The old external code system used by The Hacker is no longer supported. Instead, you should code a normal Wimp task, and use Desktop Hacker's SWIs and messages to communicate. This has the advantage that you don't need to program in ARM code - you can use C, BASIC, or any other language. Create yourself an application with a Desktop Hacker axe somewhere in the icon; ideally, the application name should begin '!dH', but this may not always be appropriate.
There are two parts to Desktop Hacker: the actual DesktopHacker module task, which provides all the hacking facilities that the user uses; and the SWIVe code (so named because it works by claiming the SWI hardware vector), which, when the hot-keys are pressed, stops the game and starts a Wimp task. SWIVe sends Wimp messages to Desktop Hacker (and external tasks; it is a broadcast message) when the game is stopped, restarted, or quit.
Desktop Hacker sends a message to SWIVe telling it to continue when the
Continue button is clicked, or when Select is clicked on the icon
bar icon, or whatever. Desktop Hacker may also send a Wimp
Message_Quit (message 0) telling SWIVe to shut the game down
entirely. Other external tasks (including the Task Manager) may send
messages to SWIVe. SWIVe will appear in the Task Display either as 'Desktop
Hacker Game' if the program interrupted did not call
Wimp_Initialise, or the real name of the stopped task if it
Apart from the memory of the SWIVe task, there are a few other details
Desktop Hacker holds. The only directly readable one is the environment
dHacker$Obey$Dir, which holds what
Obey$Dir held when the hot-keys were pressed.
This message is broadcast by SWIVe to inform Desktop Hacker and any
external tasks of a hacking session starting/ending. No parameters are
passed using the message; external tasks should call the SWI
DesktopHacker_ReadState to find out the current state.
SWIVe sends this message when:
This message is broadcast by Desktop Hacker whenever the memory of the
stopped task has been altered, either by the user, or by certain
DesktopHacker_MemoryAccess calls. External tasks that
display details in a window that depend on the contents of the stopped
game's application memory should rescan and redraw where necessary when
this message is received. No parameters are passed.
Note that this message is not broadcast when a game file is loaded
which changes the application memory contents completely; instead the
SWIVe code broadcasts
If your task requires the application memory of a hacked game, you should only allow use of the task when R0=2.
Note that the task specified in R1 does not have the same in it when stopped as when it is running. See the format of saved game files for details of what is in the application area when stopped.
If you just want to access the main application area, though, and not
the full info bundles, you should use the SWI
If you do access Desktop Hacker or its game's WimpSlot directly using
Wimp_TransferBlock, be aware that there is a bug in RISC
OS 3.7's implementation of the SWI affecting use of the call twice or
more in a row between code synchronisations. To combat this, you should
OS_SynchroniseCodeAreas once after each call to
Wimp_TransferBlock. Failure to do so on a machine equipped
with RISC OS 3.7 but not equipped with the patches produced by Acorn or
DoggySoft will result in things going wrong in inexplicable ways - you
have been warned.
This SWI loads and stores data to and from the game's WimpSlot. You
should always use this SWI to access the game's application memory,
rather than using
Wimp_TransferBlock, as (a) this SWI
automatically re-maps the word at &8000, and (b) it uses a cache in RMA
to make access much quicker (
Wimp_TransferBlock is very,
very slow). At present, the cache is 8K long. If you do alter the game
Wimp_TransferBlock, you must call
DesktopHacker_MemoryAccess 4 to invalidate the cache, or
other users of the cache may not like it.
Note, if you're searching through memory, you will find it is much quicker to search forwards rather than backwards, due to the rather simplistic cache algorithm. Only read-cacheing is performed, not write-buffering.
DesktopHacker_MemoryAccess operation may be used when
the game is not being hacked (R0 on exit from
DesktopHacker_ReadState is not 2).
Wimp_TransferBlockfor efficient transfer.
On exit R1 points to a list (see format of list files), the only difference being that the first four bytes are an offset to the first byte after the end of the list, rather than the header "List".
Note that the pointer is in Desktop Hacker's application space. If you
want to read the contents of the list you will need to use
Wimp_TransferBlock with the R0 and R1 supplied by this
SWI, and the length of block to transfer as R2.
There is no SWI provided to alter lists - doing so would be very slow
as very many calls to
Wimp_TransferBlock would be needed,
along, perhaps, with resizing of the WimpSlot which is not possible as
Desktop Hacker is not paged in. If you do want to send a list to
Desktop Hacker, simply use the data transfer protocol - make up a Wimp
message block as if a list file was dragged to Desktop Hacker (use the
icon bar (-2) as the destination window handle; the destination icon
handle is unimportant), using
transfer will be conducted as normal, and the window containing the
list will be opened. Note that Desktop Hacker does not support
This SWI sets a flag which tells Desktop Hacker to interrupt as soon as possible. Usually, this will be immediately, but it may be called later if IRQs or FIQs are disabled, or the processor is in IRQ or FIQ mode. Of course it will also only interrupt if you are the current hacking task.
In order to get all the registers for the Game Info window, not just R0-R8, this SWI is trapped in the SWIVe code; the actual SWI command code does nothing. You will not receive an error if the situation isn't suitable for a breakpoint. Instead, just the SWI command code is called, and so nothing will happen.
This SWI is only implemented on Desktop Hacker 1.06 and above.
This command is used by Desktop Hacker when a game is dragged to it. It
cannot be used from the command line. However, there is no reason why
external tasks should not use it, if they need to. It should only be
used by being passed to Wimp_StartTask, and to be sure of compatibility
with special fields, you should surround the parameter of a
Run command (if that's what you're using) with quotes. For
example, for BASIC:
SYS "Wimp_StartTask","DesktopHacker Run
Format of saved game files