[news.eclipse.platform.swt] Re: VerifyListener problem

[Eric Rizzo <eclipse-news@xxxxxxxxxxxx>]

Derek R. wrote:
> Hi all,
>
> First off, my goal is to have a Text Widget that only contains uppercase 
> input, regardless of whether shift is held or caps lock is on.  Since I 
> have not found anyway of doing this using a style bit, I am doing so 
> using the VerifyListener below (please let me know if there is a proper 
> way of telling a Text Widget to convert all input to uppercase!!):
>
> VerifyListener verifyListener = new VerifyListener()
> {
>     public void verifyText(VerifyEvent e)
>     {
>          e.text = e.text.toUpperCase();
>     }
> };
>
> Anyway, the issue I am seeing with adding a verifyListener to a Text 
> Widget is that shift+backspace does not perform a backspace for some 
> reason, as it does when the verifyListener is not added to the Text 
> Widget.  I don't believe this has anything to do with the uppercase line 
> because the same thing happens with an empty verifyText method.  Is this 
> a known issue?  Does anyone have a solution for this?

Your listener needs to be a little intelligent about how it handles the 
event; depending on how the text is modifies (single keystroke, Paste 
action, programmatic, etc) the event's fields will be populated differently.
The best thing I did was set up a simple VerifyListener and put a 
breakpoint in it so I could try different ways of modifying the text and 
inspect the resulting event. As an example, here is a verifyText() that 
I use:

public void verifyText(VerifyEvent event) {
	// Allow Delete and Backspace keys to pass through:
	if (event.keyCode == SWT.DEL || event.keyCode == SWT.BS) {
		return;
	}

	// If this is not a single keystroke, validate the entire text
	if (event.keyCode == 0) {
		event.doit = matches(event.text);
	} else {
	// Otherwise only validate the typed character:
		event.doit = matches(event.character);
	}
}


Hope this helps,
	Eric