UNLOCK image if image is zoomedOut

example/lib/screens/examples/controller_example.dart

@@ -26,7 +26,7 @@ class _ControllerExampleState extends State<ControllerExample> {
     controller = PhotoViewController();
     controller
       ..scale = defScale
-      ..scaleState = PhotoViewScaleState.zooming
+      ..scaleState = PhotoViewScaleState.initial
       ..outputStateStream.listen(onControllerState);
     super.initState();
   }
@@ -112,7 +112,6 @@ class _ControllerExampleState extends State<ControllerExample> {
                 max: max,
                 onChanged: (double newRotation) {
                   controller.rotation = newRotation;
-                  controller.scaleState = PhotoViewScaleState.zooming;
                 })),
         Text(
           "Scale ${value.scale}",
@@ -127,7 +126,9 @@ class _ControllerExampleState extends State<ControllerExample> {
                 max: maxScale,
                 onChanged: (double newScale) {
                   controller.scale = newScale;
-                  controller.scaleState = PhotoViewScaleState.zooming;
+                  controller.scaleState = newScale > defScale
+                      ? PhotoViewScaleState.zoomedIn
+                      : PhotoViewScaleState.zoomedOut;
                 })),
       ],
     );

lib/photo_view.dart

@@ -299,7 +299,7 @@ class _PhotoViewState extends State<PhotoView>
       _controlledController = false;
       controller = widget.controller;
     }
-    controller.outputStateStream.listen(scaleStateListener);
+    controller.outputScaleStateStream.listen(scaleStateListener);
   }
 
   @override
@@ -341,9 +341,8 @@ class _PhotoViewState extends State<PhotoView>
     }
   }
 
-  void scaleStateListener(PhotoViewControllerValue value) {
-    if (widget.scaleStateChangedCallback != null &&
-        controller.scaleState != controller.prevValue.scaleState) {
+  void scaleStateListener(PhotoViewScaleState scaleState) {
+    if (widget.scaleStateChangedCallback != null) {
       widget.scaleStateChangedCallback(controller.scaleState);
     }
   }
@@ -449,7 +448,8 @@ PhotoViewScaleState defaultScaleStateCycle(PhotoViewScaleState actual) {
       return PhotoViewScaleState.originalSize;
     case PhotoViewScaleState.originalSize:
       return PhotoViewScaleState.initial;
-    case PhotoViewScaleState.zooming:
+    case PhotoViewScaleState.zoomedIn:
+    case PhotoViewScaleState.zoomedOut:
       return PhotoViewScaleState.initial;
     default:
       return PhotoViewScaleState.initial;

lib/photo_view_gallery.dart

@@ -170,7 +170,10 @@ class _PhotoViewGalleryState extends State<PhotoViewGallery> {
 
   void scaleStateChangedCallback(PhotoViewScaleState scaleState) {
     setState(() {
-      _locked = scaleState != PhotoViewScaleState.initial;
+      _locked = (scaleState == PhotoViewScaleState.initial ||
+              scaleState == PhotoViewScaleState.zoomedOut)
+          ? false
+          : true;
     });
     if (widget.scaleStateChangedCallback != null) {
       widget.scaleStateChangedCallback(scaleState);

lib/src/photo_view_controller.dart

@@ -18,9 +18,12 @@ typedef ScaleStateListener = void Function(double prevScale, double nextScale);
 ///
 /// The default implementation used by [PhotoView] is [PhotoViewController].
 abstract class PhotoViewControllerBase<T extends PhotoViewControllerValue> {
-  /// The output for state updates. Usually a broadcast [Stream]
+  /// The output for state/value updates. Usually a broadcast [Stream]
   Stream<T> get outputStateStream;
 
+  /// The output for scaleState changes [Stream]
+  Stream<PhotoViewScaleState> get outputScaleStateStream;
+
   /// The state value before the last change or the initial state if trhe state has not been changed.
   T prevValue;
 
@@ -38,7 +41,7 @@ abstract class PhotoViewControllerBase<T extends PhotoViewControllerValue> {
 
   /// The scale factor to transform the child (image or a customChild).
   ///
-  /// **Important**: Avoid setting this field without setting [scaleState] to [PhotoViewScaleState.zooming].
+  /// **Important**: Avoid setting this field without setting [scaleState] to [PhotoViewScaleState.zoomedIn] or [PhotoViewScaleState.zoomedOut].  <- this has to be chnaged in the future
   double scale;
 
   /// The rotation factor to transform the child (image or a customChild).
@@ -49,7 +52,8 @@ abstract class PhotoViewControllerBase<T extends PhotoViewControllerValue> {
 
   /// A way to represent the step of the "doubletap gesture cycle" in which PhotoView is.
   ///
-  /// **Important**: This fields is rarely externally set to a value different than [PhotoViewScaleState.zooming] after setting a [scale].
+  /// **Important**: This fields is rarely externally set to a value different than [PhotoViewScaleState.zoomedIn] or [PhotoViewScaleState.zoomedOut] after setting a [scale].
+  /// future TODO: setting the controller.scale should also set the scaleState to [PhotoViewScaleState.zoomedIn] or [PhotoViewScaleState.zoomedOut]
   PhotoViewScaleState scaleState;
 
   /// Update multiple fields of the state with only one update streamed.
@@ -122,22 +126,30 @@ class PhotoViewController
     _notifier.addListener(_changeListener);
     _outputCtrl = StreamController<PhotoViewControllerValue>.broadcast();
     _outputCtrl.sink.add(initial);
+    _outputScaleStateCtrl = StreamController<PhotoViewScaleState>();
+    _outputScaleStateCtrl.sink.add(PhotoViewScaleState.initial);
   }
 
   ValueNotifier<PhotoViewControllerValue> _notifier;
   PhotoViewControllerValue initial;
 
   StreamController<PhotoViewControllerValue> _outputCtrl;
+  StreamController<PhotoViewScaleState> _outputScaleStateCtrl;
 
   @override
   Stream<PhotoViewControllerValue> get outputStateStream => _outputCtrl.stream;
 
+  @override
+  Stream<PhotoViewScaleState> get outputScaleStateStream =>
+      _outputScaleStateCtrl.stream;
+
   @override
   PhotoViewControllerValue prevValue;
 
   @override
   void reset() {
     value = initial;
+    _outputScaleStateCtrl.sink.add(PhotoViewScaleState.initial);
   }
 
   void _changeListener() {
@@ -147,6 +159,7 @@ class PhotoViewController
   @override
   void dispose() {
     _outputCtrl.close();
+    _outputScaleStateCtrl.close();
     _notifier.dispose();
   }
 
@@ -172,6 +185,7 @@ class PhotoViewController
     if (value.scale == scale) {
       return;
     }
+
     prevValue = value;
     value = PhotoViewControllerValue(
         position: position,
@@ -213,6 +227,7 @@ class PhotoViewController
         rotation: rotation,
         scaleState: scaleState,
         rotationFocusPoint: rotationFocusPoint);
+    _outputScaleStateCtrl.sink.add(scaleState);
   }
 
   @override
@@ -245,6 +260,9 @@ class PhotoViewController
     Size outerSize,
     Size childSize,
   }) {
+    if (value.scaleState != scaleState) {
+      _outputScaleStateCtrl.sink.add(scaleState);
+    }
     prevValue = value;
     value = PhotoViewControllerValue(
         position: position ?? value.position,

lib/src/photo_view_image_wrapper.dart

@@ -110,9 +110,15 @@ class _PhotoViewImageWrapperState extends State<PhotoViewImageWrapper>
   void onScaleUpdate(ScaleUpdateDetails details) {
     final double newScale = _scaleBefore * details.scale;
     final Offset delta = details.focalPoint - _normalizedPosition;
+
+    final double _initialScale = widget.scaleBoundaries.initialScale;
+
     final PhotoViewScaleState newScaleState = details.scale != 1.0
-        ? PhotoViewScaleState.zooming
+        ? (newScale > _initialScale)
+            ? PhotoViewScaleState.zoomedIn
+            : PhotoViewScaleState.zoomedOut
         : widget.controller.scaleState;
+
     widget.controller.updateMultiple(
         scaleState: newScaleState,
         scale: newScale,
@@ -249,7 +255,8 @@ class _PhotoViewImageWrapperState extends State<PhotoViewImageWrapper>
   void scaleStateListener(PhotoViewControllerValue value) {
     if (widget.controller.prevValue.scaleState !=
             widget.controller.scaleState &&
-        widget.controller.scaleState != PhotoViewScaleState.zooming) {
+        (widget.controller.scaleState != PhotoViewScaleState.zoomedIn &&
+            widget.controller.scaleState != PhotoViewScaleState.zoomedOut)) {
       final double prevScale = widget.controller.scale ??
           getScaleForScaleState(
               PhotoViewScaleState.initial, widget.scaleBoundaries);
@@ -267,11 +274,11 @@ class _PhotoViewImageWrapperState extends State<PhotoViewImageWrapper>
     final ScaleBoundaries scaleBoundaries = widget.scaleBoundaries;
     final PhotoViewControllerBase controller = widget.controller;
     final PhotoViewScaleState scaleState = controller.scaleState;
-    if (scaleState == PhotoViewScaleState.zooming) {
-      controller.scaleState = widget.scaleStateCycle(scaleState);
+    if (scaleState == PhotoViewScaleState.zoomedIn ||
+        scaleState == PhotoViewScaleState.zoomedOut) {
+      widget.controller.scaleState = widget.scaleStateCycle(scaleState);
       return;
     }
-
     final double originalScale =
         getScaleForScaleState(scaleState, scaleBoundaries);
 

lib/src/photo_view_scale_state.dart

@@ -1,2 +1,8 @@
 /// A way to represent the step of the "doubletap gesture cycle" in which PhotoView is.
-enum PhotoViewScaleState { initial, covering, originalSize, zooming }
+enum PhotoViewScaleState {
+  initial,
+  covering,
+  originalSize,
+  zoomedIn,
+  zoomedOut
+}

lib/src/photo_view_utils.dart

@@ -7,7 +7,8 @@ double getScaleForScaleState(
     PhotoViewScaleState scaleState, ScaleBoundaries scaleBoundaries) {
   switch (scaleState) {
     case PhotoViewScaleState.initial:
-    case PhotoViewScaleState.zooming:
+    case PhotoViewScaleState.zoomedIn:
+    case PhotoViewScaleState.zoomedOut:
       return _clampSize(scaleBoundaries.initialScale, scaleBoundaries);
     case PhotoViewScaleState.covering:
       return _clampSize(

test/controller_test.dart

@@ -38,8 +38,11 @@ void main() {
     controller.rotationFocusPoint = Offset.zero;
     expect(controller.rotationFocusPoint, Offset.zero);
 
-    controller.scaleState = PhotoViewScaleState.zooming;
-    expect(controller.scaleState, PhotoViewScaleState.zooming);
+    controller.scaleState = PhotoViewScaleState.zoomedIn;
+    expect(controller.scaleState, PhotoViewScaleState.zoomedIn);
+
+    // controller.scaleState = PhotoViewScaleState.zoomedOut;
+    // expect(controller.scaleState, PhotoViewScaleState.zoomedOut);
 
     controller.updateMultiple(
         position: const Offset(1, 1), scaleState: PhotoViewScaleState.initial);
@@ -63,35 +66,36 @@ void main() {
         scale: null,
         rotation: 0.0,
         rotationFocusPoint: null,
-        scaleState: PhotoViewScaleState.zooming);
+        scaleState: PhotoViewScaleState.zoomedOut);
 
     const PhotoViewControllerValue value2 = const PhotoViewControllerValue(
         position: Offset.zero,
         scale: null,
         rotation: 1.0,
         rotationFocusPoint: null,
-        scaleState: PhotoViewScaleState.zooming);
+        scaleState: PhotoViewScaleState.zoomedOut);
 
     const PhotoViewControllerValue value3 = const PhotoViewControllerValue(
         position: Offset.zero,
         scale: 3.0,
         rotation: 1.0,
         rotationFocusPoint: null,
-        scaleState: PhotoViewScaleState.zooming);
+        scaleState: PhotoViewScaleState.zoomedOut);
 
     const PhotoViewControllerValue value4 = const PhotoViewControllerValue(
         position: const Offset(1, 1),
         scale: 3.0,
         rotation: 45.0,
         rotationFocusPoint: null,
-        scaleState: PhotoViewScaleState.zooming);
+        scaleState: PhotoViewScaleState.zoomedOut);
 
     expect(controller.outputStateStream,
         emitsInOrder([value1, value2, value3, value4]));
-    controller.scaleState = PhotoViewScaleState.zooming;
+    controller.scaleState = PhotoViewScaleState.zoomedOut;
     controller.rotation = 1.0;
     controller.scale = 3.0;
 
     controller.updateMultiple(position: const Offset(1, 1), rotation: 45.0);
+    //Testing with 'zoomedIn' and 'zoomedOut' will be diffcult as long as scaleState isn't changed in the controller's scale setter
   });
 }