Description Florian Priester 2005-11-27 16:42:50 EST

SWT N20051127-0010

In my application I use StyledTexts (SWT.MULTI | SWT.WRAP) whose size
is set dynamically to always fit the text contained in the widget.
In other words, if text is set or entered for which there is not enough
room, the bounds of the StyledText will be changed to make it bigger.
Scrolling, if needed, happens at the level of the parent composite
(a kind of scrolled composite), moving the StyledText itself along with
other controls.

In order for this scenario to work, it is important that the StyledText
never attempt to scroll "inside itself" like it does when used as a
regular editor. Instead, the top/horizontal pixel must always be (0,0).

To achieve this, I found that in previous versions of StyledText
it was sufficient to create a subclass that overrode the method
Canvas#scroll and set it to do nothing. Due to the recent rewrite
of StyledText.java, this no longer works. After some failed attempts
to solve the problem by calling setTopPixel(0) and setRedraw(false/true)
in the right places, I'm currently using a subclass that also overrides
StyledText#scrollVertical as a new workaround.

This approach has a few problems:
  - As before, StyledText needs to be subclassed, something which
    is discouraged and which I would rather avoid
  - Since scrollVertical is package-private, I can only override it
    by moving my subclass into the org.eclipse.swt.custom package
    where it does not really belong because it is not part of SWT
  - Most importantly, the workaround relies on internal details
    that may change at any time. The method scrollVertical might be
    renamed or made private, and code that invokes scrolling could
    also appear in other methods anywhere in the StyledText

For this reason it would be extremely helpful if the StyledText widget
directly supported a static, non-scrolling mode. In Swing terms, the
behaviour would be like that of a JEditorPane that has not been put
inside a JViewport/JScrollPane.

The desired option could be controlled by a simple parameter, perhaps
something like setScrollable(boolean). If set to false, this would
prevent the StyledText from ever changing the viewport origin
(that is, the top/horizontal pixel) or calling Canvas#scroll.

Thanks in advance for considering this request. (And also thanks for
continuing to improve StyledText, as in bug 83405!)