mutter/pango/cogl-pango-pipeline-cache.c

/*
 * Cogl
 *
 * An object oriented GL/GLES Abstraction/Utility Layer
 *
 * Copyright (C) 2011 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, see
 * <http://www.gnu.org/licenses/>.
 *
 *
 *
 * Authors:
 *   Neil Roberts <neil@linux.intel.com>
 */

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

#include <glib.h>
#include <cogl/cogl.h>
#include "cogl-pango-pipeline-cache.h"

typedef struct _CoglPangoPipelineCacheEntry CoglPangoPipelineCacheEntry;

struct _CoglPangoPipelineCache
{
  GHashTable *hash_table;

  CoglPipeline *base_texture_alpha_pipeline;
  CoglPipeline *base_texture_rgba_pipeline;

  gboolean use_mipmapping;
};

struct _CoglPangoPipelineCacheEntry
{
  /* This will take a reference or it can be NULL to represent the
     pipeline used to render colors */
  CoglHandle texture;

  /* This will only take a weak reference */
  CoglHandle pipeline;
};

static void
_cogl_pango_pipeline_cache_key_destroy (gpointer data)
{
  if (data)
    cogl_object_unref (data);
}

static void
_cogl_pango_pipeline_cache_value_destroy (gpointer data)
{
  CoglPangoPipelineCacheEntry *cache_entry = data;

  if (cache_entry->texture)
    cogl_object_unref (cache_entry->texture);

  /* We don't need to unref the pipeline because it only takes a weak
     reference */

  g_slice_free (CoglPangoPipelineCacheEntry, cache_entry);
}

CoglPangoPipelineCache *
_cogl_pango_pipeline_cache_new (gboolean use_mipmapping)
{
  CoglPangoPipelineCache *cache = g_new (CoglPangoPipelineCache, 1);

  /* The key is the pipeline pointer. A reference is taken when the
     pipeline is used as a key so we should unref it again in the
     destroy function */
  cache->hash_table =
    g_hash_table_new_full (g_direct_hash,
                           g_direct_equal,
                           _cogl_pango_pipeline_cache_key_destroy,
                           _cogl_pango_pipeline_cache_value_destroy);

  cache->base_texture_rgba_pipeline = NULL;
  cache->base_texture_alpha_pipeline = NULL;

  cache->use_mipmapping = use_mipmapping;

  return cache;
}

static CoglPipeline *
get_base_texture_rgba_pipeline (CoglPangoPipelineCache *cache)
{
  if (cache->base_texture_rgba_pipeline == NULL)
    {
      CoglPipeline *pipeline;

      pipeline = cache->base_texture_rgba_pipeline = cogl_pipeline_new ();

      cogl_pipeline_set_layer_wrap_mode (pipeline, 0,
                                         COGL_MATERIAL_WRAP_MODE_CLAMP_TO_EDGE);

      if (cache->use_mipmapping)
        cogl_pipeline_set_layer_filters
          (pipeline, 0,
           COGL_PIPELINE_FILTER_LINEAR_MIPMAP_LINEAR,
           COGL_PIPELINE_FILTER_LINEAR);
    }

  return cache->base_texture_rgba_pipeline;
}

static CoglPipeline *
get_base_texture_alpha_pipeline (CoglPangoPipelineCache *cache)
{
  if (cache->base_texture_alpha_pipeline == NULL)
    {
      CoglPipeline *pipeline;

      pipeline = cogl_pipeline_copy (get_base_texture_rgba_pipeline (cache));
      cache->base_texture_alpha_pipeline = pipeline;

      /* The default combine mode of materials is to modulate (A x B)
       * the texture RGBA channels with the RGBA channels of the
       * previous layer (which in our case is just the font color)
       *
       * Since the RGB for an alpha texture is defined as 0, this gives us:
       *
       *  result.rgb = color.rgb * 0
       *  result.a = color.a * texture.a
       *
       * What we want is premultiplied rgba values:
       *
       *  result.rgba = color.rgb * texture.a
       *  result.a = color.a * texture.a
       */
      cogl_pipeline_set_layer_combine (pipeline, 0, /* layer */
                                       "RGBA = MODULATE (PREVIOUS, TEXTURE[A])",
                                       NULL);
    }

  return cache->base_texture_alpha_pipeline;
}

typedef struct
{
  CoglPangoPipelineCache *cache;
  CoglHandle texture;
} PipelineDestroyNotifyData;

static void
pipeline_destroy_notify_cb (void *user_data)
{
  PipelineDestroyNotifyData *data = user_data;

  g_hash_table_remove (data->cache->hash_table, data->texture);
  g_slice_free (PipelineDestroyNotifyData, data);
}

CoglPipeline *
_cogl_pango_pipeline_cache_get (CoglPangoPipelineCache *cache,
                                CoglHandle texture)
{
  CoglPangoPipelineCacheEntry *entry;
  PipelineDestroyNotifyData *destroy_data;
  static CoglUserDataKey pipeline_destroy_notify_key;

  /* Look for an existing entry */
  entry = g_hash_table_lookup (cache->hash_table, texture);

  if (entry)
    return cogl_object_ref (entry->pipeline);

  /* No existing pipeline was found so let's create another */
  entry = g_slice_new (CoglPangoPipelineCacheEntry);

  if (texture)
    {
      CoglPipeline *base;

      entry->texture = cogl_handle_ref (texture);

      if (cogl_texture_get_format (entry->texture) == COGL_PIXEL_FORMAT_A_8)
        base = get_base_texture_alpha_pipeline (cache);
      else
        base = get_base_texture_rgba_pipeline (cache);

      entry->pipeline = cogl_pipeline_copy (base);

      cogl_pipeline_set_layer_texture (entry->pipeline, 0 /* layer */, texture);
    }
  else
    {
      entry->texture = NULL;
      entry->pipeline = cogl_pipeline_new ();
    }

  /* Add a weak reference to the pipeline so we can remove it from the
     hash table when it is destroyed */
  destroy_data = g_slice_new (PipelineDestroyNotifyData);
  destroy_data->cache = cache;
  destroy_data->texture = texture;
  cogl_object_set_user_data (entry->pipeline,
                             &pipeline_destroy_notify_key,
                             destroy_data,
                             pipeline_destroy_notify_cb);

  g_hash_table_insert (cache->hash_table,
                       texture ? cogl_handle_ref (texture) : NULL,
                       entry);

  /* This doesn't take a reference on the pipeline so that it will use
     the newly created reference */
  return entry->pipeline;
}

void
_cogl_pango_pipeline_cache_free (CoglPangoPipelineCache *cache)
{
  if (cache->base_texture_rgba_pipeline)
    cogl_object_unref (cache->base_texture_rgba_pipeline);
  if (cache->base_texture_alpha_pipeline)
    cogl_object_unref (cache->base_texture_alpha_pipeline);

  g_hash_table_destroy (cache->hash_table);

  g_free (cache);
}