Adjust CSS font size rule dynamically in JavaFX

Question

I have a JavaFX application. Some Tabs in a TabPane have a class "my-view", and inside there is a complex structure, featuring labels, textfields and so on. I have a CSS rule to set the font size on these sub-items like:

.my-view .label, .my-view .my-text-field-a, .my-view .my-text-field-b {
    -fx-font-size: 12px;
}

I want to allow the user to press Ctrl-+ to dynamically increase text size. What I really want is to be able to dynamically adjust the "12px" in the above CSS, dynamically. However, I can't see a way to do this in JavaFX. The setStyle method only allows setting the style for the current node, not a rule as above. The new JavaFX 8 StyleableProperty interface seems to go in the wrong direction for me -- it allows code to read but not write CSS properties. I don't really want to have to find all the relevant text fields myself in the code and call setFont; CSS rules seem like the right mechanism here.

The only way I can currently think to do it is to create a new class for each font size that I might want to set (a bit like suggested here: Hot to update dynamically font size) and then set the appropriate class to set the size, e.g.

.my-view-12 .label, .my-view-12 .my-text-field-a, .my-view-12 .my-text-field-b {
    -fx-font-size: 12px;
}

.my-view-14 .label, .my-view-14 .my-text-field-a, .my-view-14 .my-text-field-b {
    -fx-font-size: 14px;
}

I can autogenerate the CSS (for all font sizes say 1-100), but this method just seems like an ugly hack. Are there any better ways to do this in JavaFX?

Is everything with text displayed inside the tabs with class "my-view" using the same (changeable) font size? — James_D
– James_D, Commented May 22, 2014 at 11:04
At the moment, yes, though that might not remain the case (hence my use of the my-text-field-a classes rather than text-field). Is there an easier solution in that case? I did try playing with the "inherit" value for -fx-font-size but got a lot of errors spat out on the terminal. — Neil Brown
– Neil Brown, Commented May 22, 2014 at 11:16

James_D · Accepted Answer · 2014-05-22 11:39:07Z

3

If everything with text displayed under the nodes with "my-view" style class is going to use the same font, then you can just do

.my-view {
    -fx-font-size: 12 px ;
}

in the css file.

To update, choose some node that's an ancestor of all your nodes which have the "my-view" style class (it sounds like your tab pane will work, but in general you could just use the root node of the scene) and do

for (Node n: tabPane.lookupAll(".my-view")) {
    n.setStyle("-fx-font-size: "+fontSize+"px;");
}

You obviously need to keep track of the font size in the Java code, which is simple enough (just do it from the outset).

If only a subset of the text-displaying nodes are going to have their font sized changed, you will likely have to give them a style class of their own, then do a lookup for that specific style class, instead of "my-view".

answered May 22, 2014 at 11:39

James_D

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