# FreeType-2.7.1 API Reference

# Error Enumerations

The header file ‘fterrors.h’ (which is automatically included by ‘freetype.h’ defines the handling of FreeType's enumeration constants. It can also be used to generate error message strings with a small macro trick explained below.

Error Formats

The configuration macro FT_CONFIG_OPTION_USE_MODULE_ERRORS can be defined in ‘ftoption.h’ in order to make the higher byte indicate the module where the error has happened (this is not compatible with standard builds of FreeType&nbsp;2, however). See the file ‘ftmoderr.h’ for more details.

Error Message Strings

Error definitions are set up with special macros that allow client applications to build a table of error message strings. The strings are not included in a normal build of FreeType&nbsp;2 to save space (most client applications do not use them).

To do so, you have to define the following macros before including this file.

      FT_ERROR_START_LIST

This macro is called before anything else to define the start of the error list. It is followed by several FT_ERROR_DEF calls.

      FT_ERROR_DEF( e, v, s )

This macro is called to define one single error. ‘e’ is the error code identifier (e.g., ‘Invalid_Argument’), ‘v’ is the error's numerical value, and ‘s’ is the corresponding error string.

      FT_ERROR_END_LIST

This macro ends the list.

Additionally, you have to undefine ‘FTERRORS_H_’ before #including this file.

Here is a simple example.

      #undef FTERRORS_H_
      #define FT_ERRORDEF( e, v, s )  { e, s },
      #define FT_ERROR_START_LIST     {
      #define FT_ERROR_END_LIST       { 0, NULL } };

      const struct
      {
        int          err_code;
        const char*  err_msg;
      } ft_errors[] =

      #include FT_ERRORS_H

Note that ‘FT_Err_Ok’ is not defined with ‘FT_ERRORDEF’ but with ‘FT_NOERRORDEF’; it is always zero.