Port Colorful Tabs to Peas API (#107)

- Plug TabActivatable even before delayed load
- Add Tab.color which is purely informative
- Implement (background) color in Tally
- Compute colors in ColorfulTabs extension

![screenshot from 2018-10-19 14-03-55](https://user-images.githubusercontent.com/1204189/47217253-10863f00-d3a8-11e8-84bf-d1bcd0e73023.png)

1 files changed, 58 insertions, 0 deletions

diff --git a/extensions/colorful-tabs.vala b/extensions/colorful-tabs.vala
new file mode 100644
index 00000000..0635e37a
--- /dev/null
+++ b/extensions/colorful-tabs.vala
@@ -0,0 +1,58 @@
+/*
+ Copyright (C) 2009-2018 Christian Dywan <christian@twotoasts.de>
+ Copyright (C) 2010 Samuel Creshal <creshal@arcor.de>
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ See the file COPYING for the full license text.
+*/
+
+namespace ColorfulTabs {
+    public class Tint : Peas.ExtensionBase, Midori.TabActivatable {
+        public Midori.Tab tab { owned get; set; }
+
+        public void activate () {
+            tab.notify["display-uri"].connect (apply_tint);
+            apply_tint ();
+            deactivate.connect (() => {
+                tab.notify["display-uri"].disconnect (apply_tint);
+                tab.color = null;
+            });
+        }
+
+        void apply_tint () {
+            if ("://" in tab.display_uri) {
+                Gdk.Color color;
+                // Hash the hostname without the protocol or path
+                string hostname = tab.display_uri.chr (-1, '/').offset (2).split ("/")[0];
+                string hash = Checksum.compute_for_string (ChecksumType.MD5, hostname, 1);
+                Gdk.Color.parse ("#" + hash.substring (0, 6), out color);
+                // Adjust background brightness
+                uint16 grey = 137 * 255;
+                uint16 adjustment = 78 * 255;
+                uint16 blue = 39 * 255;
+                uint16 extra = 19 * 255;
+                if (color.red < grey && color.green < grey && color.blue < grey) {
+                    color.red += adjustment;
+                    color.green += adjustment;
+                    color.blue += adjustment;
+                }
+                color.red = color.red < blue ? extra : color.red - extra;
+                color.blue = color.blue < blue ? extra : color.blue - extra;
+                color.green = color.green < blue ? extra : color.green - extra;
+                tab.color = color.to_string ();
+            } else {
+                tab.color = null;
+            }
+        }
+    }
+}
+
+[ModuleInit]
+public void peas_register_types(TypeModule module) {
+    ((Peas.ObjectModule)module).register_extension_type (
+        typeof (Midori.TabActivatable), typeof (ColorfulTabs.Tint));
+}