PDA Software Library/pdasoftwarelib.iso/PSION/1997/999/PLUGINS.TXT

Text File | 1997-04-16 | 7.5 KB | 155 lines

DPBank plugins

Because DPBank was intended to be small and fast, it is likely that you
may not find the feature you may be looking for in this program; but
still, you prefer DPBank because of it's better interface, small memory
requirements, or whatever...

To resolve this dilemna, I've added the possibility to add third party
programs with the form of "plugins". These plugins will integrate
closely with DPBank and it will look like the new features are built-in.
Indeed, all that is needed is the press of a hotkey and the plugin will
be launched dynamically. Once the plugin has terminated, you will be
prompted back to DPBank. In case you switch back to DPBank before the
plugin has terminated, DPBank will close the plugin for you
automatically because it's not possible to share the account files
between two programs.

All this happens without the user knowing it as long as the plugin
author has followed some basic instructions that you can find below.

DPBank plugins MUST be placed in an \APP\DPBANK directories in order to
be found.

TECHNICAL NOTE TO PROGRAMMERS

Since version 1.6, it's now possible to write "plugins" for DPBank. This
option is provided so people who want to use DPBank with more features
than the standard included ones can go ahead while the other users who
liked the original simplicity of the program can still use the "plain
vanilla" DPBank without having to worry about getting more memory.

This file explains what you need to do as a programmer in order to
integrate dynamically with DPBank. It also describes the file formats
you may need and what you should and should not do with the files.

Note: I have no experience with C programming, so if you want to write a
plugin in C, you'll have to give me some details because I doubt it will
work with the actual method used in DPBank. All the instructions below
apply to plugins wirtten in OPL.

First, you need to make a simple Psion Data file (without labels, ie:
with the OPL CREATE command) having the following fields:

-The name of your plugin, exactly as you called your APP. This name will
 appear in the plugin menu of DPBank and at the same time, it will be the
 shell name of the app when it will be launched.
-The filename of your plugin (but no need for the path, see below)
-First line to be displayed in the "info" field for your plugin
-The second line of info
-The third line of info
-The fourth line of info

All fields should be strings. The info lines are limited to 40
characters per line. ALL fields MUST BE PRESENT! If you don't need all 4
lines of infos, you must set them to "" be they must be present in the
data file, or else DPBank will crash.

The info will be displayed in a dialog when the user wants to know more
about your plugin. You may want to include your name, contact address,
version number or whatever else you judge interesting...

This Data file must have exactly the same name as your plugin name
except with an extension of "dpb" and must be located in an \APP\DPBANK
directory in order for DPBank to locate it and display it in the menu.

If you take for example Nick Dawkin's "Plot" plugin, you'd have the Data
file "plot.dpb" in the \APP\DPBANK directory and the application file
"plot.opa" in the \APP\DPBANK directory of any drive.

When the plugin is called from within DPBank, the program will attempt
to find the plugin application itself in the \APP\DPBANK directoy of all
drives. If it cannot find the file, it will let the user know of the
problem.

Once it has located your plugin, DPBank will launch it with the command
line parameters set to open the current account datafile. Thus, it would
be equivalent to launching your plugin from the system screen with the
name of one account (and NOT the group as with DPBank itself for
example). Your plugin must receive this info with the OPL CMD$(x)
command. In other words: CMD$(2) will contain for example "accounts.d03"
and CMD$(3) will contain for example "O" for open.

If you want your plugin to work seperately (ie: launched from the system
screen), you must make sure you give priority to the command line from
DPBank and not ask the user which account he wants to use. You can
differentiate command lines from DPBank and those of the system screen
because the system will never send a direct account name, but a group
name ("pre" extension).

Once your plugin is launched, it will have complete control over the
account data file (as DPBank had previously closed it for himself) and
you can do whatever manipulations you need with it. In fact, DPBank will
have no account files open itself.

The transactions datafile database is a plain Psion Data file with no
headers. You simply cannot open them with the normal Data application
because all fields are not strings (which is a limitation of the Data
app).

The data has the following format: (note that this WILL change fairly
soon, but once I will have changed the format (for version 2.x files), I
hope it will be more or less definitive)
-yrmody$: date of transaction in YYYYMMDD format
-desc$: description of transaction
-catego$: category of the transaction (short code)
-locamt: local amount of transaction (in money of account's default)
-cleared%: reconciled flag is bit 0. Other flags may appear later.
-foramt: foreign amount (0 if in default money)
-forcurr$: if this string is empty, then the amount is in the local
 amount of the account, otherwise, the amount is of this currency (new
 databases will have something set here always! If the amount is in
 default money, then it will still have the default money's name)
-balance: balance associated to this transaction at this position in
 list.

Note: the files are always sorted in chronological order. This is one of
the reasons you can't exit without saving your data. If your plugin
modifies anything on the data file (ie: writes to it), then YOU are
responsible of re-sorting the whole file at ALL times (since you never
know when your program will terminate).

It is highly recommended to open the database file in read-only mode for
the above reason.

Your plugin should have an exit option (Psion-x) and when activated,
DPBank will re-open the database file, move to the foreground and
re-display the transactions as to reflect any changes.

You do not need to worry about switching back to DPBank. This will be
taken care of automatically. In the case where the user would switch
manually back to DPBank, the program would send a close (eXit) process
signal to the plugin. In the event that the plugin is not responsive to
this signal, a kill signal would have to be sent! This could be
catastrophic if the plugin didn't take care to save all changes it made
to the database file at all times.

Please don't forget this important point!
*****************************************
Your plugin MUST be responsive to System EXIT messages AT ALL times!

DPBank needs to close the plugin because the program needs to have
complete control over the database file and the Psion doesn't allow to
have complete control over a file if it's already opened by another
application.

I hope I've answered all your questions with this file. In the case of
the contrary, don't hesitate to contact me by email. I will be happy to
answer any other problems you may have.

Thanks for your interest in writing a DPBank plugin. I understand that
certain people need more than simply a "Quicken frontend" if I may say,
and I hope you will take this opportunity to enhance DPBank that little
bit further. I'm sure all DPBank users will appreciate your effort.