Issue #18: Make DragDropStage open at the dropped location and be ownerless

core/src/main/java/software/coley/bentofx/building/StageBuilding.java

@@ -1,8 +1,14 @@
 package software.coley.bentofx.building;
 
+import javafx.collections.ObservableList;
+import javafx.geometry.Bounds;
+import javafx.geometry.Point2D;
+import javafx.geometry.Rectangle2D;
 import javafx.geometry.Side;
 import javafx.scene.Scene;
 import javafx.scene.layout.Region;
+import javafx.scene.robot.Robot;
+import javafx.stage.Screen;
 import javafx.stage.Stage;
 import javafx.stage.Window;
 import org.jspecify.annotations.Nullable;
@@ -22,6 +28,8 @@ public class StageBuilding {
 	private final Bento bento;
 	private StageFactory stageFactory = DEFAULT_STAGE_FACTORY;
 	private SceneFactory sceneFactory = DEFAULT_SCENE_FACTORY;
+	private boolean applyMousePosition = false;
+	private boolean applySourceAsOwner = true;
 
 	public StageBuilding(Bento bento) {
 		this.bento = bento;
@@ -121,7 +129,30 @@ public DragDropStage newStageForDockable(@Nullable Scene sourceScene,
 
 		// Copy properties from the source scene/stage.
 		if (sourceScene != null)
-			initializeFromSource(sourceScene, scene, sourceStage, stage, true);
+			initializeFromSource(sourceScene, scene, sourceStage, stage, applySourceAsOwner);
+
+		// Position the stage at the mouse position, if enabled.
+		if (applyMousePosition) {
+			final Robot robot = new Robot();
+			final Point2D mousePosition = robot.getMousePosition();
+
+			// Clamp the position to the screen bounds.
+			// We don't want a new stage that spawns on the bottom or right edge of the screen to be inaccessible.
+			double x = mousePosition.getX();
+			double y = mousePosition.getY();
+			ObservableList<Screen> screens = Screen.getScreensForRectangle(x, y, x + 1, y + 1);
+			if (!screens.isEmpty()) {
+				final Bounds dockableContainerBounds = leaf.getBoundsInLocal();
+				final Rectangle2D screenBounds = screens.getFirst().getVisualBounds();
+				final double maxX = screenBounds.getMaxX() - dockableContainerBounds.getWidth();
+				final double maxY = screenBounds.getMaxY() - dockableContainerBounds.getHeight();
+				x = Math.min(x, maxX);
+				y = Math.min(y, maxY);
+			}
+
+			stage.setX(x);
+			stage.setY(y);
+		}
 
 		return stage;
 	}
@@ -183,4 +214,25 @@ public void setSceneFactory(@Nullable SceneFactory factory) {
 			factory = DEFAULT_SCENE_FACTORY;
 		sceneFactory = factory;
 	}
+
+	/**
+	 * @param applySourceAsOwner
+	 *        {@code true} to make newly created stages have their owner set to the source stage the dockable is being dragged out of.
+	 *        {@code false} to not set an owner, allowing the new stage to be handled independently of the source stage.
+	 *
+	 * @see Stage#initOwner(Window)
+	 */
+	public void setApplySourceAsOwner(boolean applySourceAsOwner) {
+		this.applySourceAsOwner = applySourceAsOwner;
+	}
+
+	/**
+	 *
+	 * @param applyMousePosition
+	 *        {@code true} to position newly created stages at the current mouse position.
+	 *        {@code false} to not apply any special positioning, allowing the stage to be positioned automatically <i>(Generally centered)</i>.
+	 */
+	public void setApplyMousePosition(boolean applyMousePosition) {
+		this.applyMousePosition = applyMousePosition;
+	}
 }