🚚 Move shader code to GLSL files

resources/shaders/common/edgeMask.glsl

@@ -0,0 +1,22 @@
+// This method returns a mask which smoothly transitions towards zero when approaching
+// the window's borders. There is a variant which takes the transition area width in
+// pixels and one which takes this as a percentage.
+float getEdgeMask(vec2 uv, vec2 maxUV, float fadeWidth) {
+  float mask = 1.0;
+  mask *= smoothstep(0, 1, clamp(uv.x / fadeWidth, 0, 1));
+  mask *= smoothstep(0, 1, clamp(uv.y / fadeWidth, 0, 1));
+  mask *= smoothstep(0, 1, clamp((maxUV.x - uv.x) / fadeWidth, 0, 1));
+  mask *= smoothstep(0, 1, clamp((maxUV.y - uv.y) / fadeWidth, 0, 1));
+
+  return mask;
+}
+
+float getAbsoluteEdgeMask(float fadePixels) {
+  vec2 uv = cogl_tex_coord_in[0].st * uSize;
+  return getEdgeMask(uv, uSize, fadePixels);
+}
+
+float getRelativeEdgeMask(float fadeAmount) {
+  vec2 uv = cogl_tex_coord_in[0].st;
+  return getEdgeMask(uv, vec2(1.0), fadeAmount);
+}