FYI this needs to be done after most of the "redesign" pull requests are merged to avoid any conflict.

Just to clarify. In this issue can we move @theme-color-background and @theme-color-code-background to the not API file and let the colours default to @color-silver-l30 and @color-silver-l95? Or remove the new variables and replace @theme-color-background with @color-silver-l30 and @theme-color-code-background with @color-silver-l95 (that's how we usually do it currently, but can be changed if needed)

Did you mean @theme-color-code instead of @theme-color-background in your comment? @theme-color-background is themable right?

I meant where we currently use that variable in a less file instead of

color: @theme-color-code-background

we could use

color: @color-silver-l95

and remove the code less variable. That's how it's usually done currently in several places.

Alternatively we could at least do

@theme-color-code-background: @color-silver-l95

Same with the other variable.

Different topic but can be maybe done in this issue as well: In general I would only put those variables in the basic.less or simple.less or whatever:

@theme-fontFamily-base: Verdana, sans-serif;
@theme-color-brand:                    @color-red-piwik;
@theme-color-brand-contrast:           @color-white;
@theme-color-text:                     @color-black-piwik;
@theme-color-text-light:               #444;
@theme-color-text-lighter:             @color-silver-l40;
@theme-color-link:                     @color-blue-piwik;

@theme-color-menu-contrast-text: @theme-color-text-lighter;
@theme-color-menu-contrast-textActive: @theme-color-text;
@theme-color-menu-contrast-background: @theme-color-background-tinyContrast;
@theme-color-widget-title-text: @theme-color-text;
@theme-color-widget-title-background: @theme-color-background-tinyContrast;

This will make it much easier and less frustrating for plugin developers since those variables don't really impact other things that one need to change.
Eg I would remove all the background color variables in general (or move it to advanced.less). Once one starts to change the background color one kinda has to change so many other things to not make it look weird. It's a lot of work and quite hard. For example theming the background color and colors of the Map and some graphs become very hard, icons still have a white background (refs #7618). Meaning if we don't allow to change background color or put it in advanced, needing to change the code thing is basically not needed.

But the background color is the only thing we know is customized (the two currently published themes). If we speak only of what we know, then removing it wouldn't be such a good idea.

It'd put it in a advanced.less or so. Most companies that use theming do very likely not change the background color but only adjust like the widget header, brand color, link color and maybe menu color to their CI. Such themes won't be public in the marketplace.

This will make it easier for developers to get started since they will have only a few options and those are easy and one shouldn't get frustrated with those as they are straight forward. Knowing that eg background-color is in eg a advanced.less will maybe developers make clear there will be more work and it won't be easy etc. Just an idea...

OK makes sense.

PR: #7951

Developer documentation updated.