OS_PrettyPrint (changes)

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OS SWI Calls

» OS_PrettyPrint

OS_PrettyPrint

(SWI &44)

Use

The purpose of this call is to write an indirect string, with formatting, to all of the active output streams.

Notes

Compacted text uses an escape character in the print string to indicate a dictionary entry. It is followed immediately by a byte which is the dictionary entry number. If this byte is in the range 1-255, then the appropriate string in the dictionary is substituted. If it’s 0, then the special string pointed to by R2 is substituted. (This is used in particular by the *Help command.)

The format of a dictionary is a linear list of entries, which can recursively refer to other dictionary entries; each entry is a length byte (counting itself) followed by a 0 terminated string. string, This so means an that empty string has a dictionary length doesn’t byte have of to 2. have A 255 length entries byte – of it can be ended at a point with a zero terminates the dictionary. A length entry. byte of 1 is not allowed.

This call acts like OS_Write0 with several differences:

• It will break a line at a space if the next word will not fit on the line, except at hard spaces
• Compacted text is handled
• CR causes a newline to be generated
• TAB causes tabulation to the next multiple of eight columns
• ASCII 31 is acts as a hard space for formatting, but is output as 32
• ESC (ASCII 27) indicates that a dictionary entry should be substituted

See also

• OS_Write0
• RISC OS Default Dictionary
• *Help