Bug 553598 - Fire a new EmptinessChanged event from Tree after first addition or last removal of a TreeItem

Change-Id: I8c215c59864ed3b985e1c4b81d7f81b5efb671e0
Signed-off-by: Eike Stepper <[email protected]>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.swt/+/185581
Tested-by: Platform Bot <[email protected]>
Tested-by: Niraj Modi <[email protected]>
Reviewed-by: Sravan Kumar Lakkimsetti <[email protected]>
Reviewed-by: Niraj Modi <[email protected]>

Author: estepper

bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/widgets/Tree.java

@@ -62,7 +62,7 @@
  * <dt><b>Styles:</b></dt>
  * <dd>SINGLE, MULTI, CHECK, FULL_SELECTION, VIRTUAL, NO_SCROLL</dd>
  * <dt><b>Events:</b></dt>
- * <dd>Selection, DefaultSelection, Collapse, Expand, SetData, MeasureItem, EraseItem, PaintItem</dd>
+ * <dd>Selection, DefaultSelection, Collapse, Expand, SetData, MeasureItem, EraseItem, PaintItem, EmptinessChanged</dd>
  * </dl>
  * <p>
  * Note: Only one of the styles SINGLE and MULTI may be specified.
@@ -757,6 +757,11 @@ void createItem (TreeItem item, TreeItem parentItem, int index) {
 		widget.expandItem (parentItem.handle);
 	}
 	ignoreExpand = false;
+	if (parentItem == null && this.itemCount == 1) {
+		Event event = new Event ();
+		event.detail = 0;
+		sendEvent (SWT.EmptinessChanged, event);
+	}
 }
 
 @Override
@@ -988,6 +993,11 @@ void destroyItem (TreeItem item) {
 	setScrollWidth ();
 	if (this.itemCount == 0) imageBounds = null;
 	if (insertItem == item) insertItem = null;
+	if (parentItem == null && this.itemCount == 0) {
+		Event event = new Event ();
+		event.detail = 1;
+		sendEvent (SWT.EmptinessChanged, event);
+	}
 }
 
 @Override

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/SWT.java

@@ -1020,6 +1020,20 @@ public class SWT {
 	 */
 	public static final int ZoomChanged = 55;
 
+	/**
+	 * The SWT emptiness change event type (value is 56).
+	 *
+	 * <p>
+	 * This event is sent on <code>Tree</code> when the first <code>TreeItem</code> was
+	 * added to it (with the <code>detail</code> field set to 0) or the last
+	 * <code>TreeItem</code> was removed from it (with the <code>detail</code> field
+	 * set to 1).
+	 * </p>
+	 *
+	 * @since 4.22
+	 */
+	public static final int EmptinessChanged = 56;
+
 	/* Event Details */
 
 	/**

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Tree.java

@@ -67,7 +67,7 @@
  * <dt><b>Styles:</b></dt>
  * <dd>SINGLE, MULTI, CHECK, FULL_SELECTION, VIRTUAL, NO_SCROLL</dd>
  * <dt><b>Events:</b></dt>
- * <dd>Selection, DefaultSelection, Collapse, Expand, SetData, MeasureItem, EraseItem, PaintItem</dd>
+ * <dd>Selection, DefaultSelection, Collapse, Expand, SetData, MeasureItem, EraseItem, PaintItem, EmptinessChanged</dd>
  * </dl>
  * <p>
  * Note: Only one of the styles SINGLE and MULTI may be specified.
@@ -1024,6 +1024,18 @@ void createItem (TreeItem item, long parentIter, int index) {
 	int id = getId (item.handle, false);
 	items [id] = item;
 	modelChanged = true;
+
+	if (parentIter == 0 ) {
+		/*
+		 If this was the first root item fire an EmptinessChanged event.
+		 */
+		int roots = GTK.gtk_tree_model_iter_n_children (modelHandle, 0);
+		if (roots == 1) {
+			Event event = new Event ();
+			event.detail = 0;
+			sendEvent (SWT.EmptinessChanged, event);
+		}
+	}
 }
 
 void createRenderers (long columnHandle, int modelIndex, boolean check, int columnStyle) {
@@ -1277,6 +1289,16 @@ void destroyItem (TreeItem item) {
 	GTK.gtk_tree_store_remove (modelHandle, item.handle);
 	OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, CHANGED);
 	modelChanged = true;
+
+	/*
+	 If this was the last root item fire an EmptinessChanged event.
+	 */
+	int roots = GTK.gtk_tree_model_iter_n_children (modelHandle, 0);
+	if (roots == 0) {
+		Event event = new Event ();
+		event.detail = 1;
+		sendEvent (SWT.EmptinessChanged, event);
+	}
 }
 
 @Override

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Tree.java

@@ -64,7 +64,7 @@
  * <dt><b>Styles:</b></dt>
  * <dd>SINGLE, MULTI, CHECK, FULL_SELECTION, VIRTUAL, NO_SCROLL</dd>
  * <dt><b>Events:</b></dt>
- * <dd>Selection, DefaultSelection, Collapse, Expand, SetData, MeasureItem, EraseItem, PaintItem</dd>
+ * <dd>Selection, DefaultSelection, Collapse, Expand, SetData, MeasureItem, EraseItem, PaintItem, EmptinessChanged</dd>
  * </dl>
  * <p>
  * Note: Only one of the styles SINGLE and MULTI may be specified.
@@ -2158,6 +2158,14 @@ void createItem (TreeItem item, long hParent, long hInsertAfter, long hItem) {
 		 Later, setRedraw(true) will update scrollbars once.
 		 */
 		if (getDrawing ()) updateScrollBar ();
+		/*
+		 If this is the first item added fire an EmptinessChanged event.
+		 */
+		if (item != null && id == 0) {
+			Event event = new Event ();
+			event.detail = 0;
+			sendEvent (SWT.EmptinessChanged, event);
+		}
 	}
 }
 
@@ -2641,6 +2649,15 @@ void destroyItem (TreeItem item, long hItem) {
 	 Later, setRedraw(true) will update scrollbars once.
 	 */
 	if (getDrawing ()) updateScrollBar ();
+
+	/*
+	 If this is the last item removed fire an EmptinessChanged event.
+	 */
+	if (count == 0) {
+		Event event = new Event ();
+		event.detail = 1;
+		sendEvent (SWT.EmptinessChanged, event);
+	}
 }
 
 @Override

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_widgets_Tree.java

@@ -974,4 +974,52 @@ public void test_Virtual() {
 	assertTrue("SetData callback count not in range: " + dataCounter[0],
 			dataCounter[0] > visibleCount / 2 && dataCounter[0] <= visibleCount * 3);
 }
+
+@Test
+public void test_emptinessChanged() {
+	int NOT_EMPTY = 0;
+	int EMPTY = 1;
+	int[] count = { 0, 0 };
+	tree.addListener(SWT.EmptinessChanged, e -> ++count[e.detail] );
+
+	// Create first item. Expected one NOT_EMPTY event.
+	TreeItem item1 = new TreeItem(tree, SWT.NONE);
+	assertEquals(1, count[NOT_EMPTY]);
+	assertEquals(0, count[EMPTY]);
+
+	// Create second item. Expected no further event.
+	TreeItem item2 = new TreeItem(tree, SWT.NONE);
+	assertEquals(1, count[NOT_EMPTY]);
+	assertEquals(0, count[EMPTY]);
+
+	// Remove one item. Expected no further event.
+	item1.dispose();
+	assertEquals(1, count[NOT_EMPTY]);
+	assertEquals(0, count[EMPTY]);
+
+	// Remove last item. Expected one EMPTY event.
+	item2.dispose();
+	assertEquals(1, count[NOT_EMPTY]);
+	assertEquals(1, count[EMPTY]);
+
+	// Create first item. Expected one more NOT_EMPTY event.
+	item1 = new TreeItem(tree, SWT.NONE);
+	assertEquals(2, count[NOT_EMPTY]);
+	assertEquals(1, count[EMPTY]);
+
+	// Create second item as child of the first item. Expected no further event.
+	item2 = new TreeItem(item1, SWT.NONE);
+	assertEquals(2, count[NOT_EMPTY]);
+	assertEquals(1, count[EMPTY]);
+
+	// Remove both items. Expected one more EMPTY event.
+	item1.dispose();
+	assertEquals(2, count[NOT_EMPTY]);
+	assertEquals(2, count[EMPTY]);
+
+	// Noop. Expected no further event.
+	item2.dispose();
+	assertEquals(2, count[NOT_EMPTY]);
+	assertEquals(2, count[EMPTY]);
+}
 }