I have a draft PR for this now. I'd appreciate some feedback, before I flesh this out completely (I'd need to add CSS documentation for example).
https://github.com/openjdk/jfx/pull/1714 --John On 11/02/2025 23:47, John Hendrikx wrote: > > Hi list, > > I've done a little proof of concept where I've made some minor > modifications to CssStyleHelper to allow the CSS engine to offer > styleable properties on children, but defined by the container class. > > What this means is that we can make it appear that direct children of > a container like GridPane, HBox and VBox have properties like: > `vgrow`, `hgrow`, `column-index`, `margin`, `halignment`, `fill-width` > etc. The exact names can be chosen by the container in question. For > example, I could style a child of an HBox like this: > > .text-field { > > -fx-background-color: yellow; > > -fx-hbox-hgrow: ALWAYS; > > -fx-hbox-margin: 5px; > > } > > This will make it possible to do far more visual styling directly in > CSS. As usual, unrecognized properties are ignored, so if you put > this text field in a VBox, nothing will happen. > > How does it work? > > - Containers that wish to add additional styleable properties to their > direct descendants implement this interface: > > publicinterfaceChildStyleProvider { > > List<CssMetaData<Styleable, ?>> getChildCssMetaData(Node child); > > } > > - The CssMetaData they provide for these properties looks like this > for example: > > newCssMetaData<>("-fx-hbox-hgrow", > StyleConverter.getEnumConverter(Priority.class)) { > > @Override > > publicbooleanisSettable(Styleable styleable) { > > returntrue; > > } > > @Override > > publicStyleableProperty<Priority> getStyleableProperty(Styleable > styleable) { > > returnChildStyleProvider.createProp(this, "hbox-hgrow", child); > > } > > } > > - A special StyleableProperty is created as the "receiver" of CSS > styling that will store the value in the Node#getProperties map (where > normally these values are already stored when using the static methods > like HBox.setHGrow(Node, Priority) type methods). This property is > cached as part of the same getProperties map, so it is only created once. > > - The CssStyleHelper will see if the parent of the Node being styled > implements ChildStyleProvider, and if so will also process these > additional CssMetaData properties when any are present; this seems to > be fairly safe to do, as changing a Node's parent will reset all its > styling already. Some more tests are needed here, if moving this forward. > > That is basically the change in a nutshell. Not only does setting a > property like `-fx-hbox-hgrow` on a child now act as if you called > `HBox.setHGrow`, changing the style of the child can also change these > settings and HBox will instantly respond to the change. When the > style is completely removed, it will also null the hgrow value which > is translated as removing that key from the Node#getProperties map. > > If people think this proposal has some merit, I can flesh it out > further and make it into a PR. > > --John > > > >
