Bug 74708 [Encoding] IDEEncodingPreferencePage does not disable OK when invalid encoding is entered
20040921-2000 If you enter an invalid encoding in the IDEEncodingsPreferencePage you will still be able to select OK STEPS 1) Open the Editors preference page 2) Type ffff 3) You are warned but OK is still enabled.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/ResourceInfoPage.java
/**
	 * Apply the read only state and the encoding to the resource.
	 */
	public boolean performOk() {
		IResource resource = (IResource) getElement();
		encodingEditor.store();
		
		if (this.editableBox != null) {
			boolean localReadOnlyValue = editableBox.getSelection();
			if (previousReadOnlyValue != localReadOnlyValue) {
				resource.setReadOnly(localReadOnlyValue);
			}
		}
		
		if (this.derivedBox != null) {
			try {
				boolean localDerivedValue = derivedBox.getSelection();
				if (previousDerivedValue != localDerivedValue) {
					resource.setDerived(localDerivedValue);
				}
			} catch (CoreException exception) {
				ErrorDialog.openError(getShell(), IDEWorkbenchMessages
						.getString("InternalError"), 
						exception.getLocalizedMessage(), exception.getStatus());
				return false;
			}
		}
		return true;
	}
}