AngelScript: Script builder helper

# Script builder helper

Path: /sdk/add_on/scriptbuilder/

This class is a helper class for loading and building scripts, with a basic pre-processor that supports conditional compilation, include directives, and metadata declarations.

By default the script builder resolves include directives by loading the included file from the relative directory of the file it is included from. If you want to do this in another way, then you should implement the include callback which will let you process the include directive in a custom way, e.g. to load the included file from memory, or to support multiple search paths. The include callback should call the AddSectionFromFile or AddSectionFromMemory to include the section in the current build.

If you do not want process metadata then you can compile the add-on with the define AS_PROCESS_METADATA 0, which will exclude the code for processing this. This define can be made in the project settings or directly in the header.

## Public C++ interface

    class CScriptBuilder
    {
    public:
      // Start a new module
      int StartNewModule(asIScriptEngine *engine, const char *moduleName);

      // Load a script section from a file on disk
      int AddSectionFromFile(const char *filename);

      // Load a script section from memory
      int AddSectionFromMemory(const char *scriptCode,
                               const char *sectionName = "");

      // Build the added script sections
      int BuildModule();

      // Register the callback for resolving include directive
      void SetIncludeCallback(INCLUDECALLBACK_t callback, void *userParam);

      // Add a pre-processor define for conditional compilation
      void DefineWord(const char *word);

      // Get metadata declared for class types and interfaces
      const char *GetMetadataStringForType(int typeId);

      // Get metadata declared for functions
      const char *GetMetadataStringForFunc(int funcId);

      // Get metadata declared for global variables
      const char *GetMetadataStringForVar(int varIdx);
    };

### The include callback signature

    // This callback will be called for each #include directive encountered by the
    // builder. The callback should call the AddSectionFromFile or AddSectionFromMemory
    // to add the included section to the script. If the include cannot be resolved
    // then the function should return a negative value to abort the compilation.
    typedef int (*INCLUDECALLBACK_t)(const char *include, const char *from, CScriptBuilder *builder, void *userParam);

## Include directives

Example script with include directive:

      #include "commonfuncs.as"

      void main()
      {
        // Call a function from the included file
        CommonFunc();
      }

## Conditional programming

The builder supports conditional programming through the #if/#endif preprocessor directives. The application may define a word with a call to DefineWord(), then the scripts may check for this definition in the code in order to include/exclude parts of the code.

This is especially useful when scripts are shared between different binaries, for example, in a client/server application.

Example script with conditional compilation:

      class CObject
      {
        void Process()
        {
      #if SERVER
          // Do some server specific processing
      #endif

      #if CLIENT
          // Do some client specific processing
      #endif

          // Do some common processing
        }
      }

## Metadata in scripts

Metadata can be added before script class, interface, function, and global variable declarations. The metadata is removed from the script by the builder class and stored for post build lookup by the type id, function id, or variable index.

Exactly what the metadata looks like is up to the application. The builder class doesn't impose any rules, except that the metadata should be added between brackets []. After the script has been built the application can obtain the metadata strings and interpret them as it sees fit.

Example script with metadata:

      [factory func = CreateOgre,
       editable: myPosition,
       editable: myStrength [10, 100]]
      class COgre
      {
        vector3 myPosition;
        int     myStrength;
      }

      [factory]
      COgre @CreateOgre()
      {
        return @COgre();
      }

Example usage:

    CScriptBuilder builder;
    int r = builder.StartNewModule(engine, "my module");
    if( r >= 0 )
      r = builder.AddSectionFromMemory(script);
    if( r >= 0 )
      r = builder.BuildModule();
    if( r >= 0 )
    {
      // Find global variables that have been marked as editable by user
      asIScriptModule *mod = engine->GetModule("my module");
      int count = mod->GetGlobalVarCount();
      for( int n = 0; n < count; n++ )
      {
        string metadata = builder.GetMetadataStringForVar(n);
        if( metadata == "editable" )
        {
          // Show the global variable in a GUI
          ...
        }
      }
    }