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

[Christian Hergert <chergert src gnome org>]

commit c1a40ee08e94828d67ab2284b41948bdd8c41a7f
Author: Christian Hergert <chergert redhat com>
Date:   Sat Jul 1 18:00:16 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. Now that gtk+ 3.22
    is our stable branch, we can rely on more recent stable features
    such as Pango's alpha attribute.
    
    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.

 libgd/gd-two-lines-renderer.c |   17 +++++------------
 1 files changed, 5 insertions(+), 12 deletions(-)
---
diff --git a/libgd/gd-two-lines-renderer.c b/libgd/gd-two-lines-renderer.c
index 9840527..5a029f7 100644
--- a/libgd/gd-two-lines-renderer.c
+++ b/libgd/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);
 }