Thanks Philip,
meanwhile I've solved the problem so now async operations such
`require("fs").readFile("./test.js", (err, data) =>
console.log(data.toString()))` will never exit the program until the
asynchronous file read is completed.
How? Basically explicitly defining when an async operation should call
`mainloop.wait();` before executing:
https://github.com/WebReflection/jsgtk/blob/master/jsgtk_modules/jsgtk/mainloop.js
Works for `fs.stat` so far, as example, but it works for other cases too:
https://github.com/WebReflection/jsgtk/blob/master/jsgtk_modules/fs.js#L175-L187
Best Regards
On Sat, Apr 9, 2016 at 10:18 PM, <philip.chime...@gmail.com> wrote:
> On Thu, Mar 31, 2016 at 11:10 AM Andrea Giammarchi <
> andrea.giammar...@gmail.com> wrote:
>
>> I'm trying to figure out if there's a way to avoid GJS exiting when there
>> are operations going on, like a watch on a file, or folder, without
>> bothering the main Gtk loop or `imports.mainloop.run()`
>>
>
> Not sure I understand the question entirely, but I don't think you are
> supposed to be able to get access to main loop objects that you didn't
> create yourself. Even the GTK main loop will let you start or quit it, but
> it won't give you access to the main loop object itself.
>
> What I'd really like to do, is to understand if any other part of the code
>> started already a loop but I cannot find a way to reach
>> `g_main_loop_is_running()` via GJS and using `null` to receive the context,
>> when I should also pass the value `isRunning` makes little sense to me ...
>> 'cause I don't know upfront if I want the default context flagged as
>> running or not.
>>
>
> That is indeed a silly API, I don't know why that parameter is there.
>
> Depending on what you are trying to do, you _may_ be able to use
> GLib.MainContext.default().pending() to see if there are any events pending
> in the default context.
>
> But I think you are better off explicitly starting a main loop and
> explicitly exiting it when all your operations are done.
>
> The `Gtk.main_level()` gives me 0 even if `imports.mainloop.run()` has
>> never been called, and it gives me 1 or more even if a `Gtk.main_quit()`
>> has been invoked after.
>>
>> Registering a callback in the mainloop also doesn't prevent GJS from
>> exiting before it's triggered.
>>
>> I've tried to use `Gio.Application` with a dummy listener and using
>> `app.hold()` but the moment I follow that command by `app.run([])` nothing
>> after happens, so I can't set this thing up as it unless I do it after
>> another event has been scheduled.
>>
>> This makes sense because `hold` and `release` are explicit in their
>> intent, but I feel like there's no way to do what I'm trying to do.
>>
>> Let's say this is my `gjs-info` program
>>
>> ```gjs
>> #!/usr/bin/env gjs
>> const Gio = imports.gi.Gio;
>> let fd = Gio.File.new_for_path(ARGV[0]);
>> fd.query_info_async('*', Gio.FileQueryInfoFlags.NOFOLLOW_SYMLINKS, null,
>> null, (source, result) => {
>> let info = source.query_info_finish(result);
>> print(info);
>> });
>>
>> // if I write this, it will hang
>> // if I don't, it will exit
>> // imports.mainloop.run();
>> ```
>>
>> considering this is an example and what I'm trying to do has many nested
>> asynchronous operations and not just one, how could I prevent GJS from
>> exiting the program before I have results?
>>
>> Thanks for any sort of hint/outcome.
>>
>
> In this example, I would simply run the operation synchronously. But you
> say that you have many async operations. Are they run serially or in
> parallel? If serial, then I would still switch to sync.
>
> If parallel, you could very easily implement something like hold/release:
>
> let pendingOperations = 0;
> let allOperationsStarted = false;
> myInputs.forEach(input => {
> pendingOperations++;
> input.my_operation_async((obj, res) => {
> pendingOperations--;
> obj.my_operation_finish(res);
> if (pendingOperations === 0 && allOperationsStarted)
> Mainloop.quit();
> });
> });
> allOperationsStarted = true;
> Mainloop.run();
>
> This is kind of the continuation-passing equivalent of Promise.all().
>
> Best regards,
> Philip
>
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