After recent change, labels and the text from text update widgets disappear

[kasemir]

After a recent change, labels and textupdate widgets have their text disappear because their foreground color turns transparent .

[kasemir]

The problem is somehow related to the change in JFXRepresentation from #3887.

When I disable the updateBackground() change, labels show up fine.
As JFXRepresentation.updateBackground () is written in #3887, labels and text update use transparent foreground colors.

[kasemir]

It comes down to this one line from the JFXRepresentation change in #3887

phoebus/app/display/representation-javafx/src/main/java/org/csstudio/display/builder/representation/javafx/JFXRepresentation.java

Lines 964 to 965 in 51a9bf6

	// Now make the scroll pane transparent to see the parent background
	model_root.setStyle("-fx-background: transparent; -fx-background-color: transparent; ");

// Now make the scroll pane transparent to see the parent background
model_root.setStyle("-fx-background: transparent; -fx-background-color: transparent; ");

With setStyle ... transparent, the text in labels and text update widgets becomes transparent as shown in the screenshot above or here:

When I comment that line, the text shows up as expected:

[rjwills28]

@kasemir - thanks for catching this! I was wondering why I hadn't seen this as I did a significant amount of testing. It turns out I had tested that my PR fixed the scroll bar issues in both JFX21 and JFX25, BUT my tests on how it affected the widgets was done on JFX 25 only.

This issue is not there with JFX25, that is to say that the foreground text does render correctly and is not invisible. That's my bad for not fully testing it against JFX21 - sorry. How do we want to proceed - revert the commits until Phoebus moves to JFX25 - how far away from that are we?

[kasemir]

This issue is not there with JFX25

Good! I can wait 1-2 weeks, for now I've pointed our Jenkins to the last git hash before this change.

Do you understand what's going on? Is the style sheet handling in JFX21 simply broken?
Or are we just lucky that the updateBackground() changes happen to work with JFX25, and they might again break with JFX26?

[rjwills28]

If I understand correctly I think it relates to this bug: https://bugs.openjdk.org/browse/JDK-8336097, which was fixed in JFX24. It relates to the priority of styles and what can override what, (see also https://bugs.openjdk.org/browse/JDK-8317434 which is related).

I have just tested against JFX26 as well for good measure and there are no problems with invisible labels.

[kasemir]

From that it looks like you're doing the right thing, the problem is in JFX21.
Since you're not doing anything wrong, I'd hate to revert.
On the other hand this does mean that people who do "git clone.. mvn .. run" right now get a broken display.

[rjwills28]

The other option might be to put in a 'quick fix' now for JFX21 and make a note to revert that once we've moved to JFX25?

We can work round the bug by setting the foreground color using inline CSS, which has the highest priority in terms of CSS. That would look like:

label.setStyle("-fx-text-fill: "+JFXUtil.webHex(model_widget.propForegroundColor().getValue()));

We'd have to do that in both TextUpdateRepresentation and LabelRepresentation.

[kasemir]

I like that, with a // TODO Remove .... comment, so the main branch will again run without this issue