gtk/gsk/gl/gskglglyphcache.c

#include "config.h"

#include "gskglglyphcacheprivate.h"
#include "gskgldriverprivate.h"
#include "gskdebugprivate.h"
#include "gskprivate.h"
#include "gskgltextureatlasprivate.h"

#include "gdk/gdkglcontextprivate.h"

#include <graphene.h>
#include <cairo.h>
#include <epoxy/gl.h>
#include <string.h>

/* Cache eviction strategy
 *
 * We mark glyphs as accessed every time we use them.
 * Every few frames, we mark glyphs that haven't been
 * accessed since the last check as old.
 *
 * We keep count of the pixels of each atlas that are
 * taken up by old data. When the fraction of old pixels
 * gets too high, we drop the atlas and all the items it
 * contained.
 *
 * Big glyphs are not stored in the atlas, they get their
 * own texture, but they are still cached.
 */

#define MAX_FRAME_AGE (60)
#define MAX_GLYPH_SIZE 128 /* Will get its own texture if bigger */

static guint    glyph_cache_hash       (gconstpointer v);
static gboolean glyph_cache_equal      (gconstpointer v1,
                                        gconstpointer v2);
static void     glyph_cache_key_free   (gpointer      v);
static void     glyph_cache_value_free (gpointer      v);

GskGLGlyphCache *
gsk_gl_glyph_cache_new (GdkDisplay *display,
                        GskGLTextureAtlases *atlases)
{
  GskGLGlyphCache *glyph_cache;

  glyph_cache = g_new0 (GskGLGlyphCache, 1);

  glyph_cache->display = display;
  glyph_cache->hash_table = g_hash_table_new_full (glyph_cache_hash, glyph_cache_equal,
                                                   glyph_cache_key_free, glyph_cache_value_free);

  glyph_cache->atlases = gsk_gl_texture_atlases_ref (atlases);

  glyph_cache->ref_count = 1;

  return glyph_cache;
}

GskGLGlyphCache *
gsk_gl_glyph_cache_ref (GskGLGlyphCache *self)
{
  self->ref_count++;

  return self;
}

void
gsk_gl_glyph_cache_unref (GskGLGlyphCache *self)
{
  g_assert (self->ref_count > 0);

  if (self->ref_count == 1)
    {
      gsk_gl_texture_atlases_unref (self->atlases);
      g_hash_table_unref (self->hash_table);
      g_free (self);
      return;
    }

  self->ref_count--;
}

static gboolean
glyph_cache_equal (gconstpointer v1, gconstpointer v2)
{
  return memcmp (v1, v2, sizeof (CacheKeyData)) == 0;
}

static guint
glyph_cache_hash (gconstpointer v)
{
  const GlyphCacheKey *key = v;

  return key->hash;
}

static void
glyph_cache_key_free (gpointer v)
{
  GlyphCacheKey *f = v;

  g_object_unref (f->data.font);
  g_free (f);
}

static void
glyph_cache_value_free (gpointer v)
{
  g_free (v);
}

static gboolean
render_glyph (GlyphCacheKey    *key,
              GskGLCachedGlyph *value,
              GskImageRegion   *region)
{
  cairo_surface_t *surface;
  cairo_t *cr;
  cairo_scaled_font_t *scaled_font;
  PangoGlyphString glyph_string;
  PangoGlyphInfo glyph_info;
  int surface_width, surface_height;
  int stride;
  unsigned char *data;

  scaled_font = pango_cairo_font_get_scaled_font ((PangoCairoFont *)key->data.font);
  if (G_UNLIKELY (!scaled_font || cairo_scaled_font_status (scaled_font) != CAIRO_STATUS_SUCCESS))
    {
      g_warning ("Failed to get a font");
      return FALSE;
    }

  surface_width = value->draw_width * key->data.scale / 1024;
  surface_height = value->draw_height * key->data.scale / 1024;

  stride = cairo_format_stride_for_width (CAIRO_FORMAT_ARGB32, surface_width);
  data = g_malloc0 (stride * surface_height);
  surface = cairo_image_surface_create_for_data (data, CAIRO_FORMAT_ARGB32,
                                                 surface_width, surface_height,
                                                 stride);
  cairo_surface_set_device_scale (surface, key->data.scale / 1024.0, key->data.scale / 1024.0);

  cr = cairo_create (surface);

  cairo_set_scaled_font (cr, scaled_font);
  cairo_set_source_rgba (cr, 1, 1, 1, 1);

  glyph_info.glyph = key->data.glyph;
  glyph_info.geometry.width = value->draw_width * 1024;
  if (glyph_info.glyph & PANGO_GLYPH_UNKNOWN_FLAG)
    glyph_info.geometry.x_offset = 0;
  else
    glyph_info.geometry.x_offset = - value->draw_x * 1024;
  glyph_info.geometry.y_offset = - value->draw_y * 1024;

  glyph_string.num_glyphs = 1;
  glyph_string.glyphs = &glyph_info;

  pango_cairo_show_glyph_string (cr, key->data.font, &glyph_string);
  cairo_destroy (cr);

  cairo_surface_flush (surface);

  region->width = cairo_image_surface_get_width (surface);
  region->height = cairo_image_surface_get_height (surface);
  region->stride = cairo_image_surface_get_stride (surface);
  region->data = data;
  if (value->atlas)
    {
      region->x = (gsize)(value->tx * value->atlas->width);
      region->y = (gsize)(value->ty * value->atlas->height);
    }
  else
    {
      region->x = 0;
      region->y = 0;
    }

  cairo_surface_destroy (surface);

  return TRUE;
}

static void
upload_glyph (GlyphCacheKey    *key,
              GskGLCachedGlyph *value)
{
  GskImageRegion r;

  gdk_gl_context_push_debug_group_printf (gdk_gl_context_get_current (),
                                          "Uploading glyph %d",
                                          key->data.glyph);

  if (render_glyph (key, value, &r))
    {
      glPixelStorei (GL_UNPACK_ROW_LENGTH, r.stride / 4);
      glBindTexture (GL_TEXTURE_2D, value->texture_id);
      glTexSubImage2D (GL_TEXTURE_2D, 0,
                       r.x, r.y, r.width, r.height,
                       GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV,
                       r.data);
      glPixelStorei (GL_UNPACK_ROW_LENGTH, 0);
      g_free (r.data);
    }

  gdk_gl_context_pop_debug_group (gdk_gl_context_get_current ());
}

static void
add_to_cache (GskGLGlyphCache  *self,
              GlyphCacheKey    *key,
              GskGLDriver      *driver,
              GskGLCachedGlyph *value)
{
  const int width = value->draw_width * key->data.scale / 1024;
  const int height = value->draw_height * key->data.scale / 1024;

  if (width < MAX_GLYPH_SIZE && height < MAX_GLYPH_SIZE)
    {
      GskGLTextureAtlas *atlas = NULL;
      int packed_x = 0;
      int packed_y = 0;

      gsk_gl_texture_atlases_pack (self->atlases, width + 2, height + 2, &atlas, &packed_x, &packed_y);

      value->tx = (float)(packed_x + 1) / atlas->width;
      value->ty = (float)(packed_y + 1) / atlas->height;
      value->tw = (float)width / atlas->width;
      value->th = (float)height / atlas->height;
      value->used = TRUE;

      value->atlas = atlas;
      value->texture_id = atlas->texture_id;
    }
  else
    {
      value->atlas = NULL;
      value->texture_id = gsk_gl_driver_create_texture (driver, width, height);
      gsk_gl_driver_mark_texture_permanent (driver, value->texture_id);

      gsk_gl_driver_bind_source_texture (driver, value->texture_id);
      gsk_gl_driver_init_texture_empty (driver, value->texture_id, GL_LINEAR, GL_LINEAR);

      value->tx = 0.0f;
      value->ty = 0.0f;
      value->tw = 1.0f;
      value->th = 1.0f;
    }

  upload_glyph (key, value);
}

void
gsk_gl_glyph_cache_lookup_or_add (GskGLGlyphCache         *cache,
                                  GlyphCacheKey           *lookup,
                                  GskGLDriver             *driver,
                                  const GskGLCachedGlyph **cached_glyph_out)
{
  GskGLCachedGlyph *value;

  value = g_hash_table_lookup (cache->hash_table, lookup);

  if (value)
    {
      gsk_gl_glyph_cache_entry_validate (cache, value);
      *cached_glyph_out = value;
      return;
    }

  {
    GlyphCacheKey *key;
    PangoRectangle ink_rect;

    pango_font_get_glyph_extents (lookup->data.font, lookup->data.glyph, &ink_rect, NULL);
    pango_extents_to_pixels (&ink_rect, NULL);
    if (lookup->data.xshift != 0)
      ink_rect.width += 1;
    if (lookup->data.yshift != 0)
      ink_rect.height += 1;

    value = g_new0 (GskGLCachedGlyph, 1);

    value->draw_x = ink_rect.x;
    value->draw_y = ink_rect.y;
    value->draw_width = ink_rect.width;
    value->draw_height = ink_rect.height;
    value->accessed = TRUE;
    value->atlas = NULL; /* For now */

    key = g_new0 (GlyphCacheKey, 1);

    key->data.font = g_object_ref (lookup->data.font);
    key->data.glyph = lookup->data.glyph;
    key->data.xshift = lookup->data.xshift;
    key->data.yshift = lookup->data.yshift;
    key->data.scale = lookup->data.scale;
    key->hash = lookup->hash;

    if (key->data.scale > 0 &&
        value->draw_width * key->data.scale / 1024 > 0 &&
        value->draw_height * key->data.scale / 1024 > 0)
      add_to_cache (cache, key, driver, value);

    *cached_glyph_out = value;
    g_hash_table_insert (cache->hash_table, key, value);
  }
}

void
gsk_gl_glyph_cache_begin_frame (GskGLGlyphCache *self,
                                GskGLDriver     *driver,
                                GPtrArray       *removed_atlases)
{
  GHashTableIter iter;
  GlyphCacheKey *key;
  GskGLCachedGlyph *value;
  guint dropped = 0;

  self->timestamp++;

  if (removed_atlases->len > 0)
    {
      g_hash_table_iter_init (&iter, self->hash_table);
      while (g_hash_table_iter_next (&iter, (gpointer *)&key, (gpointer *)&value))
        {
          if (g_ptr_array_find (removed_atlases, value->atlas, NULL))
            {
              g_hash_table_iter_remove (&iter);
              dropped++;
            }
        }
    }

  if (self->timestamp % MAX_FRAME_AGE == 30)
    {
      g_hash_table_iter_init (&iter, self->hash_table);
      while (g_hash_table_iter_next (&iter, (gpointer *)&key, (gpointer *)&value))
        {
          if (!value->accessed)
            {
              if (value->atlas)
                {
                  if (value->used)
                    {
                      gsk_gl_texture_atlas_mark_unused (value->atlas, value->draw_width, value->draw_height);
                      value->used = FALSE;
                    }
                }
              else
                {
                  gsk_gl_driver_destroy_texture (driver, value->texture_id);
                  g_hash_table_iter_remove (&iter);

                  /* Sadly, if we drop an atlas-less cached glyph, we
                   * have to treat it like a dropped atlas and purge
                   * text node render data.
                   */
                  dropped++;
                }
            }
          else
            value->accessed = FALSE;
       }

      GSK_NOTE(GLYPH_CACHE, g_message ("%d glyphs cached", g_hash_table_size (self->hash_table)));
    }

  GSK_NOTE(GLYPH_CACHE, if (dropped > 0) g_message ("Dropped %d glyphs", dropped));

  if (dropped > 0)
    self->atlas_timestamp++;
}

void
gsk_gl_glyph_cache_entry_validate (GskGLGlyphCache  *cache,
                                   GskGLCachedGlyph *value)
{
  value->accessed = TRUE;
  if (value->atlas && !value->used)
    {
      gsk_gl_texture_atlas_mark_used (value->atlas, value->draw_width, value->draw_height);
      value->used = TRUE;
    }
}