Created attachment 171008 [details] [review]
GnomeBG: Better support for slideshows with one slide

A slideshow with one slide can be useful to support multiple sizes for a
background image.

With only one slide, we do not have to timeout for transitions.

I consider that Ray is closer than me to what is a maintainer for GnomeBG, so I'll let Ray review this :-)

Well, Søren is gnome-bg-man-extraordinaire but he's a pretty busy guy, so I'll be happy to look at this patch for you.

Review of attachment 171008 [details] [review]:

Overall, the patch looks okay.  If you just want to commit this after the freeze, I think it's a nice win and probably won't cause any issues.

Looking in get_pixbuf_for_size, though, I see:

→       →       time_until_next_change = G_MAXUINT;•
...
→       →       →       →       time_until_next_change = (guint)get_slide_timeout (slide);•
...
→       →       /* If the next slideshow step is a long time away then•    
→       →          we blow away the expensive stuff (large pixbufs) from•  
→       →          the cache */•                                           
→       →       if (time_until_next_change > KEEP_EXPENSIVE_CACHE_SECS)•   
→       →           blow_expensive_caches_in_idle (bg);•                   

So, if there is an expensive cache, it might be nice to do away with it as well.  I think we can kill both birds with one stone.

In read_slideshow_file, it already examines the queue of slides to see if there are no slides.  It would be natural, then to add 1-slide check after the 0-slide check. If there's only one slide, then override that slide's duration to some sentinal that means "no timeout" (G_MAXUINT is sort of used for that in the above code, so that's probably a good value to use).  Then get_slide_timeout () would return that duration, and ensure_timeout (which also calls get_slide_timeout ()) would just need to refuse to queue a timeout if get_slide_timeout () returns "no timeout".

If you go this route, then you don't need to modify any of the callers of ensure_timeout and everything should "just work" including the cache blowing code I think.

The following fix has been pushed:
adf18a2 gnome-bg: Do not add timeout for one-slide slideshows

Created attachment 180458 [details] [review]
gnome-bg: Do not add timeout for one-slide slideshows

If a slideshow is made of only one slide, then there's no animation. So
we just override the duration of the slide to G_MAXUINT, and we do not
add timeouts for such durations.