Currently the user is required to set a default refresh rate in Settings --> System --> Video Output, which is used for the UI when not playing a video. Then with the 'adjust display rate to match video' option enabled (for smooth playback), XBMC will generally need to switch the rate to match the video (unless it matches the UI setting) and will then switch back to whatever the UI is configured for.
However, it would be a useful option if stopping a video would simply display the UI in whatever refresh rate was last being used for playback, be it 24 hz / 50 hz / 60 hz, on the assumption that the next play of a stream is commonly the same refresh rate / format, to reduce the number of refresh rate switches the TV has to do.
e.g., I generally keep my UI set at 60 hz. If I'm watching TV channels they are broadcast in PAL so XBMC will keep switching back and forth from 60 to 50 whenever I start and stop a stream. Similarly if I'm gradually working through episodes from a Blu-ray TV series, XBMC will keep switching back and forth from 60 <--> 24 every time I finish one episode before I start the next.
How do you intend to switch refresh rate back?
I agree, there is room for improvement. I thought about an option for an indicator which suggests ideal refresh rate. Then the user can accept by pressing a button.
If XBMC is running in standalone or fullscreen why would you ever need to switch the refresh rate "back" until they quit XBMC? The UI will happily display at whatever refresh rate you've left it in. The only reason to change it again would be if the user switched to playing music with visualization or something like that?
Alternatively, I guess you could sort of do what you suggest and
1) always switch to target refresh rate when starting video playback
2) when playback is stopped, display a popup offering a choice of staying in the current refresh rate or returning to the system/ui refresh rate
However, I'm not sure why you would ever want to answer "Yes" to the second question :)
The UI is not very responsive when running on 24Hz and animations don't work well either. The majority of users won't accept this.
@FernetMenta sure I wouldn't expect it to become a default, it would be opt-in, but confluence at least is perfectly fine at 24Hz for me - and far preferable to having to suffer a ~6 seconds wait between playing two videos of the same framerate just because XBMC switches to the UI refresh rate and immediately back again.