Header containing GLSL source code is generated only after change of any of shader source files.

CMakeModules/Shaders.cmake

@@ -4,6 +4,19 @@
 # number of input files
 list( LENGTH inputFiles shadersNumber ) 
 
+# check if GLSL source files were updated since the last time
+set( update "FALSE" )
+foreach( inputFile ${inputFiles} )
+    if( ${inputFile} IS_NEWER_THAN ${outputFile} )
+        set( update "TRUE" )
+    endif( ${inputFile} IS_NEWER_THAN ${outputFile} )
+endforeach( inputFile ${inputFiles} )
+
+if( NOT update )
+    message( "Headers are up-to-date" )
+    return()
+endif( NOT update )
+
 # write header
 file( WRITE ${outputFile} "// Do not edit this file, it is autogenerated by CMake.
 
@@ -35,7 +48,6 @@ foreach( inputFile ${inputFiles} )
     string( REGEX REPLACE "\"$" "," contents "${contents}" )
 
     file( APPEND ${outputFile} "${contents}" )
-
 endforeach( inputFile ${inputFiles} )
 
 # write footer