Performance improvement and setRedraw() changes for expandable node.

Fixes eclipse-platform#1016

bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TableViewer.java

@@ -468,32 +468,43 @@ void handleExpandableNodeClicked(Widget w) {
 		if (!(data instanceof ExpandableNode expNode)) {
 			return;
 		}
-
-		Object[] sortedChildren = expNode.getRemainingElements();
-		Object[] nextChildren = applyItemsLimit(data, sortedChildren);
-		disassociate(item);
-		int index = doIndexOf(item);
-		// will also call item.dispose()
-		doRemove(new int[] { index });
-
-		if (nextChildren.length > 0) {
-			// create remaining elements
-			for (Object nextChild : nextChildren) {
-				createItem(nextChild, -1);
-			}
-			// If we've expanded but still have not reached the limit
-			// select new expandable node, so user can click through
-			// to the end
-			if (getLastElement() instanceof ExpandableNode node) {
-				setSelection(new StructuredSelection(node), true);
-			} else {
-				// reset the selection. client's selection listener should not be triggered.
-				// there was only one selection on Expandable Node.
-				int[] curSel = this.getTable().getSelectionIndices();
-				if (curSel.length == 1) {
-					this.getTable().deselect(curSel[0]);
+		boolean oldBusy = isBusy();
+		Table table = getTable();
+		try {
+			setBusy(true);
+			table.setRedraw(false);
+
+			Object[] sortedChildren = expNode.getRemainingElements();
+			Object[] nextChildren = applyItemsLimit(data, sortedChildren);
+
+			if (nextChildren.length > 0) {
+				// update the expandable node with first item.
+				doUpdateItem(item, nextChildren[0], true);
+				// create remaining elements
+				if (nextChildren.length > 1) {
+					// current index is updated so start creating from next index.
+					int index = doIndexOf(item) + 1;
+					for (int i = 1; i < nextChildren.length; i++) {
+						createItem(nextChildren[i], index++);
+					}
+				}
+				// If we've expanded but still have not reached the limit
+				// select new expandable node, so user can click through
+				// to the end
+				if (getLastElement() instanceof ExpandableNode node) {
+					setSelection(new StructuredSelection(node), true);
+				} else {
+					// reset the selection. client's selection listener should not be triggered.
+					// there was only one selection on Expandable Node.
+					int[] curSel = table.getSelectionIndices();
+					if (curSel.length == 1) {
+						table.deselect(curSel[0]);
+					}
 				}
 			}
+		} finally {
+			setBusy(oldBusy);
+			table.setRedraw(true);
 		}
 	}
 

bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreeViewer.java

@@ -1148,20 +1148,28 @@ void handleExpandableNodeClicked(Widget w) {
 			return;
 		}
 
-		Widget parent = getParentItem(item);
-		if (parent == null) {
-			parent = getControl();
-		}
-		// destroy widget
-		disassociate(item);
-		item.dispose();
+		boolean oldBusy = isBusy();
+		Tree tree = getTree();
+		try {
+			setBusy(true);
+			tree.setRedraw(false);
 
-		// create children on parent
-		for (Object element : children) {
-			createTreeItem(parent, element, -1);
-		}
+			Widget parent = getParentItem(item);
+			if (parent == null) {
+				parent = getControl();
+			}
+
+			// update widget
+			updateItem(item, children[0]);
+			updatePlus(item, children[0]);
+
+			if (children.length > 1) {
+				// create children on parent
+				for (int i = 1; i < children.length; i++) {
+					createTreeItem(parent, children[i], -1);
+				}
+			}
 
-		if (children.length > 0) {
 			// If we've expanded but still have not reached the limit
 			// select new expandable node, so user can click through
 			// to the end
@@ -1171,11 +1179,14 @@ void handleExpandableNodeClicked(Widget w) {
 			} else {
 				// reset the selection. client's selection listener should not be triggered.
 				// there was only one selection on Expandable Node.
-				Item[] curSel = this.getTree().getSelection();
+				Item[] curSel = tree.getSelection();
 				if (curSel.length == 1) {
-					this.getTree().deselect((TreeItem) curSel[0]);
+					tree.deselect((TreeItem) curSel[0]);
 				}
 			}
+		} finally {
+			tree.setRedraw(true);
+			setBusy(oldBusy);
 		}
 	}