ui/org.eclipse.pde.runtime/src/org/eclipse/pde/internal/runtime/spy/dialogs/LayoutSpyDialog.java

/*******************************************************************************
 * Copyright (c) 2016 Google Inc 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:
 *     Stefan Xenos (Google) - initial API and implementation
 *
 *******************************************************************************/
package org.eclipse.pde.internal.runtime.spy.dialogs;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.List;
import org.eclipse.core.databinding.observable.list.ComputedList;
import org.eclipse.core.databinding.observable.sideeffect.ISideEffectFactory;
import org.eclipse.core.databinding.observable.value.WritableValue;
import org.eclipse.jdt.annotation.Nullable;
import org.eclipse.jface.databinding.swt.*;
import org.eclipse.jface.databinding.viewers.*;
import org.eclipse.jface.layout.*;
import org.eclipse.jface.resource.*;
import org.eclipse.jface.util.Geometry;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.osgi.util.NLS;
import org.eclipse.pde.internal.runtime.PDERuntimePluginImages;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

/**
 * Implementation of the "layout spy" dialog, a diagnostic tool for fixing bugs
 * related to control positioning and the implementation of SWT {@link Control}s
 * and {@link Layout}s.
 */
public class LayoutSpyDialog {
	private static final int EDGE_SIZE = 4;
	private static final RGB SELECTED_PARENT_OVERLAY_COLOR = new RGB(255, 0, 0);
	private static final RGB SELECTED_CHILD_OVERLAY_COLOR = new RGB(255, 255, 0);

	/**
	 * Value used to indicate an unknown hint value
	 */
	private static final int UNKNOWN = -2;
	private Shell shell;

	// Controls
	private TableViewer childList;
	private Text details;
	private Button selectWidgetButton;
	private Button goUpButton;
	private Button goDownButton;
	private Shell overlay;

	// Model
	private WritableValue<@Nullable Composite> parentControl = new WritableValue<>(null, null);
	private WritableValue<Boolean> controlSelectorOpen = new WritableValue<>(Boolean.FALSE, null);
	private ComputedList<Control> listContents;
	private IViewerObservableValue selectedChild;
	private Color parentRectangleColor;
	private Color childRectangleColor;
	private ResourceManager resources;
	private Region region;
	private ISWTObservableValue overlayEnabled;
	private Image upImage;
	private Text diagnostics;

	/**
	 * Creates the dialog but does not make it visible.
	 * 
	 * @param parentShell
	 *            the parent shell
	 */
	public LayoutSpyDialog(Shell parentShell) {
		overlay = new Shell(SWT.ON_TOP | SWT.NO_TRIM);
		{
			overlay.addPaintListener(this::paintOverlay);
			region = new Region();
			overlay.addDisposeListener((DisposeEvent) -> {
				region.dispose();
			});
			overlay.setRegion(region);
		}

		shell = new Shell(parentShell, SWT.SHELL_TRIM);

		resources = new LocalResourceManager(JFaceResources.getResources(), shell);
		parentRectangleColor = resources.createColor(SELECTED_PARENT_OVERLAY_COLOR);
		childRectangleColor = resources.createColor(SELECTED_CHILD_OVERLAY_COLOR);
		upImage = resources.createImage(PDERuntimePluginImages.UP_NAV);

		Composite infoRegion = new Composite(shell, SWT.NONE);
		{
			Composite headerRegion = new Composite(infoRegion, SWT.NONE);
			{
				Button upButton = new Button(headerRegion, SWT.PUSH | SWT.CENTER);
				upButton.setImage(upImage);
				upButton.addListener(SWT.Selection, event -> goUp());
				GridDataFactory.fillDefaults().applyTo(upButton);

				Label childrenLabel = new Label(headerRegion, SWT.NONE);
				childrenLabel.setText(Messages.LayoutSpyDialog_label_children);
			}
			GridLayoutFactory.fillDefaults().numColumns(2).generateLayout(headerRegion);

			Label detailsLabel = new Label(infoRegion, SWT.NONE);
			detailsLabel.setText(Messages.LayoutSpyDialog_label_layout);

			childList = new TableViewer(infoRegion);
			details = new Text(infoRegion, SWT.READ_ONLY | SWT.MULTI | SWT.BORDER | SWT.V_SCROLL | SWT.H_SCROLL);
			GridDataFactory.fillDefaults().hint(300, 300).grab(true, true).applyTo(details);

			GridLayoutFactory.fillDefaults().numColumns(2).equalWidth(true).generateLayout(infoRegion);
		}

		diagnostics = new Text(shell, SWT.READ_ONLY | SWT.MULTI | SWT.BORDER | SWT.V_SCROLL | SWT.H_SCROLL);
		GridDataFactory.fillDefaults().hint(300, 300).grab(true, true).applyTo(diagnostics);

		Button showOverlayButton = new Button(shell, SWT.CHECK);
		showOverlayButton.setText(Messages.LayoutSpyDialog_button_show_overlay);

		Composite buttonBar = new Composite(shell, SWT.NONE);
		{
			selectWidgetButton = new Button(buttonBar, SWT.PUSH);
			selectWidgetButton.setText(Messages.LayoutSpyDialog_button_select_control);
			goUpButton = new Button(buttonBar, SWT.PUSH);
			goUpButton.setText(Messages.LayoutSpyDialog_button_open_parent);
			goDownButton = new Button(buttonBar, SWT.PUSH);
			goDownButton.setText(Messages.LayoutSpyDialog_button_open_child);

			GridLayoutFactory.fillDefaults().numColumns(3).generateLayout(buttonBar);
		}
		GridDataFactory.fillDefaults().align(SWT.CENTER, SWT.CENTER).applyTo(buttonBar);

		GridLayoutFactory.fillDefaults().margins(LayoutConstants.getMargins()).generateLayout(shell);

		// Attach listeners
		shell.addDisposeListener(event -> disposed());
		selectWidgetButton.addListener(SWT.Selection, event -> selectControl());
		goUpButton.addListener(SWT.Selection, event -> goUp());
		goDownButton.addListener(SWT.Selection, event -> goDown());
		childList.addOpenListener(event -> {
			goDown();
		});

		// Set up the model
		selectedChild = ViewerProperties.singleSelection().observe(childList);
		overlayEnabled = WidgetProperties.selection().observe(showOverlayButton);
		childList.setContentProvider(new ObservableListContentProvider());
		listContents = new ComputedList<Control>() {
			@Override
			protected List<Control> calculate() {
				Composite control = parentControl.getValue();
				if (control == null) {
					return Arrays.asList(Display.getCurrent().getShells());
				}
				return Arrays.asList(control.getChildren());
			}
		};
		childList.setInput(listContents);
		ISideEffectFactory sideEffectFactory = WidgetSideEffects.createFactory(shell);
		sideEffectFactory.create(this::computeParentInfo, details::setText);
		sideEffectFactory.create(this::computeChildInfo, diagnostics::setText);
		sideEffectFactory.create(this::updateOverlay);

		openComposite(parentShell);
	}

	/**
	 * Opens the dialog box, revealing it to the user.
	 */
	public void open() {
		this.shell.pack();
		this.shell.open();
	}

	/**
	 * Disposes the dialog box.
	 */
	public void close() {
		this.shell.dispose();
	}

	/**
	 * Invoked as a callback when the main shell is disposed.
	 */
	private void disposed() {
		listContents.dispose();
		selectedChild.dispose();
		parentControl.dispose();

		overlay.dispose();
	}

	private void openComposite(Composite composite) {
		parentControl.setValue(composite);
	}

	/**
	 * Returns the currently-selected child control or null if none.
	 */
	private @Nullable Control getSelectedChild() {
		return (@Nullable Control) selectedChild.getValue();
	}

	/**
	 * Opens the given control in the layout spy.
	 */
	@SuppressWarnings("unchecked")
	private void openControl(Control control) {
		Composite parent = control.getParent();

		if (parent == null) {
			if (control instanceof Composite) {
				parentControl.setValue((Composite) control);
			}
		} else {
			parentControl.setValue(parent);
			selectedChild.setValue(control);
		}
	}

	// Overlay management
	// -----------------------------------------------------------------

	/**
	 * This callback is used to update the bounds and visible region for the
	 * overlay shell. It is used as part of a side-effect, so if it makes use of
	 * any tracked getters, it will automatically be invoked again whenever one
	 * of those tracked getters changes state.
	 *
	 * @TrackedGetter
	 */
	public void updateOverlay() {
		@Nullable
		Composite parent = parentControl.getValue();

		boolean enabled = Boolean.TRUE.equals(overlayEnabled.getValue());

		overlay.setVisible(parent != null && !controlSelectorOpen.getValue() && enabled);
		if (parent == null) {
			return;
		}
		Shell shell = parent.getShell();
		Rectangle outerBounds = Geometry.copy(shell.getBounds());
		overlay.setBounds(outerBounds);
		Rectangle parentBoundsWrtDisplay = GeometryUtil.getDisplayBounds(parent);

		Rectangle parentBoundsWrtOverlay = Geometry.toControl(overlay, parentBoundsWrtDisplay);
		Rectangle innerBoundsWrtOverlay = Geometry.copy(parentBoundsWrtOverlay);
		Geometry.expand(innerBoundsWrtOverlay, -EDGE_SIZE, -EDGE_SIZE, -EDGE_SIZE, -EDGE_SIZE);
		region.dispose();
		region = new Region();
		@Nullable
		Control child = (@Nullable Control) selectedChild.getValue();
		if (child != null) {
			Rectangle childBoundsWrtOverlay = Geometry.toControl(overlay, GeometryUtil.getDisplayBounds(child));
			Rectangle childInnerBoundsWrtOverlay = Geometry.copy(childBoundsWrtOverlay);
			Geometry.expand(childInnerBoundsWrtOverlay, -EDGE_SIZE, -EDGE_SIZE, -EDGE_SIZE, -EDGE_SIZE);
			region.add(parentBoundsWrtOverlay);
			int distanceToTop = childBoundsWrtOverlay.y - innerBoundsWrtOverlay.y;
			subtractRect(region, GeometryUtil.extrudeEdge(innerBoundsWrtOverlay, distanceToTop, SWT.TOP));
			int distanceToLeft = childBoundsWrtOverlay.x - innerBoundsWrtOverlay.x;
			subtractRect(region, GeometryUtil.extrudeEdge(innerBoundsWrtOverlay, distanceToLeft, SWT.LEFT));
			int distanceToRight = GeometryUtil.getRight(innerBoundsWrtOverlay) - GeometryUtil.getRight(childBoundsWrtOverlay);
			subtractRect(region, GeometryUtil.extrudeEdge(innerBoundsWrtOverlay, distanceToRight, SWT.RIGHT));
			int distanceToBottom = GeometryUtil.getBottom(innerBoundsWrtOverlay) - GeometryUtil.getBottom(childBoundsWrtOverlay);
			subtractRect(region, GeometryUtil.extrudeEdge(innerBoundsWrtOverlay, distanceToBottom, SWT.BOTTOM));

			subtractRect(region, childInnerBoundsWrtOverlay);
		} else {
			region.add(parentBoundsWrtOverlay);
			region.subtract(innerBoundsWrtOverlay);
		}

		overlay.redraw();
		overlay.setRegion(region);
	}

	/**
	 * Paint callback for the overlay shell. This draws rectangles around the
	 * selected layout and the selected child.
	 */
	protected void paintOverlay(PaintEvent e) {
		@Nullable
		Composite parent = parentControl.getValue();
		if (parent == null) {
			return;
		}
		int halfSize = EDGE_SIZE / 2;
		Rectangle parentDisplayBounds = GeometryUtil.getDisplayBounds(parent);
		Rectangle parentBoundsWrtOverlay = Geometry.toControl(overlay, parentDisplayBounds);
		Geometry.expand(parentBoundsWrtOverlay, -halfSize, -halfSize, -halfSize, -halfSize);

		@Nullable
		Control child = (@Nullable Control) selectedChild.getValue();
		e.gc.setLineWidth(EDGE_SIZE);
		e.gc.setForeground(parentRectangleColor);
		e.gc.drawRectangle(parentBoundsWrtOverlay.x, parentBoundsWrtOverlay.y, parentBoundsWrtOverlay.width,
				parentBoundsWrtOverlay.height);

		if (child != null) {
			Rectangle childBoundsWrtOverlay = Geometry.toControl(overlay, GeometryUtil.getDisplayBounds(child));
			Geometry.expand(childBoundsWrtOverlay, -halfSize, -halfSize, -halfSize, -halfSize);
			e.gc.setForeground(childRectangleColor);
			e.gc.drawRectangle(childBoundsWrtOverlay.x, childBoundsWrtOverlay.y, childBoundsWrtOverlay.width,
					childBoundsWrtOverlay.height);
		}
	}

	// User gesture callbacks
	// -----------------------------------------------------------

	/**
	 * Invoked when the user clicks the "select control" button. It opens some
	 * UI that allows the user to select a new input control for the layout spy.
	 */
	private void selectControl() {
		this.controlSelectorOpen.setValue(true);
		this.shell.setVisible(false);
		new ControlSelector((@Nullable Control control) -> {
			if (control != null) {
				openControl(control);
			}
			this.controlSelectorOpen.setValue(false);
			this.shell.setVisible(true);
		});
	}

	/**
	 * Invoked when the user clicks the "go up" button, which opens the parent.
	 */
	@SuppressWarnings("unchecked")
	private void goUp() {
		@Nullable
		Composite parent = parentControl.getValue();
		if (parent == null) {
			return;
		}
		Composite ancestor = parent.getParent();
		openComposite(ancestor);
		this.selectedChild.setValue(parent);
	}

	/**
	 * Invoked when the user clicks the "go down" button, which opens the
	 * selected child.
	 */
	private void goDown() {
		Control child = getSelectedChild();
		if (child instanceof Composite) {
			Composite composite = (Composite) child;
			openComposite(composite);
		}
	}

	// Utility functions -----------------------------------------------------

	/**
	 * Subtracts the given rectangle from the given region unless the rectangle
	 * is empty.
	 */
	private static void subtractRect(Region region, Rectangle rect) {
		if (rect.isEmpty()) {
			return;
		}
		region.subtract(rect);
	}

	private String getWarningMessage(String string) {
		return NLS.bind(Messages.LayoutSpyDialog_warning_prefix, string);
	}

	private static String printHint(int hint) {
		if (hint == SWT.DEFAULT) {
			return "SWT.DEFAULT"; //$NON-NLS-1$
		}
		return Integer.toString(hint);
	}

	private static String printPoint(Point toPrint) {
		return NLS.bind("({0}, {1})", new Object[] { toPrint.x, toPrint.y }); //$NON-NLS-1$
	}

	// Control classification ------------------------------------------------

	private static boolean isHorizontallyScrollable(Control child) {
		return (child.getStyle() & SWT.H_SCROLL) != 0;
	}

	private static boolean isVerticallyScrollable(Control child) {
		return (child.getStyle() & SWT.V_SCROLL) != 0;
	}

	/**
	 * Computes the values that should be subtracted off the width and height
	 * hints from computeSize on the given control.
	 */
	private static Point computeHintAdjustment(Control control) {
		int widthAdjustment;
		int heightAdjustment;
		if (control instanceof Scrollable) {
			// For composites, subtract off the trim size
			Scrollable composite = (Scrollable) control;
			Rectangle trim = composite.computeTrim(0, 0, 0, 0);

			widthAdjustment = trim.width;
			heightAdjustment = trim.height;
		} else {
			// For non-composites, subtract off 2 * the border size
			widthAdjustment = control.getBorderWidth() * 2;
			heightAdjustment = widthAdjustment;
		}

		return new Point(widthAdjustment, heightAdjustment);
	}

	/**
	 * Returns true if the given control is a composite which can expand in the
	 * given dimension. Returns false if the control either cannot expand in the
	 * given dimension or if its growable characteristics cannot be computed in
	 * that dimension.
	 */
	private static boolean isGrowableLayout(Control control, boolean horizontal) {
		if (control instanceof Composite) {
			Composite composite = (Composite) control;

			Layout theLayout = composite.getLayout();
			if (theLayout instanceof GridLayout) {
				Control[] children = composite.getChildren();
				for (int i = 0; i < children.length; i++) {
					Control child = children[i];

					GridData data = (GridData) child.getLayoutData();

					if (data != null) {
						if (horizontal) {
							if (data.grabExcessHorizontalSpace) {
								return true;
							}
						} else {
							if (data.grabExcessVerticalSpace) {
								return true;
							}
						}
					}
				}
			}
		}
		return false;
	}

	/**
	 * Returns true iff another visible widget in the same shell overlaps the
	 * given control.
	 */
	private static boolean overlapsSibling(Control toFind) {
		Composite parent = toFind.getParent();
		Control current = toFind;
		Rectangle displayBounds = GeometryUtil.getDisplayBounds(toFind);

		while (parent != null && !(parent instanceof Shell)) {
			for (Control nextSibling : parent.getChildren()) {
				if (nextSibling == current) {
					continue;
				}
				if (!nextSibling.isVisible()) {
					continue;
				}
				Rectangle nextSiblingBounds = GeometryUtil.getDisplayBounds(nextSibling);
				if (nextSiblingBounds.intersects(displayBounds)) {
					return true;
				}
			}
			current = parent;
			parent = parent.getParent();
		}
		return false;
	}

	/**
	 * Computes the string that will be shown in the text box which displays
	 * information about the selected child. This is a tracked getter -- if it
	 * reads from a databinding observable, the text box will automatically
	 * refresh in response to changes in that observable.
	 * 
	 * @TrackedGetter
	 */
	private String computeChildInfo() {
		StringBuilder builder = new StringBuilder();
		Control child = getSelectedChild();

		if (child != null) {
			builder.append(child.getClass().getName());
			builder.append("\n\n"); //$NON-NLS-1$

			int widthHintFromLayoutData = UNKNOWN;
			int heightHintFromLayoutData = UNKNOWN;
			Object layoutData = child.getLayoutData();
			if (layoutData == null) {
				builder.append("getLayoutData() == null\n"); //$NON-NLS-1$
			} else if (layoutData instanceof GridData) {
				GridData grid = (GridData) layoutData;
				builder.append(GridDataFactory.createFrom(grid));
				widthHintFromLayoutData = grid.widthHint;
				heightHintFromLayoutData = grid.heightHint;

				if (!grid.grabExcessHorizontalSpace) {
					if (isHorizontallyScrollable(child) || isGrowableLayout(child, true)) {
						builder.append(getWarningMessage(
								Messages.LayoutSpyDialog_warning_grab_horizontally_scrolling));
					}
				}
				if (!grid.grabExcessVerticalSpace) {
					if (isVerticallyScrollable(child) || isGrowableLayout(child, false)) {
						builder.append(getWarningMessage(
								Messages.LayoutSpyDialog_warning_grab_vertical_scrolling));
					}
				}
			} else if (layoutData instanceof FormData) {
				FormData data = (FormData) layoutData;

				widthHintFromLayoutData = data.width;
				heightHintFromLayoutData = data.height;
			} else {
				describeObject(builder, "data", layoutData); //$NON-NLS-1$
			}

			if (isHorizontallyScrollable(child)) {
				if (widthHintFromLayoutData == SWT.DEFAULT) {
					builder.append(getWarningMessage(Messages.LayoutSpyDialog_warning_hint_for_horizontally_scrollable));
				}
			}

			if (isVerticallyScrollable(child)) {
				if (heightHintFromLayoutData == SWT.DEFAULT) {
					builder.append(getWarningMessage(Messages.LayoutSpyDialog_warning_hint_for_vertically_scrollable));
				}
			}

			builder.append("\n"); //$NON-NLS-1$

			// Print the current dimensions
			Rectangle bounds = child.getBounds();
			builder.append(NLS.bind("getBounds() = {0}", bounds.toString())); //$NON-NLS-1$
			builder.append("\n"); //$NON-NLS-1$

			Point adjustment = computeHintAdjustment(child);

			int widthHint = Math.max(0, bounds.width - adjustment.x);
			int heightHint = Math.max(0, bounds.height - adjustment.y);

			builder.append(NLS.bind("widthAdjustment = {0}, heightAdjustment = {1}", //$NON-NLS-1$
					new Object[] { adjustment.x, adjustment.y }));
			builder.append("\n\n"); //$NON-NLS-1$

			// Print the default size
			Point defaultSize = child.computeSize(SWT.DEFAULT, SWT.DEFAULT, false);
			builder.append(NLS.bind("computeSize(SWT.DEFAULT, SWT.DEFAULT, false) = {0}", printPoint(defaultSize))); //$NON-NLS-1$
			builder.append("\n"); //$NON-NLS-1$

			// Print the preferred horizontally-wrapped size:
			Point hWrappedSize = child.computeSize(widthHint, SWT.DEFAULT, false);
			builder.append(NLS.bind("computeSize({0} - widthAdjustment, SWT.DEFAULT, false) = {1}", //$NON-NLS-1$
					new Object[] { widthHint, printPoint(hWrappedSize) }));
			builder.append("\n"); //$NON-NLS-1$

			// Print the preferred vertically-wrapped size:
			Point vWrappedSize = child.computeSize(SWT.DEFAULT, heightHint, false);
			builder.append(NLS.bind("computeSize(SWT.DEFAULT, {0} - heightAdjustment, false) = {1}", //$NON-NLS-1$
					new Object[] { heightHint, printPoint(vWrappedSize) }));
			builder.append("\n"); //$NON-NLS-1$

			// Check for warnings
			Point noOpSize = child.computeSize(widthHint, heightHint, false);
			if (noOpSize.x != bounds.width || noOpSize.y != bounds.height) {
				builder.append(getWarningMessage(NLS.bind(Messages.LayoutSpyDialog_warning_unexpected_compute_size,
						new Object[] { printHint(widthHint), printHint(heightHint), printPoint(noOpSize) })));
			}

			if (bounds.height < hWrappedSize.y) {
				builder.append(
						getWarningMessage(Messages.LayoutSpyDialog_warning_shorter_than_preferred_size));
			}

			printReasonControlIsInvisible(builder, child);
		}
		return builder.toString();
	}

	/**
	 * If the control cannot be seen by the user, this method adds a warning
	 * message to the given builder explaining the reason why the control cannot
	 * be seen.
	 */
	private void printReasonControlIsInvisible(StringBuilder builder, Control control) {
		if (!control.isVisible()) {
			builder.append(getWarningMessage("isVisible() == false")); //$NON-NLS-1$
			return;
		}

		Rectangle bounds = control.getBounds();
		if (bounds.isEmpty()) {
			builder.append(getWarningMessage(Messages.LayoutSpyDialog_warning_zero_size));
			return;
		}

		Rectangle displayBounds = GeometryUtil.getDisplayBounds(control);

		Composite parent = control.getParent();
		if (parent != null) {
			Rectangle parentDisplayBounds = GeometryUtil.getDisplayBounds(parent);

			Rectangle intersection = displayBounds.intersection(parentDisplayBounds);
			if (intersection.isEmpty()) {
				builder.append(getWarningMessage(Messages.LayoutSpyDialog_warning_bounds_outside_parent));
				return;
			}

			if (intersection.width < bounds.width || intersection.height < bounds.height) {
				builder.append(getWarningMessage(Messages.LayoutSpyDialog_warning_control_partially_clipped));
				return;
			}

			if (overlapsSibling(control)) {
				builder.append(getWarningMessage(Messages.LayoutSpyDialog_warning_control_overlaps_siblings));
				return;
			}
		}
	}

	/**
	 * Computes the string that will be shown in the text box which displays
	 * information about the selected layout. This is a tracked getter: if it
	 * reads from an observable, the text box will update automatically when the
	 * observable changes.
	 * 
	 * @TrackedGetter
	 */
	private String computeParentInfo() {
		StringBuilder builder = new StringBuilder();
		@Nullable
		Composite parent = parentControl.getValue();

		if (parent != null) {
			builder.append(parent.getClass().getName());
			builder.append("\n\n"); //$NON-NLS-1$

			Rectangle parentBounds = GeometryUtil.getDisplayBounds(parent);
			Layout layout = parent.getLayout();

			if (layout != null) {
				if (layout instanceof GridLayout) {
					GridLayout grid = (GridLayout) layout;
					builder.append(GridLayoutFactory.createFrom(grid));

					boolean hasVerticallyTruncadeControls = false;
					boolean hasHorizontallyTruncadeControls = false;

					boolean hasHorizontalGrab = false;
					boolean hasVerticalGrab = false;
					for (Control next : parent.getChildren()) {
						@Nullable
						GridData data = (GridData) next.getLayoutData();
						if (data == null) {
							continue;
						}

						Rectangle childBounds = GeometryUtil.getDisplayBounds(parent);
						Rectangle intersection = childBounds.intersection(parentBounds);

						if (intersection.width < childBounds.width) {
							hasHorizontallyTruncadeControls = true;
						}

						if (intersection.height < childBounds.height) {
							hasVerticallyTruncadeControls = true;
						}

						hasHorizontalGrab = hasHorizontalGrab || data.grabExcessHorizontalSpace;
						hasVerticalGrab = hasVerticalGrab || data.grabExcessVerticalSpace;
					}

					if (hasHorizontallyTruncadeControls && !hasHorizontalGrab) {
						builder.append(getWarningMessage(
								Messages.LayoutSpyDialog_warning_not_grabbing_horizontally));
					}

					if (hasVerticallyTruncadeControls && !hasVerticalGrab) {
						builder.append(getWarningMessage(
								Messages.LayoutSpyDialog_warning_not_grabbing_vertically));
					}
				} else {
					describeObject(builder, "layout", layout); //$NON-NLS-1$
				}
			}
		} else {
			builder.append(Messages.LayoutSpyDialog_label_no_parent_control_selected);
		}

		return builder.toString();
	}

	/**
	 * Uses reflection to print the values of the given object's public fields.
	 */
	void describeObject(StringBuilder result, String variableName, Object toDescribe) {
		@SuppressWarnings("rawtypes")
		Class clazz = toDescribe.getClass();
		result.append(clazz.getName());
		result.append(" "); //$NON-NLS-1$
		result.append(variableName);
		result.append(";\n"); //$NON-NLS-1$
		Field[] fields = clazz.getFields();

		for (Field nextField : fields) {
			int modifiers = nextField.getModifiers();
			if (!Modifier.isPublic(modifiers)) {
				continue;
			}
			try {
				String next = variableName + "." + nextField.getName() + " = " + nextField.get(toDescribe) + ";"; //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$
				result.append(next);
				result.append("\n"); //$NON-NLS-1$
			} catch (IllegalArgumentException | IllegalAccessException e) {
				// Don't care
			}
		}
	}
}