Support desktop (click and drag) rotation

lib/src/gestures/flutter_map_interactive_viewer.dart

@@ -2,7 +2,8 @@ import 'dart:async';
 import 'dart:math' as math;
 
 import 'package:flutter/gestures.dart';
-import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
 import 'package:flutter_map/src/gestures/interactive_flag.dart';
 import 'package:flutter_map/src/gestures/latlng_tween.dart';
 import 'package:flutter_map/src/gestures/map_events.dart';
@@ -80,6 +81,17 @@ class FlutterMapInteractiveViewerState
   late Animation<double> _doubleTapZoomAnimation;
   late Animation<LatLng> _doubleTapCenterAnimation;
 
+  // 'CR' = cursor rotation
+  final _defaultCRTriggerKeys = {
+    LogicalKeyboardKey.control,
+    LogicalKeyboardKey.controlLeft,
+    LogicalKeyboardKey.controlRight
+  };
+  final crRotationTriggered = ValueNotifier(false);
+  double crDegrees = 0;
+  double crClickDegrees = 0;
+  double crDragDegrees = 0;
+
   int _tapUpCounter = 0;
   Timer? _doubleTapHoldMaxDelay;
 
@@ -93,17 +105,16 @@ class FlutterMapInteractiveViewerState
   void initState() {
     super.initState();
     widget.controller.interactiveViewerState = this;
-    widget.controller.addListener(_onMapStateChange);
+    widget.controller.addListener(onMapStateChange);
     _flingController
       ..addListener(_handleFlingAnimation)
       ..addStatusListener(_flingAnimationStatusListener);
     _doubleTapController
       ..addListener(_handleDoubleTapZoomAnimation)
       ..addStatusListener(_doubleTapZoomStatusListener);
-  }
 
-  void _onMapStateChange() {
-    setState(() {});
+    ServicesBinding.instance.keyboard
+        .addHandler(keyboardRotationTriggerKeyHandler);
   }
 
   @override
@@ -118,13 +129,25 @@ class FlutterMapInteractiveViewerState
 
   @override
   void dispose() {
-    widget.controller.removeListener(_onMapStateChange);
+    widget.controller.removeListener(onMapStateChange);
     _flingController.dispose();
     _doubleTapController.dispose();
-
+    crRotationTriggered.dispose();
+    ServicesBinding.instance.keyboard
+        .removeHandler(keyboardRotationTriggerKeyHandler);
     super.dispose();
   }
 
+  void onMapStateChange() => setState(() {});
+
+  bool keyboardRotationTriggerKeyHandler(KeyEvent event) {
+    crRotationTriggered.value =
+        (event is KeyRepeatEvent || event is KeyDownEvent) &&
+            (_interactionOptions.isCursorRotationKeyboardKeyTrigger ??
+                (key) => _defaultCRTriggerKeys.contains(key))(event.logicalKey);
+    return false;
+  }
+
   void updateGestures(
     InteractionOptions oldOptions,
     InteractionOptions newOptions,
@@ -186,6 +209,14 @@ class FlutterMapInteractiveViewerState
     if (emitMapEventMoveEnd) {
       widget.controller.moveEnded(MapEventSource.interactiveFlagsChanged);
     }
+
+    if (oldOptions.isCursorRotationKeyboardKeyTrigger !=
+        newOptions.isCursorRotationKeyboardKeyTrigger) {
+      ServicesBinding.instance.keyboard
+          .removeHandler(keyboardRotationTriggerKeyHandler);
+      ServicesBinding.instance.keyboard
+          .addHandler(keyboardRotationTriggerKeyHandler);
+    }
   }
 
   Map<Type, GestureRecognizerFactory> _createGestures({
@@ -253,11 +284,15 @@ class FlutterMapInteractiveViewerState
 
   @override
   Widget build(BuildContext context) {
+    crClickDegrees = 0;
+    crDragDegrees = 0;
+
     return Listener(
       onPointerDown: _onPointerDown,
       onPointerUp: _onPointerUp,
       onPointerCancel: _onPointerCancel,
       onPointerHover: _onPointerHover,
+      onPointerMove: _onPointerMove,
       onPointerSignal: _onPointerSignal,
       child: PositionedTapDetector2(
         controller: _positionedTapController,
@@ -283,6 +318,7 @@ class FlutterMapInteractiveViewerState
 
   void _onPointerDown(PointerDownEvent event) {
     ++_pointerCounter;
+    crClickDegrees = getCursorRotationDegrees(event.localPosition) - crDegrees;
 
     if (_options.onPointerDown != null) {
       final latlng = _camera.offsetToCrs(event.localPosition);
@@ -292,6 +328,7 @@ class FlutterMapInteractiveViewerState
 
   void _onPointerUp(PointerUpEvent event) {
     --_pointerCounter;
+    crDegrees = crDragDegrees;
 
     if (_options.onPointerUp != null) {
       final latlng = _camera.offsetToCrs(event.localPosition);
@@ -315,10 +352,25 @@ class FlutterMapInteractiveViewerState
     }
   }
 
+  void _onPointerMove(PointerMoveEvent event) {
+    if (!crRotationTriggered.value) return;
+
+    widget.controller.rotate(
+      crDragDegrees =
+          getCursorRotationDegrees(event.localPosition) - crClickDegrees,
+      hasGesture: true,
+      source: MapEventSource.cursorRotation,
+      id: null,
+    );
+  }
+
   void _onPointerSignal(PointerSignalEvent pointerSignal) {
     // Handle mouse scroll events if the enableScrollWheel parameter is enabled
     if (pointerSignal is PointerScrollEvent &&
-        _interactionOptions.enableScrollWheel &&
+        (InteractiveFlag.hasFlag(
+                _interactionOptions.flags, InteractiveFlag.scrollWheelZoom) ||
+            // ignore: deprecated_member_use_from_same_package
+            _interactionOptions.enableScrollWheel) &&
         pointerSignal.scrollDelta.dy != 0) {
       // Prevent scrolling of parent/child widgets simultaneously. See
       // [PointerSignalResolver] documentation for more information.
@@ -366,6 +418,17 @@ class FlutterMapInteractiveViewerState
     }
   }
 
+  // Thanks to https://stackoverflow.com/questions/48916517/javascript-click-and-drag-to-rotate
+  double getCursorRotationDegrees(Offset offset) {
+    const correctionTerm = 180; // North = cursor
+
+    final size = MediaQuery.sizeOf(context);
+    return (-math.atan2(
+                offset.dx - size.width / 2, offset.dy - size.height / 2) *
+            (180 / math.pi)) +
+        correctionTerm;
+  }
+
   void _closeFlingAnimationController(MapEventSource source) {
     _flingAnimationStarted = false;
     if (_flingController.isAnimating) {
@@ -432,6 +495,8 @@ class FlutterMapInteractiveViewerState
   }
 
   void _handleScaleDragUpdate(ScaleUpdateDetails details) {
+    if (crRotationTriggered.value) return;
+
     const eventSource = MapEventSource.onDrag;
 
     if (InteractiveFlag.hasDrag(_interactionOptions.flags)) {

lib/src/gestures/interactive_flag.dart

@@ -1,3 +1,5 @@
+import 'package:flutter_map/src/map/options.dart';
+
 /// Use [InteractiveFlag] to disable / enable certain events Use
 /// [InteractiveFlag.all] to enable all events, use [InteractiveFlag.none] to
 /// disable all events
@@ -13,27 +15,34 @@
 ///       ~[InteractiveFlag.doubleTapZoom]
 class InteractiveFlag {
   const InteractiveFlag._();
+
   static const int all =
       drag | flingAnimation | pinchMove | pinchZoom | doubleTapZoom | rotate;
   static const int none = 0;
 
-  // Enable move with one finger.
+  /// Enable panning with a single finger or cursor
   static const int drag = 1 << 0;
 
-  // Enable fling animation when drag or pinchMove have enough Fling Velocity.
+  /// Enable fling animation after panning if velocity is great enough.
   static const int flingAnimation = 1 << 1;
 
-  // Enable move with two or more fingers.
+  /// Enable panning with multiple fingers
   static const int pinchMove = 1 << 2;
 
-  // Enable pinch zoom.
+  /// Enable zooming with a multi-finger pinch gesture
   static const int pinchZoom = 1 << 3;
 
-  // Enable double tap zoom animation.
+  /// Enable zooming with a single-finger double tap gesture
   static const int doubleTapZoom = 1 << 4;
 
-  /// Enable map rotate.
-  static const int rotate = 1 << 5;
+  /// Enable zooming with a mouse scroll wheel
+  static const int scrollWheelZoom = 1 << 5;
+
+  /// Enable rotation with two-finger twist gesture
+  ///
+  /// For controlling rotation where a keyboard/cursor combination is used, see
+  /// [InteractionOptions.isCursorRotationKeyboardKeyTrigger].
+  static const int rotate = 1 << 6;
 
   /// Flags pertaining to gestures which require multiple fingers.
   static const _multiFingerFlags = pinchMove | pinchZoom | rotate;
@@ -43,9 +52,8 @@ class InteractiveFlag {
   /// [InteractiveFlag.rotate] and [rightFlags]= [InteractiveFlag.rotate] |
   /// [InteractiveFlag.flingAnimation] returns true because both have
   /// [InteractiveFlag.rotate] flag
-  static bool hasFlag(int leftFlags, int rightFlags) {
-    return leftFlags & rightFlags != 0;
-  }
+  static bool hasFlag(int leftFlags, int rightFlags) =>
+      leftFlags & rightFlags != 0;
 
   /// True if any multi-finger gesture flags are enabled.
   static bool hasMultiFinger(int flags) => hasFlag(flags, _multiFingerFlags);

lib/src/gestures/map_events.dart

@@ -23,6 +23,7 @@ enum MapEventSource {
   custom,
   scrollWheel,
   nonRotatedSizeChange,
+  cursorRotation,
 }
 
 /// Base event class which is emitted by MapController instance, the event

lib/src/map/options.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/gestures.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_map/src/geo/crs.dart';
 import 'package:flutter_map/src/geo/latlng_bounds.dart';
@@ -398,12 +399,25 @@ final class InteractionOptions {
   /// gestures will take effect see [MultiFingerGesture] for custom settings
   final int pinchMoveWinGestures;
 
-  /// If true then the map will scroll when the user uses the scroll wheel on
-  /// his mouse. This is supported on web and desktop, but might also work well
-  /// on Android. A [Listener] is used to capture the onPointerSignal events.
+  @Deprecated(
+    'Prefer `flags.scrollWheelZoom`. '
+    'This property was moved as it better suited being an `InteractiveFlag`. '
+    'This property is deprecated since v6.',
+  )
   final bool enableScrollWheel;
+
   final double scrollWheelVelocity;
 
+  /// Whether to allow rotation by moving the cursor dependent on the currently
+  /// pressed keyboard [LogicalKeyboardKey]
+  ///
+  /// Fix to returning `false` to disable cursor/keyboard rotation.
+  ///
+  /// Defaults to allowing rotation by cursor if any of the Control keys are
+  /// pressed.
+  final bool Function(LogicalKeyboardKey key)?
+      isCursorRotationKeyboardKeyTrigger;
+
   const InteractionOptions({
     this.flags = InteractiveFlag.all,
     this.debugMultiFingerGestureWinner = false,
@@ -418,6 +432,7 @@ final class InteractionOptions {
         MultiFingerGesture.pinchZoom | MultiFingerGesture.pinchMove,
     this.enableScrollWheel = true,
     this.scrollWheelVelocity = 0.005,
+    this.isCursorRotationKeyboardKeyTrigger,
   })  : assert(rotationThreshold >= 0.0),
         assert(pinchZoomThreshold >= 0.0),
         assert(pinchMoveThreshold >= 0.0);
@@ -441,6 +456,7 @@ final class InteractionOptions {
       pinchZoomWinGestures == other.pinchZoomWinGestures &&
       pinchMoveThreshold == other.pinchMoveThreshold &&
       pinchMoveWinGestures == other.pinchMoveWinGestures &&
+      // ignore: deprecated_member_use_from_same_package
       enableScrollWheel == other.enableScrollWheel &&
       scrollWheelVelocity == other.scrollWheelVelocity;
 
@@ -455,6 +471,7 @@ final class InteractionOptions {
         pinchZoomWinGestures,
         pinchMoveThreshold,
         pinchMoveWinGestures,
+        // ignore: deprecated_member_use_from_same_package
         enableScrollWheel,
         scrollWheelVelocity,
       );