Mac: Add support for zooming map via touchpad pinch.

game-app/game-core/src/main/java/games/strategy/ui/ImageScrollerLargeView.java

@@ -22,6 +22,7 @@
 import javax.swing.JOptionPane;
 import javax.swing.SwingUtilities;
 import javax.swing.Timer;
+import org.triplea.swing.gestures.Gestures;
 
 /**
  * A large image that can be scrolled according to a ImageScrollModel. Generally used in conjunction
@@ -96,14 +97,8 @@ public ImageScrollerLargeView(final Dimension dimension, final ImageScrollModel
     final MouseWheelListener mouseWheelListener =
         e -> {
           if (e.isControlDown()) {
-            final int oldWidth = model.getBoxWidth();
-            final int oldHeight = model.getBoxHeight();
             final float zoomFactor = ClientSetting.mapZoomFactor.getValueOrThrow() / 100f;
-            setScale(scale - zoomFactor * e.getPreciseWheelRotation());
-            final Point mouse = getMousePosition();
-            final int dx = (int) (mouse.getX() / getWidth() * (oldWidth - model.getBoxWidth()));
-            final int dy = (int) (mouse.getY() / getHeight() * (oldHeight - model.getBoxHeight()));
-            model.set(model.getX() + dx, model.getY() + dy);
+            setScaleViaMouseZoom(scale - zoomFactor * e.getPreciseWheelRotation());
           } else {
             if (edge == NONE) {
               insideCount = 0;
@@ -223,6 +218,8 @@ public void componentResized(final ComponentEvent e) {
           repaint();
           notifyScollListeners();
         });
+    Gestures.registerMagnificationListener(
+        this, (double factor) -> setScaleViaMouseZoom(scale * factor));
   }
 
   public boolean wasLastActionDraggingAndReset() {
@@ -309,6 +306,16 @@ public void setScale(final double value) {
     refreshBoxSize();
   }
 
+  private void setScaleViaMouseZoom(double newScale) {
+    final int oldWidth = model.getBoxWidth();
+    final int oldHeight = model.getBoxHeight();
+    setScale(newScale);
+    final Point mouse = getMousePosition();
+    final int dx = (int) (mouse.getX() / getWidth() * (oldWidth - model.getBoxWidth()));
+    final int dy = (int) (mouse.getY() / getHeight() * (oldHeight - model.getBoxHeight()));
+    model.set(model.getX() + dx, model.getY() + dy);
+  }
+
   public double getMinScale() {
     final double minScale =
         scale

game-app/game-headed/build.install4j

@@ -296,6 +296,7 @@ return Math.min(is32BitJavaRuntime ? 1024L : 2048L, halfMemoryMiB);</property>
                     <element index="0">-Xmx${installer:heapSizeMiB}M</element>
                     <element index="1">-Xms${installer:heapSizeMiB}M</element>
                     <element index="2">-Xss1250K</element>
+                    <element index="3">--add-opens java.desktop/com.apple.eawt.event=ALL-UNNAMED</element>
                   </property>
                 </serializedBean>
               </action>

lib/swing-lib/src/main/java/org/triplea/swing/gestures/Gestures.java

@@ -0,0 +1,58 @@
+package org.triplea.swing.gestures;
+
+import games.strategy.engine.framework.system.SystemProperties;
+import java.lang.reflect.Proxy;
+import javax.swing.JComponent;
+
+/**
+ * Provides support for platform-specific gestures. Currently, supports only the magnification
+ * gestures on Mac (e.g. pinch to zoom using the trackpad).
+ *
+ * <p>Since there is no cross-platform API in Swing for this, it relies on Mac-specific
+ * com.apple.eawt classes for the support, which are loaded via reflection in order for the code to
+ * compile on all platforms.
+ *
+ * <p>This implementation is based on the following sources:
+ * https://stackoverflow.com/questions/69221217/multi-touch-gestures-in-java-swing-awt-and-java-17
+ * https://gist.github.com/alanwhite/42502f20390baf879d093691ebb72066
+ *
+ * <p>Note: This functionality requires passing the following args to java when running the app:
+ * --add-opens java.desktop/com.apple.eawt.event=ALL-UNNAMED
+ */
+public class Gestures {
+  @SuppressWarnings({"rawtypes"})
+  public static void registerMagnificationListener(JComponent c, MagnificationListener listener) {
+    // The current implementation only supports Mac.
+    if (!SystemProperties.isMac()) {
+      return;
+    }
+    // Wrapped in a try, as this may fail if the specific classes or their methods are not found.
+    try {
+      Class listenerClass = Class.forName("com.apple.eawt.event.MagnificationListener");
+      Object listenerProxy =
+          Proxy.newProxyInstance(
+              listenerClass.getClassLoader(),
+              new Class[] {listenerClass},
+              (proxy, method, args) -> {
+                if (method.getName().equals("magnify")) {
+                  try {
+                    Object mag = args[0].getClass().getMethod("getMagnification").invoke(args[0]);
+                    listener.magnify(1 + (double) mag);
+                  } catch (Exception e) {
+                    e.printStackTrace();
+                  }
+                }
+                return null;
+              });
+
+      Class.forName("com.apple.eawt.event.GestureUtilities")
+          .getMethod(
+              "addGestureListenerTo",
+              Class.forName("javax.swing.JComponent"),
+              Class.forName("com.apple.eawt.event.GestureListener"))
+          .invoke(null, c, listenerProxy);
+    } catch (Exception e) {
+      e.printStackTrace();
+    }
+  }
+}

lib/swing-lib/src/main/java/org/triplea/swing/gestures/MagnificationListener.java

@@ -0,0 +1,12 @@
+package org.triplea.swing.gestures;
+
+/** Listener for magnification events (e.g. pinch gesture with a trackpad). */
+public interface MagnificationListener {
+  /**
+   * Called when a magnification event occurred.
+   *
+   * @param factor The magnification multiplier to apply over the current zoom level (e.g. 1 = no
+   *     change, 2 = double the zoom, etc).
+   */
+  void magnify(double factor);
+}