[epiphany] gd-two-lines-renderer: use Pango alpha attribute

[Michael Catanzaro <mcatanzaro src gnome org>]

commit e1bf1d4ecf4352e1f045e2cf88df9266ffc8305c
Author: Christian Hergert <chergert redhat com>
Date:   Sat Jul 1 14:57:27 2017 -0700

    gd-two-lines-renderer: use Pango alpha attribute
    
    This code was previously trying to alter the color of the second
    line by manipulating the foreground color. As Epiphany requires
    GTK+ 3.22, we can rely on the Pango alpha attr working correctly
    and therefore do not need this fallback.
    
    The problem with the code previously is that it would not
    respect the GTK_CELL_RENDERER_SELECTED state. It would draw the
    altered non-selected state with a dim-level on top of a
    selected row.
    
    By simply avoiding the foreground color altogether (and
    inheriting it from the PangoLayout state when rendering), we
    get the appropriate color and also blend into the selected row
    state properly.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=784431

 lib/widgets/contrib/gd-two-lines-renderer.c |   17 +++++------------
 1 files changed, 5 insertions(+), 12 deletions(-)
---
diff --git a/lib/widgets/contrib/gd-two-lines-renderer.c b/lib/widgets/contrib/gd-two-lines-renderer.c
index 9840527..5a029f7 100644
--- a/lib/widgets/contrib/gd-two-lines-renderer.c
+++ b/lib/widgets/contrib/gd-two-lines-renderer.c
@@ -87,15 +87,13 @@ apply_subtitle_style_to_layout (GtkStyleContext *context,
                                 GtkStateFlags    flags)
 {
   PangoFontDescription *desc;
-  GdkRGBA rgba = {0.0, 0.0, 0.0, 0.0};
   PangoAttrList *layout_attr;
-  PangoAttribute *attr_color;
+  PangoAttribute *attr_alpha;
 
   gtk_style_context_save (context);
   gtk_style_context_set_state (context, flags);
   gtk_style_context_get (context, gtk_style_context_get_state (context),
                          "font", &desc,
-                         "color", &rgba,
                          NULL);
   gtk_style_context_restore (context);
 
@@ -104,16 +102,11 @@ apply_subtitle_style_to_layout (GtkStyleContext *context,
   pango_layout_set_font_description (layout, desc);
   pango_font_description_free (desc);
 
-  /* Set the color */
-  rgba.red = CLAMP(1.0 - ((1.0 - rgba.red) * SUBTITLE_DIM_PERCENTAGE), 0.0, 1.0);
-  rgba.green = CLAMP(1.0 - ((1.0 - rgba.green) * SUBTITLE_DIM_PERCENTAGE), 0.0, 1.0);
-  rgba.blue = CLAMP(1.0 - ((1.0 - rgba.blue) * SUBTITLE_DIM_PERCENTAGE), 0.0, 1.0);
-
+  /* Set the font alpha */
   layout_attr = pango_attr_list_new ();
-  attr_color = pango_attr_foreground_new (rgba.red * 65535,
-                                          rgba.green * 65535,
-                                          rgba.blue * 65535);
-  pango_attr_list_insert (layout_attr, attr_color);
+  attr_alpha = pango_attr_foreground_alpha_new (SUBTITLE_DIM_PERCENTAGE * 65535);
+  pango_attr_list_insert (layout_attr, attr_alpha);
+
   pango_layout_set_attributes (layout, layout_attr);
   pango_attr_list_unref (layout_attr);
 }