gleffects: fix little rectangle that appears at the center of squeeze and tunnel...

These two shader will calculate the vector length and use it as denominator.
But length could be zero which will cause undefine behaviour. Add protection for
this condition

https://bugzilla.gnome.org/show_bug.cgi?id=767635

diff --git a/ext/gl/effects/gstgleffectssources.c b/ext/gl/effects/gstgleffectssources.c
index 8059aba..b83e1d7 100644 (file)
--- a/ext/gl/effects/gstgleffectssources.c
+++ b/ext/gl/effects/gstgleffectssources.c
@@ -100,7 +100,8 @@ const gchar *squeeze_fragment_source_gles2 =
   "void main () {"
   "  vec2 texturecoord = v_texcoord.xy;"
   "  vec2 normcoord = texturecoord - 0.5;"
-  "  float r = length (normcoord);"
+  /* Add a very small value to length otherwise it could be 0 */
+  "  float r = length (normcoord)+0.01;"
   "  r = pow(r, 0.40)*1.3;"
   "  normcoord = normcoord / r;"
   "  texturecoord = (normcoord + 0.5);"
@@ -136,7 +137,8 @@ const gchar *tunnel_fragment_source_gles2 =
    * rect textures */
   "  normcoord = (texturecoord - 0.5);"
   "  float r = length(normcoord);"
-  "  normcoord *= clamp (r, 0.0, 0.275) / r;"
+  "  if (r > 0.0)"
+  "    normcoord *= clamp (r, 0.0, 0.275) / r;"
   "  texturecoord = normcoord + 0.5;"
   "  gl_FragColor = texture2D (tex, texturecoord);"
   "}";