Added better user interface controls and panning.

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>nl.andrewlalis</groupId>
     <artifactId>EntityRelationMappingEditor</artifactId>
-    <version>1.1.0</version>
+    <version>1.2.0</version>
     <build>
         <plugins>
             <plugin>

src/main/java/nl/andrewlalis/erme/EntityRelationMappingEditor.java

@@ -4,7 +4,7 @@ import com.formdev.flatlaf.FlatLightLaf;
 import nl.andrewlalis.erme.view.EditorFrame;
 
 public class EntityRelationMappingEditor {
-	public static final String VERSION = "1.1.0";
+	public static final String VERSION = "1.2.0";
 
 	public static void main(String[] args) {
 		if (!FlatLightLaf.install()) {

src/main/java/nl/andrewlalis/erme/control/actions/ExportToImageAction.java

@@ -84,23 +84,13 @@ public class ExportToImageAction extends AbstractAction {
 	private BufferedImage renderModel() {
 		BufferedImage bufferedImage = new BufferedImage(1, 1, BufferedImage.TYPE_INT_RGB);
 		Graphics2D g2d = bufferedImage.createGraphics();
-		int minX = Integer.MAX_VALUE;
+		final Rectangle bounds = this.model.getViewModel().getBounds(g2d);
-		int minY = Integer.MAX_VALUE;
+		BufferedImage outputImage = new BufferedImage(bounds.width, bounds.height + 20, BufferedImage.TYPE_INT_RGB);
-		int maxX = Integer.MIN_VALUE;
-		int maxY = Integer.MIN_VALUE;
-		for (Relation r : model.getRelations()) {
-			Rectangle bounds = r.getViewModel().getBounds(g2d);
-			minX = Math.min(minX, bounds.x);
-			minY = Math.min(minY, bounds.y);
-			maxX = Math.max(maxX, bounds.x + bounds.width);
-			maxY = Math.max(maxY, bounds.y + bounds.height);
-		}
-		BufferedImage outputImage = new BufferedImage((maxX - minX), (maxY - minY) + 20, BufferedImage.TYPE_INT_RGB);
 		g2d = outputImage.createGraphics();
 		g2d.setColor(Color.WHITE);
 		g2d.fillRect(outputImage.getMinX(), outputImage.getMinY(), outputImage.getWidth(), outputImage.getHeight());
 		AffineTransform originalTransform = g2d.getTransform();
-		g2d.setTransform(AffineTransform.getTranslateInstance(-minX, -minY));
+		g2d.setTransform(AffineTransform.getTranslateInstance(-bounds.x, -bounds.y));
 
 		List<Relation> selectedRelations = this.model.getSelectedRelations();
 		this.model.getSelectedRelations().forEach(r -> r.setSelected(false));

src/main/java/nl/andrewlalis/erme/control/actions/LoadSampleModelAction.java

@@ -0,0 +1,43 @@
+package nl.andrewlalis.erme.control.actions;
+
+import lombok.Setter;
+import nl.andrewlalis.erme.model.*;
+import nl.andrewlalis.erme.view.DiagramPanel;
+
+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+
+public class LoadSampleModelAction extends AbstractAction {
+	private static LoadSampleModelAction instance;
+
+	public static LoadSampleModelAction getInstance() {
+		if (instance == null) {
+			instance = new LoadSampleModelAction();
+		}
+		return instance;
+	}
+
+	@Setter
+	private DiagramPanel diagramPanel;
+
+	public LoadSampleModelAction() {
+		super("Load Sample Model");
+		this.putValue(SHORT_DESCRIPTION, "Loads a sample ER-mapping model.");
+	}
+
+	@Override
+	public void actionPerformed(ActionEvent e) {
+		MappingModel model = new MappingModel();
+		Relation r0 = new Relation(model, new Point(50, 20), "AirplaneType");
+		r0.addAttribute(new Attribute(r0, AttributeType.ID_KEY, "name"));
+		r0.addAttribute(new Attribute(r0, AttributeType.PLAIN, "manufacturer"));
+		model.addRelation(r0);
+		Relation r1 = new Relation(model, new Point(50, 100), "Airplane");
+		r1.addAttribute(new Attribute(r1, AttributeType.ID_KEY, "id"));
+		r1.addAttribute(new Attribute(r1, AttributeType.PLAIN, "purchasedAt"));
+		r1.addAttribute(new ForeignKeyAttribute(r1, AttributeType.PLAIN, "typeName", "AirplaneType", "name"));
+		model.addRelation(r1);
+		this.diagramPanel.setModel(model);
+	}
+}

src/main/java/nl/andrewlalis/erme/control/diagram/DiagramMouseListener.java

@@ -7,7 +7,6 @@ import nl.andrewlalis.erme.view.DiagramPopupMenu;
 
 import java.awt.*;
 import java.awt.event.ActionEvent;
-import java.awt.event.InputEvent;
 import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
 
@@ -31,22 +30,29 @@ public class DiagramMouseListener extends MouseAdapter {
 	 */
 	@Override
 	public void mousePressed(MouseEvent e) {
-		DiagramPanel panel = (DiagramPanel) e.getSource();
+		final DiagramPanel panel = (DiagramPanel) e.getSource();
-		final Graphics2D g2d = panel.getGraphics2D();
+		final Graphics2D g = panel.getGraphics2D();
 		this.mouseDragStart = e.getPoint();
+		final int modelX = e.getX() - panel.getPanningTranslation().x;
+		final int modelY = e.getY() - panel.getPanningTranslation().y;
 
-		boolean isCtrlDown = (e.getModifiers() & ActionEvent.CTRL_MASK) == ActionEvent.CTRL_MASK;
+		final boolean isCtrlDown = (e.getModifiers() & ActionEvent.CTRL_MASK) == ActionEvent.CTRL_MASK;
+		final boolean isShiftDown = (e.getModifiers() & ActionEvent.SHIFT_MASK) == ActionEvent.SHIFT_MASK;
 
-		if (!isCtrlDown) {
+		if (!isShiftDown && !isCtrlDown) {// A simple click anywhere should reset selection.
 			this.model.getRelations().forEach(r -> r.setSelected(false));
 		}
+
+		if (!isShiftDown) {// If the user clicked or CTRL+clicked, try and select the relation they clicked on.
 			for (Relation r : this.model.getRelations()) {
-			if (r.getViewModel().getBounds(g2d).contains(e.getX(), e.getY())) {
+				if (r.getViewModel().getBounds(g).contains(modelX, modelY)) {
 					r.setSelected(!r.isSelected());
 					break;
 				}
 			}
+		}
 
+		// If the user right-clicked, show a popup menu.
 		if (e.getButton() == MouseEvent.BUTTON3) {
 			DiagramPopupMenu popupMenu = new DiagramPopupMenu(this.model);
 			popupMenu.show(panel, e.getX(), e.getY());
@@ -62,15 +68,24 @@ public class DiagramMouseListener extends MouseAdapter {
 
 	@Override
 	public void mouseDragged(MouseEvent e) {
-		int dx = this.mouseDragStart.x - e.getX();
+		final int dx = this.mouseDragStart.x - e.getX();
-		int dy = this.mouseDragStart.y - e.getY();
+		final int dy = this.mouseDragStart.y - e.getY();
+		final boolean isShiftDown = (e.getModifiers() & ActionEvent.SHIFT_MASK) == ActionEvent.SHIFT_MASK;
 		boolean changed = false;
+
+		if (isShiftDown) {
+			final DiagramPanel panel = (DiagramPanel) e.getSource();
+			panel.translate(-dx, -dy);
+			panel.repaint();
+		} else {
 			for (Relation r : this.model.getRelations()) {
 				if (r.isSelected()) {
 					r.setPosition(new Point(r.getPosition().x - dx, r.getPosition().y - dy));
 					changed = true;
 				}
 			}
+		}
+
 		if (changed) {
 			this.model.fireChangedEvent();
 		}

src/main/java/nl/andrewlalis/erme/model/Attribute.java

@@ -59,4 +59,8 @@ public class Attribute implements Serializable {
 	public String toString() {
 		return this.getName();
 	}
+
+	public Attribute copy(Relation newRelation) {
+		return new Attribute(newRelation, this.getType(), this.getName());
+	}
 }

src/main/java/nl/andrewlalis/erme/model/ForeignKeyAttribute.java

@@ -31,4 +31,9 @@ public class ForeignKeyAttribute extends Attribute {
 	public String toString() {
 		return super.toString() + "->" + this.getFullReferenceName();
 	}
+
+	@Override
+	public ForeignKeyAttribute copy(Relation newRelation) {
+		return new ForeignKeyAttribute(newRelation, this.getType(), this.getName(), this.getReference());
+	}
 }

src/main/java/nl/andrewlalis/erme/model/MappingModel.java

@@ -1,7 +1,10 @@
 package nl.andrewlalis.erme.model;
 
 import lombok.Getter;
+import nl.andrewlalis.erme.view.view_models.MappingModelViewModel;
+import nl.andrewlalis.erme.view.view_models.ViewModel;
 
+import java.awt.*;
 import java.io.Serializable;
 import java.util.HashSet;
 import java.util.List;
@@ -13,7 +16,7 @@ import java.util.stream.Collectors;
  * This model contains all the information about a single mapping diagram,
  * including each mapped table and the links between them.
  */
-public class MappingModel implements Serializable {
+public class MappingModel implements Serializable, Viewable {
 	@Getter
 	private final Set<Relation> relations;
 
@@ -79,6 +82,23 @@ public class MappingModel implements Serializable {
 		this.changeListeners.forEach(ModelChangeListener::onModelChanged);
 	}
 
+	/**
+	 * Updates the positions of all relations so that the bounding box for this
+	 * model starts at 0, 0.
+	 */
+	public final void normalizeRelationPositions() {
+		int minX = Integer.MAX_VALUE;
+		int minY = Integer.MAX_VALUE;
+		for (Relation r : this.getRelations()) {
+			minX = Math.min(minX, r.getPosition().x);
+			minY = Math.min(minY, r.getPosition().y);
+		}
+		for (Relation r : this.getRelations()) {
+			final Point current = r.getPosition();
+			r.setPosition(new Point(current.x - minX, current.y - minY));
+		}
+	}
+
 	@Override
 	public boolean equals(Object o) {
 		if (this == o) return true;
@@ -91,4 +111,15 @@ public class MappingModel implements Serializable {
 	public int hashCode() {
 		return Objects.hash(this.getRelations());
 	}
+
+	@Override
+	public ViewModel getViewModel() {
+		return new MappingModelViewModel(this);
+	}
+
+	public MappingModel copy() {
+		MappingModel c = new MappingModel();
+		this.getRelations().forEach(r -> c.addRelation(r.copy(c)));
+		return c;
+	}
 }

src/main/java/nl/andrewlalis/erme/model/Relation.java

@@ -2,6 +2,7 @@ package nl.andrewlalis.erme.model;
 
 import lombok.Getter;
 import nl.andrewlalis.erme.view.view_models.RelationViewModel;
+import nl.andrewlalis.erme.view.view_models.ViewModel;
 
 import java.awt.*;
 import java.io.Serializable;
@@ -14,7 +15,7 @@ import java.util.stream.Collectors;
  * Represents a single "relation" or table in the diagram.
  */
 @Getter
-public class Relation implements Serializable {
+public class Relation implements Serializable, Viewable {
 	private final MappingModel model;
 	private Point position;
 	private String name;
@@ -59,7 +60,8 @@ public class Relation implements Serializable {
 		}
 	}
 
-	public RelationViewModel getViewModel() {
+	@Override
+	public ViewModel getViewModel() {
 		if (this.viewModel == null) {
 			this.viewModel = new RelationViewModel(this);
 		}
@@ -89,4 +91,10 @@ public class Relation implements Serializable {
 	public String toString() {
 		return this.getName();
 	}
+
+	public Relation copy(MappingModel newModel) {
+		Relation c = new Relation(newModel, new Point(this.getPosition()), this.getName());
+		this.getAttributes().forEach(a -> c.addAttribute(a.copy(c)));
+		return c;
+	}
 }

src/main/java/nl/andrewlalis/erme/model/Viewable.java

@@ -0,0 +1,7 @@
+package nl.andrewlalis.erme.model;
+
+import nl.andrewlalis.erme.view.view_models.ViewModel;
+
+public interface Viewable {
+	ViewModel getViewModel();
+}

src/main/java/nl/andrewlalis/erme/view/DiagramPanel.java

@@ -1,10 +1,7 @@
 package nl.andrewlalis.erme.view;
 
 import lombok.Getter;
-import nl.andrewlalis.erme.control.actions.ExportToImageAction;
+import nl.andrewlalis.erme.control.actions.*;
-import nl.andrewlalis.erme.control.actions.LoadAction;
-import nl.andrewlalis.erme.control.actions.NewModelAction;
-import nl.andrewlalis.erme.control.actions.SaveAction;
 import nl.andrewlalis.erme.control.actions.edits.AddAttributeAction;
 import nl.andrewlalis.erme.control.actions.edits.AddRelationAction;
 import nl.andrewlalis.erme.control.actions.edits.RemoveAttributeAction;
@@ -12,10 +9,11 @@ import nl.andrewlalis.erme.control.actions.edits.RemoveRelationAction;
 import nl.andrewlalis.erme.control.diagram.DiagramMouseListener;
 import nl.andrewlalis.erme.model.MappingModel;
 import nl.andrewlalis.erme.model.ModelChangeListener;
-import nl.andrewlalis.erme.view.view_models.MappingModelViewModel;
 
 import javax.swing.*;
 import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.KeyEvent;
 import java.awt.event.MouseListener;
 import java.awt.event.MouseMotionListener;
 
@@ -26,8 +24,30 @@ public class DiagramPanel extends JPanel implements ModelChangeListener {
 	@Getter
 	private MappingModel model;
 
+	@Getter
+	private final Point panningTranslation;
+
 	public DiagramPanel(MappingModel model) {
 		super(true);
+		this.panningTranslation = new Point();
+		InputMap inputMap = this.getInputMap(WHEN_IN_FOCUSED_WINDOW);
+		inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, KeyEvent.SHIFT_DOWN_MASK), "PAN_RESET");
+		inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, KeyEvent.CTRL_DOWN_MASK), "CENTER_MODEL");
+		this.getActionMap().put("PAN_RESET", new AbstractAction() {
+			@Override
+			public void actionPerformed(ActionEvent e) {
+				resetTranslation();
+				repaint();
+			}
+		});
+		this.getActionMap().put("CENTER_MODEL", new AbstractAction() {
+			@Override
+			public void actionPerformed(ActionEvent e) {
+				model.normalizeRelationPositions();
+				centerModel();
+				repaint();
+			}
+		});
 		this.setModel(model);
 	}
 
@@ -44,13 +64,38 @@ public class DiagramPanel extends JPanel implements ModelChangeListener {
 		this.addMouseListener(listener);
 		this.addMouseMotionListener(listener);
 		this.updateActionModels();
+		this.centerModel();
 		this.repaint();
 	}
 
+	public void translate(int dx, int dy) {
+		this.panningTranslation.x += dx;
+		this.panningTranslation.y += dy;
+	}
+
+	public void resetTranslation() {
+		this.panningTranslation.x = 0;
+		this.panningTranslation.y = 0;
+	}
+
+	public void centerModel() {
+		if (this.getGraphics() == null) {
+			return;
+		}
+		final Rectangle modelBounds = this.getModel().getViewModel().getBounds(this.getGraphics2D());
+		final int modelCenterX = modelBounds.x + modelBounds.width / 2;
+		final int modelCenterY = modelBounds.y + modelBounds.height / 2;
+		final int panelCenterX = this.getWidth() / 2;
+		final int panelCenterY = this.getHeight() / 2;
+		this.resetTranslation();
+		this.translate(panelCenterX - modelCenterX, panelCenterY - modelCenterY);
+	}
+
 	@Override
 	protected void paintComponent(Graphics g) {
 		super.paintComponent(g);
-		new MappingModelViewModel(this.model).draw(this.getGraphics2D(g));
+		g.translate(this.panningTranslation.x, this.panningTranslation.y);
+		this.model.getViewModel().draw(this.getGraphics2D(g));
 	}
 
 	public Graphics2D getGraphics2D(Graphics g) {
@@ -83,5 +128,6 @@ public class DiagramPanel extends JPanel implements ModelChangeListener {
 		RemoveRelationAction.getInstance().setModel(this.model);
 		AddAttributeAction.getInstance().setModel(this.model);
 		RemoveAttributeAction.getInstance().setModel(this.model);
+		LoadSampleModelAction.getInstance().setDiagramPanel(this);
 	}
 }

src/main/java/nl/andrewlalis/erme/view/EditorFrame.java

@@ -16,7 +16,7 @@ public class EditorFrame extends JFrame {
 		this.setMinimumSize(new Dimension(400, 400));
 		this.setPreferredSize(new Dimension(800, 800));
 		this.pack();
-		this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
+		this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
 		this.setLocationRelativeTo(null);
 	}
 }

src/main/java/nl/andrewlalis/erme/view/EditorMenuBar.java

@@ -45,6 +45,7 @@ public class EditorMenuBar extends JMenuBar {
 	private JMenu buildHelpMenu() {
 		JMenu menu = new JMenu("Help");
 		menu.add(InstructionsAction.getInstance());
+		menu.add(LoadSampleModelAction.getInstance());
 		menu.add(AboutAction.getInstance());
 		return menu;
 	}

src/main/java/nl/andrewlalis/erme/view/view_models/AttributeViewModel.java

@@ -9,6 +9,9 @@ import java.awt.font.TextAttribute;
 import java.awt.geom.Rectangle2D;
 import java.text.AttributedString;
 
+/**
+ * View model for rendering a single attribute of a relation.
+ */
 public class AttributeViewModel implements ViewModel {
 	public static final int PADDING_X = 5;
 	public static final int PADDING_Y = 5;
@@ -25,7 +28,7 @@ public class AttributeViewModel implements ViewModel {
 	@Override
 	public void draw(Graphics2D g) {
 		AttributedString as = this.getAttributedString(g);
-		Rectangle r = this.getBoxBounds(g, as);
+		Rectangle r = this.getBounds(g, as);
 		g.setColor(BACKGROUND_COLOR);
 		g.fillRect(r.x, r.y, r.width, r.height);
 		g.setColor(FONT_COLOR);
@@ -40,12 +43,18 @@ public class AttributeViewModel implements ViewModel {
 		}
 	}
 
-	private Rectangle getBoxBounds(Graphics2D g, AttributedString as) {
+	@Override
+	public Rectangle getBounds(Graphics2D g) {
+		return this.getBounds(g, this.getAttributedString(g));
+	}
+
+	private Rectangle getBounds(Graphics2D g, AttributedString as) {
+		final RelationViewModel relationViewModel = (RelationViewModel) this.attribute.getRelation().getViewModel();
 		int x = this.attribute.getRelation().getPosition().x + RelationViewModel.PADDING_X;
-		int y = this.attribute.getRelation().getPosition().y + this.attribute.getRelation().getViewModel().getNameBounds(g).height + RelationViewModel.ATTRIBUTE_SEPARATION;
+		int y = this.attribute.getRelation().getPosition().y + relationViewModel.getNameBounds(g).height + RelationViewModel.ATTRIBUTE_SEPARATION;
 		int i = 0;
 		while (!this.attribute.getRelation().getAttributes().get(i).equals(this.attribute)) {
-			x += this.attribute.getRelation().getAttributes().get(i).getViewModel().getBoxBounds(g).width;
+			x += this.attribute.getRelation().getAttributes().get(i).getViewModel().getBounds(g).width;
 			i++;
 		}
 		Rectangle2D nameRect = g.getFontMetrics().getStringBounds(as.getIterator(), 0, this.attribute.getName().length(), g);
@@ -62,10 +71,6 @@ public class AttributeViewModel implements ViewModel {
 		return new Rectangle(x, y, width, height);
 	}
 
-	public Rectangle getBoxBounds(Graphics2D g) {
-		return this.getBoxBounds(g, this.getAttributedString(g));
-	}
-
 	private AttributedString getAttributedString(Graphics2D g) {
 		AttributedString as = new AttributedString(this.attribute.getName());
 		as.addAttribute(TextAttribute.FONT, g.getFont());

src/main/java/nl/andrewlalis/erme/view/view_models/MappingModelViewModel.java

@@ -5,6 +5,9 @@ import nl.andrewlalis.erme.model.Relation;
 
 import java.awt.*;
 
+/**
+ * View model for rendering an entire {@code MappingModel} object.
+ */
 public class MappingModelViewModel implements ViewModel {
 	private final MappingModel model;
 
@@ -18,4 +21,20 @@ public class MappingModelViewModel implements ViewModel {
 			r.getViewModel().draw(g);
 		}
 	}
+
+	@Override
+	public Rectangle getBounds(Graphics2D g) {
+		int minX = Integer.MAX_VALUE;
+		int minY = Integer.MAX_VALUE;
+		int maxX = Integer.MIN_VALUE;
+		int maxY = Integer.MIN_VALUE;
+		for (Relation r : model.getRelations()) {
+			Rectangle bounds = r.getViewModel().getBounds(g);
+			minX = Math.min(minX, bounds.x);
+			minY = Math.min(minY, bounds.y);
+			maxX = Math.max(maxX, bounds.x + bounds.width);
+			maxY = Math.max(maxY, bounds.y + bounds.height);
+		}
+		return new Rectangle(minX, minY, Math.abs(maxX - minX), Math.abs(maxY - minY));
+	}
 }

src/main/java/nl/andrewlalis/erme/view/view_models/RelationViewModel.java

@@ -8,11 +8,28 @@ import java.awt.font.TextAttribute;
 import java.awt.geom.Rectangle2D;
 import java.text.AttributedString;
 
+/**
+ * View model which handles rendering a single relation.
+ */
 public class RelationViewModel implements ViewModel {
+	/**
+	 * Padding that should be added to the left and right of the true bounds.
+	 */
 	public static final int PADDING_X = 5;
+
+	/**
+	 * Padding that should be added to the top and bottom of the true bounds.
+	 */
 	public static final int PADDING_Y = 5;
+
+	/**
+	 * The space between the relation's name and any attributes.
+	 */
 	public static final int ATTRIBUTE_SEPARATION = 10;
 
+	public static final Color SELECTED_COLOR = new Color(204, 224, 255);
+	public static final Color NAME_COLOR = Color.BLACK;
+
 	private final Relation relation;
 
 	public RelationViewModel(Relation relation) {
@@ -23,17 +40,23 @@ public class RelationViewModel implements ViewModel {
 	public void draw(Graphics2D g) {
 		AttributedString as = this.getAttributedString(g);
 		Rectangle bounds = this.getBounds(g);
-		g.setColor(Color.BLACK);
+		if (this.relation.isSelected()) {
+			g.setColor(SELECTED_COLOR);
+			g.fillRect(bounds.x, bounds.y, bounds.width, bounds.height);
+		}
+		g.setColor(NAME_COLOR);
 		g.drawString(as.getIterator(), bounds.x + PADDING_X, bounds.y + this.getNameBounds(g).height - PADDING_Y);
 		for (Attribute a : this.relation.getAttributes()) {
 			a.getViewModel().draw(g);
 		}
-		if (this.relation.isSelected()) {
-			g.setColor(Color.BLUE);
-			g.drawRect(bounds.x, bounds.y, bounds.width, bounds.height);
-		}
 	}
 
+	/**
+	 * Obtains the bounding box for the relation that'll be drawn. The bounding
+	 * box contains the name of the relation and any attributes in it.
+	 * @param g The graphics context.
+	 * @return A rectangle describing the bounding box.
+	 */
 	public Rectangle getBounds(Graphics2D g) {
 		Rectangle rect = new Rectangle();
 		rect.x = this.relation.getPosition().x;
@@ -41,7 +64,7 @@ public class RelationViewModel implements ViewModel {
 		int totalAttributeWidth = 0;
 		int maxAttributeHeight = 0;
 		for (Attribute a : this.relation.getAttributes()) {
-			Rectangle attributeBounds = a.getViewModel().getBoxBounds(g);
+			Rectangle attributeBounds = a.getViewModel().getBounds(g);
 			totalAttributeWidth += attributeBounds.width;
 			maxAttributeHeight = Math.max(maxAttributeHeight, attributeBounds.height);
 		}
@@ -51,12 +74,24 @@ public class RelationViewModel implements ViewModel {
 		return rect;
 	}
 
+	/**
+	 * Gets the bounding box around the relation's name, according to the font,
+	 * font size, weight, etc.
+	 * @param g The graphics context.
+	 * @return A rectangle describing the name's bounding box.
+	 */
 	public Rectangle getNameBounds(Graphics2D g) {
 		AttributedString as = this.getAttributedString(g);
 		Rectangle2D nameBounds = g.getFontMetrics().getStringBounds(as.getIterator(), 0, this.relation.getName().length(), g);
 		return nameBounds.getBounds();
 	}
 
+	/**
+	 * Gets an instance of AttributedString that can be used for display and
+	 * reference purposes.
+	 * @param g The graphics context.
+	 * @return The attributed string, with all necessary attributes set.
+	 */
 	private AttributedString getAttributedString(Graphics2D g) {
 		AttributedString as = new AttributedString(this.relation.getName());
 		as.addAttribute(TextAttribute.FONT, g.getFont());

src/main/java/nl/andrewlalis/erme/view/view_models/ViewModel.java

@@ -4,4 +4,6 @@ import java.awt.*;
 
 public interface ViewModel {
 	void draw(Graphics2D g);
+
+	Rectangle getBounds(Graphics2D g);
 }

src/main/resources/html/instructions.html

@@ -28,7 +28,7 @@
         The <em>Edit</em> menu contains options for making changes to the current model, such as adding or removing relations and attributes, or undoing/redoing actions.
     </li>
     <li>
-        The <em>Help</em> menu contains some items with additional information about the application, like this help page and a simple <em>About</em> popup with version information.
+        The <em>Help</em> menu contains some items with additional information about the application, like this help page and a simple <em>About</em> popup with version information. There's also a <em>Load Sample Model</em> option, which will load a very basic sample model into the application that you are free to mess around with.
     </li>
 </ul>
 <p>
@@ -47,6 +47,12 @@
     <li>
         Right-click on different areas to access a context menu with some helpful actions.
     </li>
+    <li>
+        Hold <em>Shift</em> while dragging the mouse to pan across the model. To reset panning, press <em>Shift + Space</em>.
+    </li>
+    <li>
+        Press <em>Control + Space</em> to move the view so that the diagram is centered.
+    </li>
     <li>
         When exporting the model to an image, be sure to add the desired image file extension (.png, .jpg, .bmp, etc.), or the application will default to .png.
     </li>