _COGL_GET_CONTEXT (ctx, NO_RETVAL);

  COGL_TIMER_START (_cogl_uprof_context, log_timer);

  if (ctx->logged_vertices->len == 0)
    _cogl_journal_init ();

  /* The vertex data is logged into a separate array in a layout that can be
   * directly passed to OpenGL
   */

  /* XXX: See definition of GET_JOURNAL_VB_STRIDE_FOR_N_LAYERS for details
   * about how we pack our vertex data */
  stride = GET_JOURNAL_VB_STRIDE_FOR_N_LAYERS (n_layers);
  /* NB: stride is in 32bit words */
  byte_stride = stride * 4;

  next_vert = ctx->logged_vertices->len;
  g_array_set_size (ctx->logged_vertices, next_vert + 4 * stride);
  v = &g_array_index (ctx->logged_vertices, GLfloat, next_vert);
  c = (GLubyte *)(v + POS_STRIDE);

  /* XXX: All the jumping around to fill in this strided buffer doesn't
   * seem ideal. */

  /* XXX: we could defer expanding the vertex data for GL until we come
   * to flushing the journal. */

  /* FIXME: This is a hacky optimization, since it will break if we
   * change the definition of CoglColor: */
  _cogl_material_get_colorubv (material, c);
  src_c = c;
  for (i = 0; i < 3; i++)
    {
      c += byte_stride;
      memcpy (c, src_c, 4);
    }

  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_DISABLE_SOFTWARE_TRANSFORM))
    {
      v[0] = x_1; v[1] = y_1;
      v += stride;
      v[0] = x_1; v[1] = y_2;
      v += stride;
      v[0] = x_2; v[1] = y_2;
      v += stride;
      v[0] = x_2; v[1] = y_1;
    }
  else
    {
      CoglMatrix  mv;
      float       x, y, z, w;

      cogl_get_modelview_matrix (&mv);

      x = x_1, y = y_1, z = 0; w = 1;
      cogl_matrix_transform_point (&mv, &x, &y, &z, &w);
      v[0] = x; v[1] = y; v[2] = z;
      v += stride;
      x = x_1, y = y_2, z = 0; w = 1;
      cogl_matrix_transform_point (&mv, &x, &y, &z, &w);
      v[0] = x; v[1] = y; v[2] = z;
      v += stride;
      x = x_2, y = y_2, z = 0; w = 1;
      cogl_matrix_transform_point (&mv, &x, &y, &z, &w);
      v[0] = x; v[1] = y; v[2] = z;
      v += stride;
      x = x_2, y = y_1, z = 0; w = 1;
      cogl_matrix_transform_point (&mv, &x, &y, &z, &w);
      v[0] = x; v[1] = y; v[2] = z;
    }

  for (i = 0; i < n_layers; i++)
    {
      /* XXX: See definition of GET_JOURNAL_VB_STRIDE_FOR_N_LAYERS for details
       * about how we pack our vertex data */
      GLfloat *t = &g_array_index (ctx->logged_vertices, GLfloat,
                                   next_vert +  POS_STRIDE +
                                   COLOR_STRIDE + TEX_STRIDE * i);

      t[0] = tex_coords[0]; t[1] = tex_coords[1];
      t += stride;
      t[0] = tex_coords[0]; t[1] = tex_coords[3];
      t += stride;
      t[0] = tex_coords[2]; t[1] = tex_coords[3];
      t += stride;
      t[0] = tex_coords[2]; t[1] = tex_coords[1];
    }

  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_JOURNAL))
    {
      g_print ("Logged new quad:\n");
      v = &g_array_index (ctx->logged_vertices, GLfloat, next_vert);
      _cogl_journal_dump_quad_vertices ((guint8 *)v, n_layers);
    }

  next_entry = ctx->journal->len;
  g_array_set_size (ctx->journal, next_entry + 1);
  entry = &g_array_index (ctx->journal, CoglJournalEntry, next_entry);

  disable_layers = (1 << n_layers) - 1;
  disable_layers = ~disable_layers;

  entry->material = _cogl_material_journal_ref (material);
  entry->n_layers = n_layers;
  entry->flush_options.flags =
    COGL_MATERIAL_FLUSH_FALLBACK_MASK |
    COGL_MATERIAL_FLUSH_DISABLE_MASK |
    COGL_MATERIAL_FLUSH_SKIP_GL_COLOR;
  entry->flush_options.fallback_layers = fallback_layers;
  entry->flush_options.disable_layers = disable_layers;
  if (layer0_override_texture)
    {
      entry->flush_options.flags |= COGL_MATERIAL_FLUSH_LAYER0_OVERRIDE;
      entry->flush_options.layer0_override_texture = layer0_override_texture;
    }
  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_DISABLE_SOFTWARE_TRANSFORM))
    cogl_get_modelview_matrix (&entry->model_view);

  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_DISABLE_BATCHING
                  || cogl_debug_flags & COGL_DEBUG_RECTANGLES))
    _cogl_journal_flush ();

  COGL_TIMER_STOP (_cogl_uprof_context, log_timer);
}