REALBasic tutorial in old MacFormat magazine - creating extensions

[aladds]

Years ago I remember reading a tutorial in an old MacFormat (UK) magazine which had an example of converting a regular application into an extension by changing the type code with ResEdit and making sure that the application didn't have a UI (I think they actually hid the UI off the screen). A pretty ugly hack I am sure, but I can't for the life of me remember how it worked. You changed the type to something like "APPE" (from "APPL") but I've tried that and it doesn't work.

I think this was from maybe early to mid 2000, so issues around 90-95. The DVD for 92 is archived and has a REALBasic "how-to" example (Internet Call Cost Calculator) but none of the articles for the issues around that time seem to be archived.

Does anyone have this issue kicking around or have any memory of what I am on about?

 

[cheesestraws]

You changed the type to something like "APPE" (from "APPL") but I've tried that and it doesn't work.

It needs to be 'appe' in lowercase.

 

[aladds]

Ah so it does! Thankyou

I was so close, hah!

It's times like this that I am both amazed by my memory but annoyed that the details are so spotty. I am also sad that I didn't keep all of my old magazines. I do still have a good selection but many have been lost to time. I suppose I should try to archive what I do have!

 

[adespoton]

Ah so it does! Thankyou

I was so close, hah!

It's times like this that I am both amazed by my memory but annoyed that the details are so spotty. I am also sad that I didn't keep all of my old magazines. I do still have a good selection but many have been lost to time. I suppose I should try to archive what I do have!

A lot of them have been digitized online now. Oddly, Archive.org seems to have mostly the Spanish ones and not the UK ones (only a handful of those), despite having the full collection of the floppies/CDs.

 

[Snial]

Hang on, I thought system extensions were kernel-side things: device drivers with interrupt requirements etc. I am aware that classic Mac OS prior to System 7 didn’t have a kernel-side and even after don’t have protection, but I’d be surprised to learn an extension is just an app.

 

[aladds]

They're not really extensions so much as "background only applications" and since I now know what to search for this tech note does a much better job than I would ever manage: https://preterhuman.net/macstuff/technotes/tn/tn1070.html

 

[cheesestraws]

Hang on, I thought system extensions were kernel-side things: device drivers with interrupt requirements etc. I am aware that classic Mac OS prior to System 7 didn’t have a kernel-side and even after don’t have protection, but I’d be surprised to learn an extension is just an app.

Think 'daemon', not driver.

Remember, the term "extension" is really "something that adds functionality but doesn't have a UI", it doesn't represent a single kind of hook or entry point. When each thing is loaded and how depends, as usual, on its type. An 'appe' is a background-only application, which falls under the umbrella of "adds functionality but doesn't have a UI". In stock System 7, for example, the File Sharing Extension is actually an 'appe'.

'INIT' and friends ('scri' etc) are just blocks of code that are run during system startup and can patch things; they don't actually have much life other than 'a block of code that's run at a predictable point'. Anything else they want they have to wrest from the System's cold dead heap. They can load drivers, but they don't have to: my Force32 for example has no existence in the system after it's finished running.

Other stuff also got lumped into this semantic category, too...

 

[croissantking]

What would be a practical example of when converting an APPL into an appe would be useful/interesting?

 

[cheesestraws]

What would be a practical example of when converting an APPL into an appe would be useful/interesting?

An existing application? It's not very useful because 'appe's aren't allowed to have a user interface and IIRC will break if you try. It's most useful when you are building something that runs like an application (i.e. has an event loop, can get away with only running when the process manager is, etc) but you want it to just always run in the background and maybe be controlled by a preferences file or a control panel or something.

So, something like the File Sharing server or, say, a web server would be good candidates. I keep meaning to go and retrofit mac-minivnc to be able to work as an 'appe' but I haven't been motivated enough to do so yet.

 

[adespoton]

An existing application? It's not very useful because 'appe's aren't allowed to have a user interface and IIRC will break if you try. It's most useful when you are building something that runs like an application (i.e. has an event loop, can get away with only running when the process manager is, etc) but you want it to just always run in the background and maybe be controlled by a preferences file or a control panel or something.

So, something like the File Sharing server or, say, a web server would be good candidates. I keep meaning to go and retrofit mac-minivnc to be able to work as an 'appe' but I haven't been motivated enough to do so yet.

Something I've done is created two VNC server apps... one as appl and one as appe. The appe one goes in my Startup Items folder, and if I need to edit the settings, I use the appl one.

IIRC, There's at least one screen saver app that works this way too (Dark Side?). Pretty much anything where you don't need to patch the kernel or the toolbox but do want to run code in the background can be run as an appe.

There's a number of apps that have a UI where I've just changed the type to appe and it runs perfectly fine without displaying anything on-screen. Then I use Peek-A-Boo 1.6 to quit the app if I want it to stop running.