Starting module tasks

As some will know, I’ve developed a TaskRunner module. Mainly to support running subprocesses in python but it could be useful elsewhere too. I have been updating it (mainly to not soak up CPU) and trying to get it in order for a release.

However, I’m not totally clear how you should start a module task, other than by double-clicking on the module. In the case of Python, I can’t “just” *RMRun it, and *RMLoad will load the module but not start the wimp task. I’ve added a Desktop_TaskRunner command to do that, so the sequence would be something to decide if the module needs loading, if it does *RMLoad it then *WimpTask Desktop_TaskRunner.

Is this the “right way” or is there a better one? I don’t want to insist on the module being there and check load it in !Run – you can run python without it if you don’t use subprocess. I’d therefore like to load it when subprocess is imported.

I’ve seen you mention TaskRunner before. What does it do?

It’s a way to run things using TaskWindow (the module, not the actual windows provided by an editor) and control it from a SWI interface. This allows the parent task to be running in a task window (in the more usual sense). It was created to support Python’s ‘subprocess’ (with limitations).

Neat

The way I prefer to do it is via TaskManager_StartTask. You can call it in your module’s init routine.

Issues:

• The task will only start on the next Wimp_Poll call (or thereabouts), so anything which needs to interact with the task immediately will fail.
• It’s only available on more recent versions of RISC OS (I think I’ve seen RISC OS 3.8 mentioned somewhere – so in practical terms, 4, 5 and 6).

Is that the same as doing *StartDesktopTask?

@Jeffray – Thanks -that seems much neater.

I think I can live with those limits:

The SWI interface side can queue up things until the task has started. Obviously it won’t start running unitl later, but “created but not running” is a valid state.

I can’t see anyone using python3 on RISC OS 3.x systems, it’s apparntly slow on an Iyonix so who knows what it’d be like on anything older.

I assume convention would be the command is “Desktop_TaskRunner” ?

Is that the same as doing *StartDesktopTask?

Yes (*StartDesktopTask is just a wrapper around TaskManager_StartTask)

I assume convention would be the command is “Desktop_TaskRunner” ?

Yes. Although if a module doesn’t need to do anything special I guess there’s no reason why it can’t just tell TaskManager_StartTask to “RMRun MyModule” directly.

Chris, please can you make sure it uses Wimp_PollIdle before release, chewing half a million null polls a second is not helpful.

Chris, please can you make sure it uses Wimp_PollIdle before release, chewing half a million null polls a second is not helpful.

I’m actually using a poll word now to get around that problem. The main reason for the release is to fix the null poll CPU soaking.