[nautilus] Shade rubberbands on the desktop by the wallpaper

[Ryan Lortie <ryanl src gnome org>]

commit d532ab4f91d374beb53bbd091cf8a3f0fb288c97
Author: Ted Gould <ted gould cx>
Date:   Mon Apr 29 10:47:45 2013 -0700

    Shade rubberbands on the desktop by the wallpaper
    
    Use the _GNOME_BACKGROUND_REPRESENTATIVE_COLORS X atom to decide how to
    shade the rubberband when selecting icons on the desktop.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=695689

 libnautilus-private/nautilus-canvas-container.c |   85 ++++++++++++++++++++---
 1 files changed, 76 insertions(+), 9 deletions(-)
---
diff --git a/libnautilus-private/nautilus-canvas-container.c b/libnautilus-private/nautilus-canvas-container.c
index 1450565..8df1e47 100644
--- a/libnautilus-private/nautilus-canvas-container.c
+++ b/libnautilus-private/nautilus-canvas-container.c
@@ -26,6 +26,8 @@
 */
 
 #include <config.h>
+#include <X11/Xlib.h>
+#include <X11/Xatom.h>
 #include <math.h>
 #include "nautilus-canvas-container.h"
 
@@ -2327,6 +2329,79 @@ rubberband_timeout_callback (gpointer data)
 }
 
 static void
+get_rubber_color (NautilusCanvasContainer *container,
+                  GdkRGBA *bgcolor,
+                  GdkRGBA *bordercolor)
+{
+       Atom         real_type;
+       gint         result;
+       gint         real_format;
+       gulong       items_read = 0;
+       gulong       items_left = 0;
+       gchar       *colors;
+       Atom         representative_colors_atom;
+       Display     *display;
+
+       if (nautilus_canvas_container_get_is_desktop (container)) {
+               representative_colors_atom = gdk_x11_get_xatom_by_name 
("_GNOME_BACKGROUND_REPRESENTATIVE_COLORS");
+               display = gdk_x11_display_get_xdisplay (gdk_display_get_default ());
+
+               gdk_error_trap_push ();
+               result = XGetWindowProperty (display,
+                                            GDK_ROOT_WINDOW (),
+                                            representative_colors_atom,
+                                            0L,
+                                            G_MAXLONG,
+                                            False,
+                                            XA_STRING,
+                                            &real_type,
+                                            &real_format,
+                                            &items_read,
+                                            &items_left,
+                                            (guchar **) &colors);
+               gdk_error_trap_pop_ignored ();
+       }
+
+       if (result == Success && items_read) {
+               /* by treating the result as a nul-terminated string, we
+                * select the first colour in the list.
+                */
+               GdkRGBA read;
+               gdouble shade;
+
+               gdk_rgba_parse (&read, colors);
+               XFree (colors);
+
+               /* Border
+                *
+                * We shade darker colours to be slightly lighter and
+                * lighter ones to be slightly darker.
+                */
+               shade = read.green < 0.5 ? 1.1 : 0.9;
+               bordercolor->red = read.red * shade;
+               bordercolor->green = read.green * shade;
+               bordercolor->blue = read.blue * shade;
+               bordercolor->alpha = 1.0;
+
+               /* Background */
+               *bgcolor = read;
+               bgcolor->alpha = 0.6;
+       } else {
+               /* Fallback to the style context if we can't get the Atom */
+               GtkStyleContext *context;
+
+               context = gtk_widget_get_style_context (GTK_WIDGET (container));
+               gtk_style_context_save (context);
+               gtk_style_context_add_class (context, GTK_STYLE_CLASS_RUBBERBAND);
+
+               gtk_style_context_get_background_color (context, GTK_STATE_FLAG_NORMAL, bgcolor);
+               gtk_style_context_get_border_color (context, GTK_STATE_FLAG_NORMAL, bordercolor);
+
+               gtk_style_context_restore (context);
+       }
+}
+
+static void
 start_rubberbanding (NautilusCanvasContainer *container,
                     GdkEventButton *event)
 {
@@ -2336,7 +2411,6 @@ start_rubberbanding (NautilusCanvasContainer *container,
        GdkRGBA bg_color, border_color;
        GList *p;
        NautilusCanvasIcon *icon;
-       GtkStyleContext *context;
 
        details = container->details;
        band_info = &details->rubberband_info;
@@ -2353,14 +2427,7 @@ start_rubberbanding (NautilusCanvasContainer *container,
                (EEL_CANVAS (container), event->x, event->y,
                 &band_info->start_x, &band_info->start_y);
 
-       context = gtk_widget_get_style_context (GTK_WIDGET (container));
-       gtk_style_context_save (context);
-       gtk_style_context_add_class (context, GTK_STYLE_CLASS_RUBBERBAND);
-
-       gtk_style_context_get_background_color (context, GTK_STATE_FLAG_NORMAL, &bg_color);
-       gtk_style_context_get_border_color (context, GTK_STATE_FLAG_NORMAL, &border_color);
-
-       gtk_style_context_restore (context);
+       get_rubber_color (container, &bg_color, &border_color);
 
        band_info->selection_rectangle = eel_canvas_item_new
                (eel_canvas_root