mutter/src/compositor/meta-shadow-factory.c

/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/*
 * MetaShadowFactory:
 *
 * Create and cache shadow textures for abritrary window shapes
 *
 * Copyright 2010 Red Hat, Inc.
 * Copyright 2010 Intel Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */
#include <config.h>
#include <math.h>
#include <string.h>

#include "meta-shadow-factory-private.h"
#include "region-utils.h"

/* This file implements blurring the shape of a window to produce a
 * shadow texture. The details are discussed below; a quick summary
 * of the optimizations we use:
 *
 * - If the window shape is along the lines of a rounded rectangle -
 *   a rectangular center portion with stuff at the corners - then
 *   the blur of this - the shadow - can also be represented as a
 *   9-sliced texture and the same texture can be used for different
 *   size.
 *
 * - We use the fact that a Gaussian blur is separable to do a
 *   2D blur as 1D blur of the rows followed by a 1D blur of the
 *   columns.
 *
 * - For better cache efficiency, we blur rows, transpose the image
 *   in blocks, blur rows again, and then transpose back.
 *
 * - We approximate the 1D gaussian blur as 3 successive box filters.
 */

typedef struct _MetaShadowCacheKey  MetaShadowCacheKey;
typedef struct _MetaShadowClassInfo MetaShadowClassInfo;

struct _MetaShadowCacheKey
{
  MetaWindowShape *shape;
  int radius;
  int top_fade;
};

struct _MetaShadow
{
  int ref_count;

  MetaShadowFactory *factory;
  MetaShadowCacheKey key;
  CoglHandle texture;
  CoglHandle material;

  /* The outer order is the distance the shadow extends outside the window
   * shape; the inner border is the unscaled portion inside the window
   * shape */
  int outer_border_top;
  int inner_border_top;
  int outer_border_right;
  int inner_border_right;
  int outer_border_bottom;
  int inner_border_bottom;
  int outer_border_left;
  int inner_border_left;

  guint scale_width : 1;
  guint scale_height : 1;
};

struct _MetaShadowClassInfo
{
  const char *name; /* const so we can reuse for static definitions */
  MetaShadowParams focused;
  MetaShadowParams unfocused;
};

struct _MetaShadowFactory
{
  GObject parent_instance;

  /* MetaShadowCacheKey => MetaShadow; the shadows are not referenced
   * by the factory, they are simply removed from the table when freed */
  GHashTable *shadows;

  /* class name => MetaShadowClassInfo */
  GHashTable *shadow_classes;
};

struct _MetaShadowFactoryClass
{
  GObjectClass parent_class;
};

enum
{
  CHANGED,

  LAST_SIGNAL
};

static guint signals[LAST_SIGNAL] = { 0 };

/* The first element in this array also defines the default parameters
 * for newly created classes */
MetaShadowClassInfo default_shadow_classes[] = {
  { "normal",       { 12, -1, 0, 8, 255 }, { 6, -1, 0, 4, 255 } },
  { "dialog",       { 12, -1, 0, 8, 255 }, { 6, -1, 0, 4, 255 } },
  { "modal_dialog", { 12, -1, 0, 8, 255 }, { 6, -1, 0, 4, 255 } },
  { "utility",      { 12, -1, 0, 8, 255 }, { 6, -1, 0, 4, 255 } },
  { "border",       { 12, -1, 0, 8, 255 }, { 6, -1, 0, 4, 255 } },
  { "menu",         { 12, -1, 0, 8, 255 }, { 6, -1, 0, 4, 255 } },

  { "popup-menu",    { 6, -1, 0, 4, 255 }, { 6, -1, 0, 4, 255 } },

  { "dropdown-menu", { 6, 25, 0, 4, 255 }, { 6, 100, 0, 4, 255 } },
  { "attached",      { 6, 25, 0, 4, 255 }, { 6, 100, 0, 4, 255 } }
};

G_DEFINE_TYPE (MetaShadowFactory, meta_shadow_factory, G_TYPE_OBJECT);

static guint
meta_shadow_cache_key_hash (gconstpointer val)
{
  const MetaShadowCacheKey *key = val;

  return 59 * key->radius + 67 * key->top_fade + 73 * meta_window_shape_hash (key->shape);
}

static gboolean
meta_shadow_cache_key_equal (gconstpointer a,
                             gconstpointer b)
{
  const MetaShadowCacheKey *key_a = a;
  const MetaShadowCacheKey *key_b = b;

  return (key_a->radius == key_b->radius && key_a->top_fade == key_b->top_fade &&
          meta_window_shape_equal (key_a->shape, key_b->shape));
}

MetaShadow *
meta_shadow_ref (MetaShadow *shadow)
{
  shadow->ref_count++;

  return shadow;
}

void
meta_shadow_unref (MetaShadow *shadow)
{
  shadow->ref_count--;
  if (shadow->ref_count == 0)
    {
      if (shadow->factory)
        {
          g_hash_table_remove (shadow->factory->shadows,
                               &shadow->key);
        }

      meta_window_shape_unref (shadow->key.shape);
      cogl_handle_unref (shadow->texture);
      cogl_handle_unref (shadow->material);

      g_slice_free (MetaShadow, shadow);
    }
}

/**
 * meta_shadow_paint:
 * @window_x: x position of the region to paint a shadow for
 * @window_y: y position of the region to paint a shadow for
 * @window_width: actual width of the region to paint a shadow for
 * @window_height: actual height of the region to paint a shadow for
 *
 * Paints the shadow at the given position, for the specified actual
 * size of the region. (Since a #MetaShadow can be shared between
 * different sizes with the same extracted #MetaWindowShape the
 * size needs to be passed in here.)
 */
void
meta_shadow_paint (MetaShadow *shadow,
                   int         window_x,
                   int         window_y,
                   int         window_width,
                   int         window_height,
                   guint8      opacity)
{
  float texture_width = cogl_texture_get_width (shadow->texture);
  float texture_height = cogl_texture_get_height (shadow->texture);
  int i, j;
  float src_x[4];
  float src_y[4];
  float dest_x[4];
  float dest_y[4];
  int n_x, n_y;

  cogl_material_set_color4ub (shadow->material,
                              opacity, opacity, opacity, opacity);

  cogl_set_source (shadow->material);

  if (shadow->scale_width)
    {
      n_x = 3;

      src_x[0] = 0.0;
      src_x[1] = (shadow->inner_border_left + shadow->outer_border_left) / texture_width;
      src_x[2] = (texture_width - (shadow->inner_border_right + shadow->outer_border_right)) / texture_width;
      src_x[3] = 1.0;

      dest_x[0] = window_x - shadow->outer_border_left;
      dest_x[1] = window_x + shadow->inner_border_left;
      dest_x[2] = window_x + window_width - shadow->inner_border_right;
      dest_x[3] = window_x + window_width + shadow->outer_border_right;
    }
  else
    {
      n_x = 1;

      src_x[0] = 0.0;
      src_x[1] = 1.0;

      dest_x[0] = window_x - shadow->outer_border_left;
      dest_x[1] = window_x + window_width + shadow->outer_border_right;
    }

  if (shadow->scale_height)
    {
      n_y = 3;

      src_y[0] = 0.0;
      src_y[1] = (shadow->inner_border_top + shadow->outer_border_top) / texture_height;
      src_y[2] = (texture_height - (shadow->inner_border_bottom + shadow->outer_border_bottom)) / texture_height;
      src_y[3] = 1.0;

      dest_y[0] = window_y - shadow->outer_border_top;
      dest_y[1] = window_y + shadow->inner_border_top;
      dest_y[2] = window_y + window_height - shadow->inner_border_bottom;
      dest_y[3] = window_y + window_height + shadow->outer_border_bottom;
    }
  else
    {
      n_y = 1;

      src_y[0] = 0.0;
      src_y[1] = 1.0;

      dest_y[0] = window_y - shadow->outer_border_top;
      dest_y[1] = window_y + window_height + shadow->outer_border_bottom;
    }

  for (j = 0; j < n_y; j++)
    for (i = 0; i < n_x; i++)
      cogl_rectangle_with_texture_coords (dest_x[i], dest_y[j],
                                          dest_x[i + 1], dest_y[j + 1],
                                          src_x[i], src_y[j],
                                          src_x[i + 1], src_y[j + 1]);
}

/**
 * meta_shadow_get_bounds:
 * @shadow: a #MetaShadow
 * @window_x: x position of the region to paint a shadow for
 * @window_y: y position of the region to paint a shadow for
 * @window_width: actual width of the region to paint a shadow for
 * @window_height: actual height of the region to paint a shadow for
 *
 * Computes the bounds of the pixels that will be affected by
 * meta_shadow_paints()
 */
void
meta_shadow_get_bounds  (MetaShadow            *shadow,
                         int                    window_x,
                         int                    window_y,
                         int                    window_width,
                         int                    window_height,
                         cairo_rectangle_int_t *bounds)
{
  bounds->x = window_x - shadow->outer_border_left;
  bounds->y = window_x - shadow->outer_border_top;
  bounds->width = window_width + shadow->outer_border_left + shadow->outer_border_right;
  bounds->height = window_height + shadow->outer_border_top + shadow->outer_border_bottom;
}

static void
meta_shadow_class_info_free (MetaShadowClassInfo *class_info)
{
  g_free ((char *)class_info->name);
  g_slice_free (MetaShadowClassInfo, class_info);
}

static void
meta_shadow_factory_init (MetaShadowFactory *factory)
{
  guint i;

  factory->shadows = g_hash_table_new (meta_shadow_cache_key_hash,
                                       meta_shadow_cache_key_equal);

  factory->shadow_classes = g_hash_table_new_full (g_str_hash,
                                                   g_str_equal,
                                                   NULL,
                                                   (GDestroyNotify)meta_shadow_class_info_free);

  for (i = 0; i < G_N_ELEMENTS (default_shadow_classes); i++)
    {
      MetaShadowClassInfo *class_info = g_slice_new (MetaShadowClassInfo);

      *class_info = default_shadow_classes[i];
      class_info->name = g_strdup (class_info->name);

      g_hash_table_insert (factory->shadow_classes,
                           (char *)class_info->name, class_info);
    }
}

static void
meta_shadow_factory_finalize (GObject *object)
{
  MetaShadowFactory *factory = META_SHADOW_FACTORY (object);
  GHashTableIter iter;
  gpointer key, value;

  /* Detach from the shadows in the table so we won't try to
   * remove them when they're freed. */
  g_hash_table_iter_init (&iter, factory->shadows);
  while (g_hash_table_iter_next (&iter, &key, &value))
    {
      MetaShadow *shadow = key;
      shadow->factory = NULL;
    }

  g_hash_table_destroy (factory->shadows);
  g_hash_table_destroy (factory->shadow_classes);

  G_OBJECT_CLASS (meta_shadow_factory_parent_class)->finalize (object);
}

static void
meta_shadow_factory_class_init (MetaShadowFactoryClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);

  object_class->finalize = meta_shadow_factory_finalize;

  signals[CHANGED] =
    g_signal_new ("changed",
                  G_TYPE_FROM_CLASS (object_class),
                  G_SIGNAL_RUN_LAST,
                  0,
                  NULL, NULL,
                  g_cclosure_marshal_VOID__VOID,
                  G_TYPE_NONE, 0);
}

MetaShadowFactory *
meta_shadow_factory_new (void)
{
  return g_object_new (META_TYPE_SHADOW_FACTORY, NULL);
}

/**
 * meta_shadow_factory_get_default:
 *
 * Return value: (transfer none): the global singleton shadow factory
 */
MetaShadowFactory *
meta_shadow_factory_get_default (void)
{
  static MetaShadowFactory *factory;

  if (factory == NULL)
    factory = meta_shadow_factory_new ();

  return factory;
}

/* We emulate a 1D Gaussian blur by using 3 consecutive box blurs;
 * this produces a result that's within 3% of the original and can be
 * implemented much faster for large filter sizes because of the
 * efficiency of implementation of a box blur. Idea and formula
 * for choosing the box blur size come from:
 *
 * http://www.w3.org/TR/SVG/filters.html#feGaussianBlurElement
 *
 * The 2D blur is then done by blurring the rows, flipping the
 * image and blurring the columns. (This is possible because the
 * Gaussian kernel is separable - it's the product of a horizontal
 * blur and a vertical blur.)
 */
static int
get_box_filter_size (int radius)
{
  return (int)(0.5 + radius * (0.75 * sqrt(2*M_PI)));
}

/* The "spread" of the filter is the number of pixels from an original
 * pixel that it's blurred image extends. (A no-op blur that doesn't
 * blur would have a spread of 0.) See comment in blur_rows() for why the
 * odd and even cases are different
 */
static int
get_shadow_spread (int radius)
{
  int d = get_box_filter_size (radius);

  if (d % 2 == 1)
    return 3 * (d / 2);
  else
    return 3 * (d / 2) - 1;
}

/* This applies a single box blur pass to a horizontal range of pixels;
 * since the box blur has the same weight for all pixels, we can
 * implement an efficient sliding window algorithm where we add
 * in pixels coming into the window from the right and remove
 * them when they leave the windw to the left.
 *
 * d is the filter width; for even d shift indicates how the blurred
 * result is aligned with the original - does ' x ' go to ' yy' (shift=1)
 * or 'yy ' (shift=-1)
 */
static void
blur_xspan (guchar *row,
            guchar *tmp_buffer,
            int     row_width,
            int     x0,
            int     x1,
            int     d,
            int     shift)
{
  int offset;
  int sum = 0;
  int i;

  if (d % 2 == 1)
    offset = d / 2;
  else
    offset = (d - shift) / 2;

  /* All the conditionals in here look slow, but the branches will
   * be well predicted and there are enough different possibilities
   * that trying to write this as a series of unconditional loops
   * is hard and not an obvious win. The main slow down here seems
   * to be the integer division for pixel; one possible optimization
   * would be to accumulate into two 16-bit integer buffers and
   * only divide down after all three passes. (SSE parallel implementation
   * of the divide step is possible.)
   */
  for (i = x0 - d + offset; i < x1 + offset; i++)
    {
      if (i >= 0 && i < row_width)
	sum += row[i];

      if (i >= x0 + offset)
	{
	  if (i >= d)
	    sum -= row[i - d];

	  tmp_buffer[i - offset] = (sum + d / 2) / d;
	}
    }

  memcpy(row + x0, tmp_buffer + x0, x1 - x0);
}

static void
blur_rows (cairo_region_t   *convolve_region,
           int               x_offset,
           int               y_offset,
	   guchar           *buffer,
	   int               buffer_width,
	   int               buffer_height,
           int               d)
{
  int i, j;
  int n_rectangles;
  guchar *tmp_buffer;

  tmp_buffer = g_malloc (buffer_width);

  n_rectangles = cairo_region_num_rectangles (convolve_region);
  for (i = 0; i < n_rectangles; i++)
    {
      cairo_rectangle_int_t rect;

      cairo_region_get_rectangle (convolve_region, i, &rect);

      for (j = y_offset + rect.y; j < y_offset + rect.y + rect.height; j++)
	{
	  guchar *row = buffer + j * buffer_width;
	  int x0 = x_offset + rect.x;
	  int x1 = x0 + rect.width;

          /* We want to produce a symmetric blur that spreads a pixel
           * equally far to the left and right. If d is odd that happens
           * naturally, but for d even, we approximate by using a blur
           * on either side and then a centered blur of size d + 1.
           * (techique also from the SVG specification)
           */
	  if (d % 2 == 1)
	    {
	      blur_xspan (row, tmp_buffer, buffer_width, x0, x1, d, 0);
	      blur_xspan (row, tmp_buffer, buffer_width, x0, x1, d, 0);
	      blur_xspan (row, tmp_buffer, buffer_width, x0, x1, d, 0);
	    }
	  else
	    {
	      blur_xspan (row, tmp_buffer, buffer_width, x0, x1, d, 1);
	      blur_xspan (row, tmp_buffer, buffer_width, x0, x1, d, -1);
	      blur_xspan (row, tmp_buffer, buffer_width, x0, x1, d + 1, 0);
	    }
	}
    }

  g_free (tmp_buffer);
}

static void
fade_bytes (guchar *bytes,
            int     width,
            int     distance,
            int     total)
{
  guint32 multiplier = (distance * 0x10000 + 0x8000) / total;
  int i;

  for (i = 0; i < width; i++)
    bytes[i] = (bytes[i] * multiplier) >> 16;
}

/* Swaps width and height. Either swaps in-place and returns the original
 * buffer or allocates a new buffer, frees the original buffer and returns
 * the new buffer.
 */
static guchar *
flip_buffer (guchar *buffer,
	     int     width,
             int     height)
{
  /* Working in blocks increases cache efficiency, compared to reading
   * or writing an entire column at once */
#define BLOCK_SIZE 16

  if (width == height)
    {
      int i0, j0;

      for (j0 = 0; j0 < height; j0 += BLOCK_SIZE)
	for (i0 = 0; i0 <= j0; i0 += BLOCK_SIZE)
	  {
	    int max_j = MIN(j0 + BLOCK_SIZE, height);
	    int max_i = MIN(i0 + BLOCK_SIZE, width);
	    int i, j;

	    if (i0 == j0)
	      {
		for (j = j0; j < max_j; j++)
		  for (i = i0; i < j; i++)
		    {
		      guchar tmp = buffer[j * width + i];
		      buffer[j * width + i] = buffer[i * width + j];
		      buffer[i * width + j] = tmp;
		    }
	      }
	    else
	      {
		for (j = j0; j < max_j; j++)
		  for (i = i0; i < max_i; i++)
		    {
		      guchar tmp = buffer[j * width + i];
		      buffer[j * width + i] = buffer[i * width + j];
		      buffer[i * width + j] = tmp;
		    }
	      }
	  }

      return buffer;
    }
  else
    {
      guchar *new_buffer = g_malloc (height * width);
      int i0, j0;

      for (i0 = 0; i0 < width; i0 += BLOCK_SIZE)
        for (j0 = 0; j0 < height; j0 += BLOCK_SIZE)
	  {
	    int max_j = MIN(j0 + BLOCK_SIZE, height);
	    int max_i = MIN(i0 + BLOCK_SIZE, width);
	    int i, j;

            for (i = i0; i < max_i; i++)
              for (j = j0; j < max_j; j++)
		new_buffer[i * height + j] = buffer[j * width + i];
	  }

      g_free (buffer);

      return new_buffer;
    }
#undef BLOCK_SIZE
}

/* Creates a material with a single layer. Using a common template
 * allows sharing a shader between all shadows. To share the same
 * shader with all other materials that are just texture plus
 * opacity would require cogl fixes. Based on
 * gnome-shell/src/st/_st_create_texture_material.c
 */
static CoglHandle
create_texture_material (CoglHandle src_texture)
{
  static CoglHandle texture_material_template = COGL_INVALID_HANDLE;
  CoglHandle material;

  g_return_val_if_fail (src_texture != COGL_INVALID_HANDLE,
                        COGL_INVALID_HANDLE);

  /* We use a material that has a dummy texture as a base for all
     texture materials. The idea is that only the Cogl texture object
     would be different in the children so it is likely that Cogl will
     be able to share GL programs between all the textures. */
  if (G_UNLIKELY (texture_material_template == COGL_INVALID_HANDLE))
    {
      static const guint8 white_pixel[] = { 0xff, 0xff, 0xff, 0xff };
      CoglHandle dummy_texture;

      dummy_texture =
        cogl_texture_new_from_data (1, 1,
                                    COGL_TEXTURE_NONE,
                                    COGL_PIXEL_FORMAT_RGBA_8888_PRE,
                                    COGL_PIXEL_FORMAT_ANY,
                                    4, white_pixel);

      texture_material_template = cogl_material_new ();
      cogl_material_set_layer (texture_material_template, 0, dummy_texture);
      cogl_handle_unref (dummy_texture);
    }

  material = cogl_material_copy (texture_material_template);

  cogl_material_set_layer (material, 0, src_texture);

  return material;
}

static void
make_shadow (MetaShadow     *shadow,
             cairo_region_t *region)
{
  int d = get_box_filter_size (shadow->key.radius);
  int spread = get_shadow_spread (shadow->key.radius);
  cairo_rectangle_int_t extents;
  cairo_region_t *row_convolve_region;
  cairo_region_t *column_convolve_region;
  guchar *buffer;
  int buffer_width;
  int buffer_height;
  int x_offset;
  int y_offset;
  int n_rectangles, j, k;

  cairo_region_get_extents (region, &extents);

  /* In the case where top_fade >= 0 and the portion above the top
   * edge of the shape will be cropped, it seems like we could create
   * a smaller buffer and omit the top portion, but actually, in our
   * multi-pass blur algorithm, the blur into the area above the window
   * in the first pass will contribute back to the final pixel values
   * for the top pixels, so we create a buffer as if we weren't cropping
   * and only crop when creating the CoglTexture.
   */

  buffer_width = extents.width + 2 * spread;
  buffer_height = extents.height + 2 * spread;

  /* Round up so we have aligned rows/columns */
  buffer_width = (buffer_width + 3) & ~3;
  buffer_height = (buffer_height + 3) & ~3;

  /* Square buffer allows in-place swaps, which are roughly 70% faster, but we
   * don't want to over-allocate too much memory.
   */
  if (buffer_height < buffer_width && buffer_height > (3 * buffer_width) / 4)
    buffer_height = buffer_width;
  if (buffer_width < buffer_height && buffer_width > (3 * buffer_height) / 4)
    buffer_width = buffer_height;

  buffer = g_malloc0 (buffer_width * buffer_height);

  /* Blurring with multiple box-blur passes is fast, but (especially for
   * large shadow sizes) we can improve efficiency by restricting the blur
   * to the region that actually needs to be blurred.
   */
  row_convolve_region = meta_make_border_region (region, spread, spread, FALSE);
  column_convolve_region = meta_make_border_region (region, 0, spread, TRUE);

  /* Offsets between coordinates of the regions and coordinates in the buffer */
  x_offset = spread;
  y_offset = spread;

  /* Step 1: unblurred image */
  n_rectangles = cairo_region_num_rectangles (region);
  for (k = 0; k < n_rectangles; k++)
    {
      cairo_rectangle_int_t rect;

      cairo_region_get_rectangle (region, k, &rect);
      for (j = y_offset + rect.y; j < y_offset + rect.y + rect.height; j++)
	memset (buffer + buffer_width * j + x_offset + rect.x, 255, rect.width);
    }

  /* Step 2: swap rows and columns */
  buffer = flip_buffer (buffer, buffer_width, buffer_height);

  /* Step 3: blur rows (really columns) */
  blur_rows (column_convolve_region, y_offset, x_offset,
             buffer, buffer_height, buffer_width,
             d);

  /* Step 4: swap rows and columns */
  buffer = flip_buffer (buffer, buffer_height, buffer_width);

  /* Step 5: blur rows */
  blur_rows (row_convolve_region, x_offset, y_offset,
             buffer, buffer_width, buffer_height,
             d);

  /* Step 6: fade out the top, if applicable */
  if (shadow->key.top_fade >= 0)
    {
      for (j = y_offset; j < y_offset + MIN (shadow->key.top_fade, extents.height + shadow->outer_border_bottom); j++)
        fade_bytes(buffer + j * buffer_width, buffer_width, j - y_offset, shadow->key.top_fade);
    }

  /* We offset the passed in pixels to crop off the extra area we allocated at the top
   * in the case of top_fade >= 0. We also account for padding at the left for symmetry
   * though that doesn't currently occur.
   */
  shadow->texture = cogl_texture_new_from_data (shadow->outer_border_left + extents.width + shadow->outer_border_right,
                                                shadow->outer_border_top + extents.height + shadow->outer_border_bottom,
                                                COGL_TEXTURE_NONE,
                                                COGL_PIXEL_FORMAT_A_8,
                                                COGL_PIXEL_FORMAT_ANY,
                                                buffer_width,
                                                (buffer +
                                                 (y_offset - shadow->outer_border_top) * buffer_width +
                                                 (x_offset - shadow->outer_border_left)));

  cairo_region_destroy (row_convolve_region);
  cairo_region_destroy (column_convolve_region);
  g_free (buffer);

  shadow->material = create_texture_material (shadow->texture);
}

static MetaShadowParams *
get_shadow_params (MetaShadowFactory *factory,
                   const char        *class_name,
                   gboolean           focused,
                   gboolean           create)
{
  MetaShadowClassInfo *class_info = g_hash_table_lookup (factory->shadow_classes,
                                                         class_name);
  if (class_info == NULL)
    {
      if (create)
        {
          class_info = g_slice_new0 (MetaShadowClassInfo);
          *class_info = default_shadow_classes[0];
          class_info->name = g_strdup (class_info->name);

          g_hash_table_insert (factory->shadow_classes,
                               (char *)class_info->name, class_info);
        }
      else
        {
          class_info = &default_shadow_classes[0];
        }
    }

  if (focused)
    return &class_info->focused;
  else
    return &class_info->unfocused;
}

/**
 * meta_shadow_factory_get_shadow:
 * @factory: a #MetaShadowFactory
 * @shape: the size-invariant shape of the window's region
 * @width: the actual width of the window's region
 * @height: the actual height of the window's region
 * @class_name: name of the class of window shadows
 * @focused: whether the shadow is for a focused window
 *
 * Gets the appropriate shadow object for drawing shadows for the
 * specified window shape. The region that we are shadowing is specified
 * as a combination of a size-invariant extracted shape and the size.
 * In some cases, the same shadow object can be shared between sizes;
 * in other cases a different shadow object is used for each size.
 *
 * Return value: (transfer full): a newly referenced #MetaShadow; unref with
 *  meta_shadow_unref()
 */
MetaShadow *
meta_shadow_factory_get_shadow (MetaShadowFactory *factory,
                                MetaWindowShape   *shape,
                                int                width,
                                int                height,
                                const char        *class_name,
                                gboolean           focused)
{
  MetaShadowParams *params;
  MetaShadowCacheKey key;
  MetaShadow *shadow;
  cairo_region_t *region;
  int spread;
  int shape_border_top, shape_border_right, shape_border_bottom, shape_border_left;
  int inner_border_top, inner_border_right, inner_border_bottom, inner_border_left;
  int outer_border_top, outer_border_right, outer_border_bottom, outer_border_left;
  gboolean scale_width, scale_height;
  gboolean cacheable;
  int center_width, center_height;

  g_return_val_if_fail (META_IS_SHADOW_FACTORY (factory), NULL);
  g_return_val_if_fail (shape != NULL, NULL);

  /* Using a single shadow texture for different window sizes only works
   * when there is a central scaled area that is greater than twice
   * the spread of the gaussian blur we are applying to get to the
   * shadow image.
   *                         *********          ***********
   *  /----------\         *###########*      *#############*
   *  |          |   =>   **#*********#** => **#***********#**
   *  |          |        **#**     **#**    **#**       **#**
   *  |          |        **#*********#**    **#***********#**
   *  \----------/         *###########*      *#############*
   *                         **********         ************
   *   Original                Blur            Stretched Blur
   *
   * For smaller sizes, we create a separate shadow image for each size;
   * since we assume that there will be little reuse, we don't try to
   * cache such images but just recreate them. (Since the current cache
   * policy is to only keep around referenced shadows, there wouldn't
   * be any harm in caching them, it would just make the book-keeping
   * a bit tricker.)
   *
   * In the case where we are fading a the top, that also has to fit
   * within the top unscaled border.
   */

  params = get_shadow_params (factory, class_name, focused, FALSE);

  spread = get_shadow_spread (params->radius);
  meta_window_shape_get_borders (shape,
                                 &shape_border_top,
                                 &shape_border_right,
                                 &shape_border_bottom,
                                 &shape_border_left);

  inner_border_top = MAX (shape_border_top + spread, params->top_fade);
  outer_border_top = params->top_fade >= 0 ? 0 : spread;
  inner_border_right = shape_border_right + spread;
  outer_border_right = spread;
  inner_border_bottom = shape_border_bottom + spread;
  outer_border_bottom = spread;
  inner_border_left = shape_border_left + spread;
  outer_border_left = spread;

  scale_width = inner_border_left + inner_border_right <= width;
  scale_height = inner_border_top + inner_border_bottom <= height;
  cacheable = scale_width && scale_height;

  if (cacheable)
    {
      key.shape = shape;
      key.radius = params->radius;
      key.top_fade = params->top_fade;

      shadow = g_hash_table_lookup (factory->shadows, &key);
      if (shadow)
        return meta_shadow_ref (shadow);
    }

  shadow = g_slice_new0 (MetaShadow);

  shadow->ref_count = 1;
  shadow->factory = factory;
  shadow->key.shape = meta_window_shape_ref (shape);
  shadow->key.radius = params->radius;
  shadow->key.top_fade = params->top_fade;

  shadow->outer_border_top = outer_border_top;
  shadow->inner_border_top = inner_border_top;
  shadow->outer_border_right = outer_border_right;
  shadow->inner_border_right = inner_border_right;
  shadow->outer_border_bottom = outer_border_bottom;
  shadow->inner_border_bottom = inner_border_bottom;
  shadow->outer_border_left = outer_border_left;
  shadow->inner_border_left = inner_border_left;

  shadow->scale_width = scale_width;
  if (scale_width)
    center_width = inner_border_left + inner_border_right - (shape_border_left + shape_border_right);
  else
    center_width = width - (shape_border_left + shape_border_right);

  shadow->scale_height = scale_height;
  if (scale_height)
    center_height = inner_border_top + inner_border_bottom - (shape_border_top + shape_border_bottom);
  else
    center_height = height - (shape_border_top + shape_border_bottom);

  g_assert (center_width >= 0 && center_height >= 0);

  region = meta_window_shape_to_region (shape, center_width, center_height);
  make_shadow (shadow, region);

  cairo_region_destroy (region);

  if (cacheable)
    g_hash_table_insert (factory->shadows, &shadow->key, shadow);

  return shadow;
}

/**
 * meta_shadow_factory_set_params:
 * @factory: a #MetaShadowFactory
 * @class_name: name of the class of shadow to set the params for.
 *  the default shadow classes are the names of the different
 *  theme frame types (normal, dialog, modal_dialog, utility,
 *  border, menu, attached) and in addition, popup-menu
 *  and dropdown-menu.
 * @focused: whether the shadow is for a focused window
 * @params: new parameter values
 *
 * Updates the shadow parameters for a particular class of shadows
 * for either the focused or unfocused state. If the class name
 * does not name an existing class, a new class will be created
 * (the other focus state for that class will have default values
 * assigned to it.)
 */
void
meta_shadow_factory_set_params (MetaShadowFactory *factory,
                                const char        *class_name,
                                gboolean           focused,
                                MetaShadowParams  *params)
{
  MetaShadowParams *stored_params;

  g_return_if_fail (META_IS_SHADOW_FACTORY (factory));
  g_return_if_fail (class_name != NULL);
  g_return_if_fail (params != NULL);
  g_return_if_fail (params->radius >= 0);

  stored_params = get_shadow_params (factory, class_name, focused, TRUE);

  *stored_params = *params;

  g_signal_emit (factory, signals[CHANGED], 0);
}

/**
 * meta_shadow_factory_get_params:
 * @factory: a #MetaShadowFactory
 * @class_name: name of the class of shadow to get the params for
 * @focused: whether the shadow is for a focused window
 * @params: (out caller-allocates): location to store the current parameter values
 *
 * Gets the shadow parameters for a particular class of shadows
 * for either the focused or unfocused state. If the class name
 * does not name an existing class, default values will be returned
 * without printing an error.
 */
void
meta_shadow_factory_get_params (MetaShadowFactory *factory,
                                const char        *class_name,
                                gboolean           focused,
                                MetaShadowParams  *params)
{
  MetaShadowParams *stored_params;

  g_return_if_fail (META_IS_SHADOW_FACTORY (factory));
  g_return_if_fail (class_name != NULL);

  stored_params = get_shadow_params (factory, class_name, focused, FALSE);

  if (params)
    *params = *stored_params;
}