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Removing messages from MessageManager may throw Exception [message #1791757]

Wed, 04 July 2018 21:08

Chris Fairhall

Messages: 221
Registered: February 2011

Senior Member

I've just seen an exception in my test environment

org.eclipse.swt.SWTException: Widget is disposed
	at org.eclipse.swt.SWT.error(SWT.java:3708) ~[org.eclipse.rap.rwt_3.2.0.20161006-0240.jar:?]
	at org.eclipse.swt.SWT.error(SWT.java:3631) ~[org.eclipse.rap.rwt_3.2.0.20161006-0240.jar:?]
	at org.eclipse.swt.SWT.error(SWT.java:3602) ~[org.eclipse.rap.rwt_3.2.0.20161006-0240.jar:?]
	at org.eclipse.swt.widgets.Widget.error(Widget.java:1018) ~[org.eclipse.rap.rwt_3.2.0.20161006-0240.jar:?]
	at org.eclipse.swt.widgets.Widget.getDisplay(Widget.java:397) ~[org.eclipse.rap.rwt_3.2.0.20161006-0240.jar:?]
	at org.eclipse.swt.widgets.Widget.isValidThread(Widget.java:972) ~[org.eclipse.rap.rwt_3.2.0.20161006-0240.jar:?]
	at org.eclipse.swt.widgets.Widget.checkWidget(Widget.java:955) ~[org.eclipse.rap.rwt_3.2.0.20161006-0240.jar:?]
	at org.eclipse.swt.internal.widgets.ControlDecorator.setText(ControlDecorator.java:71) ~[org.eclipse.rap.rwt_3.2.0.20161006-0240.jar:?]
	at org.eclipse.jface.fieldassist.ControlDecoration.setDescriptionText(ControlDecoration.java:922) ~[org.eclipse.rap.jface_3.2.0.20160811-0840.jar:?]
	at org.eclipse.ui.internal.forms.MessageManager$ControlDecorator.update(MessageManager.java:275) ~[org.eclipse.rap.ui.forms_3.2.0.20160811-0840.jar:?]
	at org.eclipse.ui.internal.forms.MessageManager$ControlDecorator.removeMessages(MessageManager.java:269) ~[org.eclipse.rap.ui.forms_3.2.0.20160811-0840.jar:?]
	at org.eclipse.ui.internal.forms.MessageManager.removeAllMessages(MessageManager.java:429) ~[org.eclipse.rap.ui.forms_3.2.0.20160811-0840.jar:?]

How exactly this happened, I don't know. That exception was thrown on the UIThread.
I looked at the code in ControlDecorator and the commented out original code has a check for disposed controls in the commented up #update method.

  public void setDescriptionText(String text) {
//		this.descriptionText = text;
//		update();
	    // RAP [if]
	    decorator.setText( text );
	}

//
//	/**
//	 * Something has changed, requiring redraw. Redraw the decoration and update
//	 * the hover text if appropriate.
//	 */
//	protected void update() {
//		if (control == null || control.isDisposed()) {
//			return;
//		}
...

decorator.setText does a disposed check and throws an SWTException.
The commented out method from the original JFace code does a disposed check and silently returns, no exceptions.

Any reason RAP throws an exception in a case where RCP wouldn't?

I don't know how the tester caused this issue and I don't know how to reliably reproduce it.

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