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';
@@ -14,6 +15,17 @@ import 'package:flutter_map/src/misc/point.dart';
 import 'package:flutter_map/src/misc/private/positioned_tap_detector_2.dart';
 import 'package:latlong2/latlong.dart';
 
+extension on LogicalKeyboardKey {
+ bool get isControlKey {
+ return switch (this) {
+ LogicalKeyboardKey.control => true,
+ LogicalKeyboardKey.controlLeft => true,
+ LogicalKeyboardKey.controlRight => true,
+ _ => false,
+ };
+ }
+}
+
 /// Applies interactions (gestures/scroll/taps etc) to the current [MapCamera]
 /// via the internal [controller].
 class FlutterMapInteractiveViewer extends StatefulWidget {
@@ -80,6 +92,12 @@ class FlutterMapInteractiveViewerState
  late Animation<double> _doubleTapZoomAnimation;
  late Animation<LatLng> _doubleTapCenterAnimation;
 
+ final ctrlPressedNotifier = ValueNotifier<bool>(false);
+ Offset? initialPointerDownPos;
+ double cursorRotation = 0;
+ double clickDegrees = 0;
+ double dragDegrees = 0;
+
  int _tapUpCounter = 0;
  Timer? _doubleTapHoldMaxDelay;
 
@@ -100,6 +118,8 @@ class FlutterMapInteractiveViewerState
  _doubleTapController
  ..addListener(_handleDoubleTapZoomAnimation)
  ..addStatusListener(_doubleTapZoomStatusListener);
+
+ ServicesBinding.instance.keyboard.addHandler(keyHandler);
  }
 
  void _onMapStateChange() {
@@ -121,10 +141,19 @@ class FlutterMapInteractiveViewerState
  widget.controller.removeListener(_onMapStateChange);
  _flingController.dispose();
  _doubleTapController.dispose();
-
+ ctrlPressedNotifier.dispose();
+ ServicesBinding.instance.keyboard.removeHandler(keyHandler);
  super.dispose();
  }
 
+ bool keyHandler(KeyEvent event) {
+ if (event.logicalKey.isControlKey) {
+ ctrlPressedNotifier.value =
+ event is KeyDownEvent || event is KeyRepeatEvent;
+ }
+ return false;
+ }
+
  void updateGestures(
  InteractionOptions oldOptions,
  InteractionOptions newOptions,
@@ -253,11 +282,15 @@ class FlutterMapInteractiveViewerState
 
  @override
  Widget build(BuildContext context) {
+ clickDegrees = 0;
+ dragDegrees = 0;
+
  return Listener(
  onPointerDown: _onPointerDown,
  onPointerUp: _onPointerUp,
  onPointerCancel: _onPointerCancel,
  onPointerHover: _onPointerHover,
+ onPointerMove: _onPointerMove,
  onPointerSignal: _onPointerSignal,
  child: PositionedTapDetector2(
  controller: _positionedTapController,
@@ -283,6 +316,8 @@ class FlutterMapInteractiveViewerState
 
  void _onPointerDown(PointerDownEvent event) {
  ++_pointerCounter;
+ clickDegrees =
+ getCursorRotationDegrees(event.localPosition, context) - cursorRotation;
 
  if (_options.onPointerDown != null) {
  final latlng = _camera.offsetToCrs(event.localPosition);
@@ -292,6 +327,7 @@ class FlutterMapInteractiveViewerState
 
  void _onPointerUp(PointerUpEvent event) {
  --_pointerCounter;
+ cursorRotation = dragDegrees;
 
  if (_options.onPointerUp != null) {
  final latlng = _camera.offsetToCrs(event.localPosition);
@@ -315,6 +351,18 @@ class FlutterMapInteractiveViewerState
  }
  }
 
+ void _onPointerMove(PointerMoveEvent event) {
+ if (!ctrlPressedNotifier.value) return;
+
+ widget.controller.rotate(
+ dragDegrees =
+ getCursorRotationDegrees(event.localPosition, context) - clickDegrees,
+ 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 &&
@@ -366,6 +414,14 @@ class FlutterMapInteractiveViewerState
  }
  }
 
+ // Thanks to https://stackoverflow.com/questions/48916517/javascript-click-and-drag-to-rotate
+ double getCursorRotationDegrees(Offset offset, BuildContext context) =>
+ round((math.atan2(offset.dx - MediaQuery.sizeOf(context).width / 2,
+ offset.dy - MediaQuery.sizeOf(context).height / 2) *
+ (180 / pi) *
+ -1) +
+ 100);
+
  void _closeFlingAnimationController(MapEventSource source) {
  _flingAnimationStarted = false;
  if (_flingController.isAnimating) {
@@ -432,6 +488,8 @@ class FlutterMapInteractiveViewerState
  }
 
  void _handleScaleDragUpdate(ScaleUpdateDetails details) {
+ if (ctrlPressedNotifier.value) return;
+
  const eventSource = MapEventSource.onDrag;
 
  if (InteractiveFlag.hasDrag(_interactionOptions.flags)) {

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