Emulate GLSL #import via Xcode build

Question

A few of my GLSL fragment shaders share common functions and constants. I can't find any #import-like functionality in GLSL (understandably), but it'd be super-cool if I could emulate that in Xcode's build stage. It could be as simple as appending a common file to all my fragment shaders before copying them to my resources folder.

But my script-fu is weak. Anyone want to help me out or point me in the right direction?

Answer 1

I don't know very much about XCode, but it shouldn't be too difficult to implement in your own code.

This is exceptionally easy if you load the code line-by-line. As each line is loaded, check if is has the form #import "filename". If so, then load that file before continuing. Something like this C++ code:

 string loadGLSL(string fileName)
 {
      ifstream inputStream(fileName);
      string fileContents, line;

      while(inputFile.good())
      {
          getline(inputStream, line);
          if(isImportDirective(line))
               loadGLSL(getFileNamePart(line));
          else
              fileContents += line + '\n';
      }
 }

I'll let you work out the details of isImportDirective and getFileNamePart, but it shouldn't be too difficult at all. I also didn't pay attention to multiple #imports of the same file - such a redundancy should be check for if you wish to achieve functionality analagous to Objective-C's #import.

Of course, you could also load the entire file first, then search for the string #import and then swap the required file contents for that line. Whatever you think works best.

Hope this helps.