Fix map dragging state management in DefaultTool

src/main/java/net/rptools/maptool/client/tool/DefaultTool.java

@@ -14,10 +14,12 @@
  */
 package net.rptools.maptool.client.tool;
 
+import java.awt.Point;
 import java.awt.dnd.DragSource;
 import java.awt.event.*;
 import java.util.Map;
 import java.util.Set;
+import javax.annotation.Nullable;
 import javax.swing.*;
 import net.rptools.maptool.client.AppPreferences;
 import net.rptools.maptool.client.AppState;
@@ -43,16 +45,22 @@ public abstract class DefaultTool extends Tool
 
   private Zone.Layer selectedLayer;
   private boolean isDraggingMap;
-  private int dragStartX;
-  private int dragStartY;
+
+  /**
+   * The origin point for a map drag, or {@code null} if there is no drag possible.
+   *
+   * <p>Will be non-null when a drag is possible (right button pressed). To check whether the drag
+   * is actually happening, use {@link #isDraggingMap()}. This field will be non-{@code null}
+   * whenever {@link #isDraggingMap} is {@code true}, but it is also possible to be non-{@code null}
+   * even if {@link #isDraggingMap} is {@code false}.
+   */
+  private @Nullable Point mapDragStart;
+
   private int dragThreshold = DragSource.getDragThreshold();
 
   protected int mouseX;
   protected int mouseY;
 
-  // This is to manage overflowing of map move events (keep things snappy)
-  private int mapDX, mapDY;
-
   // TBD
   private boolean isTouchScreen = false;
 
@@ -87,10 +95,16 @@ protected void detachFrom(ZoneRenderer renderer) {
     super.detachFrom(renderer);
   }
 
-  public boolean isDraggingMap() {
+  protected boolean isDraggingMap() {
     return isDraggingMap;
   }
 
+  /** Stop dragging the map. */
+  protected void cancelMapDrag() {
+    mapDragStart = null;
+    isDraggingMap = false;
+  }
+
   protected void repaintZone() {
     renderer.repaint();
   }
@@ -198,24 +212,18 @@ public void mousePressed(MouseEvent e) {
    * @param y the y coordinate of the drag start
    */
   public void setDragStart(int x, int y) {
-    dragStartX = x;
-    dragStartY = y;
+    mapDragStart = new Point(x, y);
   }
 
   @Override
   public void mouseReleased(MouseEvent e) {
-    if (isDraggingMap && isRightMouseButton(e)) {
-      renderer.maybeForcePlayersView();
-    }
-    // Cleanup
-    isDraggingMap = false;
-  }
+    if (isRightMouseButton(e) && mapDragStart != null) {
+      if (isDraggingMap) {
+        renderer.maybeForcePlayersView();
+      }
 
-  /**
-   * @param isDraggingMap whether the user drags the map
-   */
-  void setDraggingMap(boolean isDraggingMap) {
-    this.isDraggingMap = isDraggingMap;
+      cancelMapDrag();
+    }
   }
 
   /*
@@ -277,20 +285,18 @@ public void mouseDragged(MouseEvent e) {
       MapTool.getFrame().getCoordinateStatusBar().clear();
     }
     // MAP MOVEMENT
-    if (isRightMouseButton(e)) {
-
-      mapDX += mX - dragStartX;
-      mapDY += mY - dragStartY;
+    // Sometimes the mousePressed() event can come after the first mouseDragged() event when the
+    // right button is pressed. So check that we are actually intending to drag the map.
+    if (isRightMouseButton(e) && mapDragStart != null) {
+      var mapDX = mX - mapDragStart.x;
+      var mapDY = mY - mapDragStart.y;
 
       if (mapDX * mapDX + mapDY * mapDY > dragThreshold * dragThreshold) {
         isDraggingMap = true;
       }
 
       setDragStart(mX, mY);
-
       renderer.moveViewBy(mapDX, mapDY);
-      mapDX = 0;
-      mapDY = 0;
     }
   }
 

src/main/java/net/rptools/maptool/client/tool/PointerTool.java

@@ -495,7 +495,7 @@ public void mouseReleased(MouseEvent e) {
     // WAYPOINT
     if (SwingUtilities.isRightMouseButton(e) && tokenDragOp != null) {
       tokenDragOp.setWaypoint();
-      setDraggingMap(false); // We no longer drag the map. Fixes bug #616
+      cancelMapDrag(); // We no longer drag the map. Fixes bug #616
       return;
     }