css: Add a -gtk-icon-style property

The values can be:
  "requested" - the style as requested
  "regular"   - use a regular full-color icon
  "symbolic"  - use a symbolic icon

The property defaults to "requested", so no changes should be seen
unless CSS overrides it.
It is also inherited, so that using this CSS
  .toolbar { -gtk-icon-style: symbolic; }
is enough to force the whole toolbar to use symbolic icons.

gtk/gtkcssenumvalue.c

@@ -706,3 +706,57 @@ _gtk_css_image_effect_value_get (const GtkCssValue *value)
 
   return value->value;
 }
+
+/* GtkCssIconStyle */
+
+static const GtkCssValueClass GTK_CSS_VALUE_ICON_STYLE = {
+  gtk_css_value_enum_free,
+  gtk_css_value_enum_compute,
+  gtk_css_value_enum_equal,
+  gtk_css_value_enum_transition,
+  gtk_css_value_enum_print
+};
+
+static GtkCssValue icon_style_values[] = {
+  { &GTK_CSS_VALUE_ICON_STYLE, 1, GTK_CSS_ICON_STYLE_REQUESTED, "requested" },
+  { &GTK_CSS_VALUE_ICON_STYLE, 1, GTK_CSS_ICON_STYLE_REGULAR, "regular" },
+  { &GTK_CSS_VALUE_ICON_STYLE, 1, GTK_CSS_ICON_STYLE_SYMBOLIC, "symbolic" }
+};
+
+GtkCssValue *
+_gtk_css_icon_style_value_new (GtkCssIconStyle icon_style)
+{
+  guint i;
+
+  for (i = 0; i < G_N_ELEMENTS (icon_style_values); i++)
+    {
+      if (icon_style_values[i].value == icon_style)
+        return _gtk_css_value_ref (&icon_style_values[i]);
+    }
+
+  g_return_val_if_reached (NULL);
+}
+
+GtkCssValue *
+_gtk_css_icon_style_value_try_parse (GtkCssParser *parser)
+{
+  guint i;
+
+  g_return_val_if_fail (parser != NULL, NULL);
+
+  for (i = 0; i < G_N_ELEMENTS (icon_style_values); i++)
+    {
+      if (_gtk_css_parser_try (parser, icon_style_values[i].name, TRUE))
+        return _gtk_css_value_ref (&icon_style_values[i]);
+    }
+
+  return NULL;
+}
+
+GtkCssIconStyle
+_gtk_css_icon_style_value_get (const GtkCssValue *value)
+{
+  g_return_val_if_fail (value->class == &GTK_CSS_VALUE_ICON_STYLE, GTK_CSS_ICON_STYLE_REQUESTED);
+
+  return value->value;
+}

gtk/gtkcssenumvalueprivate.h

@@ -68,6 +68,10 @@ GtkCssValue *     _gtk_css_image_effect_value_new       (GtkCssImageEffect  imag
 GtkCssValue *     _gtk_css_image_effect_value_try_parse (GtkCssParser      *parser);
 GtkCssImageEffect _gtk_css_image_effect_value_get       (const GtkCssValue *value);
 
+GtkCssValue *   _gtk_css_icon_style_value_new         (GtkCssIconStyle    icon_style);
+GtkCssValue *   _gtk_css_icon_style_value_try_parse   (GtkCssParser      *parser);
+GtkCssIconStyle _gtk_css_icon_style_value_get         (const GtkCssValue *value);
+
 G_END_DECLS
 
 #endif /* __GTK_CSS_ENUM_VALUE_PRIVATE_H__ */

gtk/gtkcssstylepropertyimpl.c

@@ -477,6 +477,18 @@ image_effect_parse (GtkCssStyleProperty *property,
   return value;
 }
 
+static GtkCssValue *
+icon_style_parse (GtkCssStyleProperty *property,
+		  GtkCssParser        *parser)
+{
+  GtkCssValue *value = _gtk_css_icon_style_value_try_parse (parser);
+
+  if (value == NULL)
+    _gtk_css_parser_error (parser, "unknown value for property");
+
+  return value;
+}
+
 static GtkCssValue *
 bindings_value_parse_one (GtkCssParser *parser)
 {
@@ -981,6 +993,14 @@ _gtk_css_style_property_init_properties (void)
                                           NULL,
                                           NULL,
                                           _gtk_css_shadows_value_new_none ());
+  gtk_css_style_property_register        ("-gtk-icon-style",
+                                          GTK_CSS_PROPERTY_ICON_STYLE,
+                                          G_TYPE_NONE,
+                                          GTK_STYLE_PROPERTY_INHERIT | GTK_STYLE_PROPERTY_NO_RESIZE,
+                                          icon_style_parse,
+                                          NULL,
+                                          NULL,
+                                          _gtk_css_icon_style_value_new (GTK_CSS_ICON_STYLE_REQUESTED));
   gtk_css_style_property_register        ("-gtk-icon-transform",
                                           GTK_CSS_PROPERTY_ICON_TRANSFORM,
                                           G_TYPE_NONE,

gtk/gtkcsstypesprivate.h

@@ -82,6 +82,7 @@ enum { /*< skip >*/
   GTK_CSS_PROPERTY_TEXT_SHADOW,
   GTK_CSS_PROPERTY_ICON_SOURCE,
   GTK_CSS_PROPERTY_ICON_SHADOW,
+  GTK_CSS_PROPERTY_ICON_STYLE,
   GTK_CSS_PROPERTY_ICON_TRANSFORM,
   GTK_CSS_PROPERTY_BOX_SHADOW,
   GTK_CSS_PROPERTY_MARGIN_TOP,
@@ -177,6 +178,12 @@ typedef enum /*< skip >*/ {
   GTK_CSS_IMAGE_EFFECT_DIM
 } GtkCssImageEffect;
 
+typedef enum /*< skip >*/ {
+  GTK_CSS_ICON_STYLE_REQUESTED,
+  GTK_CSS_ICON_STYLE_REGULAR,
+  GTK_CSS_ICON_STYLE_SYMBOLIC
+} GtkCssIconStyle;
+
 typedef enum /*< skip >*/ {
   /* relative font sizes */
   GTK_CSS_FONT_SIZE_SMALLER,