Emscripten, webassembly/asm.js, and taskwarrior

[Mark Scannell]

Hello all --

I've been playing with taskwarrior source code and was thinking about how it'd be great if I could have taskwarrior with me everywhere. Particularly with a Chromebook.

I've been working with emscripten compiling taskwarrior into asm.js and have been successful so far. I have it running in the browser, synchronizing the in-memory files with Google Files, saving them to indexdb, and have a little interactive shell. (using hterm.js) I plan on releasing this as open source at some point. (My employer has a process.)

There's a lot of little nuances, of course, and have had to turn off all confirmation in taskwarrior (no working stdin).

So far I haven't had to make any changes to taskwarrior source code except one somewhat major one: the global context.

In the asm.js context, I use the main() function as if it was a library and keep calling it again and again. This causes issues with the global context being already-initialised.

My solution:
- Remove it as a global, and have a global "registry" of the current context.
- main() has its own context on its stack. It then registers this as the current context when it starts.
- All calls to context gets the "current context".

This has proved remarkably successful, including having all of the tests pass.

So my question:
Would taskwarrior entertain such a patch? Or a patch which would achieve a similar outcome? There may be other more elegant solutions, of course.

This is a bit off-the-wall I realize...

Thanks!
Mark

[Thomas Lauf]

Hi Mark,

sorry for the late answer, but can you provide a patch with the changes
you described? It would be easier for me to review your changes then.

Thanks
Thomas

[Mark Scannell]

Thomas,

I've attached the patch.

This is very much a proof of concept -- there are many ways to make this code simpler, more elegant, etc, but I wanted to see if I could make main() usefully re-entrant first. It seems to work. The main problem is that Context is a static global object, so if you treat main() like a library then it will have the constructor but never be destroyed.

If you could give me feedback on the approach of hosting the global context in the Context object as a static with getter/setters, and, if you're happy with that, I could look to make the accessing of context more elegant than just replacing "context" with "Context::getContext()" globally.

I couldn't figure out any other simpler way to manage the state of context as it appears everywhere.

Mark

[Thomas Lauf]

Hi Mark,

thanks for the patch. I will take a look at it as soon as I find time
for it. Thanks in advance for your patience.

Regards
Thomas

[Mark Scannell]

Thomas,

No rush at all. My day job and rest of life has taken over again!

Mark

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[scan...@google.com]

Thomas,

Any thoughts?

I'm looking for feedback on the general approach I've taken -- happy to adjust it to something different.

Mark

[Paul Beckingham]

Hi Mark,

I don’t know how I missed this entire thread. I apologize.

The goal is good, the approach is good, the patch will no longer apply, but that’s not a problem because it’s mostly just a big search/replace.

I will take your earlier patch, and do what I can with it, and see what happens. I’ll respond here.

Paul

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[Mark Scannell]

Paul,

No worries. Have a look and give me feedback. I'm happy to adapt to the latest source code, rename the search-and-replace, re-apply it, whatever. I just want to ensure any work I do goes in the direction of being a worthwhile patch.

Mark

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[Thomas Lauf]

Hi Mark

> Any thoughts?
> I'm looking for feedback on the general approach I've taken -- happy to adjust it to something different.

Sorry, your patch got buried under a lot of other things. I've seen that
Paul has taken over, so maybe he can inform me, when we meet next time :)

Regards

Thomas

[Paul Beckingham]

Sorry Thomas, did I take a fun toy away from you there?

I’ve taken Mark’s patch and munged/applied it to 2.6.0. I made a few more changes, because it was incomplete, and no, all the tests did not pass. The patch in general is a minor step backwards in readability (“context.” becomes “Context::getContext ().”) but for a nice gain. At this point I’m happy to merge my version of the patch.

Mark, will this satisfy all the emscripten needs?

Thanks,

P

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[Thomas Lauf]

> Sorry Thomas, did I take a fun toy away from you there?

Nope, somehow (don't ask me how) I thought it concerned TimeWarrior =)
Happy the patch found a home after all...

Thomas

[Mark Scannell]

Paul,

I compiled it and have been running it with just those changes. That should be sufficient.

There are some features that are incompatible with the web environment (eg stdin), but for everything like that so far I've been able to disable it using the normal configuration.

Mark

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