From bd347ef9efff76e2d14846214860109f5539d86c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adam=20Bie=C5=84kowski?= <donadigos159@gmail.com>
Date: Mon, 5 Aug 2019 21:34:44 +0200
Subject: [PATCH] Add setting for greyscale

---
 data/org.pantheon.desktop.gala.gschema.xml.in |  4 +++
 src/Settings.vala                             |  1 +
 src/WindowManager.vala                        | 35 +++++++++++++++++--
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/data/org.pantheon.desktop.gala.gschema.xml.in b/data/org.pantheon.desktop.gala.gschema.xml.in
index 6e5ecb05..4d443397 100644
--- a/data/org.pantheon.desktop.gala.gschema.xml.in
+++ b/data/org.pantheon.desktop.gala.gschema.xml.in
@@ -155,6 +155,10 @@
 			<summary>Attach modal dialogs</summary>
 			<description>When true, instead of having independent titlebars, modal dialogs appear attached to the titlebar of the parent window and are moved together with the parent window.</description>
 		</key>
+        <key type="b" name="greyscale">
+            <default>false</default>
+            <summary>If the display should be greyscale</summary>
+        </key>
 		<key type="s" name="button-layout">
 			<default>'close:maximize'</default>
 			<summary>Arrangement of buttons on the titlebar</summary>
diff --git a/src/Settings.vala b/src/Settings.vala
index d19d3e2d..26c2d7b1 100644
--- a/src/Settings.vala
+++ b/src/Settings.vala
@@ -74,6 +74,7 @@ namespace Gala
 		public bool attach_modal_dialogs { get; set; }
 		public bool dim_parents { get; set; }
 		public string workspace_switcher_background { get; set; }
+        public bool greyscale { get; set; }
 
 		static AppearanceSettings? instance = null;
 
diff --git a/src/WindowManager.vala b/src/WindowManager.vala
index b15c32fa..5d9f5f91 100644
--- a/src/WindowManager.vala
+++ b/src/WindowManager.vala
@@ -70,7 +70,9 @@ namespace Gala
 		Clutter.Actor? last_hotcorner;
 		ScreenSaver? screensaver;
 
-		Clutter.Actor? tile_preview;
+        Clutter.Actor? tile_preview;
+        
+        Clutter.ShaderEffect? greyscale_effect;
 
 		Window? moving; //place for the window that is being moved over
 
@@ -310,7 +312,9 @@ namespace Gala
 
 			update_input_area ();
 
-			stage.show ();
+            stage.show ();
+            toggle_greyscale ();
+            AppearanceSettings.get_default ().notify["greyscale"].connect (toggle_greyscale);
 
 			// let the session manager move to the next phase
 			Meta.register_with_session ();
@@ -323,6 +327,33 @@ namespace Gala
 			return false;
 		}
 
+        void toggle_greyscale ()
+        {
+            if (greyscale_effect == null) {
+                greyscale_effect = new Clutter.ShaderEffect (Clutter.ShaderType.FRAGMENT_SHADER);
+                greyscale_effect.set_name ("greyscale");
+                greyscale_effect.set_shader_source ("""
+                    uniform sampler2D texture;
+                    void main () {
+                        vec4 color = texture2D (texture, cogl_tex_coord0_in.xy);
+                        float gray = dot(color.rgb, vec3(0.299, 0.587, 0.114));
+                        cogl_color_out = vec4(vec3(gray), 1.0);
+                    }
+                """);
+                greyscale_effect.set_uniform_value ("texture", 0);
+            }
+
+            if (AppearanceSettings.get_default ().greyscale) {
+                if (ui_group.get_effect ("greyscale") == null) {
+                    ui_group.add_effect (greyscale_effect);
+                }
+            } else {
+                if (ui_group.get_effect ("greyscale") != null) {
+                    ui_group.remove_effect (greyscale_effect);
+                }
+            }
+        }
+
 		void configure_hotcorners ()
 		{
 			var geometry = get_screen ().get_monitor_geometry (get_screen ().get_primary_monitor ());