src/main/java/ovh/gasser/newshapes/ui/Controller.java

@@ -5,6 +5,15 @@ import org.slf4j.LoggerFactory;
 import ovh.gasser.newshapes.HTMLExporter;
 import ovh.gasser.newshapes.Selection;
 import ovh.gasser.newshapes.attributes.ColorAttributes;
+import ovh.gasser.newshapes.persistence.DrawingSerializer;
+import ovh.gasser.newshapes.command.AddShapeCommand;
+import ovh.gasser.newshapes.command.ChangeColorCommand;
+import ovh.gasser.newshapes.command.Command;
+import ovh.gasser.newshapes.command.CommandHistory;
+import ovh.gasser.newshapes.command.CommandHistoryListener;
+import ovh.gasser.newshapes.command.MoveShapeCommand;
+import ovh.gasser.newshapes.command.RemoveShapeCommand;
+import ovh.gasser.newshapes.command.ResizeShapeCommand;
 import ovh.gasser.newshapes.shapes.ResizeHandle;
 import ovh.gasser.newshapes.shapes.SCollection;
 import ovh.gasser.newshapes.shapes.SText;
@@ -13,18 +22,28 @@ import ovh.gasser.newshapes.ui.listeners.SelectionListener;
 
 import javax.swing.*;
 import java.awt.*;
+import java.awt.event.InputEvent;
 import java.awt.event.KeyAdapter;
 import java.awt.event.KeyEvent;
 import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
 import java.io.FileNotFoundException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
 import java.util.Optional;
+import java.util.function.Function;
 
 public class Controller {
-    private final static Logger logger = LoggerFactory.getLogger(Controller.class);
+    private static final Logger logger = LoggerFactory.getLogger(Controller.class);
+
     private final ShapesView view;
     private final SCollection model;
     private final Selection selection;
+    private final CommandHistory commandHistory;
 
     private Point lastMousePos;
     private boolean addingText;
@@ -35,11 +54,24 @@ public class Controller {
     private Point selectionBoxStart;
     private Point selectionBoxEnd;
     private boolean boxSelecting;
+    private Point dragStartMousePos;
+    private Map<Shape, Rectangle> dragStartBounds = Map.of();
+    private final Runnable onModelChanged;
+    private java.util.List<Shape> clipboard = java.util.List.of();
+    private int pasteCount = 0;
+    private static final int PASTE_OFFSET = 20;
+    private boolean additiveBoxSelection;
 
     Controller(ShapesView view, SCollection model) {
+        this(view, model, () -> { });
+    }
+
+    Controller(ShapesView view, SCollection model, Runnable onModelChanged) {
         this.view = view;
         this.model = model;
+        this.onModelChanged = onModelChanged;
         this.selection = new Selection();
+        this.commandHistory = new CommandHistory();
 
         var adapter = new MouseAdapter() {
             @Override
@@ -54,14 +86,7 @@ public class Controller {
 
             @Override
             public void mouseReleased(MouseEvent evt) {
-                resizing = false;
+                handleMouseReleased(evt);
-                activeHandle = null;
-                resizeOrigin = null;
-                boxSelecting = false;
-                selectionBoxStart = null;
-                selectionBoxEnd = null;
-                view.setCurrentSelectionBox(null);
-                view.repaint();
             }
         };
         this.view.addMouseMotionListener(adapter);
@@ -74,6 +99,249 @@ public class Controller {
         });
     }
 
+    public void addShape(Shape shape) {
+        executeAndRefresh(new AddShapeCommand(model, shape));
+    }
+
+    public void addSelectionChangeListener(SelectionListener listener) {
+        selection.addListener(listener);
+    }
+
+    public void addHistoryChangeListener(CommandHistoryListener listener) {
+        commandHistory.addListener(listener);
+    }
+
+    public boolean canUndo() {
+        return commandHistory.canUndo();
+    }
+
+    public boolean canRedo() {
+        return commandHistory.canRedo();
+    }
+
+    public void undo() {
+        if (!commandHistory.canUndo()) {
+            return;
+        }
+
+        resetSelection();
+        commandHistory.undo();
+        view.repaint();
+    }
+
+    public void redo() {
+        if (!commandHistory.canRedo()) {
+            return;
+        }
+
+        resetSelection();
+        commandHistory.redo();
+        view.repaint();
+    }
+
+    public void saveDrawing(java.io.File file) {
+        try {
+            new DrawingSerializer().save(model, file);
+            logger.info("Saved drawing to {}", file.getAbsolutePath());
+        } catch (java.io.IOException e) {
+            logger.error("Failed to save drawing: {}", e.getMessage());
+            JOptionPane.showMessageDialog(view, "Failed to save: " + e.getMessage(), "Save Error", JOptionPane.ERROR_MESSAGE);
+        }
+    }
+
+    public void loadDrawing(java.io.File file) {
+        try {
+            SCollection loaded = new DrawingSerializer().load(file);
+            model.stream().toList().forEach(model::remove);
+            loaded.forEach(model::add);
+            resetSelection();
+            view.repaint();
+            logger.info("Loaded drawing from {}", file.getAbsolutePath());
+        } catch (java.io.IOException e) {
+            logger.error("Failed to load drawing: {}", e.getMessage());
+            JOptionPane.showMessageDialog(view, "Failed to load: " + e.getMessage(), "Load Error", JOptionPane.ERROR_MESSAGE);
+        }
+    }
+
+    public void enterTextMode() {
+        addingText = true;
+    }
+
+    public void deleteSelected() {
+        List<Shape> selectedShapes = selection.getSelectedShapes();
+        if (selectedShapes.isEmpty()) {
+            return;
+        }
+
+        logger.debug("Deleting selected shape(s)");
+        executeAndRefresh(new RemoveShapeCommand(model, selectedShapes));
+        resetSelection();
+    }
+
+    public void copySelection() {
+        List<Shape> selectedShapes = selection.getSelectedShapes();
+        if (selectedShapes.isEmpty()) {
+            logger.debug("No selection to copy");
+            return;
+        }
+
+        clipboard = selectedShapes.stream()
+                .map(Shape::clone)
+                .toList();
+        pasteCount = 0;
+    }
+
+    public void cutSelection() {
+        List<Shape> selectedShapes = selection.getSelectedShapes();
+        if (selectedShapes.isEmpty()) {
+            logger.debug("No selection to cut");
+            return;
+        }
+
+        clipboard = selectedShapes.stream()
+                .map(Shape::clone)
+                .toList();
+        pasteCount = 0;
+
+        for (Shape shape : selectedShapes) {
+            model.remove(shape);
+        }
+        resetSelection();
+        onModelChanged.run();
+        view.repaint();
+    }
+
+    public void pasteClipboard() {
+        if (clipboard.isEmpty()) {
+            logger.debug("Clipboard is empty");
+            return;
+        }
+
+        pasteCount++;
+        int offset = PASTE_OFFSET * pasteCount;
+
+        resetSelection();
+
+        for (Shape original : clipboard) {
+            Shape clone = original.clone();
+            clone.translate(offset, offset);
+            model.add(clone);
+            selection.add(clone);
+        }
+
+        onModelChanged.run();
+        view.repaint();
+    }
+
+    public void group() {
+        List<Shape> selectedShapes = selection.getSelectedShapes();
+        if (selectedShapes.size() < 2) {
+            logger.debug("Need at least 2 shapes to group");
+            return;
+        }
+
+        int minIndex = selectedShapes.stream()
+                .mapToInt(model::indexOf)
+                .min()
+                .orElse(0);
+
+        for (Shape shape : selectedShapes) {
+            model.remove(shape);
+            shape.addAttributes(new ovh.gasser.newshapes.attributes.SelectionAttributes(false));
+        }
+
+        Shape[] shapesArray = selectedShapes.toArray(new Shape[0]);
+        SCollection group = SCollection.of(shapesArray);
+
+        model.insert(minIndex, group);
+        resetSelection();
+        selection.add(group);
+        onModelChanged.run();
+        view.repaint();
+    }
+
+    public void ungroup() {
+        List<Shape> selectedShapes = selection.getSelectedShapes();
+        if (selectedShapes.size() != 1) {
+            logger.debug("Can only ungroup a single selected group");
+            return;
+        }
+
+        Shape selected = selectedShapes.get(0);
+        if (!(selected instanceof SCollection group)) {
+            logger.debug("Selected shape is not a group");
+            return;
+        }
+
+        List<Shape> children = new ArrayList<>();
+        group.forEach(children::add);
+
+        model.remove(group);
+
+        for (Shape child : children) {
+            model.add(child);
+        }
+
+        resetSelection();
+        for (Shape child : children) {
+            selection.add(child);
+        }
+        onModelChanged.run();
+        view.repaint();
+    }
+
+    public void changeSelectionColor() {
+        changeColors(shape -> new ColorAttributes(false, true, Color.BLACK, randomColor()));
+    }
+
+    public void changeSelectionFillColor(Color filledColor) {
+        if (filledColor == null) {
+            return;
+        }
+
+        changeColors(shape -> {
+            ColorAttributes current = currentColor(shape);
+            if (shape instanceof SText) {
+                return new ColorAttributes(current.filled, current.stroked, filledColor, filledColor);
+            }
+            return new ColorAttributes(true, current.stroked, filledColor, current.strokedColor);
+        });
+    }
+
+    public void changeSelectionBorderColor(Color strokedColor) {
+        if (strokedColor == null) {
+            return;
+        }
+
+        changeColors(shape -> {
+            ColorAttributes current = currentColor(shape);
+            if (shape instanceof SText) {
+                return new ColorAttributes(current.filled, current.stroked, strokedColor, strokedColor);
+            }
+            return new ColorAttributes(current.filled, true, current.filledColor, strokedColor);
+        });
+    }
+
+    public void setSelectionBorder(boolean state) {
+        changeColors(shape -> {
+            if (shape instanceof SText) {
+                return null;
+            }
+            ColorAttributes current = currentColor(shape);
+            return new ColorAttributes(current.filled, state, current.filledColor, current.strokedColor);
+        });
+    }
+
+    public void setSelectionFilled(boolean state) {
+        changeColors(shape -> {
+            if (shape instanceof SText) {
+                return null;
+            }
+            ColorAttributes current = currentColor(shape);
+            return new ColorAttributes(state, current.stroked, current.filledColor, current.strokedColor);
+        });
+    }
+
     private void handleMouseDragged(MouseEvent evt) {
         if (boxSelecting) {
             selectionBoxEnd = evt.getPoint();
@@ -84,35 +352,19 @@ public class Controller {
             return;
         }
 
-        boxSelecting = false;
-
         if (resizeMode && resizing && activeHandle != null) {
-            logger.debug("RESIZING with handle {} at ({}, {})", activeHandle, evt.getX(), evt.getY());
             int dx = evt.getX() - resizeOrigin.x;
             int dy = evt.getY() - resizeOrigin.y;
-            logger.debug("About to resize {} shapes, dx={}, dy={}", selection.getSelectedShapes().size(), dx, dy);
             for (Shape shape : selection) {
-                logger.debug("Calling resize on shape: {}", shape);
                 shape.resize(activeHandle, dx, dy);
             }
             resizeOrigin = evt.getPoint();
-        } else if (resizeMode && !selection.isEmpty()) {
+        } else if (!selection.isEmpty()) {
-            lastMousePos = evt.getPoint();
-            ResizeHandle handle = getHandleAt(evt.getPoint());
-            if (handle != null) {
-                resizing = true;
-                activeHandle = handle;
-                resizeOrigin = evt.getPoint();
-            }
-        } else {
-            resizing = false;
-            activeHandle = null;
             if (lastMousePos == null) {
                 lastMousePos = evt.getPoint();
             }
             int dx = evt.getX() - lastMousePos.x;
             int dy = evt.getY() - lastMousePos.y;
-            logger.debug("MOVING shapes with delta ({}, {})", dx, dy);
             for (Shape shape : selection) {
                 shape.translate(dx, dy);
             }
@@ -127,18 +379,17 @@ public class Controller {
             return;
         }
 
-        resizing = false;
+        resizeDragState();
-        activeHandle = null;
+        boxSelecting = false;
-        resizeOrigin = null;
+        view.setCurrentSelectionBox(null);
-        boxSelecting = false; // Clear box selection mode when clicking
 
         if (resizeMode && !selection.isEmpty()) {
             ResizeHandle handle = getHandleAt(evt.getPoint());
-            logger.debug("In resize mode, checking handle at ({}, {}): {}", evt.getX(), evt.getY(), handle);
             if (handle != null) {
                 resizing = true;
                 activeHandle = handle;
                 resizeOrigin = evt.getPoint();
+                beginDrag(evt.getPoint());
                 view.repaint();
                 return;
             }
@@ -151,96 +402,86 @@ public class Controller {
                                 resetSelection();
                             }
                             if (!selection.getSelectedShapes().contains(s)) {
-                                lastMousePos = evt.getPoint();
                                 selection.add(s);
-                                logger.debug("Selecting {}", s);
                             }
+                            beginDrag(evt.getPoint());
                         },
                         () -> {
-                            // Clicked on empty space - start box selection
+                            additiveBoxSelection = evt.isShiftDown();
-                            resetSelection();
+                            if (!additiveBoxSelection) {
+                                resetSelection();
+                            }
                             selectionBoxStart = evt.getPoint();
+                            selectionBoxEnd = evt.getPoint();
                             boxSelecting = true;
+                            dragStartMousePos = null;
+                            dragStartBounds = Map.of();
                         }
                 );
     }
 
-    private void placeTextAt(Point point) {
+    private void handleMouseReleased(MouseEvent evt) {
-        String input = JOptionPane.showInputDialog(view, "Enter text:", "Add text", JOptionPane.PLAIN_MESSAGE);
+        finishDragCommand();
-        addingText = false;
+        resizeDragState();
-        if (input == null) {
+        boxSelecting = false;
-            return;
+        selectionBoxStart = null;
-        }
+        selectionBoxEnd = null;
-
+        dragStartMousePos = null;
-        model.add(SText.create(point.x, point.y, input));
+        dragStartBounds = Map.of();
-        resetSelection();
+        view.setCurrentSelectionBox(null);
         view.repaint();
     }
 
-    public void enterTextMode() {
+    private void handleKeyPressed(KeyEvent evt) {
-        addingText = true;
+        int modifiers = evt.getModifiersEx();
-    }
 
-    private ResizeHandle getHandleAt(Point point) {
+        if ((modifiers & InputEvent.CTRL_DOWN_MASK) != 0) {
-        final int handleSize = 10;
+            switch (evt.getKeyCode()) {
-        for (Shape shape : selection) {
+                case KeyEvent.VK_Z -> {
-            Rectangle bounds = shape.getBounds();
+                    if ((modifiers & InputEvent.SHIFT_DOWN_MASK) != 0) {
-            
+                        redo();
-            // Always-present SE corner handle
+                    } else {
-            if (point.x >= bounds.x + bounds.width && point.x <= bounds.x + bounds.width + handleSize &&
+                        undo();
-                point.y >= bounds.y + bounds.height && point.y <= bounds.y + bounds.height + handleSize) {
+                    }
-                return ResizeHandle.SE;
+                    evt.consume();
-            }
+                    return;
-
-            // Resize handles are only active in resize mode
-            if (resizeMode) {
-                // NW corner
-                if (point.x >= bounds.x - handleSize && point.x <= bounds.x &&
-                    point.y >= bounds.y - handleSize && point.y <= bounds.y) {
-                    return ResizeHandle.NW;
                 }
-                // NE corner
+                case KeyEvent.VK_Y -> {
-                if (point.x >= bounds.x + bounds.width && point.x <= bounds.x + bounds.width + handleSize &&
+                    redo();
-                    point.y >= bounds.y - handleSize && point.y <= bounds.y) {
+                    evt.consume();
-                    return ResizeHandle.NE;
+                    return;
                 }
-                // SW corner
+                case KeyEvent.VK_C -> {
-                if (point.x >= bounds.x - handleSize && point.x <= bounds.x &&
+                    copySelection();
-                    point.y >= bounds.y + bounds.height && point.y <= bounds.y + bounds.height + handleSize) {
+                    evt.consume();
-                    return ResizeHandle.SW;
+                    return;
                 }
-                // N edge
+                case KeyEvent.VK_X -> {
-                int edgeX = bounds.x + bounds.width / 2 - handleSize / 2;
+                    cutSelection();
-                if (point.x >= edgeX && point.x <= edgeX + handleSize &&
+                    evt.consume();
-                    point.y >= bounds.y - handleSize && point.y <= bounds.y) {
+                    return;
-                    return ResizeHandle.N;
                 }
-                // S edge
+                case KeyEvent.VK_V -> {
-                if (point.x >= edgeX && point.x <= edgeX + handleSize &&
+                    pasteClipboard();
-                    point.y >= bounds.y + bounds.height && point.y <= bounds.y + bounds.height + handleSize) {
+                    evt.consume();
-                    return ResizeHandle.S;
+                    return;
                 }
-                // W edge
+                case KeyEvent.VK_G -> {
-                int edgeY = bounds.y + bounds.height / 2 - handleSize / 2;
+                    group();
-                if (point.x >= bounds.x - handleSize && point.x <= bounds.x &&
+                    evt.consume();
-                    point.y >= edgeY && point.y <= edgeY + handleSize) {
+                    return;
-                    return ResizeHandle.W;
                 }
-                // E edge
+                case KeyEvent.VK_U -> {
-                if (point.x >= bounds.x + bounds.width && point.x <= bounds.x + bounds.width + handleSize &&
+                    ungroup();
-                    point.y >= edgeY && point.y <= edgeY + handleSize) {
+                    evt.consume();
-                    return ResizeHandle.E;
+                    return;
                 }
             }
         }
-        return null;
-    }
 
-    private void handleKeyPressed(KeyEvent evt) {
         switch (evt.getKeyCode()) {
             case KeyEvent.VK_R -> toggleResizeMode();
             case KeyEvent.VK_DELETE -> deleteSelected();
-            case KeyEvent.VK_C -> copySelection();
             case KeyEvent.VK_A -> changeSelectionColor();
             case KeyEvent.VK_H -> exportHtml();
             default -> logger.warn("Pressed unhandled key: {}", evt.getKeyChar());
@@ -264,55 +505,134 @@ public class Controller {
         }
     }
 
-    private void changeSelectionColor(){
+    private void placeTextAt(Point point) {
-        if (selection == null) {
+        String input = JOptionPane.showInputDialog(view, "Enter text:", "Add text", JOptionPane.PLAIN_MESSAGE);
-            logger.debug("No selection to change color of");
+        addingText = false;
+        if (input == null) {
             return;
         }
 
-        for (Shape s : selection) {
+        addShape(SText.create(point.x, point.y, input));
-            if (s instanceof SCollection collection) {
+        resetSelection();
-                collection.forEach(shape -> shape.addAttributes(new ColorAttributes(false, true, Color.BLACK, new Color((int) (Math.random() * 0x1000000)))));
+    }
-            } else {
+
-                s.addAttributes(new ColorAttributes(false, true, Color.BLACK, new Color((int) (Math.random() * 0x1000000))));
+    private ResizeHandle getHandleAt(Point point) {
+        final int handleSize = 10;
+        for (Shape shape : selection) {
+            Rectangle bounds = shape.getBounds();
+
+            if (point.x >= bounds.x + bounds.width && point.x <= bounds.x + bounds.width + handleSize &&
+                    point.y >= bounds.y + bounds.height && point.y <= bounds.y + bounds.height + handleSize) {
+                return ResizeHandle.SE;
+            }
+
+            if (resizeMode) {
+                if (point.x >= bounds.x - handleSize && point.x <= bounds.x &&
+                        point.y >= bounds.y - handleSize && point.y <= bounds.y) {
+                    return ResizeHandle.NW;
+                }
+                if (point.x >= bounds.x + bounds.width && point.x <= bounds.x + bounds.width + handleSize &&
+                        point.y >= bounds.y - handleSize && point.y <= bounds.y) {
+                    return ResizeHandle.NE;
+                }
+                if (point.x >= bounds.x - handleSize && point.x <= bounds.x &&
+                        point.y >= bounds.y + bounds.height && point.y <= bounds.y + bounds.height + handleSize) {
+                    return ResizeHandle.SW;
+                }
+                int edgeX = bounds.x + bounds.width / 2 - handleSize / 2;
+                if (point.x >= edgeX && point.x <= edgeX + handleSize &&
+                        point.y >= bounds.y - handleSize && point.y <= bounds.y) {
+                    return ResizeHandle.N;
+                }
+                if (point.x >= edgeX && point.x <= edgeX + handleSize &&
+                        point.y >= bounds.y + bounds.height && point.y <= bounds.y + bounds.height + handleSize) {
+                    return ResizeHandle.S;
+                }
+                int edgeY = bounds.y + bounds.height / 2 - handleSize / 2;
+                if (point.x >= bounds.x - handleSize && point.x <= bounds.x &&
+                        point.y >= edgeY && point.y <= edgeY + handleSize) {
+                    return ResizeHandle.W;
+                }
+                if (point.x >= bounds.x + bounds.width && point.x <= bounds.x + bounds.width + handleSize &&
+                        point.y >= edgeY && point.y <= edgeY + handleSize) {
+                    return ResizeHandle.E;
+                }
             }
         }
-
+        return null;
-        view.repaint();
     }
 
-    private void copySelection() {
+    private void changeColors(Function<Shape, ColorAttributes> updater) {
-        if (selection == null) {
+        Map<Shape, ColorAttributes> before = new LinkedHashMap<>();
-            logger.debug("No selection to copy");
+        Map<Shape, ColorAttributes> after = new LinkedHashMap<>();
+        List<Shape> targets = flattenSelection(selection.getSelectedShapes());
+
+        for (Shape shape : targets) {
+            ColorAttributes current = currentColor(shape);
+            if (current == null) {
+                continue;
+            }
+
+            ColorAttributes updated = updater.apply(shape);
+            if (updated == null || sameColor(current, updated)) {
+                continue;
+            }
+
+            before.put(shape, copy(current));
+            after.put(shape, copy(updated));
+        }
+
+        if (before.isEmpty()) {
             return;
         }
 
-        for (Shape shape : selection) {
+        executeAndRefresh(new ChangeColorCommand(before.keySet(), before, after));
-            this.model.add(shape.clone());
-        }
-
-        view.repaint();
     }
 
-    public void deleteSelected() {
+    private void beginDrag(Point point) {
-        if (selection == null) return;
+        lastMousePos = point;
-        logger.debug("Deleting selected shape(s)");
+        dragStartMousePos = point;
-        for (Shape s : selection) {
+        dragStartBounds = captureBounds(selection.getSelectedShapes());
-            this.model.remove(s);
+    }
+
+    private void finishDragCommand() {
+        if (boxSelecting || dragStartBounds.isEmpty()) {
+            return;
         }
-        resetSelection();
+
+        List<Shape> selectedShapes = selection.getSelectedShapes();
+        if (selectedShapes.isEmpty()) {
+            return;
+        }
+
+        if (resizing && boundsChanged(selectedShapes, dragStartBounds)) {
+            Map<Shape, Rectangle> afterBounds = captureBounds(selectedShapes);
+            Command command = new ResizeShapeCommand(selectedShapes, dragStartBounds, afterBounds);
+            command.undo();
+            executeAndRefresh(command);
+            return;
+        }
+
+        if (boundsChanged(selectedShapes, dragStartBounds)) {
+            Shape reference = selectedShapes.get(0);
+            Rectangle before = dragStartBounds.get(reference);
+            Rectangle after = reference.getBounds();
+            Command command = new MoveShapeCommand(selectedShapes, after.x - before.x, after.y - before.y);
+            command.undo();
+            executeAndRefresh(command);
+        }
+    }
+
+    private void executeAndRefresh(Command command) {
+        commandHistory.execute(command);
+        onModelChanged.run();
         view.repaint();
     }
 
     private void resetSelection() {
-        logger.debug("Resetting selection");
         selection.clear();
     }
 
-    public void addSelectionChangeListener(SelectionListener listener) {
-        selection.addListener(listener);
-    }
-
     private Optional<Shape> getTarget(MouseEvent evt, SCollection sc) {
         return sc.stream()
                 .filter(s -> s.getBounds().contains(evt.getPoint()))
@@ -328,9 +648,71 @@ public class Controller {
     }
 
     private void updateSelectionFromBox(Rectangle box) {
-        resetSelection();
+        if (!additiveBoxSelection) {
+            resetSelection();
+        }
         model.stream()
                 .filter(s -> s.getBounds().intersects(box))
                 .forEach(selection::add);
     }
+
+    private void resizeDragState() {
+        resizing = false;
+        activeHandle = null;
+        resizeOrigin = null;
+        lastMousePos = null;
+    }
+
+    private Map<Shape, Rectangle> captureBounds(Collection<Shape> shapes) {
+        Map<Shape, Rectangle> bounds = new LinkedHashMap<>();
+        for (Shape shape : shapes) {
+            bounds.put(shape, shape.getBounds());
+        }
+        return bounds;
+    }
+
+    private boolean boundsChanged(Collection<Shape> shapes, Map<Shape, Rectangle> before) {
+        for (Shape shape : shapes) {
+            Rectangle previous = before.get(shape);
+            if (previous != null && !previous.equals(shape.getBounds())) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private List<Shape> flattenSelection(Collection<Shape> selectedShapes) {
+        LinkedHashSet<Shape> flattened = new LinkedHashSet<>();
+        for (Shape shape : selectedShapes) {
+            flattenShape(shape, flattened);
+        }
+        return new ArrayList<>(flattened);
+    }
+
+    private void flattenShape(Shape shape, Collection<Shape> flattened) {
+        if (shape instanceof SCollection collection) {
+            collection.forEach(child -> flattenShape(child, flattened));
+            return;
+        }
+        flattened.add(shape);
+    }
+
+    private ColorAttributes currentColor(Shape shape) {
+        return (ColorAttributes) shape.getAttributes(ColorAttributes.ID);
+    }
+
+    private ColorAttributes copy(ColorAttributes attrs) {
+        return new ColorAttributes(attrs.filled, attrs.stroked, attrs.filledColor, attrs.strokedColor);
+    }
+
+    private boolean sameColor(ColorAttributes left, ColorAttributes right) {
+        return left.filled == right.filled
+                && left.stroked == right.stroked
+                && left.filledColor.equals(right.filledColor)
+                && left.strokedColor.equals(right.strokedColor);
+    }
+
+    private Color randomColor() {
+        return new Color((int) (Math.random() * 0x1000000));
+    }
 }

src/main/java/ovh/gasser/newshapes/ui/ShapeDraftman.java

@@ -117,6 +117,30 @@ public class ShapeDraftman implements ShapeVisitor {
         drawHandlerIfSelected(text);
     }
 
+    @Override
+    public void visitPolygon(SPolygon polygon) {
+        ColorAttributes colAttrs = (ColorAttributes) polygon.getAttributes(ColorAttributes.ID);
+        if (colAttrs == null) {
+            colAttrs = DEFAULT_COLOR_ATTRIBUTES;
+        }
+
+        java.util.List<Point> points = polygon.getPoints();
+        int[] xPoints = points.stream().mapToInt(p -> p.x).toArray();
+        int[] yPoints = points.stream().mapToInt(p -> p.y).toArray();
+        int nPoints = points.size();
+
+        if (colAttrs.filled) {
+            this.g2d.setColor(colAttrs.filledColor);
+            this.g2d.fillPolygon(xPoints, yPoints, nPoints);
+        }
+        if (colAttrs.stroked) {
+            this.g2d.setColor(colAttrs.strokedColor);
+            this.g2d.drawPolygon(xPoints, yPoints, nPoints);
+        }
+
+        drawHandlerIfSelected(polygon);
+    }
+
     private Color resolveTextColor(ColorAttributes attrs) {
         if (attrs == null) {
             return Color.BLACK;

src/main/java/ovh/gasser/newshapes/ui/ShapesView.java

@@ -16,8 +16,12 @@ public class ShapesView extends JPanel {
     private Rectangle currentSelectionBox;
 
     public ShapesView(SCollection model) {
+        this(model, () -> { });
+    }
+
+    public ShapesView(SCollection model, Runnable onModelChanged) {
         this.model = model;
-        this.controller = new Controller(this, model);
+        this.controller = new Controller(this, model, onModelChanged);
     }
 
     @Override

src/test/java/ovh/gasser/newshapes/ui/BoxSelectionTest.java

@@ -0,0 +1,128 @@
+package ovh.gasser.newshapes.ui;
+
+import org.junit.jupiter.api.Test;
+import ovh.gasser.newshapes.attributes.SelectionAttributes;
+import ovh.gasser.newshapes.shapes.SCollection;
+import ovh.gasser.newshapes.shapes.SRectangle;
+import ovh.gasser.newshapes.shapes.Shape;
+
+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.InputEvent;
+import java.awt.event.MouseEvent;
+import java.awt.image.BufferedImage;
+import java.lang.reflect.InvocationTargetException;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class BoxSelectionTest {
+
+    @Test
+    void draggingSelectionBoxSelectsAllIntersectingShapes() throws Exception {
+        SRectangle first = SRectangle.create(20, 20, 30, 30);
+        SRectangle second = SRectangle.create(80, 80, 30, 30);
+        SRectangle outside = SRectangle.create(160, 160, 30, 30);
+        ShapesView view = createView(first, second, outside);
+
+        dragSelection(view, new Point(5, 5), new Point(100, 100), 0);
+
+        assertTrue(isSelected(first));
+        assertTrue(isSelected(second));
+        assertFalse(isSelected(outside));
+    }
+
+    @Test
+    void shiftDraggingSelectionBoxAddsToExistingSelection() throws Exception {
+        SRectangle first = SRectangle.create(10, 10, 30, 30);
+        SRectangle second = SRectangle.create(80, 10, 30, 30);
+        SRectangle outside = SRectangle.create(160, 10, 30, 30);
+        ShapesView view = createView(first, second, outside);
+
+        click(view, new Point(20, 20), 0);
+        dragSelection(view, new Point(70, 5), new Point(120, 50), InputEvent.SHIFT_DOWN_MASK);
+
+        assertTrue(isSelected(first));
+        assertTrue(isSelected(second));
+        assertFalse(isSelected(outside));
+    }
+
+    @Test
+    void shapesViewPaintsSelectionBoxDuringRendering() throws Exception {
+        ShapesView view = createView();
+
+        BufferedImage withoutSelectionBox = paintView(view, null);
+        BufferedImage withSelectionBox = paintView(view, new Rectangle(10, 10, 40, 40));
+
+        assertTrue(imagesDiffer(withoutSelectionBox, withSelectionBox));
+    }
+
+    private ShapesView createView(Shape... shapes) throws InvocationTargetException, InterruptedException {
+        final ShapesView[] ref = new ShapesView[1];
+        SwingUtilities.invokeAndWait(() -> {
+            ref[0] = new ShapesView(SCollection.of(shapes));
+            ref[0].setOpaque(true);
+            ref[0].setBackground(Color.WHITE);
+            ref[0].setSize(240, 240);
+        });
+        return ref[0];
+    }
+
+    private void click(ShapesView view, Point point, int modifiers) throws InvocationTargetException, InterruptedException {
+        dispatch(view, MouseEvent.MOUSE_PRESSED, point, modifiers);
+        dispatch(view, MouseEvent.MOUSE_RELEASED, point, modifiers);
+    }
+
+    private void dragSelection(ShapesView view, Point start, Point end, int modifiers) throws InvocationTargetException, InterruptedException {
+        dispatch(view, MouseEvent.MOUSE_PRESSED, start, modifiers);
+        dispatch(view, MouseEvent.MOUSE_DRAGGED, end, modifiers);
+        dispatch(view, MouseEvent.MOUSE_RELEASED, end, modifiers);
+    }
+
+    private void dispatch(ShapesView view, int eventId, Point point, int modifiers)
+            throws InvocationTargetException, InterruptedException {
+        SwingUtilities.invokeAndWait(() -> view.dispatchEvent(new MouseEvent(
+                view,
+                eventId,
+                System.currentTimeMillis(),
+                modifiers,
+                point.x,
+                point.y,
+                1,
+                false,
+                MouseEvent.BUTTON1
+        )));
+    }
+
+    private BufferedImage paintView(ShapesView view, Rectangle box)
+            throws InvocationTargetException, InterruptedException {
+        final BufferedImage[] ref = new BufferedImage[1];
+        SwingUtilities.invokeAndWait(() -> {
+            view.setCurrentSelectionBox(box);
+            BufferedImage image = new BufferedImage(240, 240, BufferedImage.TYPE_INT_ARGB);
+            Graphics2D graphics = image.createGraphics();
+            try {
+                view.paint(graphics);
+            } finally {
+                graphics.dispose();
+            }
+            ref[0] = image;
+        });
+        return ref[0];
+    }
+
+    private boolean imagesDiffer(BufferedImage first, BufferedImage second) {
+        for (int y = 0; y < first.getHeight(); y++) {
+            for (int x = 0; x < first.getWidth(); x++) {
+                if (first.getRGB(x, y) != second.getRGB(x, y)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    private boolean isSelected(Shape shape) {
+        return ((SelectionAttributes) shape.getAttributes(SelectionAttributes.ID)).selected;
+    }
+}