Make themes a first-class concept in JavaFX

[Pedro Duque Vieira]

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

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