Support setExpanded for ExpandableNode to render next block of items.

Search View result navigator is updated to use above fix. Now Next
search result should expand the ExpandableNode and try to find next
Result.
This also enables incremental display feature for SearchView.

Fixes eclipse-platform#1024

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

@@ -2596,6 +2596,7 @@ public void setExpandedState(Object elementOrTreePath, boolean expanded) {
 		Assert.isNotNull(elementOrTreePath);
 		if (checkBusy())
 			return;
+
 		Widget item = internalExpand(elementOrTreePath, false);
 		if (item instanceof Item) {
 			if (expanded) {

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

@@ -1203,4 +1203,18 @@ Object getLastElement(Widget parent) {
 		}
 		return items[length - 1].getData();
 	}
+
+	@Override
+	public void setExpandedState(Object elementOrTreePath, boolean expanded) {
+		// Special behavior for ExpandableNode. Expand the it if it's widget is found
+		// otherwise do not expand it.
+		if (isExpandableNode(elementOrTreePath)) {
+			Widget expItem = findItem(elementOrTreePath);
+			if (expItem != null) {
+				handleExpandableNodeClicked(expItem);
+			}
+			return;
+		}
+		super.setExpandedState(elementOrTreePath, expanded);
+	}
 }

bundles/org.eclipse.search/new search/org/eclipse/search/ui/text/AbstractTextSearchViewPage.java

@@ -51,6 +51,7 @@
 import org.eclipse.jface.dialogs.ErrorDialog;
 import org.eclipse.jface.dialogs.IDialogSettings;
 import org.eclipse.jface.util.OpenStrategy;
+import org.eclipse.jface.viewers.ColumnViewer;
 import org.eclipse.jface.viewers.DecoratingLabelProvider;
 import org.eclipse.jface.viewers.IBaseLabelProvider;
 import org.eclipse.jface.viewers.IOpenListener;
@@ -84,6 +85,7 @@
 import org.eclipse.ui.part.Page;
 import org.eclipse.ui.part.PageBook;
 import org.eclipse.ui.progress.UIJob;
+import org.eclipse.ui.views.WorkbenchViewerSetup;
 
 import org.eclipse.ui.texteditor.IUpdate;
 
@@ -731,7 +733,7 @@ private void createViewer(Composite parent, int layout) {
 			fCollapseAllAction.setViewer(viewer);
 			fExpandAllAction.setViewer(viewer);
 		}
-
+		WorkbenchViewerSetup.setupViewer((ColumnViewer) fViewer);
 		fCopyToClipboardAction.setViewer(fViewer);
 		fSelectAllAction.setViewer(fViewer);
 

bundles/org.eclipse.search/new search/org/eclipse/search2/internal/ui/basic/views/TreeViewerNavigator.java

@@ -108,6 +108,11 @@ private TreeItem getNextItemForward(TreeItem currentItem) {
 			return child;
 		TreeItem nextSibling= getNextSibling(currentItem, true);
 		if (nextSibling != null) {
+			// expand the node first and fetch the sibling again.
+			if (fViewer.isExpandableNode(nextSibling.getData())) {
+				fViewer.setExpandedState(nextSibling.getData(), true);
+				nextSibling = getNextSibling(currentItem, true);
+			}
 			if (hasMatches(nextSibling))
 				return nextSibling;
 			return getFirstChildWithMatches(nextSibling);
@@ -116,6 +121,11 @@ private TreeItem getNextItemForward(TreeItem currentItem) {
 		while (parent != null) {
 			nextSibling= getNextSibling(parent, true);
 			if (nextSibling != null) {
+				// expand the node first and fetch the sibling again.
+				if (fViewer.isExpandableNode(nextSibling.getData())) {
+					fViewer.setExpandedState(nextSibling.getData(), true);
+					nextSibling = getNextSibling(parent, true);
+				}
 				if (hasMatches(nextSibling))
 					return nextSibling;
 				return getFirstChildWithMatches(nextSibling);