src/main/java/ovh/gasser/newshapes/shapes/AbstractShape.java

@@ -77,6 +77,14 @@ public abstract class AbstractShape implements Shape {
         return new Rectangle(this.bounds);
     }
 
+    public void setBounds(Rectangle newBounds) {
+        this.bounds.setBounds(newBounds);
+        onBoundsChanged();
+    }
+
+    protected void onBoundsChanged() {
+    }
+
     @Override
     public String toString() {
         return String.format("x=%d, y=%d, width=%d, height=%d", bounds.x, bounds.y, bounds.width, bounds.height);

src/main/java/ovh/gasser/newshapes/shapes/SCircle.java

@@ -53,6 +53,14 @@ public class SCircle extends AbstractShape {
         return radius;
     }
 
+    @Override
+    protected void onBoundsChanged() {
+        int diameter = Math.max(bounds.width, bounds.height);
+        bounds.width = diameter;
+        bounds.height = diameter;
+        this.radius = diameter / 2;
+    }
+
     public static SCircle create(int x, int y, int radius) {
         return create(x, y, radius, Color.BLACK);
     }

src/main/java/ovh/gasser/newshapes/shapes/SCollection.java

@@ -9,7 +9,6 @@ import ovh.gasser.newshapes.attributes.ColorAttributes;
 import ovh.gasser.newshapes.attributes.SelectionAttributes;
 import ovh.gasser.newshapes.util.Streamable;
 
-import javax.swing.text.html.Option;
 import java.awt.*;
 import java.util.*;
 import java.util.List;
@@ -19,6 +18,7 @@ public class SCollection extends AbstractShape implements Streamable<Shape> {
     private final List<Shape> children;
 
     private SCollection(Shape... shapes) {
+        super(new Rectangle());
         this.children = new ArrayList<>(List.of(shapes));
     }
 
@@ -57,6 +57,29 @@ public class SCollection extends AbstractShape implements Streamable<Shape> {
         children.forEach(s -> s.translate(dx, dy));
     }
 
+    @Override
+    public void resize(ResizeHandle handle, int dx, int dy) {
+        if (children.isEmpty()) {
+            return;
+        }
+
+        Rectangle currentBounds = getBounds();
+        Rectangle resizedBounds = resizeBounds(currentBounds, handle, dx, dy);
+        double scaleX = resizedBounds.width / (double) currentBounds.width;
+        double scaleY = resizedBounds.height / (double) currentBounds.height;
+
+        for (Shape child : children) {
+            Rectangle childBounds = child.getBounds();
+            Rectangle targetChildBounds = new Rectangle(
+                    resizedBounds.x + (int) Math.round((childBounds.x - currentBounds.x) * scaleX),
+                    resizedBounds.y + (int) Math.round((childBounds.y - currentBounds.y) * scaleY),
+                    Math.max(1, (int) Math.round(childBounds.width * scaleX)),
+                    Math.max(1, (int) Math.round(childBounds.height * scaleY))
+            );
+            resizeChild(child, targetChildBounds);
+        }
+    }
+
     @Override
     public Iterator<Shape> iterator() {
         return children.iterator();
@@ -71,12 +94,45 @@ public class SCollection extends AbstractShape implements Streamable<Shape> {
         children.add(s);
     }
 
+    public void clear() {
+        children.clear();
+    }
+
+    public void replaceWith(SCollection other) {
+        if (other == this) {
+            return;
+        }
+
+        clear();
+        other.stream().forEach(children::add);
+    }
+
+    public void add(int index, Shape s) {
+        children.add(index, s);
+    }
+
+    public void insert(int index, Shape s) {
+        children.add(Math.max(0, Math.min(index, children.size())), s);
+    }
+
     public void remove(Shape s) {
         if (!children.remove(s)) {
             logger.error("Unable to delete shape: {}", s);
         }
     }
 
+    public int indexOf(Shape s) {
+        return children.indexOf(s);
+    }
+
+    public int size() {
+        return children.size();
+    }
+
+    public boolean contains(Shape s) {
+        return children.contains(s);
+    }
+
     @Override
     public Attributes getAttributes(String key) {
         if (key.equals(ColorAttributes.ID)) {
@@ -110,4 +166,69 @@ public class SCollection extends AbstractShape implements Streamable<Shape> {
         collection.addAttributes(new SelectionAttributes());
         return collection;
     }
+
+    private static Rectangle resizeBounds(Rectangle bounds, ResizeHandle handle, int dx, int dy) {
+        Rectangle resizedBounds = new Rectangle(bounds);
+
+        switch (handle) {
+            case E -> resizedBounds.width += dx;
+            case W -> {
+                resizedBounds.x += dx;
+                resizedBounds.width -= dx;
+            }
+            case S -> resizedBounds.height += dy;
+            case N -> {
+                resizedBounds.y += dy;
+                resizedBounds.height -= dy;
+            }
+            case SE -> {
+                resizedBounds.width += dx;
+                resizedBounds.height += dy;
+            }
+            case SW -> {
+                resizedBounds.x += dx;
+                resizedBounds.width -= dx;
+                resizedBounds.height += dy;
+            }
+            case NE -> {
+                resizedBounds.width += dx;
+                resizedBounds.y += dy;
+                resizedBounds.height -= dy;
+            }
+            case NW -> {
+                resizedBounds.x += dx;
+                resizedBounds.width -= dx;
+                resizedBounds.y += dy;
+                resizedBounds.height -= dy;
+            }
+        }
+
+        if (resizedBounds.width < 1) {
+            resizedBounds.width = 1;
+        }
+        if (resizedBounds.height < 1) {
+            resizedBounds.height = 1;
+        }
+
+        return resizedBounds;
+    }
+
+    private static void resizeChild(Shape child, Rectangle targetChildBounds) {
+        if (child instanceof SCollection collection) {
+            Rectangle currentBounds = collection.getBounds();
+            collection.translate(targetChildBounds.x - currentBounds.x, targetChildBounds.y - currentBounds.y);
+
+            Rectangle translatedBounds = collection.getBounds();
+            collection.resize(
+                    ResizeHandle.SE,
+                    targetChildBounds.width - translatedBounds.width,
+                    targetChildBounds.height - translatedBounds.height
+            );
+            return;
+        }
+
+        if (child instanceof AbstractShape abstractShape) {
+            abstractShape.setBounds(targetChildBounds);
+        }
+    }
 }

src/test/java/ovh/gasser/newshapes/shapes/SCollectionTest.java

@@ -114,6 +114,51 @@ class SCollectionTest {
         assertEquals(30, bounds.y);
     }
 
+    @Test
+    void testResizeEmptyCollectionIsNoOp() {
+        SCollection collection = SCollection.of();
+
+        assertDoesNotThrow(() -> collection.resize(ResizeHandle.SE, 25, 25));
+        assertEquals(new Rectangle(App.WIN_SIZE), collection.getBounds());
+    }
+
+    @Test
+    void testResizeSingleChildResizesChildAndCollection() {
+        SRectangle rect = SRectangle.create(10, 20, 100, 50);
+        SCollection collection = SCollection.of(rect);
+
+        collection.resize(ResizeHandle.E, 20, 0);
+
+        assertEquals(new Rectangle(10, 20, 120, 50), rect.getBounds());
+        assertEquals(new Rectangle(10, 20, 120, 50), collection.getBounds());
+    }
+
+    @Test
+    void testResizeMultipleChildrenScalesChildrenProportionally() {
+        SRectangle rect1 = SRectangle.create(0, 0, 10, 10);
+        SRectangle rect2 = SRectangle.create(20, 10, 20, 10);
+        SCollection collection = SCollection.of(rect1, rect2);
+
+        collection.resize(ResizeHandle.SE, 20, 10);
+
+        assertEquals(new Rectangle(0, 0, 15, 15), rect1.getBounds());
+        assertEquals(new Rectangle(30, 15, 30, 15), rect2.getBounds());
+        assertEquals(new Rectangle(0, 0, 60, 30), collection.getBounds());
+    }
+
+    @Test
+    void testResizeFromNorthWestRepositionsAndScalesChildren() {
+        SRectangle rect1 = SRectangle.create(0, 0, 10, 10);
+        SRectangle rect2 = SRectangle.create(10, 10, 10, 10);
+        SCollection collection = SCollection.of(rect1, rect2);
+
+        collection.resize(ResizeHandle.NW, 10, 10);
+
+        assertEquals(new Rectangle(10, 10, 5, 5), rect1.getBounds());
+        assertEquals(new Rectangle(15, 15, 5, 5), rect2.getBounds());
+        assertEquals(new Rectangle(10, 10, 10, 10), collection.getBounds());
+    }
+
     @Test
     void testClone() {
         SRectangle rect = SRectangle.create(10, 20, 100, 50);