Spacebar scrolls the scrollpane

[IMurdocI]

Hello,

I'm using the the CodeEditor as an editabele object on Pane that is inside a scrollpane. (see it like a TextField in MS Word).

I have the issue, that when pressing the spacebar inside the CodeEditor, my Scrollpane scrolls down, without me adding any code that may change the vvalue of the scrollpane!

[TomasMikula]

Hi! Does it also add a space to the editor or not?

[IMurdocI]

hey,
Yes, space is also added to the Editor!

[TomasMikula]

Thanks. Scroll by spacebar is probably the desired behavior of the ScrollPane. The problem probably is that the event is not consumed by the CodeArea. There are a two events fired when a character key is pressed: KEY_PRESSED and KEY_TYPED. CodeArea handles the KEY_TYPED event and inserts a space character, but does not handle the KEY_PRESSED event, so it propagates up and is handled by the ScrollPane as a command to scroll down. This is an interesting problem that questions the design of key handling in JavaFX.

Luckily for you, there is a simple workaround: you can add an event handler to CodeArea that consumes the KEY_PRESSED event for space:

codeArea.addEventHandler(KeyEvent.KEY_PRESSED, event -> {
    if(event.getCode() == KeyCode.SPACE) {
        event.consume();
    }
});

[IMurdocI]

great, thank you very much for the help.
Should have thought of the event.consume myself.

[TomasMikula]

Seems like I can solve this in RichTextFX, by checking whether a KEY_PRESSED event isLetterKey(), isDigitKey() or isWhitespaceKey() and only consume it in that case, otherwise let it bubble up. I will leave this open so that I don't forget about it.

[TomasMikula]

I'm not sure whether that will work for characters like .,:;+-=_(){}[]\/?!@#$%^&*~, but should be useful anyway.

[IMurdocI]

by just consuming the event only when spacebar is pressed (as you mentioned in your second post) everything works fine, all characters and whitespaces (space/tab)!

[TomasMikula]

Thanks for confirming.

It is not a general solution, though, because the problem would re-appear for someone who puts a CodeArea as a child of a node that, for example, uses KEY_PRESSED handler on Z or any other character. CodeArea handles KEY_TYPED for Z, but not KEY_PRESSED for Z.

[TomasMikula]

My proposed more general solution would work for letters (A-Z), digits (0-9) and whitespace characters, but not for other special characters as mentioned above.

[IMurdocI]

okay, seems like a good start solution!

[TomasMikula]

I asked about a general solution on the JavaFX mailing list, with no answer so far, so I proceeded with a fix the way I proposed above.