[gnome-shell] windowManager: shade the actor, not the texture

[Owen Taylor <otaylor src gnome org>]

commit fb30822860100779955fe8444c30824c7c363a39
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Tue Sep 20 14:21:45 2011 -0400

    windowManager: shade the actor, not the texture
    
    Applying the "dim window" effect to the MetaWindowActor has two avantages:
    first it avoids triggering bugs where ClutterOffscreenEffect doesn't handle
    clone paint correctly. Second, it avoids showing the window as dimmed in
    alt-Tab and the overview, which is weird.
    
    The small downside of this is that the shadow becomes slightly gray when
    the window dimmed, which is wrong - if we switched from blending with gray
    to a combination of desaturation and darkening, this problem wouldn't
    happen.
    
    Revert out the addition of startY to the shader, since we don't need it
    and fix the application of alpha, since we need to handle alpha correctly
    for the shadow.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=659634

 data/shaders/dim-window.glsl |    9 +++------
 js/ui/windowManager.js       |   26 +++++++++++---------------
 2 files changed, 14 insertions(+), 21 deletions(-)
---
diff --git a/data/shaders/dim-window.glsl b/data/shaders/dim-window.glsl
index 5f9ad9c..c7c8c1b 100644
--- a/data/shaders/dim-window.glsl
+++ b/data/shaders/dim-window.glsl
@@ -1,6 +1,5 @@
 #version 110
 uniform sampler2D tex;
-uniform float startY;
 uniform float fraction;
 uniform float height;
 const float c = -0.2;
@@ -17,14 +16,12 @@ void main()
   float y = height * cogl_tex_coord_in[0].y;
 
   // To reduce contrast, blend with a mid gray
-  cogl_color_out = color * contrast - off * c;
+  cogl_color_out = color * contrast - off * c * color.a;
 
-  // We only fully dim at a distance of BORDER_MAX_HEIGHT from startY and
+  // We only fully dim at a distance of BORDER_MAX_HEIGHT from the top and
   // when the fraction is 1.0. For other locations and fractions we linearly
   // interpolate back to the original undimmed color, so the top of the window
   // is at full color.
-  cogl_color_out = color + (cogl_color_out - color) * max(min((y - startY) / border_max_height, 1.0), 0.0);
+  cogl_color_out = color + (cogl_color_out - color) * max(min(y / border_max_height, 1.0), 0.0);
   cogl_color_out = color + (cogl_color_out - color) * fraction;
-
-  cogl_color_out *= color.a;
 }
diff --git a/js/ui/windowManager.js b/js/ui/windowManager.js
index 2ca6deb..95cf4ac 100644
--- a/js/ui/windowManager.js
+++ b/js/ui/windowManager.js
@@ -31,16 +31,15 @@ function getTopInvisibleBorder(metaWindow) {
     return outerRect.y - inputRect.y;
 }
 
-function WindowDimmer(actor, window) {
-    this._init(actor, window);
+function WindowDimmer(actor) {
+    this._init(actor);
 }
 
 WindowDimmer.prototype = {
-    _init: function(actor, window) {
+    _init: function(actor) {
         this.effect = new Clutter.ShaderEffect({ shader_type: Clutter.ShaderType.FRAGMENT_SHADER });
         this.effect.set_shader_source(getDimShaderSource());
 
-        this.window = window;
         this.actor = actor;
     },
 
@@ -52,7 +51,6 @@ WindowDimmer.prototype = {
         }
 
         if (fraction > 0.01) {
-            Shell.shader_effect_set_double_uniform(this.effect, 'startY', getTopInvisibleBorder(this.window));
             Shell.shader_effect_set_double_uniform(this.effect, 'height', this.actor.get_height());
             Shell.shader_effect_set_double_uniform(this.effect, 'fraction', fraction);
 
@@ -71,11 +69,11 @@ WindowDimmer.prototype = {
     _dimFraction: 0.0
 };
 
-function getWindowDimmer(texture, window) {
-    if (!texture._windowDimmer)
-        texture._windowDimmer = new WindowDimmer(texture, window);
+function getWindowDimmer(actor) {
+    if (!actor._windowDimmer)
+        actor._windowDimmer = new WindowDimmer(actor);
 
-    return texture._windowDimmer;
+    return actor._windowDimmer;
 }
 
 function WindowManager() {
@@ -270,30 +268,28 @@ WindowManager.prototype = {
         let actor = window.get_compositor_private();
         if (!actor)
             return;
-        let texture = actor.get_texture();
         if (animate)
-            Tweener.addTween(getWindowDimmer(texture, window),
+            Tweener.addTween(getWindowDimmer(actor),
                              { dimFraction: 1.0,
                                time: DIM_TIME,
                                transition: 'linear'
                              });
         else
-            getWindowDimmer(texture, window).dimFraction = 1.0;
+            getWindowDimmer(actor).dimFraction = 1.0;
     },
 
     _undimWindow: function(window, animate) {
         let actor = window.get_compositor_private();
         if (!actor)
             return;
-        let texture = actor.get_texture();
         if (animate)
-            Tweener.addTween(getWindowDimmer(texture, window),
+            Tweener.addTween(getWindowDimmer(actor),
                              { dimFraction: 0.0,
                                time: UNDIM_TIME,
                                transition: 'linear'
                              });
         else
-            getWindowDimmer(texture, window).dimFraction = 0.0;
+            getWindowDimmer(actor).dimFraction = 0.0;
     },
 
     _mapWindow : function(shellwm, actor) {