Once a function has been provided, a null pointer can be supplied in a subsequent call to astGrfSet to reset the function to the corresponding function in the graphics interface selected at link-time.
The first parameter ("grfcon") for each function is an AST KeyMap pointer that can be used by the called function to establish the context in which it is being called. The contents of the KeyMap are determined by the calling application, which should obtain a pointer to the KeyMap using the astGetGrfContext function, and then store any necessary information in the KeyMap using the methods of the KeyMap class. Note, the functions listed below should never annul or delete the supplied KeyMap pointer.
int Attr( AstObject grfcon, int attr, double value, double old_value, int prim )
int BBuf( AstObject grfcon )
int Cap( AstObject grfcon, int cap, int value )
GRF__MJUST: This function should return a non-zero value if the "Text" and "TxExt" functions recognise "M" as a character in the justification string. If the first character of a justification string is "M", then the text should be justified with the given reference point at the bottom of the bounding box. This is different to "B" justification, which requests that the reference point be put on the baseline of the text, since some characters hang down below the baseline. If the "Text" or "TxExt" function cannot differentiate between "M" and "B", then this function should return zero, in which case "M" justification will never be requested by Plot. The supplied "value" argument should be ignored.
GRF__ESC: This function should return a non-zero value if the "Text" and "TxExt" functions can recognise and interpret graphics escape sequences within the supplied string (see attribute Escape). Zero should be returned if escape sequences cannot be interpreted (in which case the Plot class will interpret them itself if needed). The supplied "value" argument should be ignored only if escape sequences cannot be interpreted by "Text" and "TxExt". Otherwise, "value" indicates whether "Text" and "TxExt" should interpret escape sequences in subsequent calls. If "value" is non-zero then escape sequences should be interpreted by "Text" and "TxExt". Otherwise, they should be drawn as literal text.
int EBuf( AstObject grfcon )
int Flush( AstObject grfcon )
int Line( AstObject grfcon, int n, const float x, const float y )
int Mark( AstObject grfcon, int n, const float x, const float y, int type )
int Qch( AstObject grfcon, float chv, float chh )
int Scales( AstObject grfcon, float alpha, float beta )
int Text( AstObject grfcon, const char text, float x, float y, const char just, float upx, float upy )
int TxExt( AstObject grfcon, const char text, float x, float y, const char just, float upx, float upy, float xb, float yb )
AST A Library for Handling World Coordinate Systems in Astronomy