Evidently #if FOO is illegal in GLSL if FOO is not defined,
unlike in C++. Reported by Dan Dennedy.
+// GLSL is pickier than the C++ preprocessor in if-testing for undefined
+// tokens; do some fixups here to keep it happy.
+
+#ifndef YCBCR_OUTPUT_PLANAR
+#define YCBCR_OUTPUT_PLANAR 0
+#endif
+
+#ifndef YCBCR_OUTPUT_SPLIT_Y_AND_CBCR
+#define YCBCR_OUTPUT_SPLIT_Y_AND_CBCR 0
+#endif
+
+#ifndef YCBCR_ALSO_OUTPUT_RGBA
+#define YCBCR_ALSO_OUTPUT_RGBA 0
+#endif
+
#if YCBCR_OUTPUT_PLANAR
out vec4 Y;
out vec4 Cb;
+// See footer.frag for details about this if statement.
+#ifndef YCBCR_ALSO_OUTPUT_RGBA
+#define YCBCR_ALSO_OUTPUT_RGBA 0
+#endif
+
uniform sampler2D PREFIX(tex_y);
uniform sampler2D PREFIX(tex_cb);
uniform sampler2D PREFIX(tex_cr);