Re: Input event reduction

[Stefan Salewski <mail ssalewski de>]

On Thu, 2017-03-30 at 11:10 +0200, Nicola Fontana wrote:
>  
>
> As said you can leverage the main loop and unroll yours, e.g.:
>
> gboolean my_idle_callback()
> {
>     gint n;
>     for (n = 0; n < 100; ++n) {
>         ...
>     }
>     return FALSE;
> }
>
> should become:
>
> gboolean my_unrolled_idle_callback()
> {
>     static gint n = 0;
>     ...
>     ++n;
>     return n < 100;
> }
>
> Depending on your use case, the above could or could not be
> possible.

Ah yes, that is an interesting idea.

> > So I have to go back to my initial idea -- create a thread which
> > gets a
> > message for each "changed" signal, and then calls an idle function
> > only
> > for the last message in the queue each. I have to use
> > gdk_threads_add_idle() then.
>
> This is probably the cleanest solution, although I don't
> understand why you would have to use gdk_threads_add_idle().

I think gdk_threads_add_idle() is the recommended way to update the GTK
GUI from inside a second thread. I am doing it in the current version
of the editor already for querying and displaying extended symbol
information, see https://github.com/ngtk3/NEd

Here is where gdk_threads_add_idle() was suggested:
https://developer.gnome.org/gdk3/stable/gdk3-Threads.html
"You can schedule work in the main thread safely from other threads by
using gdk_threads_add_idle() and gdk_threads_add_timeout()"

> > The task of that idle function in my current use case would be to
> > get
> > highlight syntax information from the IDE process called nimsuggest
> > and
> > then to apply the corresponding tags to gtksource textbuffer.
>
> IMO it is essential to split your code in two parts: (1) gathering
> the highlight information and (2) applying it to the textbuffer.

Yes, that was my thoughts too. It would imply some additional code, but
may be the best solution.

> (1) can be run entirely in the working thread (hence non-blocking)
> while (2) must be implemented as a callback to be run in the GTK+
> thread. I cannot believe (2) takes tenths of second.
>
> When you are ready from (1) you can spawn the idle callback with
> g_source_attach()... no needs for gdk_threads_add_idle(). In the
> following StackOverflow answer I provided an example in C:
>
> http://stackoverflow.com/questions/27950493/safety-of-using-pthreads-
> in-gtk2-0-application#27990662

Thanks for that suggestion, I will look at the stackoverflow example.
And indeed, applying the text tags to the gtksource buffer is finally
the only critical part. I dont know how fast that really is, I would
assume that it takes less than 50 ms, what would be fine. If it really
is slow, I may split it in multiple parts/calls.