viewer: fixed flickering on first scale animation in some cases

CHANGELOG.md

@@ -4,11 +4,12 @@ All notable changes to this project will be documented in this file.
 
 ## <a id="unreleased"></a>[Unreleased]
 
-## <a id="v1.8.4"></a>[v1.8.4] - 2023-03-17
-
 ### Fixed
 
 - permission confusion when removable volume changes
+- Viewer: flickering on first scale animation in some cases
+
+## <a id="v1.8.4"></a>[v1.8.4] - 2023-03-17
 
 ### Added
 

plugins/aves_magnifier/lib/src/controller/controller.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:ui';
 
 import 'package:aves_magnifier/src/controller/state.dart';
 import 'package:aves_magnifier/src/scale/scale_boundaries.dart';
@@ -20,17 +19,13 @@ class AvesMagnifierController {
   AvesMagnifierController({
     MagnifierState? initialState,
   }) : super() {
-    initial = initialState ??
-        const MagnifierState(
-          position: Offset.zero,
-          scale: null,
-          source: ChangeSource.internal,
-        );
+    const source = ChangeSource.internal;
+    initial = initialState ?? const MagnifierState(position: Offset.zero, scale: null, source: source);
     previousState = initial;
     _currentState = initial;
     _setState(initial);
 
-    const _initialScaleState = ScaleStateChange(state: ScaleState.initial, source: ChangeSource.internal);
+    const _initialScaleState = ScaleStateChange(state: ScaleState.initial, source: source);
     previousScaleState = _initialScaleState;
     _currentScaleState = _initialScaleState;
     _setScaleState(_initialScaleState);

plugins/aves_magnifier/lib/src/controller/controller_delegate.dart

@@ -80,15 +80,20 @@ mixin AvesMagnifierControllerDelegate on State<MagnifierCore> {
 
   Offset get position => controller.position;
 
+  double? recalcScale() {
+    final scaleState = controller.scaleState.state;
+    final newScale = controller.getScaleForScaleState(scaleState);
+    markNeedsScaleRecalc = false;
+    setScale(newScale, ChangeSource.internal);
+    return newScale;
+  }
+
   double? get scale {
     final scaleState = controller.scaleState.state;
     final needsRecalc = markNeedsScaleRecalc && !(scaleState == ScaleState.zoomedIn || scaleState == ScaleState.zoomedOut);
     final scaleExistsOnController = controller.scale != null;
     if (needsRecalc || !scaleExistsOnController) {
-      final newScale = controller.getScaleForScaleState(scaleState);
-      markNeedsScaleRecalc = false;
-      setScale(newScale, ChangeSource.internal);
-      return newScale;
+      return recalcScale();
     }
     return controller.scale;
   }

plugins/aves_magnifier/lib/src/core/core.dart

@@ -72,6 +72,9 @@ class _MagnifierCoreState extends State<MagnifierCore> with TickerProviderStateM
       ..addStatusListener(onAnimationStatus);
     _positionAnimationController = AnimationController(vsync: this)..addListener(handlePositionAnimate);
     _registerWidget(widget);
+    // force delegate scale computing on initialization
+    // so that it does not happen lazily at the beginning of a scale animation
+    recalcScale();
   }
 
   @override