how to change background picture using a button?

[Tzela Yaish]

I have a button to switch between dark and light mode, but I also have a background picture and not a default background color.

How do I change the background picture in click of button? 

thank you !

[Soren Bjornstad]

How about this:

<$button set="$:/themes/tiddlywiki/vanilla/settings/backgroundimage" setTo="FirstImageTiddler">

    Image 1

</$button>

<$button set="$:/themes/tiddlywiki/vanilla/settings/backgroundimage" setTo="SecondImageTiddler">

    Image 2

</$button>

If you want an action widget instead because you want to be able to do multiple actions on the same widget, you could instead use an $action-setfield widget, like:

\define setAction(imageName) <$action-setfield $tiddler="$:/themes/tiddlywiki/vanilla/settings/backgroundimage" text="""$imageName$"""/>

<$button actions=<<setAction "FirstImageTiddler">>>

    Image 1

</$button>