[Sitemap] Add optional conditional rules for icon

[lolodomo]

This allows dynamic icons based on items states even with non OH icon sources.
This also allows overwritting the default handling with state done by the icon servlet.

Example: icon=[item1>0=temperature,==0=material:settings,f7:house]

Related to openhab/openhab-webui#1938

Closes #1046

Signed-off-by: Laurent Garnier lg.hc@free.fr

[lolodomo]

Please note that this enhancement of the sitemap syntax remains fully backward compatible.

@openhab/android-maintainers
@openhab/ios-maintainers

The boolean staticIcon returned by the sitemap REST API will tell you if you have to use or not the item state when requesting the icon.
The SSE event will contain 2 new fields: icon and reloadIcon. icon will contain the icon reference, this field was already existing but was never set by the server until this change. reloadIcon (boolean) will tell if you have to reload or not the icon.

[maniac103]

And when receiving SSE updates, either the icon field is filled and you must reload the icon, or it is null and you must not reload the icon.

I'd rather want to see 'null means no icon' in SSE events as well. Otherwise there's ambiguity between 'null means no icon' and 'null means no change'.

[lolodomo]

And when receiving SSE updates, either the icon field is filled and you must reload the icon, or it is null and you must not reload the icon.

I'd rather want to see 'null means no icon' in SSE events as well. Otherwise there's ambiguity between 'null means no icon' and 'null means no change'.

In that case, an additional boolean field would be required to indicate if the icon must be reloaded or not. I can call it reloadIcon. Is it ok for you ?

[maniac103]

It's fine as far as I am concerned. The Android app doesn't need it either way since the OkHttp layer uses the URL (built from icon, state etc.) as caching key, so if there's no change in the parameters used for building the URL, no reload will happen.

[lolodomo]

Changes done, I have updated my second message.

[kaikreuzer]

lgtm, thanks.