Move viewConfiguration parsing from PlatformDispatcher to _hooks (#44787)

This PR moves the code that parses `viewConfiguration` from
`PlatformDispatcher` to `_hooks`. This makes `PlatformDispatcher`'s API
cleaner by hiding the encoding implementation of `ViewConfiguration` in
`_hooks`, and allows more APIs to pass view configuration, such as the
`addView` that will be introduced in
#42991.

This PR should not need unit tests since it's just a refactor, and the
code path that contains `_updateWindowMetrics` has been tested in
existing unit tests.

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Author: dkwingsmt

lib/ui/hooks.dart

@@ -30,9 +30,98 @@ void _updateDisplays(
   PlatformDispatcher.instance._updateDisplays(displays);
 }
 
+List<DisplayFeature> _decodeDisplayFeatures({
+  required List<double> bounds,
+  required List<int> type,
+  required List<int> state,
+  required double devicePixelRatio,
+}) {
+  assert(bounds.length / 4 == type.length, 'Bounds are rectangles, requiring 4 measurements each');
+  assert(type.length == state.length);
+  final List<DisplayFeature> result = <DisplayFeature>[];
+  for(int i = 0; i < type.length; i++) {
+    final int rectOffset = i * 4;
+    result.add(DisplayFeature(
+      bounds: Rect.fromLTRB(
+        bounds[rectOffset] / devicePixelRatio,
+        bounds[rectOffset + 1] / devicePixelRatio,
+        bounds[rectOffset + 2] / devicePixelRatio,
+        bounds[rectOffset + 3] / devicePixelRatio,
+      ),
+      type: DisplayFeatureType.values[type[i]],
+      state: state[i] < DisplayFeatureState.values.length
+          ? DisplayFeatureState.values[state[i]]
+          : DisplayFeatureState.unknown,
+    ));
+  }
+  return result;
+}
+
+_ViewConfiguration _buildViewConfiguration(
+  double devicePixelRatio,
+  double width,
+  double height,
+  double viewPaddingTop,
+  double viewPaddingRight,
+  double viewPaddingBottom,
+  double viewPaddingLeft,
+  double viewInsetTop,
+  double viewInsetRight,
+  double viewInsetBottom,
+  double viewInsetLeft,
+  double systemGestureInsetTop,
+  double systemGestureInsetRight,
+  double systemGestureInsetBottom,
+  double systemGestureInsetLeft,
+  double physicalTouchSlop,
+  List<double> displayFeaturesBounds,
+  List<int> displayFeaturesType,
+  List<int> displayFeaturesState,
+  int displayId,
+) {
+  return _ViewConfiguration(
+    devicePixelRatio: devicePixelRatio,
+    geometry: Rect.fromLTWH(0.0, 0.0, width, height),
+    viewPadding: ViewPadding._(
+      top: viewPaddingTop,
+      right: viewPaddingRight,
+      bottom: viewPaddingBottom,
+      left: viewPaddingLeft,
+    ),
+    viewInsets: ViewPadding._(
+      top: viewInsetTop,
+      right: viewInsetRight,
+      bottom: viewInsetBottom,
+      left: viewInsetLeft,
+    ),
+    padding: ViewPadding._(
+      top: math.max(0.0, viewPaddingTop - viewInsetTop),
+      right: math.max(0.0, viewPaddingRight - viewInsetRight),
+      bottom: math.max(0.0, viewPaddingBottom - viewInsetBottom),
+      left: math.max(0.0, viewPaddingLeft - viewInsetLeft),
+    ),
+    systemGestureInsets: ViewPadding._(
+      top: math.max(0.0, systemGestureInsetTop),
+      right: math.max(0.0, systemGestureInsetRight),
+      bottom: math.max(0.0, systemGestureInsetBottom),
+      left: math.max(0.0, systemGestureInsetLeft),
+    ),
+    gestureSettings: GestureSettings(
+      physicalTouchSlop: physicalTouchSlop == _kUnsetGestureSetting ? null : physicalTouchSlop,
+    ),
+    displayFeatures: _decodeDisplayFeatures(
+      bounds: displayFeaturesBounds,
+      type: displayFeaturesType,
+      state: displayFeaturesState,
+      devicePixelRatio: devicePixelRatio,
+    ),
+    displayId: displayId,
+  );
+}
+
 @pragma('vm:entry-point')
 void _updateWindowMetrics(
-  int id,
+  int viewId,
   double devicePixelRatio,
   double width,
   double height,
@@ -54,8 +143,7 @@ void _updateWindowMetrics(
   List<int> displayFeaturesState,
   int displayId,
 ) {
-  PlatformDispatcher.instance._updateWindowMetrics(
-    id,
+  final _ViewConfiguration viewConfiguration = _buildViewConfiguration(
     devicePixelRatio,
     width,
     height,
@@ -77,6 +165,7 @@ void _updateWindowMetrics(
     displayFeaturesState,
     displayId,
   );
+  PlatformDispatcher.instance._updateWindowMetrics(viewId, viewConfiguration);
 }
 
 typedef _LocaleClosure = String Function();

lib/ui/platform_dispatcher.dart

@@ -263,107 +263,19 @@ class PlatformDispatcher {
   // Called from the engine, via hooks.dart
   //
   // Updates the metrics of the window with the given id.
-  void _updateWindowMetrics(
-    int id,
-    double devicePixelRatio,
-    double width,
-    double height,
-    double viewPaddingTop,
-    double viewPaddingRight,
-    double viewPaddingBottom,
-    double viewPaddingLeft,
-    double viewInsetTop,
-    double viewInsetRight,
-    double viewInsetBottom,
-    double viewInsetLeft,
-    double systemGestureInsetTop,
-    double systemGestureInsetRight,
-    double systemGestureInsetBottom,
-    double systemGestureInsetLeft,
-    double physicalTouchSlop,
-    List<double> displayFeaturesBounds,
-    List<int> displayFeaturesType,
-    List<int> displayFeaturesState,
-    int displayId,
-  ) {
-    final _ViewConfiguration viewConfiguration = _ViewConfiguration(
-      devicePixelRatio: devicePixelRatio,
-      geometry: Rect.fromLTWH(0.0, 0.0, width, height),
-      viewPadding: ViewPadding._(
-        top: viewPaddingTop,
-        right: viewPaddingRight,
-        bottom: viewPaddingBottom,
-        left: viewPaddingLeft,
-      ),
-      viewInsets: ViewPadding._(
-        top: viewInsetTop,
-        right: viewInsetRight,
-        bottom: viewInsetBottom,
-        left: viewInsetLeft,
-      ),
-      padding: ViewPadding._(
-        top: math.max(0.0, viewPaddingTop - viewInsetTop),
-        right: math.max(0.0, viewPaddingRight - viewInsetRight),
-        bottom: math.max(0.0, viewPaddingBottom - viewInsetBottom),
-        left: math.max(0.0, viewPaddingLeft - viewInsetLeft),
-      ),
-      systemGestureInsets: ViewPadding._(
-        top: math.max(0.0, systemGestureInsetTop),
-        right: math.max(0.0, systemGestureInsetRight),
-        bottom: math.max(0.0, systemGestureInsetBottom),
-        left: math.max(0.0, systemGestureInsetLeft),
-      ),
-      gestureSettings: GestureSettings(
-        physicalTouchSlop: physicalTouchSlop == _kUnsetGestureSetting ? null : physicalTouchSlop,
-      ),
-      displayFeatures: _decodeDisplayFeatures(
-        bounds: displayFeaturesBounds,
-        type: displayFeaturesType,
-        state: displayFeaturesState,
-        devicePixelRatio: devicePixelRatio,
-      ),
-      displayId: displayId,
-    );
-
-    final FlutterView? view = _views[id];
-    if (id == _kImplicitViewId && view == null) {
+  void _updateWindowMetrics(int viewId, _ViewConfiguration viewConfiguration) {
+    final FlutterView? view = _views[viewId];
+    if (viewId == _kImplicitViewId && view == null) {
       // TODO(goderbauer): Remove the implicit creation of the implicit view
       //   when we have an addView API and the implicit view is added via that.
-      _views[id] = FlutterView._(id, this, viewConfiguration);
+      _views[viewId] = FlutterView._(viewId, this, viewConfiguration);
     } else {
       assert(view != null);
       view!._viewConfiguration = viewConfiguration;
     }
-
     _invoke(onMetricsChanged, _onMetricsChangedZone);
   }
 
-  List<DisplayFeature> _decodeDisplayFeatures({
-    required List<double> bounds,
-    required List<int> type,
-    required List<int> state,
-    required double devicePixelRatio,
-  }) {
-    assert(bounds.length / 4 == type.length, 'Bounds are rectangles, requiring 4 measurements each');
-    assert(type.length == state.length);
-    final List<DisplayFeature> result = <DisplayFeature>[];
-    for(int i = 0; i < type.length; i++) {
-      final int rectOffset = i * 4;
-      result.add(DisplayFeature(
-        bounds: Rect.fromLTRB(
-          bounds[rectOffset] / devicePixelRatio,
-          bounds[rectOffset + 1] / devicePixelRatio,
-          bounds[rectOffset + 2] / devicePixelRatio,
-          bounds[rectOffset + 3] / devicePixelRatio,
-        ),
-        type: DisplayFeatureType.values[type[i]],
-        state: state[i] < DisplayFeatureState.values.length
-            ? DisplayFeatureState.values[state[i]]
-            : DisplayFeatureState.unknown,
-      ));
-    }
-    return result;
-  }
 
   /// A callback invoked when any view begins a frame.
   ///