Bug 137073 [Preferences] Encoding field editor never fires value change events
The class AbstractEncodingFieldEditor never fires VALUE property change events unless the validaty of the value has also changed. I will attach a patch that corrects the problem.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/dialogs/AbstractEncodingFieldEditor.java
showErrorMessage(IDEWorkbenchMessages.WorkbenchPreference_unsupportedEncoding);
			}
			fireStateChanged(IS_VALID, !isValid, isValid);
			String newValue = getSelectedEncoding();
			if (isValid && !newValue.equals(oldSelectedEncoding)) {
				fireValueChanged(VALUE, oldSelectedEncoding, newValue);
				oldSelectedEncoding = newValue;
			}
		}
	}
	/**
	 * Returns the currently selected encoding.
	 * 
	 * @return the currently selected encoding
	 */
	protected String getSelectedEncoding() {
		if (defaultEncodingButton.getSelection()) {
			return defaultEnc;
		}
		return encodingCombo.getText();
	}
	private boolean isEncodingValid() {
		return defaultEncodingButton.getSelection()
				|| isValidEncoding(encodingCombo.getText());
	}
	/**
	 * Returns whether or not the given encoding is valid.
	 * 
	 * @param enc
	 *            the encoding to validate