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

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

1 files changed, 4 insertions, 2 deletions

diff --git a/ext/gl/effects/gstgleffectssources.c b/ext/gl/effects/gstgleffectssources.c
index 8059abafd..b83e1d7cc 100644
--- 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);"
   "}";