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Set custom metafile input-stream handler functions. - Parameters: 
 - 
| API  | 
the API handle  |  
| fp_read  | 
function to read a byte  |  
| fp_seek  | 
function to set position  |  
| fp_tell  | 
function to get position  |  
| user_data  | 
handle for user data |  
 
  libwmf has simple methods for reading either from file or from memory, but many applications will want to use customized variants of these. wmf_bbuf_input() enables this.
 
typedef int  (*wmfRead) (void* user_data);
typedef int  (*wmfSeek) (void* user_data,long position);
typedef long (*wmfTell) (void* user_data);
  
wmfRead returns unsigned char cast to int, or EOF (cf. fgetc())
 
wmfSeek returns (-1) on error, otherwise 0 (cf. fseek())
 
wmfTell returns (-1) on error, otherwise current position (cf. ftell())
 
 - Returns: 
 - 
Returns the library error state (wmf_E_None on success). Possible library error state of wmf_E_Glitch, if any of the three functions is zero. 
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