Zoomer: add a user definable predicate for panning (#631)

* Zoomer: add a user definable predicate for panning
* ZoomerSample: add a chart with a user-defined panning predicate

---------

Co-authored-by: Markus Weber <we@ichaus.de>

Author: ichaus-we

chartfx-chart/src/main/java/io/fair_acc/chartfx/plugins/Zoomer.java

@@ -84,8 +84,9 @@ public class Zoomer extends ChartPlugin {
     private static final String ICON_ZOOM_V = "fa-arrows-v:" + FONT_SIZE;
 
     /**
-     * Default pan mouse filter passing on left mouse button with {@link MouseEvent#isControlDown() control key down}.
+     * Default pan mouse filter passing on middle mouse button {@link MouseEventsHelper#isOnlyMiddleButtonDown()}.
      */
+    @Deprecated
     public static final Predicate<MouseEvent> DEFAULT_MOUSE_FILTER = MouseEventsHelper::isOnlyMiddleButtonDown;
     private double panShiftX;
     private double panShiftY;
@@ -94,26 +95,6 @@ public class Zoomer extends ChartPlugin {
     private final BooleanProperty autoZoomEnable = new SimpleBooleanProperty(this, "enableAutoZoom", false);
     private final IntegerProperty autoZoomThreshold = new SimpleIntegerProperty(this, "autoZoomThreshold",
             DEFAULT_AUTO_ZOOM_THRESHOLD);
-    private final EventHandler<MouseEvent> panStartHandler = event -> {
-        if (isPannerEnabled() && DEFAULT_MOUSE_FILTER.test(event)) {
-            panStarted(event);
-            event.consume();
-        }
-    };
-
-    private final EventHandler<MouseEvent> panDragHandler = event -> {
-        if (panOngoing()) {
-            panDragged(event);
-            event.consume();
-        }
-    };
-
-    private final EventHandler<MouseEvent> panEndHandler = event -> {
-        if (panOngoing()) {
-            panEnded();
-            event.consume();
-        }
-    };
 
     /**
      * Default zoom-in mouse filter passing on left mouse button (only).
@@ -125,6 +106,11 @@ public class Zoomer extends ChartPlugin {
      */
     public final Predicate<MouseEvent> defaultZoomOutMouseFilter = event -> MouseEventsHelper.isOnlySecondaryButtonDown(event) && MouseEventsHelper.modifierKeysUp(event) && isMouseEventWithinCanvas(event);
 
+    /**
+     * Default pan mouse filter passing on middle mouse button (only).
+     */
+    public final Predicate<MouseEvent> defaultPanMouseFilter = event -> MouseEventsHelper.isOnlyMiddleButtonDown(event) && MouseEventsHelper.modifierKeysUp(event) && isMouseEventWithinCanvas(event);
+
     /**
      * Default zoom-origin mouse filter passing on right mouse button with {@link MouseEvent#isControlDown() control key
      * down}.
@@ -138,6 +124,7 @@ public class Zoomer extends ChartPlugin {
 
     private Predicate<MouseEvent> zoomInMouseFilter = defaultZoomInMouseFilter;
     private Predicate<MouseEvent> zoomOutMouseFilter = defaultZoomOutMouseFilter;
+    private Predicate<MouseEvent> panMouseFilter = defaultPanMouseFilter;
     private Predicate<MouseEvent> zoomOriginMouseFilter = defaultZoomOriginFilter;
     private Predicate<ScrollEvent> zoomScrollFilter = defaultScrollFilter;
 
@@ -226,6 +213,27 @@ protected void invalidated() {
         }
     };
 
+    private final EventHandler<MouseEvent> panStartHandler = event -> {
+        if (isPannerEnabled() && (panMouseFilter == null || panMouseFilter.test(event))) {
+            panStarted(event);
+            event.consume();
+        }
+    };
+
+    private final EventHandler<MouseEvent> panDragHandler = event -> {
+        if (panOngoing()) {
+            panDragged(event);
+            event.consume();
+        }
+    };
+
+    private final EventHandler<MouseEvent> panEndHandler = event -> {
+        if (panOngoing()) {
+            panEnded();
+            event.consume();
+        }
+    };
+
     private final EventHandler<MouseEvent> zoomOriginHandler = event -> {
         if (getZoomOriginMouseFilter() == null || getZoomOriginMouseFilter().test(event)) {
             final boolean zoomOutPerformed = zoomOrigin();
@@ -462,6 +470,16 @@ public Predicate<MouseEvent> getZoomOutMouseFilter() {
         return zoomOutMouseFilter;
     }
 
+    /**
+     * Returns pan mouse filter.
+     *
+     * @return pan mouse filter
+     * @see #setPanMouseFilter(Predicate)
+     */
+    public Predicate<MouseEvent> getPanMouseFilter() {
+        return panMouseFilter;
+    }
+
     /**
      * Returns zoom-scroll filter.
      *
@@ -649,6 +667,17 @@ public void setZoomOutMouseFilter(final Predicate<MouseEvent> zoomOutMouseFilter
         this.zoomOutMouseFilter = zoomOutMouseFilter;
     }
 
+    /**
+     * Sets filter on {@link MouseEvent#MOUSE_CLICKED MOUSE_CLICKED} events that should start pan operation.
+     *
+     * @param panMouseFilter the filter to accept pan mouse event. If {@code null} then any MOUSE_CLICKED event
+     *            will start pan operation. By default it's set to {@link #defaultPanMouseFilter}.
+     * @see #getPanMouseFilter()
+     */
+    public void setPanMouseFilter(final Predicate<MouseEvent> panMouseFilter) {
+        this.panMouseFilter = panMouseFilter;
+    }
+
     /**
      * Sets filter on {@link MouseEvent#MOUSE_CLICKED MOUSE_CLICKED} events that should trigger zoom-origin operation.
      *

chartfx-samples/src/main/java/io/fair_acc/sample/chart/ZoomerSample.java

@@ -20,6 +20,7 @@
 import io.fair_acc.chartfx.XYChart;
 import io.fair_acc.chartfx.axes.Axis;
 import io.fair_acc.chartfx.axes.AxisMode;
+import io.fair_acc.chartfx.plugins.MouseEventsHelper;
 import io.fair_acc.chartfx.plugins.Zoomer;
 import io.fair_acc.chartfx.plugins.Zoomer.ZoomState;
 import io.fair_acc.dataset.DataSet;
@@ -68,13 +69,20 @@ public Node getChartPanel(final Stage primaryStage) {
         registerZoomerChangeListener(zoomer3, chart3.getTitle());
         chart3.getPlugins().add(zoomer3);
 
-        // chart with x-only zoom
+        // chart with y-only zoom
         final Chart chart4 = getTestChart("y-only zoom", testDataSet);
         Zoomer zoomer4 = new Zoomer(AxisMode.Y);
         registerZoomerChangeListener(zoomer4, chart4.getTitle());
         chart4.getPlugins().add(zoomer4);
 
-        root.getChildren().addAll(chart1, chart2, chart3, chart4, label);
+        // chart with control + LMB pan
+        final Chart chart5 = getTestChart("control + primary (left) button to pan", testDataSet);
+        Zoomer zoomer5 = new Zoomer();
+        zoomer5.setPanMouseFilter(event -> MouseEventsHelper.isOnlyPrimaryButtonDown(event) && MouseEventsHelper.isOnlyCtrlModifierDown(event));
+        registerZoomerChangeListener(zoomer5, chart5.getTitle());
+        chart5.getPlugins().add(zoomer5);
+
+        root.getChildren().addAll(chart1, chart2, chart3, chart4, chart5, label);
 
         return root;
     }