From: pcolmer@acorn.co.uk (Philip Colmer)
Subject: Useful hints and tips #1: !Run files
Date: 14 Jun 93 15:17:23 GMT

1. Loading modules from !System
-------------------------------

 Often, applications that may or may not need to load modules from !System
simply check System$Path before seeing whether or not anything does need to
be loaded from !System. This is particularly annoying with RISC OS 3 since
there currently shouldn't be any need for OS-originated modules.

 A way around this problem would be to use something along the lines of:

RMEnsure UtilityModule 3.00 If "<System$Path>" = "" Then Error 0 System
resources cannot be found

Set System$Path_Message System resources cannot be found

 The first line basically states that if the machine hasn't got RISC OS
3.00 orlater, and System$Path isn't set, then complain. This would be the
default action under RISC OS 2, so nothing has changed there.

 The second line uses a new feature of RISC OS 3. Basically what the line
is saying is that if there is an access to System: and System$Path isn't
defined, give the error 'System resources cannot be found'.

2. Duplication of !Boot
-----------------------

 If you look at a lot of applications, the !Run files fall into three categories:

 1. They run !Boot at some point
 2. They include the commands in !Boot
 3. There is no common ground at all.

 The third is obviously flawed since the !Boot file may not have been
executed. It is therefore necessary, in some way, to execute the commands
that the !Boot file contains. The best way to do this is to COPY the
commands from the !Boot file and put them into the !Run file.

 Doing it this way is more network-friendly that running the !Boot file
form the !Run file.

 An associated point is that if the !Boot file just contains:

 IconSprites <Obey$Dir>.!Sprites

then it is a waste of time and space. In the absence of a !Boot file, the
Filer will do this anyway.

3. Careful setting of slot sizes
--------------------------------

 When setting the slot size for your application, exercise some caution and
try to test your application on a small-paged machine. This is important
because the page size varies from 8K up to 32K depending on the amount of
memory that your machine has.

 It is also worth remembering that the Window Manager rounds the requested
slot size UP to the nearest page size, which holds hidden perils if you
have specified a slot size too small for an 8K page size machine but which,
when rounded up, works fine on a 32K page size machine.

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