[gtk/filter-image: 1/2] css: Implement filter() for images

[Matthias Clasen <matthiasc src gnome org>]

commit 79a0f183ec0b09d0f262f2b096071decf9fac4c0
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Feb 6 18:48:16 2021 -0500

    css: Implement filter() for images
    
    We have all the pieces, so this is suprisingly easy.

 docs/reference/gtk/css-properties.md |  25 ++++
 gtk/gtkcssimage.c                    |   2 +
 gtk/gtkcssimagefilter.c              | 216 +++++++++++++++++++++++++++++++++++
 gtk/gtkcssimagefilterprivate.h       |  58 ++++++++++
 gtk/meson.build                      |   1 +
 5 files changed, 302 insertions(+)
---
diff --git a/docs/reference/gtk/css-properties.md b/docs/reference/gtk/css-properties.md
index 8fa9819fc7..9a62c4a2e1 100644
--- a/docs/reference/gtk/css-properties.md
+++ b/docs/reference/gtk/css-properties.md
@@ -80,6 +80,31 @@ and in some cases a number as arguments.
 
 ## Images
 
+CSS allows to specify images in various forms, the most simple one being
+a url for an image file. Beyond that, images can be specified as
+
+`linear-gradient(Angle, ColorStops)`
+`repeating-linear-gradient(Angle, ColorStops)`
+: creates a linear gradient.
+
+`radial-gradient(Shape, ColorStops)`
+`repeating-radial-gradient(Shape, ColorStops)`
+: creates a radial gradient.
+
+`conic-gradient(Angle, ColorStops)`
+: creates a conic gradient.
+
+`cross-fade(Percentage Image,…)`
+: combines two or more images.
+
+`image(Image,… Color)`
+: falls back to the first valid image, or to a solid color.
+
+`filter(Image, Filters)`
+: applies filters to an image.
+
+For more details, see [CSS Image Level 4](https://www.w3.org/TR/css-images-4/).
+
 GTK extends the CSS syntax for images and also uses it for specifying icons.
 To load a themed icon, use
 
diff --git a/gtk/gtkcssimage.c b/gtk/gtkcssimage.c
index 616ac74f0a..95b3cd87a7 100644
--- a/gtk/gtkcssimage.c
+++ b/gtk/gtkcssimage.c
@@ -35,6 +35,7 @@
 #include "gtk/gtkcssimageurlprivate.h"
 #include "gtk/gtkcssimagescaledprivate.h"
 #include "gtk/gtkcssimagerecolorprivate.h"
+#include "gtk/gtkcssimagefilterprivate.h"
 
 G_DEFINE_ABSTRACT_TYPE (GtkCssImage, _gtk_css_image, G_TYPE_OBJECT)
 
@@ -524,6 +525,7 @@ gtk_css_image_get_parser_type (GtkCssParser *parser)
     { "repeating-radial-gradient", _gtk_css_image_radial_get_type },
     { "conic-gradient", gtk_css_image_conic_get_type },
     { "cross-fade", gtk_css_image_cross_fade_get_type },
+    { "filter", gtk_css_image_filter_get_type },
     { "image", _gtk_css_image_fallback_get_type }
   };
   guint i;
diff --git a/gtk/gtkcssimagefilter.c b/gtk/gtkcssimagefilter.c
new file mode 100644
index 0000000000..69dfde0cfc
--- /dev/null
+++ b/gtk/gtkcssimagefilter.c
@@ -0,0 +1,216 @@
+/*
+ * Copyright © 2021 Red Hat Inc.
+ *
+ * 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 2.1 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: Matthias Clasen <mclasen redhat com>
+ */
+
+#include "config.h"
+
+#include <math.h>
+#include <string.h>
+
+#include "gtkcssimagefilterprivate.h"
+
+#include "gtkcssfiltervalueprivate.h"
+
+
+G_DEFINE_TYPE (GtkCssImageFilter, gtk_css_image_filter, GTK_TYPE_CSS_IMAGE)
+
+static int
+gtk_css_image_filter_get_width (GtkCssImage *image)
+{
+  GtkCssImageFilter *self = GTK_CSS_IMAGE_FILTER (image);
+
+  return _gtk_css_image_get_width (self->image);
+}
+
+static int
+gtk_css_image_filter_get_height (GtkCssImage *image)
+{
+  GtkCssImageFilter *self = GTK_CSS_IMAGE_FILTER (image);
+
+  return _gtk_css_image_get_height (self->image);
+}
+
+static gboolean
+gtk_css_image_filter_equal (GtkCssImage *image1,
+                            GtkCssImage *image2)
+{
+  GtkCssImageFilter *filter1 = GTK_CSS_IMAGE_FILTER (image1);
+  GtkCssImageFilter *filter2 = GTK_CSS_IMAGE_FILTER (image2);
+
+  return _gtk_css_image_equal (filter1->image, filter2->image) &&
+         _gtk_css_value_equal (filter1->filter, filter2->filter);
+}
+
+static gboolean
+gtk_css_image_filter_is_dynamic (GtkCssImage *image)
+{
+  GtkCssImageFilter *self = GTK_CSS_IMAGE_FILTER (image);
+
+  return gtk_css_image_is_dynamic (self->image);
+}
+
+static GtkCssImage *
+gtk_css_image_filter_get_dynamic_image (GtkCssImage *image,
+                                        gint64       monotonic_time)
+{
+  GtkCssImageFilter *self = GTK_CSS_IMAGE_FILTER (image);
+
+  return gtk_css_image_filter_new (gtk_css_image_get_dynamic_image (self->image, monotonic_time),
+                                   self->filter);
+}
+
+static void
+gtk_css_image_filter_snapshot (GtkCssImage *image,
+                               GtkSnapshot *snapshot,
+                               double       width,
+                               double       height)
+{
+  GtkCssImageFilter *self = GTK_CSS_IMAGE_FILTER (image);
+
+  gtk_css_filter_value_push_snapshot (self->filter, snapshot);
+  gtk_css_image_snapshot (self->image, snapshot, width, height);
+  gtk_css_filter_value_pop_snapshot (self->filter, snapshot);
+}
+
+static guint
+gtk_css_image_filter_parse_arg (GtkCssParser *parser,
+                                guint         arg,
+                                gpointer      data)
+{
+  GtkCssImageFilter *self = data;
+
+  switch (arg)
+    {
+    case 0:
+      self->image = _gtk_css_image_new_parse (parser);
+      if (self->image == NULL)
+        return 0;
+      return 1;
+
+    case 1:
+      self->filter = gtk_css_filter_value_parse (parser);
+      if (self->filter == NULL)
+        return 0;
+      return 1;
+
+    default:
+      g_assert_not_reached ();
+      return 0;
+    }
+}
+
+static gboolean
+gtk_css_image_filter_parse (GtkCssImage  *image,
+                            GtkCssParser *parser)
+{
+  if (!gtk_css_parser_has_function (parser, "filter"))
+    {
+      gtk_css_parser_error_syntax (parser, "Expected 'filter('");
+      return FALSE;
+    }
+
+  return gtk_css_parser_consume_function (parser, 2, 2, gtk_css_image_filter_parse_arg, image);
+}
+
+static void
+gtk_css_image_filter_print (GtkCssImage *image,
+                            GString     *string)
+{
+  GtkCssImageFilter *self = GTK_CSS_IMAGE_FILTER (image);
+
+  g_string_append (string, "filter(");
+  _gtk_css_image_print (self->image, string);
+  g_string_append (string, ",");
+  _gtk_css_value_print (self->filter, string);
+  g_string_append (string, ")");
+}
+
+static GtkCssImage *
+gtk_css_image_filter_compute (GtkCssImage      *image,
+                              guint             property_id,
+                              GtkStyleProvider *provider,
+                              GtkCssStyle      *style,
+                              GtkCssStyle      *parent_style)
+{
+  GtkCssImageFilter *self = GTK_CSS_IMAGE_FILTER (image);
+
+  return gtk_css_image_filter_new (_gtk_css_image_compute (self->image, property_id, provider, style, 
parent_style),
+                                   _gtk_css_value_compute (self->filter, property_id, provider, style, 
parent_style));
+}
+
+static void
+gtk_css_image_filter_dispose (GObject *object)
+{
+  GtkCssImageFilter *self = GTK_CSS_IMAGE_FILTER (object);
+
+  g_clear_object (&self->image);
+  g_clear_pointer (&self->filter, _gtk_css_value_unref);
+
+  G_OBJECT_CLASS (gtk_css_image_filter_parent_class)->dispose (object);
+}
+
+static gboolean
+gtk_css_image_filter_is_computed (GtkCssImage *image)
+{
+  GtkCssImageFilter *self = GTK_CSS_IMAGE_FILTER (image);
+
+  return gtk_css_image_is_computed (self->image) &&
+         gtk_css_value_is_computed (self->filter);
+}
+
+static void
+gtk_css_image_filter_class_init (GtkCssImageFilterClass *klass)
+{
+  GtkCssImageClass *image_class = GTK_CSS_IMAGE_CLASS (klass);
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  image_class->get_width = gtk_css_image_filter_get_width;
+  image_class->get_height = gtk_css_image_filter_get_height;
+  image_class->compute = gtk_css_image_filter_compute;
+  image_class->equal = gtk_css_image_filter_equal;
+  image_class->snapshot = gtk_css_image_filter_snapshot;
+  image_class->is_dynamic = gtk_css_image_filter_is_dynamic;
+  image_class->get_dynamic_image = gtk_css_image_filter_get_dynamic_image;
+  image_class->parse = gtk_css_image_filter_parse;
+  image_class->print = gtk_css_image_filter_print;
+  image_class->is_computed = gtk_css_image_filter_is_computed;
+
+  object_class->dispose = gtk_css_image_filter_dispose;
+}
+
+static void
+gtk_css_image_filter_init (GtkCssImageFilter *self)
+{
+}
+
+GtkCssImage *
+gtk_css_image_filter_new (GtkCssImage *image,
+                          GtkCssValue *filter)
+{
+  GtkCssImageFilter *self;
+
+  g_return_val_if_fail (GTK_IS_CSS_IMAGE (image), NULL);
+
+  self = g_object_new (GTK_TYPE_CSS_IMAGE_FILTER, NULL);
+
+  self->image = g_object_ref (image);
+  self->filter = gtk_css_value_ref (filter);
+
+  return GTK_CSS_IMAGE (self);
+}
+
diff --git a/gtk/gtkcssimagefilterprivate.h b/gtk/gtkcssimagefilterprivate.h
new file mode 100644
index 0000000000..e5419e5bb8
--- /dev/null
+++ b/gtk/gtkcssimagefilterprivate.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright © 2021 Red Hat Inc.
+ *
+ * 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 2.1 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: Matthias Clasen <mclasen redhat com>
+ */
+
+#ifndef __GTK_CSS_IMAGE_FILTER_PRIVATE_H__
+#define __GTK_CSS_IMAGE_FILTER_PRIVATE_H__
+
+#include "gtk/gtkcssimageprivate.h"
+#include "gtk/gtkcssvalueprivate.h"
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_CSS_IMAGE_FILTER           (gtk_css_image_filter_get_type ())
+#define GTK_CSS_IMAGE_FILTER(obj)           (G_TYPE_CHECK_INSTANCE_CAST (obj, GTK_TYPE_CSS_IMAGE_FILTER, 
GtkCssImageFilter))
+#define GTK_CSS_IMAGE_FILTER_CLASS(cls)     (G_TYPE_CHECK_CLASS_CAST (cls, GTK_TYPE_CSS_IMAGE_FILTER, 
GtkCssImageFilterClass))
+#define GTK_IS_CSS_IMAGE_FILTER(obj)        (G_TYPE_CHECK_INSTANCE_TYPE (obj, GTK_TYPE_CSS_IMAGE_FILTER))
+#define GTK_IS_CSS_IMAGE_FILTER_CLASS(obj)  (G_TYPE_CHECK_CLASS_TYPE (obj, GTK_TYPE_CSS_IMAGE_FILTER))
+#define GTK_CSS_IMAGE_FILTER_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj), GTK_TYPE_CSS_IMAGE_FILTER, 
GtkCssImageFilterClass))
+
+typedef struct _GtkCssImageFilter           GtkCssImageFilter;
+typedef struct _GtkCssImageFilterClass      GtkCssImageFilterClass;
+
+struct _GtkCssImageFilter
+{
+  GtkCssImage parent;
+
+  GtkCssImage *image;
+  GtkCssValue *filter;
+};
+
+struct _GtkCssImageFilterClass
+{
+  GtkCssImageClass parent_class;
+};
+
+GType          gtk_css_image_filter_get_type              (void) G_GNUC_CONST;
+
+GtkCssImage *  gtk_css_image_filter_new                  (GtkCssImage *image,
+                                                          GtkCssValue *filter);
+
+G_END_DECLS
+
+#endif /* __GTK_CSS_IMAGE_FILTER_PRIVATE_H__ */
diff --git a/gtk/meson.build b/gtk/meson.build
index 42cb07a205..afa99915e2 100644
--- a/gtk/meson.build
+++ b/gtk/meson.build
@@ -66,6 +66,7 @@ gtk_private_sources = files([
   'gtkcssimageconic.c',
   'gtkcssimagecrossfade.c',
   'gtkcssimagefallback.c',
+  'gtkcssimagefilter.c',
   'gtkcssimageicontheme.c',
   'gtkcssimageinvalid.c',
   'gtkcssimagelinear.c',