[gtk+] css: Implement font-kerning

[Matthias Clasen <matthiasc src gnome org>]

commit cee4622567f8eea0a2e168cbe641855cabd6e7ce
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Sep 17 21:27:59 2017 -0400

    css: Implement font-kerning
    
    This gets translated to the OpenType feature kern.

 gtk/gtkcssstyle.c             |    7 +++++++
 gtk/gtkcssstylepropertyimpl.c |   21 +++++++++++++++++++++
 gtk/gtkcsstypesprivate.h      |    1 +
 3 files changed, 29 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkcssstyle.c b/gtk/gtkcssstyle.c
index 250371f..dcce352 100644
--- a/gtk/gtkcssstyle.c
+++ b/gtk/gtkcssstyle.c
@@ -225,6 +225,7 @@ gtk_css_style_get_pango_attributes (GtkCssStyle *style)
   const GdkRGBA *color;
   const GdkRGBA *decoration_color;
   gint letter_spacing;
+  GtkCssValue *kerning;
 
   /* text-decoration */
   decoration_line = _gtk_css_text_decoration_line_value_get (gtk_css_style_get_value (style, 
GTK_CSS_PROPERTY_TEXT_DECORATION_LINE));
@@ -260,6 +261,12 @@ gtk_css_style_get_pango_attributes (GtkCssStyle *style)
       attrs = add_pango_attr (attrs, pango_attr_letter_spacing_new (letter_spacing * PANGO_SCALE));
     }
 
+  kerning = gtk_css_style_get_value (style, GTK_CSS_PROPERTY_FONT_KERNING);
+  if (strcmp (_gtk_css_ident_value_get (kerning), "normal") == 0)
+    attrs = add_pango_attr (attrs, pango_attr_font_features_new ("kern 1"));
+  else if (strcmp (_gtk_css_ident_value_get (kerning), "none") == 0)
+    attrs = add_pango_attr (attrs, pango_attr_font_features_new ("kern 0"));
+
   return attrs;
 }
 
diff --git a/gtk/gtkcssstylepropertyimpl.c b/gtk/gtkcssstylepropertyimpl.c
index d50b2d3..bf98160 100644
--- a/gtk/gtkcssstylepropertyimpl.c
+++ b/gtk/gtkcssstylepropertyimpl.c
@@ -531,6 +531,19 @@ parse_text_decoration_style (GtkCssStyleProperty *property,
 }
 
 static GtkCssValue *
+parse_font_kerning (GtkCssStyleProperty *property,
+                    GtkCssParser        *parser)
+{
+  GtkCssValue *value = NULL;
+
+  value = _gtk_css_ident_value_try (parser, "auto", "normal", "none", NULL);
+  if (value == NULL)
+    _gtk_css_parser_error (parser, "unknown value for property");
+
+  return value;
+}
+
+static GtkCssValue *
 box_shadow_value_parse (GtkCssStyleProperty *property,
                         GtkCssParser        *parser)
 {
@@ -1015,6 +1028,14 @@ _gtk_css_style_property_init_properties (void)
                                           parse_text_decoration_style,
                                           NULL,
                                           _gtk_css_text_decoration_style_value_new 
(GTK_CSS_TEXT_DECORATION_STYLE_SOLID));
+  gtk_css_style_property_register        ("font-kerning",
+                                          GTK_CSS_PROPERTY_FONT_KERNING,
+                                          G_TYPE_NONE,
+                                          0,
+                                          GTK_CSS_AFFECTS_TEXT | GTK_CSS_AFFECTS_TEXT_ATTRS,
+                                          parse_font_kerning,
+                                          NULL,
+                                          _gtk_css_ident_value_new ("auto"));
 
   gtk_css_style_property_register        ("text-shadow",
                                           GTK_CSS_PROPERTY_TEXT_SHADOW,
diff --git a/gtk/gtkcsstypesprivate.h b/gtk/gtkcsstypesprivate.h
index 27d9af8..b4f79fb 100644
--- a/gtk/gtkcsstypesprivate.h
+++ b/gtk/gtkcsstypesprivate.h
@@ -163,6 +163,7 @@ enum { /*< skip >*/
   GTK_CSS_PROPERTY_TEXT_DECORATION_LINE,
   GTK_CSS_PROPERTY_TEXT_DECORATION_COLOR,
   GTK_CSS_PROPERTY_TEXT_DECORATION_STYLE,
+  GTK_CSS_PROPERTY_FONT_KERNING,
   GTK_CSS_PROPERTY_TEXT_SHADOW,
   GTK_CSS_PROPERTY_BOX_SHADOW,
   GTK_CSS_PROPERTY_MARGIN_TOP,