Implement pan and zoom with mouse

src/main/java/ee/ut/dendroloj/GraphGUI.java

@@ -1,8 +1,18 @@
 package ee.ut.dendroloj;
 
 import org.graphstream.graph.Graph;
-
 import org.graphstream.graph.implementations.SingleGraph;
+import org.graphstream.ui.geom.Point2;
+import org.graphstream.ui.geom.Point3;
+import org.graphstream.ui.swing_viewer.SwingViewer;
+import org.graphstream.ui.swing_viewer.util.DefaultMouseManager;
+import org.graphstream.ui.view.View;
+import org.graphstream.ui.view.camera.Camera;
+import org.graphstream.ui.view.util.MouseManager;
+
+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.*;
 
 class GraphGUI {
     public static void init(double uiScale) {
@@ -42,6 +52,104 @@ public static void init(double uiScale) {
                 """, Math.sqrt(uiScale), uiScale * 12, uiScale + 1, Math.sqrt(uiScale) * 10, uiScale * 12, uiScale + 1));
 
         SimpleTreeLayout.setGraph(graph);
-        graph.display(false);
+
+        SwingViewer viewer = new SwingViewer(graph, SwingViewer.ThreadingModel.GRAPH_IN_ANOTHER_THREAD);
+        View view = viewer.addDefaultView(false);
+        Component viewComponent = (Component) view;
+
+        // GraphStream DefaultMouseManager but with event handling enabled only for left click to prevent interference with panning.
+        MouseManager restrictedDefaultMouseManager = new DefaultMouseManager() {
+            @Override
+            public void mousePressed(MouseEvent event) {
+                if (SwingUtilities.isLeftMouseButton(event)) {
+                    super.mousePressed(event);
+                }
+            }
+
+            @Override
+            public void mouseReleased(MouseEvent event) {
+                if (SwingUtilities.isLeftMouseButton(event)) {
+                    super.mouseReleased(event);
+                }
+            }
+
+            @Override
+            public void mouseDragged(MouseEvent event) {
+                if (SwingUtilities.isLeftMouseButton(event)) {
+                    if (curElement != null) {
+                        elementMoving(curElement, event);
+                        viewComponent.repaint(); // Doing this makes moving elements appear much smoother.
+                    } else {
+                        view.selectionGrowsAt(event.getX(), event.getY());
+                    }
+                }
+            }
+        };
+        view.setMouseManager(restrictedDefaultMouseManager);
+
+        MouseAdapter zoomAndPanAdapter = new MouseAdapter() {
+            private static final double ZOOM_FACTOR = 1.25;
+
+            private final Point lastPxCursor = new Point();
+
+            @Override
+            public void mouseWheelMoved(MouseWheelEvent event) {
+                event.consume();
+
+                // Zoom towards cursor with scroll wheel. Adapted from https://stackoverflow.com/a/52929241.
+                int i = event.getWheelRotation();
+                double factor = Math.pow(ZOOM_FACTOR, i);
+                Camera cam = view.getCamera();
+                double zoom = cam.getViewPercent() * factor;
+                Point2 pxCenter = cam.transformGuToPx(cam.getViewCenter().x, cam.getViewCenter().y, 0);
+                Point3 guCursor = cam.transformPxToGu(event.getX(), event.getY());
+                double newRatioPx2Gu = cam.getMetrics().ratioPx2Gu / factor;
+                double x = guCursor.x + (pxCenter.x - event.getX()) / newRatioPx2Gu;
+                double y = guCursor.y - (pxCenter.y - event.getY()) / newRatioPx2Gu;
+                cam.setViewCenter(x, y, 0);
+                cam.setViewPercent(zoom);
+
+                viewComponent.repaint();
+            }
+
+            public void mousePressed(MouseEvent event) {
+                if (SwingUtilities.isRightMouseButton(event)) {
+                    event.consume();
+
+                    lastPxCursor.setLocation(event.getPoint());
+                }
+            }
+
+            @Override
+            public void mouseDragged(MouseEvent event) {
+                if (SwingUtilities.isRightMouseButton(event)) {
+                    event.consume();
+
+                    Point newPxCursor = event.getPoint();
+                    Camera cam = view.getCamera();
+                    Point2 viewCenter = cam.getViewCenter();
+                    double ratioPx2Gu = cam.getMetrics().ratioPx2Gu;
+                    double x = viewCenter.x + (lastPxCursor.x - newPxCursor.x) / ratioPx2Gu;
+                    double y = viewCenter.y - (lastPxCursor.y - newPxCursor.y) / ratioPx2Gu;
+                    cam.setViewCenter(x, y, 0);
+                    lastPxCursor.setLocation(newPxCursor);
+
+                    viewComponent.repaint();
+                }
+            }
+        };
+        viewComponent.addMouseListener(zoomAndPanAdapter);
+        viewComponent.addMouseMotionListener(zoomAndPanAdapter);
+        viewComponent.addMouseWheelListener(zoomAndPanAdapter);
+
+        JFrame root = new JFrame();
+        root.setTitle("dendroloj");
+        root.setLayout(new BorderLayout());
+        root.add(viewComponent, BorderLayout.CENTER);
+        root.setSize(800, 600);
+        root.setLocationRelativeTo(null);
+        root.addWindowListener((WindowListener) viewComponent);
+        root.addComponentListener((ComponentListener) viewComponent);
+        root.setVisible(true);
     }
 }