The MessageTrans module
From: RMokady@acorn.co.uk (Ran Mokady) Subject: Re: MessageTrans Date: 13 Mar 91 16:31:35 GMT As requested here is the MessageTrans documentation. Overview -------- This document describes the SWI interface to the MessageTrans module, which provides message translation services, and the format of the message files that it uses. SWI MessageTrans_FileInfo In R1 -> filename Out R0 = flag word: bit 0 set => file is held in memory (can be accessed directly) bits 1..31 reserved (ignore them) R2 = size of buffer required to hold file if R0 bit 0 set, the buffer is not required for read-only access SWI MessageTrans_OpenFile In R0 -> 4-word data structure must be held in the RMA if R2=0 on entry R1 -> filename, held in the RMA if R2=0 on entry (NOTE: FILENAME MUST REMAIN UNCHANGED FOR THE DURATION OG THE FILE BEING OPEN) R2 -> buffer to hold file data 0 => allocate some space in the RMA, or use the file directly if possible Error: "Message file already open" if R0 points to a structure already known to MessageTrans (ie. already open). An application may decide that it would like to buffer the file in its own workspace (rather than the RMA) if it needs to be loaded, or use the file directly if it is already in memory. To do this: SYS "MessageTrans_FileInfo",,filename$ TO flags%,,size% IF flags% AND 1 THEN buffer%=0 ELSE buffer%=FNalloc(size%) SYS "OS_Module",6,,,17+LENfilename$ TO ,,filedesc% $(filedesc%+16)=filename$ SYS "MessageTrans_OpenFile",filedesc%,filedesc%+16,buffer% where FNalloc() allocates a buffer of a given size, by using the Wimp_SlotSize or "END=" command. Note that in fact the filename and file descriptor only need to be in the RMA if R2=0 on entry to MessageTrans_OpenFile. Note: If R2=0 on entry to this SWI, and the application uses direct pointers into the file (rather than copying the messages out) or uses MessageTrans_MakeMenus, it should also trap Service_MessageFileClosed, in case the file is unloaded. SWI MessageTrans_Lookup In R0 -> 4-word data structure passed to MessageTrans_OpenFile R1 -> token, terminated by any char <= 32, or "," or ")" or token:default message terminated by 0 char. R2 -> buffer to hold result (0 => don't copy it) R3 = buffer size (if R2 non-0) R4 -> parameter 0 (0 => don't substitute for "%0") R5 -> parameter 1 (0 => don't substitute for "%1") R6 -> parameter 2 (0 => don't substitute for "%2") R7 -> parameter 3 (0 => don't substitute for "%3") Out R1 -> terminator of token R2 -> result string (read-only with no sustitution if R2=0 on entry) R3 = size of result before terminator (terminator = 10 if R2=0 on entry, else 0) This SWI allows a message token to be translated into a string, with optional parameter substitution. The application must have called MessageTrans_OpenFile beforehand in order to use this SWI, although you can still call it if the file has been automatically closed by the system, because it will automatically re-open it as well. If the message token does not match, the error "Message token not found" is returned unless the token was followed by ":default value", in which case the default value is returned (I.E. either copied to the buffer or pointed at). This error is also given if the value to be returned is on the last line of the file, and does not have a terminating CHR$(10). See the "File format" section for further details. SWI MessageTrans_MakeMenus In R0 -> 4-word data structure passed to MessageTrans_OpenFile R1 -> menu definition (see below) R2 -> RAM buffer to hold menu structure R3 = size of RAM buffer Out [R1..] = menu data R3 = bytes remaining in buffer (should be 0 if you got it right) "Buffer overflow" error if buffer is too small Menu structure: +0 (n) Token for menu title, terminated by any char <= 32, or "," or ")" null => no more menus, otherwise: +n (1) menu title foreground and frame colour (1) menu title background colour (1) menu work area foreground colour (1) menu work area background colour (1) height of menu items (1) gap between items Menu items: (n) Token for menu item, terminated by any char <= 32, or "," or ")" Word-align to here (addr := (addr+3) AND (NOT 3)) (4) Menu flags (bit 7 set => last item) (4) Offset from RAM menu start to RAM submenu start 0 => no submenu (4) Icon flags This SWI allows a menu structure to be set up from a structure containing references to tokens, and sets up menu widths. Parameter substitution is not allowed. The application must have called MessageTrans_OpenFile beforehand in order to use this SWI, although you can still call it if the file has been automatically closed by the system, because it will automatically re-open it as well. If the icon flags have bit 8 clear (ie. they are not indirected), the message text for the icon will be read into the 12-byte block that forms the icon data, otherwise the icon data will be set up to point to the message text inside the file data. In the latter case they are read-only. If the menu item flags bit 2 is set (writeable) and the icon is indirected, the 3 words of the icondata in the RAM buffer are assumed to have already been set up by the calling program. The result of looking up the message token is copied into the buffer indicated by the first word of the icon data (truncated if it gets bigger than the buffer size indicated in [icondata,#8]). SWI MessageTrans_CloseFile In R0 -> 4-word data structure passed to MessageTrans_OpenFile Service_MessageFileClosed In R0 -> 4-word data structure passed to MessageTrans_OpenFile Out If the application recognises the value of R0 passed in, and it has any direct pointers into the message data that it relates to, it should re-initialise itself by calling MessageTrans_OpenFile again to re-open the file, and recache its pointers. If it has used MessageTrans_MakeMenus, it should call Wimp_GetMenuState to see if its menu tree it open, and delete it using Wimp_CreateMenu(-1) if so. This service call is only ever issued if the file is not held in the user's own buffer. It tells the application that its file data has been thrown away, for example if the file is held inside a module which is then reloaded. It is only necessary to trap this service call if direct pointers into the file data are being used. Otherwise, the MessageTrans module will make a note in the file descriptor that the file has been closed, and simply re-open it when MessageTrans_Lookup or MessageTrans_MakeMenus is next called on that file. It is recommended that applications that cannot trap service calls do not use direct pointers into the file data (eg. indirected icons with MessageTrans_MakeMenus). They can still use such indirected icons, if they provide a buffer pointer in R2 on entry to MessageTrans_OpenFile (so that the message file data is copied into the buffer). Service_Reset Since MessageTrans does not close message files on a soft reset, applications that do not wish their message files to be open once they leave the desktop should call MessageTrans_CloseFile for all their open files at this point. However, it is perfectly legal for message files to be left open over soft reset. File format ----------- Message files contain a series of one-line token / value pairs, terminated by character 10 (linefeed).