From 6ef9ab6a0b3c4af177b511eef80595b4140cb9db Mon Sep 17 00:00:00 2001
From: Adel Gadllah <adel.gadllah@gmail.com>
Date: Fri, 22 Mar 2013 17:19:26 +0100
Subject: [PATCH] st-scroll-view-fade: Don't fade out gradient

The changes from commit b4f5f1e4617434 and b394d184cc7fa6 increased the
instructions required for the fade fragment shader. This is over the limit
for some hardware (like intel gen3), which causes the driver to fallback
to software rendering for the shader. The result is that painting a scrollview
that has a fade effect takes around 30 (!!) seconds.

So lets go back to the old effect for 3.8 until we find a solution.

https://bugzilla.gnome.org/show_bug.cgi?id=696404
---
 src/st/st-scroll-view-fade.glsl | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/src/st/st-scroll-view-fade.glsl b/src/st/st-scroll-view-fade.glsl
index 4324c00b7..0c76c5396 100644
--- a/src/st/st-scroll-view-fade.glsl
+++ b/src/st/st-scroll-view-fade.glsl
@@ -36,13 +36,6 @@ uniform float hvalue;
  */
 uniform mat2 fade_area;
 
-/*
- * Scale from [0.0, 1.0] to [1.0, 1.0]. Do this by
- * changing it to scaling [1.0, 0.0] to [0.0, 0.0]
- * and then transforming the end result.
- */
-#define FADE(gradient, factor) (1.0 - (1.0 - gradient) * factor)
-
 void main ()
 {
     cogl_color_out = cogl_color_in * texture2D (tex, vec2 (cogl_tex_coord_in[0].xy));
@@ -66,20 +59,20 @@ void main ()
 
         float vfade_scale = height / vfade_offset;
         if (fade_top) {
-            ratio *= FADE((y / vfade_offset), min(sqrt(vvalue) * vfade_scale, 1.0));
+            ratio *= y / vfade_offset;
         }
 
         if (fade_bottom) {
-            ratio *= FADE((fade_area[1][1] - y)/(fade_area[1][1] - fade_bottom_start), min(sqrt(1.0 - vvalue) * vfade_scale, 1.0));
+            ratio *= (fade_area[1][1] - y) / (fade_area[1][1] - fade_bottom_start);
         }
 
         float hfade_scale = width / hfade_offset;
         if (fade_left) {
-            ratio *= FADE(x / hfade_offset, min(sqrt(hvalue) * hfade_scale, 1.0));
+            ratio *= x / hfade_offset;
         }
 
         if (fade_right) {
-            ratio *= FADE((fade_area[1][0] - x)/(fade_area[1][0] - fade_right_start), min(sqrt(1.0 - hvalue) * hfade_scale, 1.0));
+            ratio *= (fade_area[1][0] - x) / (fade_area[1][0] - fade_right_start);
         }
 
         cogl_color_out *= ratio;