Bug 127132 - [GTK] TableColumn#pack does not work for virtual table

Fixed NPE when invoking pack on virtual table caused by previous patch.

Change-Id: I3f1f6a995294d20a86c964d3b697888ebd427aac
Signed-off-by: Xi Yan <xixiyan@redhat.com>
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/TableColumn.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/TableColumn.java
index bb5ac91..b4ee6d0 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/TableColumn.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/TableColumn.java
@@ -462,9 +462,9 @@
 		}
 		for (int i=0; i<parent.items.length; i++) {
 			TableItem item = parent.items [i];
-			if (itemBounds == null) itemBounds = item.getBounds();
+			if (itemBounds == null && item != null) itemBounds = item.getBounds();
 			boolean isVisible = false;
-			if (!calcWidth) {
+			if (!calcWidth && itemBounds != null) {
 				int itemTopBound = itemBounds.y + itemBounds.height * i + i;
 				int itemBottomBound = itemTopBound + itemBounds.height;
 				isVisible = (itemTopBound > 0 && itemBottomBound < tableHeight);
diff --git a/tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Bug127132_VirtualTablePackNPE.java b/tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Bug127132_VirtualTablePackNPE.java
new file mode 100644
index 0000000..31e7938
--- /dev/null
+++ b/tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Bug127132_VirtualTablePackNPE.java
@@ -0,0 +1,136 @@
+/*******************************************************************************
+ * Copyright (c) 2018 Red Hat and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Thomas Singer - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.swt.tests.gtk.snippets;
+
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.events.SelectionAdapter;
+import org.eclipse.swt.events.SelectionEvent;
+import org.eclipse.swt.graphics.Point;
+import org.eclipse.swt.graphics.Rectangle;
+import org.eclipse.swt.layout.FillLayout;
+import org.eclipse.swt.widgets.Button;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Listener;
+import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.Table;
+import org.eclipse.swt.widgets.TableColumn;
+import org.eclipse.swt.widgets.TableItem;
+
+public class Bug127132_VirtualTablePackNPE {
+
+	// Constants ==============================================================
+
+	static final int COUNT1 = 1000;
+	static final int COUNT2 = 100;
+
+	private static boolean packPending = true;
+
+	// Static =================================================================
+
+	public static void main(String[] args) {
+		final Display display = new Display();
+		final Shell shell = new Shell(display);
+		shell.setLayout(new FillLayout(SWT.VERTICAL));
+
+		final Button button = new Button(shell, SWT.NONE);
+		final Button packButton = new Button(shell, SWT.NONE);
+
+		final Table table = new Table(shell, SWT.VIRTUAL | SWT.BORDER | SWT.FULL_SELECTION | SWT.H_SCROLL | SWT.V_SCROLL);
+		button.setText("Change content");
+		button.addSelectionListener(new SelectionAdapter() {
+			@Override
+			public void widgetSelected(SelectionEvent e) {
+				table.setItemCount(table.getItemCount() == COUNT1 ? COUNT2 : COUNT1);
+			}
+		});
+
+		packButton.setText("Pack");
+		packButton.addSelectionListener(new SelectionAdapter() {
+			@Override
+			public void widgetSelected(SelectionEvent e) {
+				for (TableColumn c : table.getColumns()) {
+					c.pack();
+				}
+			}
+		});
+
+		table.setHeaderVisible(true);
+		final Listener listener = event -> {
+			final TableItem item = (TableItem)event.item;
+			if (event.type == SWT.EraseItem) {
+				if (event.index < 2) {
+					event.detail &= ~SWT.FOREGROUND;
+				}
+			}
+			else if (event.type == SWT.PaintItem) {
+				if (event.index == 0) {
+					event.gc.drawText((String)item.getData(), event.x, event.y, true);
+				}
+				else if (event.index == 1) {
+					final String text1 = (String)item.getData();
+					final Point size = event.gc.textExtent(text1);
+					final Rectangle bounds = item.getBounds(event.index);
+					event.gc.drawText(text1, bounds.x + bounds.width - size.x, bounds.y + bounds.height - size.y, true);
+				}
+			}
+			else if (event.type == SWT.MeasureItem) {
+				final String text2 = (String)item.getData();
+				final Point point = event.gc.textExtent(text2);
+				event.height = point.y * 2;
+				event.width = Math.max(event.width, point.x);
+			}
+			else if (event.type == SWT.SetData) {
+				final int index = table.indexOf(item);
+				final String data = "Item " + index;
+				item.setText(2, data);
+				item.setData(data);
+
+				if (packPending) {
+					packPending = false;
+					display.asyncExec(() -> {
+						table.setRedraw(false);
+						for (TableColumn column : table.getColumns()) {
+							column.pack();
+						}
+						table.setRedraw(true);
+					});
+				}
+			}
+		};
+		table.addListener(SWT.EraseItem, listener);
+		table.addListener(SWT.SetData, listener);
+		table.addListener(SWT.MeasureItem, listener);
+		table.addListener(SWT.PaintItem, listener);
+
+		createColumn(SWT.LEFT, "OD Left", table);
+		createColumn(SWT.RIGHT, "OD Right", table);
+		createColumn(SWT.LEFT, "Primitive", table);
+
+		table.setItemCount(COUNT1);
+		table.setTopIndex(50000);
+
+		shell.setSize(400, 500);
+		shell.open();
+		while (!shell.isDisposed()) {
+			if (!display.readAndDispatch()) {
+				display.sleep();
+			}
+		}
+		display.dispose();
+	}
+
+	private static void createColumn(int style, String text, Table table) {
+		final TableColumn tableColumn = new TableColumn(table, style);
+		tableColumn.setText(text);
+		tableColumn.setMoveable(true);
+		tableColumn.setWidth(20);
+	}
+}
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