Re: A simple GtkSpinner is very costly in CPU cycles

[Kian Karas <kian karas dev gmail com>]

On Wed, Mar 21, 2018 at 10:17 AM, Emmanuele Bassi <ebassi gmail com> wrote:

> On 20 March 2018 at 14:06, Kian Karas <kian karas dev gmail com> wrote:
>
> > Hi smart people
> >
> > I just introduced animation, in the form of a GtkSpinner, to my
> > application
> > for the first time. When the spinner is animating, the application takes
> > up
> > 45 % of the CPU resources (the application is otherwise idle at 0-2,6 %).
> > The CPU is a single core ARM Cortex-A7 running at 528 MHz (maximum).
> >
> > This seems like a lot of MIPS for rotating an image of approximately 20x20
> > px.
> The rotation is performed through CSS, in order to be stylable by themes;
> this means that the CSS state has to be invalidated in order to recompute
> the next frame, and this is there the cost lies.
>
> Of course, 45% is a pretty big chunk of a core, so it's indeed problematic
> on single core, low performance devices. It's going to be the case for
> every animation involving CSS, though, so you may elect to either disable
> animations on your platform, or use a static placeholder image. There's
> also the option of using a theme that does not have as many states for the
> spinner animation, thus causing fewer invalidations.
>
> I'm new to GTK (and CSS). Thus, I don't know the option you mention in
above last sentence. Do you know of a source where I can learn about doing
that? I mean, is there are tutorial touching on the spinner animation?

It's for an embedded system, so I do not need support for different themes.
Thus, unless I can figure out how to do above, I'll just make my own
progress indication using slower update of a GtkImage (cycling through
different images).

We are actively working to fix the issue on GTK 4, but changing the CSS
> subsystem has the potential of breaking GTK 3 applications, so it's not on
> the roadmap, outside of low impact optimizations.
>
> Ciao,
>  Emmanuele.
>
> --
> https://www.bassi.io
> [@] ebassi [@gmail.com]