This document is an attempt to list the may possible options available to the OPL-Programmer, which are normally only to be found in the SIBO 'C'-Programming Guides.
The various tips and tricks are illustrated with examples in Standard OPL.
There is no particular order to the points listed. The information can be freely distributed, but is Psion GmbH. Thanks to David Wood at Psion PLC for helping me with these routines over the past few months.
Neither the Author, nor Psion GmbH, takes any responsibility for and damage or loss of data which occurs as result of using information in this document. The information is subject to change without notice.
Comments are shown in italics.
Use of CALL and OS
CALLs and OSs take a particular format. This is briefly explained in the OPL Programming Manual, but is repeated here for reference.
Using the 'Service' and 'Interrupt' reference in the 'C'-Programming Guide, it is possible to access the specific operating system call desired.
Format for Call:
ret%=CALL($xxyy,...,) xx = Service, yy = Interrupt
Format for OS:
LOCAL ax%,bx%,cx%,dx%,si%,di% keep these together
LOCAL flags%
ax%=$xxyy xx = Service, yy = AL (parameter)
flags%=OS($zz,addr(ax%)) zz = Interrupt
If an error occurs when using OS, (flags% AND 1) will be true,
the error code is given by ax% AND $ff00.
Starting another process
Here we start another process, and specify the name of the file to be opened. The command line starts with 'C' for create, or 'O' for open. The filename is stored in f$. The 'Record' at the beginning of the command line in this example is the name of the icon under which the filename will appear in the System Screen. If this is not a valid (ie. installed) icon, then the filename will appear under RunImg.
eg. Recorder with a filename
PROC Record:(f$)
LOCAL cmdl$(128),helpnm$(128),hpid%,ret%
cmdl$="CRecord"+chr$(0)+".WVE"+" "+chr$(0)+f$+chr$(0) command line
Each process has an ID number. Here we read the ID number for a specific process.
eg. Get the process ID for the system shell. pid% is defined globally to hold this variable.
name$="sys$shll.*"
pid%=call($0188,addr(name$)+1) ProcIdByName
Getting the Process ID for the current process
This short piece of code reads the ID for the current process.
LOCAL pid%
pid%=CALL($0088)
Setting the priority of the process
Once we have the ID for a process, we can change the priority of this process.
LOCAL ax%,bx%,cx%,dx%,si%,di% keep these together
LOCAL flags% NB: pid% must be defined to be the process id
bx%=pid%
ax%=$0398
flags%=OS($88,addr(ax%)) ProcSetPriority
Changing the position of a process
We can also change the position of this process, ie. whether it is in foreground or background.
CALL($998d,pos%,pid%)
For the current process, pid% can be set to zero.
For foreground, use pos%=0, for background, pos%=100.
Language Code
Programs written by Psion are in the majority Multi-lingual. This means that if they run on an English machine, they run in English, on a German machine they run in German, and so on.
Each language is assigned a number, which is used to recognise the machine in use.
This example returns a string containing the number of the code for the resource file.
PROC Lang$:
LOCAL ax%,bx%,cx%,dx%,si%,di% Keep these variables together
LOCAL flags%,a$(2)
ax%=$1B00 GetLangData
flags%=OS($008B,ADDR(ax%)) General Services
IF flags% AND 1
RETURN("01") an error occured
ELSE
a$=NUM$(ax%,2)
IF LEN(a$)<2 :a$="0"+a$ :ENDIF makes two digits for filenames
ENDIF
ENDP
The numbers currently in use are:
1 English
2 French
3 German
4 Spanish
5 Italian
6 Swedish
7 Danish
8 Norwegen
9 Finish
10 American
11 Swiss French
12 Swiss German
13 Portuguese
14 Turkish
15 Icelandic
16 Russian
17 Hungarian
18 Dutch
19 Belgian Flemish
20 Australian
21 New Zealand
22 Austrian
23 Belgian French
Simulating a key press
There is a technique for the Series3a to simulate a keypress in another application. This method only works for Object-oriented applicaitions.
The following must be globally defined:
GLOBAL k%,m% keep these two together
pid% is the process id, k% is the keycode, m% is the modifier
CALL($0483,pid%,$31,0,addr(k%)) MessSend
Capturing a key in background
We can also when a particular key is pressed, even if the process requiring this key is not current.
call($c58d,26,$404) wCaptureKey
This example captures key 26, ie. Ctrl-Z.
Capturing the off key
The following parameters will capture the 'OFF' key.
call($c58d,$2003,$e08)
keya(kstat%,k%(1) queues for a key press
The value returned in kstat% will NOT be -46 if a key is pressed, and for the off key,
k%(1) will be $2003.
Reading an environment variable
Environment variables are used to store data which is used by all applications. Space for these variables is limited, and should normally not be used by OPL applications.
PROC EnvGet:
LOCAL ax%,bx%,cx%,dx%,si%,di% keep these together
LOCAL flags%
LOCAL env$(6),penv%,lenenv%
LOCAL buff$(255),pbuff%,lenbuff%
env$="$WP_PW" name of the variable to search for, eg. $WP_PW
penv%=ADDR(env$+1)
lenenv%=LEN(env$)
pbuff%=ADDR(buff$)+1
ax%=$2100
bx%=0
di%=penv%
dx%=lenenv%
si%=pbuff%
flags%=OS($008b,ADDR(ax%)) GenEnvBufferGet
IF flags% AND 1
An error has occured, error code: ax% OR $ff00
ELSE
lenbuff%=ax%
POKEB ADDR(buff$),lenbuff% Insert leading count
ENDIF
ENDP
Reading the user details
User details are stored in environment variable $WS_PW.
Bytes 4, 8, 12, and 16 contain the length (in bytes) of each of the four lines.
The first line begins at byte 19.
Reading the current printer driver
The printer destination is stored in environment variable P$D. Zero for parallel, one for serial, and two for file.
The printer driver is stored in environment variable P$M. This is generally a filename.
If printing to a file, the name is stored in P$F.
Asynchronous WVE Playing
This procedure will play a .WVE file asynchronously.
