[news.eclipse.platform.swt] Re: Bug in Text.setSelection?

[Doug Pearson <doug-list@xxxxxxxxxxxxxx>]

In my case, the text window is read-only, so this isn't a problem.

However, doing what you suggest in an editable control should work fine. 
 Incoming text would continue to be added below as they typed 
away--inserting their keystrokes higher up in the window.

Doug

Bob Foster wrote:

> And what happens when the user sets the caret one character before the 
> end of the visible text and types two characters?
>
> Bob
>
> Doug Pearson wrote:
>
> > Hi Steve,
> >
> > I tried your suggestion and indeed you are correct sir -- the control 
> > scrolls anyway, so changing the API would have no effect (at least on 
> > Windows).
> >
> > Fortunately, in tinkering I found a workaround.  Turning off redraw 
> > while moving the selection prevents the scroll from happening.  It 
> > does result in a flicker (as the control is repainted when turning 
> > redraw back on) but at least the functionality is there.
> >
> > Thanks for your input,
> >
> > Doug
> >
> > Steve Northover wrote:
> >
> > > All of the setSelection() methods in SWT, in addition to setting the
> > > selection, scroll or do whatever work is necessary to bring the 
> > > selection to
> > > the attention of the user.  So, to get what you want would requre new 
> > > API.
> > > However, I believe that (due to a bug in Windows), the EM_SCROLLCARET 
> > > is not
> > > necessary and that the text control will scroll anyways.  Try 
> > > commenting the
> > > line out and see if it doesn't scroll.
> > >
> > > "Doug Pearson" <doug-list@xxxxxxxxxxxxxx> wrote in message
> > > news:d9d85q$120$1@xxxxxxxxxxxxxxxxxxx
> > >
> > > > The code for the Text widget's set selection on Windows looks like 
> > > > this:
> > > >
> > > > public void setSelection (int start) {
> > > > checkWidget ();
> > > > if (OS.IsDBLocale) start = wcsToMbcsPos (start);
> > > > OS.SendMessage (handle, OS.EM_SETSEL, start, start);
> > > > OS.SendMessage (handle, OS.EM_SCROLLCARET, 0, 0);
> > > > }
> > > >
> > > > I'm looking to implement a common pattern with a text widget, where if
> > > > the user has set the caret to a position other than the end of the
> > > > widget the window doesn't scroll as new text is added.
> > > >
> > > > The underlying control supports this but because of the call to
> > > > "EM_SCROLLCARET" in this method I don't think it's possible to 
> > > > implement
> > > > this in SWT.  (You need to move the selection to add text to the end of
> > > > the control and then move it back).
> > > >
> > > > This scroll caret call seems clearly unnecessary as there's a separate
> > > > showSelection() method:
> > > >
> > > > public void showSelection () {
> > > > checkWidget ();
> > > > OS.SendMessage (handle, OS.EM_SCROLLCARET, 0, 0);
> > > > }
> > > >
> > > > so if you want the scroll behavior you can call this method.
> > > >
> > > > So my question is simple: is there any reason not to treat this as a 
> > > > bug
> > > > or shall I go ahead and write it up?
> > > >
> > > > Thanks,
> > > >
> > > > Doug