Add support for null values in combos

JFace ComboViewers do not like null values in their possible choices,
but null is a legitimate choice for optional references (meaning
"unset"). Replace nulls with a special value (with no risk of conflict
with anything elese) when filling the combo, and convert it back to null
when passing it to the controller if the users chooses it.

Also avoid triggering the controller's updateValue() callback during
refresh when we configure the combo to show the current value.

Change-Id: Ic3d4f53f8c7f5c11a6aee02ef59708024bd63154
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>

1 files changed, 26 insertions, 4 deletions

diff --git a/plugins/org.eclipse.eef.ide.ui/src/org/eclipse/eef/ide/ui/internal/widgets/EEFSelectLifecycleManager.java b/plugins/org.eclipse.eef.ide.ui/src/org/eclipse/eef/ide/ui/internal/widgets/EEFSelectLifecycleManager.java
index 1b1d86610..3da8eaebf 100644
--- a/plugins/org.eclipse.eef.ide.ui/src/org/eclipse/eef/ide/ui/internal/widgets/EEFSelectLifecycleManager.java
+++ b/plugins/org.eclipse.eef.ide.ui/src/org/eclipse/eef/ide/ui/internal/widgets/EEFSelectLifecycleManager.java
@@ -55,6 +55,17 @@ import org.eclipse.ui.forms.widgets.FormToolkit;
  * @author mbats
  */
 public class EEFSelectLifecycleManager extends AbstractEEFWidgetLifecycleManager {
+
+	/**
+	 * Special value to replace "null" as a combo value.
+	 */
+	private static final Object NO_VALUE = new Object() {
+		@Override
+		public String toString() {
+			return "<null>"; //$NON-NLS-1$
+		}
+	};
+
 	/**
 	 * The description.
 	 */
@@ -197,9 +208,14 @@ public class EEFSelectLifecycleManager extends AbstractEEFWidgetLifecycleManager
 		this.selectionListener = new SelectionListener() {
 			@Override
 			public void widgetSelected(SelectionEvent e) {
-				IStructuredSelection selection = getStructuredSelection(comboViewer);
-				Object newValue = selection.getFirstElement();
-				controller.updateValue(newValue);
+				if (!EEFSelectLifecycleManager.this.container.isRenderingInProgress()) {
+					IStructuredSelection selection = getStructuredSelection(comboViewer);
+					Object newValue = selection.getFirstElement();
+					if (newValue == NO_VALUE) {
+						newValue = null;
+					}
+					controller.updateValue(newValue);
+				}
 			}
 
 			@Override
@@ -234,7 +250,13 @@ public class EEFSelectLifecycleManager extends AbstractEEFWidgetLifecycleManager
 			public void apply(List<Object> value) {
 				if (!combo.isDisposed()) {
 					if (value != null) {
-						comboViewer.setInput(value.toArray());
+						Object[] candidates = value.toArray();
+						for (int i = 0; i < candidates.length; i++) {
+							if (candidates[i] == null) {
+								candidates[i] = NO_VALUE;
+							}
+						}
+						comboViewer.setInput(candidates);
 					} else {
 						comboViewer.setInput(null);
 					}