On Jun 18, 2013, at 3:54 PM, Mario Torre <[email protected]> wrote:
> Hi all!
>
> I was trying to figure out how JavaFX parses and uses the style under
> the hood and I stumbled on something I don't fully understand (I admit
> I'm not really a CSS expert yet :).
>
> In the modena.css, right at the .root selector we have:
>
> /* These are needed for Popup */
> -fx-background-color: inherit;
> -fx-background-radius: inherit;
> -fx-background-insets: inherit;
> -fx-padding: inherit;
>
> and then, few lines below:
>
> -fx-background-color: -fx-background;
>
> Is this intentional? How does JavaFX understand which value to choose?
I've got a sticky note on my desk reminding me to take a look at those
"inherit" lines. They were needed at one point in time, but I'm not sure they
are needed now. I guess I should enter that sticky note into JIRA!
>
> It seems (but I'm far from discovering the trick) that both values are
> preserved, but how does the system know which one to use?
CSS uses cascade rules to determine which to use. In the case of
-fx-background-color, the second declaration will be used. In the modena theme,
if the root node of the scene is a Region, then the background-color of the
Region will be whatever -fx-background is.
>
> I assume that "inherit" is what is doing the magic here, probably by
> delegating to the closest matching declaration, but it's still not clear
> to me how everything is resolved.
In the case of the others (radius, insets, padding), if the root node is a
Region, then css will try to find a parent with that style. This doesn't do
much in the case of the root of a Scene since the root node doesn't have a
parent. In the case of a popup, the parent of the root can be considered to be
the ownerNode and these styles are intended to make it such that the
background-radius, fill, insets and padding of the popup match those of the
ownerNode (if there is one). That is the intention, but whether these actually
work, I can't say for certain. And whether they are actually needed is another
question.
>
> Also, is there a way to retrive fully resolved values? I would like
> something like this, basically:
>
> Button.getStyle("-fx-backgroud-color").getValue();
>
> Or such.
There is, but not through public API. You can call List<Style>
Node.impl_getMatchingStyles(CssMetaData cssMetaData, Styleable styleable). For
example
Button button = new Button("Button");
CssMetaData fillMetaData =
((StyleableProperty)button.fillProperty).getCssMetaData();
List<Style> styles = Node.impl_getMatchingStyles(fillMetaData, button);
This is the API that SceneBuilder uses and has a JIRA against it to make it (or
something similar) public.
>
> I found a way to match declared styles and basically get a StyleMap, but
> this uses internal API I wanted to check if I'm missing some obvious
> way, perhaps?
>
> Cheers,
> Mario
>
>
