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gnome-shell/src/st/st-private.c
Daniel van Vugt 48d5740443 st/private: Set sampling_radius to match the blur radius 
From [the spec](https://www.w3.org/TR/css-backgrounds-3/#shadow-blur):

> the resulting shadow must approximate (with each pixel being within 5%
> of its expected value) the image that would be generated by applying to
> the shadow a Gaussian blur with a standard deviation [sigma] equal to
> half the blur radius

This does not change the value of `sigma`, it only corrects the value of
`sampling_radius` used to size the shadow texture. Since the texture is
no longer being slightly oversized it won't get scaled down when rendered
according to the dimensions provided by `st_shadow_get_box` in
`_st_paint_shadow_with_opacity`.

Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/4409
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1897>
2021-06-29 22:32:24 +00:00

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/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/*
* st-private.h: Private declarations and functions
*
* Copyright 2009, 2010 Red Hat, Inc.
* Copyright 2010 Florian Müllner
* Copyright 2010 Intel Corporation
* Copyright 2010 Giovanni Campagna
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU Lesser General Public License,
* version 2.1, as published by the Free Software Foundation.
*
* This program is distributed in the hope 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 program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <math.h>
#include <string.h>
#include "st-private.h"
/**
* _st_actor_get_preferred_width:
* @actor: a #ClutterActor
* @for_height: as with clutter_actor_get_preferred_width()
* @y_fill: %TRUE if @actor will fill its allocation vertically
* @min_width_p: as with clutter_actor_get_preferred_width()
* @natural_width_p: as with clutter_actor_get_preferred_width()
*
* Like clutter_actor_get_preferred_width(), but if @y_fill is %FALSE,
* then it will compute a width request based on the assumption that
* @actor will be given an allocation no taller than its natural
* height.
*/
void
_st_actor_get_preferred_width (ClutterActor *actor,
gfloat for_height,
gboolean y_fill,
gfloat *min_width_p,
gfloat *natural_width_p)
{
if (!y_fill && for_height != -1)
{
ClutterRequestMode mode;
gfloat natural_height;
mode = clutter_actor_get_request_mode (actor);
if (mode == CLUTTER_REQUEST_WIDTH_FOR_HEIGHT)
{
clutter_actor_get_preferred_height (actor, -1, NULL, &natural_height);
if (for_height > natural_height)
for_height = natural_height;
}
}
clutter_actor_get_preferred_width (actor, for_height, min_width_p, natural_width_p);
}
/**
* _st_actor_get_preferred_height:
* @actor: a #ClutterActor
* @for_width: as with clutter_actor_get_preferred_height()
* @x_fill: %TRUE if @actor will fill its allocation horizontally
* @min_height_p: as with clutter_actor_get_preferred_height()
* @natural_height_p: as with clutter_actor_get_preferred_height()
*
* Like clutter_actor_get_preferred_height(), but if @x_fill is
* %FALSE, then it will compute a height request based on the
* assumption that @actor will be given an allocation no wider than
* its natural width.
*/
void
_st_actor_get_preferred_height (ClutterActor *actor,
gfloat for_width,
gboolean x_fill,
gfloat *min_height_p,
gfloat *natural_height_p)
{
if (!x_fill && for_width != -1)
{
ClutterRequestMode mode;
gfloat natural_width;
mode = clutter_actor_get_request_mode (actor);
if (mode == CLUTTER_REQUEST_HEIGHT_FOR_WIDTH)
{
clutter_actor_get_preferred_width (actor, -1, NULL, &natural_width);
if (for_width > natural_width)
for_width = natural_width;
}
}
clutter_actor_get_preferred_height (actor, for_width, min_height_p, natural_height_p);
}
/**
* _st_set_text_from_style:
* @text: Target #ClutterText
* @theme_node: Source #StThemeNode
*
* Set various GObject properties of the @text object using
* CSS information from @theme_node.
*/
void
_st_set_text_from_style (ClutterText *text,
StThemeNode *theme_node)
{
ClutterColor color;
StTextDecoration decoration;
PangoAttrList *attribs = NULL;
const PangoFontDescription *font;
PangoAttribute *foreground;
StTextAlign align;
gdouble spacing;
gchar *font_features;
font = st_theme_node_get_font (theme_node);
clutter_text_set_font_description (text, (PangoFontDescription *) font);
attribs = pango_attr_list_new ();
st_theme_node_get_foreground_color (theme_node, &color);
clutter_text_set_cursor_color (text, &color);
foreground = pango_attr_foreground_new (color.red * 255,
color.green * 255,
color.blue * 255);
pango_attr_list_insert (attribs, foreground);
if (color.alpha != 255)
{
PangoAttribute *alpha;
/* An alpha value of 0 means "system inherited", so the
* minimum regular value is 1.
*/
if (color.alpha == 0)
alpha = pango_attr_foreground_alpha_new (1);
else
alpha = pango_attr_foreground_alpha_new (color.alpha * 255);
pango_attr_list_insert (attribs, alpha);
}
decoration = st_theme_node_get_text_decoration (theme_node);
if (decoration)
{
if (decoration & ST_TEXT_DECORATION_UNDERLINE)
{
PangoAttribute *underline = pango_attr_underline_new (PANGO_UNDERLINE_SINGLE);
pango_attr_list_insert (attribs, underline);
}
if (decoration & ST_TEXT_DECORATION_LINE_THROUGH)
{
PangoAttribute *strikethrough = pango_attr_strikethrough_new (TRUE);
pango_attr_list_insert (attribs, strikethrough);
}
/* Pango doesn't have an equivalent attribute for _OVERLINE, and we deliberately
* skip BLINK (for now...)
*/
}
spacing = st_theme_node_get_letter_spacing (theme_node);
if (spacing)
{
PangoAttribute *letter_spacing = pango_attr_letter_spacing_new ((int)(.5 + spacing) * PANGO_SCALE);
pango_attr_list_insert (attribs, letter_spacing);
}
font_features = st_theme_node_get_font_features (theme_node);
if (font_features)
{
pango_attr_list_insert (attribs, pango_attr_font_features_new (font_features));
g_free (font_features);
}
clutter_text_set_attributes (text, attribs);
if (attribs)
pango_attr_list_unref (attribs);
align = st_theme_node_get_text_align (theme_node);
if (align == ST_TEXT_ALIGN_JUSTIFY)
{
clutter_text_set_justify (text, TRUE);
clutter_text_set_line_alignment (text, PANGO_ALIGN_LEFT);
}
else
{
clutter_text_set_justify (text, FALSE);
clutter_text_set_line_alignment (text, (PangoAlignment) align);
}
}
/**
* _st_create_texture_pipeline:
* @src_texture: The CoglTexture for the pipeline
*
* Creates a simple pipeline which contains the given texture as a
* single layer.
*/
CoglPipeline *
_st_create_texture_pipeline (CoglTexture *src_texture)
{
static CoglPipeline *texture_pipeline_template = NULL;
CoglPipeline *pipeline;
g_return_val_if_fail (src_texture != NULL, NULL);
/* The only state used in the pipeline that would affect the shader
generation is the texture type on the layer. Therefore we create
a template pipeline which sets this state and all texture
pipelines are created as a copy of this. That way Cogl can find
the shader state for the pipeline more quickly by looking at the
pipeline ancestry instead of resorting to the shader cache. */
if (G_UNLIKELY (texture_pipeline_template == NULL))
{
CoglContext *ctx =
clutter_backend_get_cogl_context (clutter_get_default_backend ());
texture_pipeline_template = cogl_pipeline_new (ctx);
cogl_pipeline_set_layer_null_texture (texture_pipeline_template, 0);
}
pipeline = cogl_pipeline_copy (texture_pipeline_template);
if (src_texture != NULL)
cogl_pipeline_set_layer_texture (pipeline, 0, src_texture);
return pipeline;
}
/*****
* Shadows
*****/
static gdouble *
calculate_gaussian_kernel (gdouble sigma,
guint n_values)
{
gdouble *ret, sum;
gdouble exp_divisor;
int half, i;
g_return_val_if_fail (sigma > 0, NULL);
half = n_values / 2;
ret = g_malloc (n_values * sizeof (gdouble));
sum = 0.0;
exp_divisor = 2 * sigma * sigma;
/* n_values of 1D Gauss function */
for (i = 0; i < (int)n_values; i++)
{
ret[i] = exp (-(i - half) * (i - half) / exp_divisor);
sum += ret[i];
}
/* normalize */
for (i = 0; i < (int)n_values; i++)
ret[i] /= sum;
return ret;
}
static guchar *
blur_pixels (guchar *pixels_in,
gint width_in,
gint height_in,
gint rowstride_in,
gdouble blur,
gint *width_out,
gint *height_out,
size_t *rowstride_out)
{
guchar *pixels_out;
gdouble sigma;
/* The CSS specification defines (or will define) the blur radius as twice
* the Gaussian standard deviation. See:
*
* http://lists.w3.org/Archives/Public/www-style/2010Sep/0002.html
*/
sigma = blur / 2.;
if ((guint) blur == 0)
{
*width_out = width_in;
*height_out = height_in;
*rowstride_out = rowstride_in;
pixels_out = g_memdup2 (pixels_in, *rowstride_out * *height_out);
}
else
{
gdouble *kernel;
guchar *line;
gint n_values, half;
gint x_in, y_in, x_out, y_out, i;
n_values = (gint) 5 * sigma;
half = n_values / 2;
*width_out = width_in + 2 * half;
*height_out = height_in + 2 * half;
*rowstride_out = (*width_out + 3) & ~3;
pixels_out = g_malloc0 (*rowstride_out * *height_out);
line = g_malloc0 (*rowstride_out);
kernel = calculate_gaussian_kernel (sigma, n_values);
/* vertical blur */
for (x_in = 0; x_in < width_in; x_in++)
for (y_out = 0; y_out < *height_out; y_out++)
{
guchar *pixel_in, *pixel_out;
gint i0, i1;
y_in = y_out - half;
/* We read from the source at 'y = y_in + i - half'; clamp the
* full i range [0, n_values) so that y is in [0, height_in).
*/
i0 = MAX (half - y_in, 0);
i1 = MIN (height_in + half - y_in, n_values);
pixel_in = pixels_in + (y_in + i0 - half) * rowstride_in + x_in;
pixel_out = pixels_out + y_out * *rowstride_out + (x_in + half);
for (i = i0; i < i1; i++)
{
*pixel_out += *pixel_in * kernel[i];
pixel_in += rowstride_in;
}
}
/* horizontal blur */
for (y_out = 0; y_out < *height_out; y_out++)
{
memcpy (line, pixels_out + y_out * *rowstride_out, *rowstride_out);
for (x_out = 0; x_out < *width_out; x_out++)
{
gint i0, i1;
guchar *pixel_out, *pixel_in;
/* We read from the source at 'x = x_out + i - half'; clamp the
* full i range [0, n_values) so that x is in [0, width_out).
*/
i0 = MAX (half - x_out, 0);
i1 = MIN (*width_out + half - x_out, n_values);
pixel_in = line + x_out + i0 - half;
pixel_out = pixels_out + *rowstride_out * y_out + x_out;
*pixel_out = 0;
for (i = i0; i < i1; i++)
{
*pixel_out += *pixel_in * kernel[i];
pixel_in++;
}
}
}
g_free (kernel);
g_free (line);
}
return pixels_out;
}
CoglPipeline *
_st_create_shadow_pipeline (StShadow *shadow_spec,
CoglTexture *src_texture,
float resource_scale)
{
ClutterBackend *backend = clutter_get_default_backend ();
CoglContext *ctx = clutter_backend_get_cogl_context (backend);
g_autoptr (ClutterPaintNode) texture_node = NULL;
g_autoptr (ClutterPaintNode) blur_node = NULL;
g_autoptr (CoglOffscreen) offscreen = NULL;
g_autoptr (GError) error = NULL;
ClutterPaintContext *paint_context;
CoglFramebuffer *fb;
CoglPipeline *pipeline;
CoglTexture *texture;
float sampling_radius;
float sigma;
int src_height, dst_height;
int src_width, dst_width;
static CoglPipeline *shadow_pipeline_template = NULL;
g_return_val_if_fail (shadow_spec != NULL, NULL);
g_return_val_if_fail (src_texture != NULL, NULL);
sampling_radius = resource_scale * shadow_spec->blur;
sigma = sampling_radius / 2.f;
sampling_radius = ceilf (sampling_radius);
src_width = cogl_texture_get_width (src_texture);
src_height = cogl_texture_get_height (src_texture);
dst_width = src_width + 2 * sampling_radius;
dst_height = src_height + 2 * sampling_radius;
texture = cogl_texture_2d_new_with_size (ctx, dst_width, dst_height);
if (!texture)
return NULL;
offscreen = cogl_offscreen_new_with_texture (texture);
fb = COGL_FRAMEBUFFER (offscreen);
if (!cogl_framebuffer_allocate (fb, &error))
{
cogl_clear_object (&texture);
return NULL;
}
cogl_framebuffer_clear4f (fb, COGL_BUFFER_BIT_COLOR, 0.f, 0.f, 0.f, 0.f);
cogl_framebuffer_orthographic (fb, 0, 0, dst_width, dst_height, 0, 1.0);
/* Blur */
blur_node = clutter_blur_node_new (dst_width, dst_height, sigma);
clutter_paint_node_add_rectangle (blur_node,
&(ClutterActorBox) {
0.f, 0.f,
dst_width, dst_height,
});
/* Texture */
texture_node = clutter_texture_node_new (src_texture,
0,
CLUTTER_SCALING_FILTER_NEAREST,
CLUTTER_SCALING_FILTER_NEAREST);
clutter_paint_node_add_child (blur_node, texture_node);
clutter_paint_node_add_rectangle (texture_node,
&(ClutterActorBox) {
.x1 = sampling_radius,
.y1 = sampling_radius,
.x2 = src_width + sampling_radius,
.y2 = src_height + sampling_radius,
});
paint_context =
clutter_paint_context_new_for_framebuffer (fb, NULL, CLUTTER_PAINT_FLAG_NONE);
clutter_paint_node_paint (blur_node, paint_context);
clutter_paint_context_destroy (paint_context);
if (G_UNLIKELY (shadow_pipeline_template == NULL))
{
shadow_pipeline_template = cogl_pipeline_new (ctx);
/* We set up the pipeline to blend the shadow texture with the combine
* constant, but defer setting the latter until painting, so that we can
* take the actor's overall opacity into account. */
cogl_pipeline_set_layer_combine (shadow_pipeline_template, 0,
"RGBA = MODULATE (CONSTANT, TEXTURE[A])",
NULL);
}
pipeline = cogl_pipeline_copy (shadow_pipeline_template);
cogl_pipeline_set_layer_texture (pipeline, 0, texture);
cogl_clear_object (&texture);
return pipeline;
}
CoglPipeline *
_st_create_shadow_pipeline_from_actor (StShadow *shadow_spec,
ClutterActor *actor)
{
ClutterContent *image = NULL;
CoglPipeline *shadow_pipeline = NULL;
float resource_scale;
float width, height;
ClutterPaintContext *paint_context;
g_return_val_if_fail (clutter_actor_has_allocation (actor), NULL);
clutter_actor_get_size (actor, &width, &height);
if (width == 0 || height == 0)
return NULL;
resource_scale = clutter_actor_get_resource_scale (actor);
width = ceilf (width * resource_scale);
height = ceilf (height * resource_scale);
image = clutter_actor_get_content (actor);
if (image && CLUTTER_IS_IMAGE (image))
{
CoglTexture *texture;
texture = clutter_image_get_texture (CLUTTER_IMAGE (image));
if (texture &&
cogl_texture_get_width (texture) == width &&
cogl_texture_get_height (texture) == height)
shadow_pipeline = _st_create_shadow_pipeline (shadow_spec, texture,
resource_scale);
}
if (shadow_pipeline == NULL)
{
CoglTexture *buffer;
CoglOffscreen *offscreen;
CoglFramebuffer *fb;
CoglContext *ctx;
CoglColor clear_color;
GError *catch_error = NULL;
float x, y;
ctx = clutter_backend_get_cogl_context (clutter_get_default_backend ());
buffer = cogl_texture_2d_new_with_size (ctx, width, height);
if (buffer == NULL)
return NULL;
offscreen = cogl_offscreen_new_with_texture (buffer);
fb = COGL_FRAMEBUFFER (offscreen);
if (!cogl_framebuffer_allocate (fb, &catch_error))
{
g_error_free (catch_error);
g_object_unref (offscreen);
cogl_object_unref (buffer);
return NULL;
}
cogl_color_init_from_4ub (&clear_color, 0, 0, 0, 0);
clutter_actor_get_position (actor, &x, &y);
x *= resource_scale;
y *= resource_scale;
cogl_framebuffer_clear (fb, COGL_BUFFER_BIT_COLOR, &clear_color);
cogl_framebuffer_translate (fb, -x, -y, 0);
cogl_framebuffer_orthographic (fb, 0, 0, width, height, 0, 1.0);
cogl_framebuffer_scale (fb, resource_scale, resource_scale, 1);
clutter_actor_set_opacity_override (actor, 255);
paint_context =
clutter_paint_context_new_for_framebuffer (fb, NULL,
CLUTTER_PAINT_FLAG_NONE);
clutter_actor_paint (actor, paint_context);
clutter_paint_context_destroy (paint_context);
clutter_actor_set_opacity_override (actor, -1);
g_object_unref (fb);
shadow_pipeline = _st_create_shadow_pipeline (shadow_spec, buffer,
resource_scale);
cogl_object_unref (buffer);
}
return shadow_pipeline;
}
/**
* _st_create_shadow_cairo_pattern:
* @shadow_spec: the definition of the shadow
* @src_pattern: surface pattern for which we create the shadow
* (must be a surface pattern)
*
* This is a utility function for creating shadows used by
* st-theme-node.c; it's in this file to share the gaussian
* blur implementation. The usage of this function is quite different
* depending on whether shadow_spec->inset is %TRUE or not. If
* shadow_spec->inset is %TRUE, the caller should pass in a @src_pattern
* which is the <i>inverse</i> of what they want shadowed, and must take
* care of the spread and offset from the shadow spec themselves. If
* shadow_spec->inset is %FALSE then the caller should pass in what they
* want shadowed directly, and this function takes care of the spread and
* the offset.
*/
cairo_pattern_t *
_st_create_shadow_cairo_pattern (StShadow *shadow_spec_in,
cairo_pattern_t *src_pattern)
{
g_autoptr(StShadow) shadow_spec = NULL;
static cairo_user_data_key_t shadow_pattern_user_data;
cairo_t *cr;
cairo_surface_t *src_surface;
cairo_surface_t *surface_in;
cairo_surface_t *surface_out;
cairo_pattern_t *dst_pattern;
guchar *pixels_in, *pixels_out;
gint width_in, height_in, rowstride_in;
gint width_out, height_out;
size_t rowstride_out;
cairo_matrix_t shadow_matrix;
double xscale_in, yscale_in;
int i, j;
g_return_val_if_fail (shadow_spec_in != NULL, NULL);
g_return_val_if_fail (src_pattern != NULL, NULL);
if (cairo_pattern_get_surface (src_pattern, &src_surface) != CAIRO_STATUS_SUCCESS)
/* The most likely reason we can't get the pattern is that sizing went hairwire
* and the caller tried to create a surface too big for memory, leaving us with
* a pattern in an error state; we return a transparent pattern for the shadow.
*/
return cairo_pattern_create_rgba(1.0, 1.0, 1.0, 0.0);
width_in = cairo_image_surface_get_width (src_surface);
height_in = cairo_image_surface_get_height (src_surface);
cairo_surface_get_device_scale (src_surface, &xscale_in, &yscale_in);
if (xscale_in != 1.0 || yscale_in != 1.0)
{
/* Scale the shadow specifications in a temporary copy so that
* we can work everywhere in absolute surface coordinates */
double scale = (xscale_in + yscale_in) / 2.0;
shadow_spec = st_shadow_new (&shadow_spec_in->color,
shadow_spec_in->xoffset * xscale_in,
shadow_spec_in->yoffset * yscale_in,
shadow_spec_in->blur * scale,
shadow_spec_in->spread * scale,
shadow_spec_in->inset);
}
else
{
shadow_spec = st_shadow_ref (shadow_spec_in);
}
/* We want the output to be a color agnostic alpha mask,
* so we need to strip the color channels from the input
*/
if (cairo_image_surface_get_format (src_surface) != CAIRO_FORMAT_A8)
{
surface_in = cairo_image_surface_create (CAIRO_FORMAT_A8,
width_in, height_in);
cr = cairo_create (surface_in);
cairo_set_source_surface (cr, src_surface, 0, 0);
cairo_paint (cr);
cairo_destroy (cr);
}
else
{
surface_in = cairo_surface_reference (src_surface);
}
pixels_in = cairo_image_surface_get_data (surface_in);
rowstride_in = cairo_image_surface_get_stride (surface_in);
pixels_out = blur_pixels (pixels_in, width_in, height_in, rowstride_in,
shadow_spec->blur,
&width_out, &height_out, &rowstride_out);
cairo_surface_destroy (surface_in);
/* Invert pixels for inset shadows */
if (shadow_spec->inset)
{
for (j = 0; j < height_out; j++)
{
guchar *p = pixels_out + rowstride_out * j;
for (i = 0; i < width_out; i++, p++)
*p = ~*p;
}
}
surface_out = cairo_image_surface_create_for_data (pixels_out,
CAIRO_FORMAT_A8,
width_out,
height_out,
rowstride_out);
cairo_surface_set_device_scale (surface_out, xscale_in, yscale_in);
cairo_surface_set_user_data (surface_out, &shadow_pattern_user_data,
pixels_out, (cairo_destroy_func_t) g_free);
dst_pattern = cairo_pattern_create_for_surface (surface_out);
cairo_surface_destroy (surface_out);
cairo_pattern_get_matrix (src_pattern, &shadow_matrix);
if (shadow_spec->inset)
{
/* Scale the matrix in surface absolute coordinates */
cairo_matrix_scale (&shadow_matrix, 1.0 / xscale_in, 1.0 / yscale_in);
/* For inset shadows, offsets and spread radius have already been
* applied to the original pattern, so all left to do is shift the
* blurred image left, so that it aligns centered under the
* unblurred one
*/
cairo_matrix_translate (&shadow_matrix,
(width_out - width_in) / 2.0,
(height_out - height_in) / 2.0);
/* Scale back the matrix in original coordinates */
cairo_matrix_scale (&shadow_matrix, xscale_in, yscale_in);
cairo_pattern_set_matrix (dst_pattern, &shadow_matrix);
return dst_pattern;
}
/* Read all the code from the cairo_pattern_set_matrix call
* at the end of this function to here from bottom to top,
* because each new affine transformation is applied in
* front of all the previous ones */
/* 6. Invert the matrix back */
cairo_matrix_invert (&shadow_matrix);
/* Scale the matrix in surface absolute coordinates */
cairo_matrix_scale (&shadow_matrix, 1.0 / xscale_in, 1.0 / yscale_in);
/* 5. Adjust based on specified offsets */
cairo_matrix_translate (&shadow_matrix,
shadow_spec->xoffset,
shadow_spec->yoffset);
/* 4. Recenter the newly scaled image */
cairo_matrix_translate (&shadow_matrix,
- shadow_spec->spread,
- shadow_spec->spread);
/* 3. Scale up the blurred image to fill the spread */
cairo_matrix_scale (&shadow_matrix,
(width_in + 2.0 * shadow_spec->spread) / width_in,
(height_in + 2.0 * shadow_spec->spread) / height_in);
/* 2. Shift the blurred image left, so that it aligns centered
* under the unblurred one */
cairo_matrix_translate (&shadow_matrix,
- (width_out - width_in) / 2.0,
- (height_out - height_in) / 2.0);
/* Scale back the matrix in scaled coordinates */
cairo_matrix_scale (&shadow_matrix, xscale_in, yscale_in);
/* 1. Invert the matrix so we can work with it in pattern space
*/
cairo_matrix_invert (&shadow_matrix);
cairo_pattern_set_matrix (dst_pattern, &shadow_matrix);
return dst_pattern;
}
void
_st_paint_shadow_with_opacity (StShadow *shadow_spec,
CoglFramebuffer *framebuffer,
CoglPipeline *shadow_pipeline,
ClutterActorBox *box,
guint8 paint_opacity)
{
ClutterActorBox shadow_box;
CoglColor color;
g_return_if_fail (shadow_spec != NULL);
g_return_if_fail (shadow_pipeline != NULL);
st_shadow_get_box (shadow_spec, box, &shadow_box);
cogl_color_init_from_4ub (&color,
shadow_spec->color.red * paint_opacity / 255,
shadow_spec->color.green * paint_opacity / 255,
shadow_spec->color.blue * paint_opacity / 255,
shadow_spec->color.alpha * paint_opacity / 255);
cogl_color_premultiply (&color);
cogl_pipeline_set_layer_combine_constant (shadow_pipeline, 0, &color);
cogl_framebuffer_draw_rectangle (framebuffer,
shadow_pipeline,
shadow_box.x1, shadow_box.y1,
shadow_box.x2, shadow_box.y2);
}
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