Make themes a first-class concept in JavaFX

[Pedro Duque Vieira]

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,



On Mon, May 24, 2021 at 11:48 PM Michael Strauß <michaelstrau2 at gmail.com>
wrote:

> I can understand that parsing string values feels like a very
> lackluster API. But let me offer a counterpoint:
>
> If we provided a set of APIs that exposed particular OS concepts
> (light/dark mode, accent coloring, etc.), we would commit ourselves to
> supporting these APIs for new versions of all kinds of operating
> systems. We'd also need additional APIs to expose whether or not the
> particular concept is even available on the current OS. I think
> developers would then also expect us to keep track of the changing
> trends of OS design and keep offering up-to-date APIs for new features
> and design trends. That's a significant cost, considering that JavaFX
> currently doesn't even offer a theme that would need all these APIs
> (except for high contrast).
>
> On the other hand, assuming the proposed minimal `Theme` API, it would
> be pretty straightforward for a third-party library to implement
> `Theme` adapters that offer all of the first-class APIs that you
> discussed.
>
> As to you other point: in order to be able to extend the build-in
> themes, their theme implementations would need to be public API. In
> general I think that's okay, provided that the inner workings of the
> default themes remain a "black box".
>
>
>
> Am Mo., 24. Mai 2021 um 17:48 Uhr schrieb Pedro Duque Vieira
> <pedro.duquevieira at gmail.com>:
> >
> > Hi,
> >
> > I've been developing JMetro:
> https://pixelduke.com/java-javafx-theme-jmetro/
> > , it's a javafx I've been developing since 2013 when I have some free
> spare
> > time.
> >
> > I thought I'd chime in since this has been an interest of mine for quite
> > some time.
> >
> > A few issues I experience with the current JavaFX API:
> >
> > 1 - Like Michael said here, the current way all themes are usually
> > developed is to extend the default JavaFX theme (currently modena). This
> > has a few problems:
> > 1.1 - If you want it to be a user agent stylesheet you have to copy
> > everything from the default theme into your theme
> > 1.2 - If you're NOT going to go for it being an user agent stylesheet,
> you
> > simply add your theme "on top" of the default user agent stylesheet (e.g.
> > Modena) but this has a problem because now the rules of your theme will
> > have precedence over rules set through code (e.g. style rules in FXML,
> > style rules in code).. which can be unexpected from a user using the
> theme.
> >
> > 2 - There's no built-in support for new theme features existing in most
> > Operating Systems nowadays like: dark/light style, chosen accent color...
> >
> > ---
> >
> > I think adding an API to solve this is a good idea.
> > As a first comment and focusing only on the stuff I would change, I don't
> > particularly like the "void platformThemeChanged(Map<String, String>
> > properties);"
> > Namely the fact that we're using strings to identify properties like
> > whether we use dark or light style, etc. I would prefer as a developer to
> > not have to match strings, etc (which can be a problem if you misspell a
> > string and you'll only notice these problems during runtime).
> > I would like for there to be an API for the user to say whether he wants
> > the dark or light style, also for whether light or dark style is selected
> > in the OS itself. I would also like to have an API for selecting the
> accent
> > color and to know which accent color is set in the OS.
> > Potentially we could have javafx properties for each one of these, at
> least
> > for whether we want light or dark style and which accent color we're
> using.
> >
> > I would also like for there to be some API where one could say whether
> the
> > theme is supposed to be a user agent stylesheet or not. Allowing one to
> > build on top of the default theme stylesheet (Modena) without copying the
> > default theme definitions but still being able to say that you want your
> > custom theme to be a user agent stylesheet.
> >
> > I don't have much time right now to comment further on the API or give
> > precise suggestions (I'll probably have more time next week) but here's
> my
> > 2 cents.
> >
> > Thanks,
> >
> >
> >
> > --
> > Pedro Duque Vieira - https://www.pixelduke.com
>


-- 
Pedro Duque Vieira - https://www.pixelduke.com