Make themes a first-class concept in JavaFX

[Michael Strauß]

Maybe others will chime in regarding the thin vs. rich API discussion.

Regarding the extensibility of themes:

If Modena and Caspian were public API, you could extend those themes
simply by subclassing:

public class CustomTheme extends Modena {
    private final ObservableList<String> allStylesheets =
            FXCollections.observableArrayList();

    private final ObservableList<String> customStylesheets =
            FXCollections.observableArrayList();

    public CustomTheme(Map<String, String> properties) {
        super(properties);

        // Add custom stylesheets here
        customStylesheets.add("com/example/custom.css");

        // Combine with Modena stylesheets
        allStylesheets = new ListBinding<>() {
           {  bind(super.getStylesheets(), customStylesheets); }

           @Override
           protected ObservableList<String> computeValue() {
               return FXCollections.concat(
                   super.getStylesheets(), customStylesheets);
           }
        };
    }

    @Override
    public ObservableList<String> getStylesheets() {
        return allStylesheets;
    }
}



Am Di., 25. Mai 2021 um 13:06 Uhr schrieb Pedro Duque Vieira
<pedro.duquevieira at gmail.com>:
>
> Again thanks for bringing this up into discussion and for taking the time to file a PR, etc. I like the idea of having better support for themes.
>
> Regarding your first point:
> 1 - To keep it simple we can discard the idea of having an API to be able to check what are the OS settings for dark/light, accent color, etc, for now. I think that this can be a separate discussion.
> We could simply start by having an API that a theme has to implement (probably an interface that the theme has to implement like what I think happens with your proposed API). That API has properties: dark/light style, accent color, etc. Each theme can decide to respond or not to changes in those properties hence decide whether or not to support these features.
>
> Regarding the second point:
> 2 - Not sure I explained myself well.
> What I meant was that right now, and it happens to all themes I know of, theme creators decide to extend the Modena theme. What I mean by "extend" is that they add stylesheets to the Scene/Parent (without being user agent stylesheets). This means they simply build on top of the rules in Modena which is much easier/better but also means that the rules they define in their stylesheets will trump any rules defined by the theme users in their FXMLs, stylesheets (depending on specificity of their rules in their stylesheets), code...
> I think this can be confusing and not ideal for users of these themes, and I find most of the time theme users don't even know about JavaFX user agent stylesheets feature vs Scene/Parent stylesheets and what that implies.
> What I would propose is to have an API, perhaps in this theme interface, that toggles whether the theme, theme creators are creating will be a user agent stylesheet or a regular stylesheet. The advantage would be that if it is a user agent stylesheet developers won't need to copy all Modena definitions into their theme stylesheets, they can simply toggle this boolean to say what kind of stylesheet they want their theme to be.
>
> Thanks,