Refactor loading of background shader

shader/background.geom

@@ -5,6 +5,7 @@ in vec4 vParams [];
 in vec2 vWinSize [];
 out vec2 gTexPos;
 
+uniform vec2 winSize;
 uniform vec2 translation;
 uniform float zoom;
 uniform float rotation;
@@ -23,8 +24,8 @@ void main()
 //  float zoom = vParams[0].w;
   float rot  = 0 - rotation;
       
-  float x = vWinSize[0].x / (500*zoom) ;
-  float y = vWinSize[0].y / (500*zoom) ;
+  float x = winSize.x / (500*zoom) ;
+  float y = winSize.y / (500*zoom) ;
   gTexPos = cPos + rotBy(-rot , vec2(x,y));
   gl_Position = vec4 (1,1,0.9,1);
   EmitVertex();