Improve transition shader portability

Use #version 120 explicitly, and adapt the shader shader code
accordingly, to use strictly only GLSL 1.20 constructs. Also, use less
vertex attribute data in the Vortex vertex shader: We can pack the
per-vertex tile x and y index and in-tile vertex index information
into one float. Also, the shader can calculate the center of the tile
a vertex belongs to based on the knowledge of which tile it is.

Now the shader transitions work on OS X, too.

Change-Id: I93e8b5069a6d06d2e412ffee322b1eb32805e606

6 files changed, 22 insertions, 5 deletions

diff --git a/slideshow/opengl/basicVertexShader.glsl b/slideshow/opengl/basicVertexShader.glsl
index 4ca615a57689..da8355465f9d 100644
--- a/slideshow/opengl/basicVertexShader.glsl
+++ b/slideshow/opengl/basicVertexShader.glsl
@@ -26,6 +26,8 @@
  *
  ************************************************************************/
 
+#version 120
+
 varying vec2 v_texturePosition;
 
 void main( void )
diff --git a/slideshow/opengl/dissolveFragmentShader.glsl b/slideshow/opengl/dissolveFragmentShader.glsl
index c6e80e2a6931..6ce3d539d114 100644
--- a/slideshow/opengl/dissolveFragmentShader.glsl
+++ b/slideshow/opengl/dissolveFragmentShader.glsl
@@ -26,6 +26,8 @@
  *
  ************************************************************************/
 
+#version 120
+
 uniform sampler2D leavingSlideTexture;
 uniform sampler2D enteringSlideTexture;
 uniform sampler2D permTexture;
diff --git a/slideshow/opengl/rippleFragmentShader.glsl b/slideshow/opengl/rippleFragmentShader.glsl
index 83677e4d6390..ac6b8ac37099 100644
--- a/slideshow/opengl/rippleFragmentShader.glsl
+++ b/slideshow/opengl/rippleFragmentShader.glsl
@@ -7,6 +7,8 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
+#version 120
+
 #define M_PI 3.1415926535897932384626433832795
 
 uniform sampler2D leavingSlideTexture;
diff --git a/slideshow/opengl/staticFragmentShader.glsl b/slideshow/opengl/staticFragmentShader.glsl
index cd47c5ad6fd7..ab4913de766c 100644
--- a/slideshow/opengl/staticFragmentShader.glsl
+++ b/slideshow/opengl/staticFragmentShader.glsl
@@ -26,6 +26,8 @@
  *
  ************************************************************************/
 
+#version 120
+
 uniform sampler2D leavingSlideTexture;
 uniform sampler2D enteringSlideTexture;
 uniform sampler2D permTexture;
diff --git a/slideshow/opengl/vortexFragmentShader.glsl b/slideshow/opengl/vortexFragmentShader.glsl
index a8a976731034..9b7741acb100 100755
--- a/slideshow/opengl/vortexFragmentShader.glsl
+++ b/slideshow/opengl/vortexFragmentShader.glsl
@@ -7,6 +7,8 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
+#version 120
+
 uniform sampler2D leavingSlideTexture;
 uniform sampler2D enteringSlideTexture;
 uniform float time;
diff --git a/slideshow/opengl/vortexVertexShader.glsl b/slideshow/opengl/vortexVertexShader.glsl
index 532260d748a9..1dffbbd187df 100755
--- a/slideshow/opengl/vortexVertexShader.glsl
+++ b/slideshow/opengl/vortexVertexShader.glsl
@@ -7,15 +7,14 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
+#version 120
+
 #define M_PI 3.1415926535897932384626433832795
 
 uniform float time;
 uniform ivec2 numTiles;
 uniform sampler2D permTexture;
-attribute vec2 tileCenter;
-attribute int tileXIndex;
-attribute int tileYIndex;
-attribute int vertexIndexInTile;
+attribute float tileInfo;
 varying vec2 v_texturePosition;
 varying float v_textureSelect;
 
@@ -52,9 +51,17 @@ void main( void )
     // at time=0.5, when the tiles there (the rightmost ones) start
     // moving.
 
+    // In GLSL 1.20 we don't have any bitwise operators, sigh
+
+    int tileXIndex = int(mod(int(tileInfo), 256));
+    int tileYIndex = int(mod(int(tileInfo) / 256, 256));
+    int vertexIndexInTile = int(mod(int(tileInfo) / (256*256), 256));
+
     float startTime = float(tileXIndex)/(numTiles.x-1) * 0.5;
     float endTime = startTime + 0.5;
 
+    vec2 tileCenter = vec2(-1 + 1.5 * tileXIndex * (2.0/numTiles.x), -1 + 1.5 * tileYIndex * (2.0/numTiles.y));
+
     if (time <= startTime)
     {
         // Still at start location, nothing needed
@@ -86,7 +93,7 @@ void main( void )
         v.z += (fuzz < 0.5 ? -1 : 1) * tileCenter.x * sin(moveTime*M_PI);
 
         // Perturb z a bit randomly
-        v.z += ((((tileXIndex << 3) ^ tileYIndex) % 10) - 5) * (1 - abs(time-0.5)*2);
+        v.z += (fuzz - 0.5) * 5 * (1 - abs(time-0.5)*2);
 
         v_textureSelect = float(rotation > 0.5);
     }