[feature request] add interface support to CSS class processor

[derstruct]

It would be great to allow custom CSS class providers

Currently it supports multiple concrete types, including []CSSClass where CSSClass is an interface with ClassName() string func.

Probably the easiest way to go is to add CSSClass support itself here:

runtime.go: 122

func (cp *cssProcessor) Add(item any) {
	switch c := item.(type) {
	/* ... */
	case []CSSClass:
		for _, item := range c {
			cp.Add(item)
		}
	case func() CSSClass: 
		cp.AddClassName(c().ClassName(), true)
	case CSSClass: // <---------------------
		cp.AddClassName(c.ClassName(), true)
	default:
		cp.AddClassName(unknownTypeClassName, true)
	}
}

Thanks.

[derstruct]

I wrote tailwind DSL compiler that makes tailwind usable with templ / .

It would more ergonomic if instead of:

<button class={ UI.Button.Primary.Class() }>Click</button>

You can just:

<button class={ UI.Button.Primary }>Click</button>

[joerdav]

I'm not sure I understand the friction on this, sorry. Can UI.Button.Primary not just be a string? Or a slice of strings?

[derstruct]

It can't, access to specific style set is done by navigating object propertiesUI.Button.Primary
UI has Button field, and Button has Primary field. Primary could have .Small variant (UI.Button.Primary.Small) for example and UI.Button could have styles itself for the base button design.
I could make navigation via Methods, but templ expects concrete string type (in fact 11 concrete types in total). Having an interface option is very useful (like templ.Attributer for attributes is already there - nice design).

[joerdav]

In that case, I think it makes sense for us to accept CSSClass as you suggest. We already support it as a slice type, a single CSSClass makes sense to be acceptable.