[web] Add dynamic view sizing for non-implicit views.

lib/web_ui/lib/platform_dispatcher.dart

@@ -80,8 +80,6 @@ abstract class PlatformDispatcher {
 
   void scheduleFrame();
 
-  void render(Scene scene, [FlutterView view]);
-
   AccessibilityFeatures get accessibilityFeatures;
 
   VoidCallback? get onAccessibilityFeaturesChanged;

lib/web_ui/lib/src/engine/canvaskit/rasterizer.dart

@@ -30,8 +30,8 @@ class Rasterizer {
 
   /// Creates a new frame from this rasterizer's surface, draws the given
   /// [LayerTree] into it, and then submits the frame.
-  void draw(LayerTree layerTree) {
-    final ui.Size frameSize = view.physicalSize;
+  void draw(LayerTree layerTree, { ui.Size? size }) {
+    final ui.Size frameSize = size ?? view.physicalSize;
     if (frameSize.isEmpty) {
       // Available drawing area is empty. Skip drawing.
       return;

lib/web_ui/lib/src/engine/canvaskit/renderer.dart

@@ -402,7 +402,7 @@ class CanvasKitRenderer implements Renderer {
     CkParagraphBuilder(style);
 
   @override
-  void renderScene(ui.Scene scene, ui.FlutterView view) {
+  void renderScene(ui.Scene scene, ui.FlutterView view, { ui.Size? size }) {
     // "Build finish" and "raster start" happen back-to-back because we
     // render on the same thread, so there's no overhead from hopping to
     // another thread.
@@ -417,7 +417,7 @@ class CanvasKitRenderer implements Renderer {
         "Unable to render to a view which hasn't been registered");
     final Rasterizer rasterizer = _rasterizers[view.viewId]!;
 
-    rasterizer.draw((scene as LayerScene).layerTree);
+    rasterizer.draw((scene as LayerScene).layerTree, size: size);
     frameTimingsOnRasterFinish();
   }
 

lib/web_ui/lib/src/engine/html/renderer.dart

@@ -323,7 +323,7 @@ class HtmlRenderer implements Renderer {
     CanvasParagraphBuilder(style as EngineParagraphStyle);
 
   @override
-  void renderScene(ui.Scene scene, ui.FlutterView view) {
+  void renderScene(ui.Scene scene, ui.FlutterView view, { ui.Size? size }) {
     final EngineFlutterView implicitView = EnginePlatformDispatcher.instance.implicitView!;
     implicitView.dom.setScene((scene as SurfaceScene).webOnlyRootElement!);
     frameTimingsOnRasterFinish();

lib/web_ui/lib/src/engine/js_interop/js_app.dart

@@ -25,11 +25,31 @@ extension JsFlutterViewOptionsExtension on JsFlutterViewOptions {
     return _hostElement!;
   }
 
+  @JS('viewConstraints')
+  external JsViewConstraints? get _viewConstraints;
+  JsViewConstraints? get viewConstraints {
+    // Assert constraints are valid?
+    return _viewConstraints;
+  }
+
   @JS('initialData')
   external JSObject? get _initialData;
   Object? get initialData => _initialData?.toObjectDeep;
 }
 
+/// The JS bindings for a [ViewConstraints] object.
+@JS()
+@staticInterop
+class JsViewConstraints {}
+
+/// The attributes of a [JsViewConstraints] object.
+extension JsViewConstraintsExtension on JsViewConstraints {
+  external double? get maxHeight;
+  external double? get maxWidth;
+  external double? get minHeight;
+  external double? get minWidth;
+}
+
 /// The public JS API of a running Flutter Web App.
 @JS()
 @anonymous

lib/web_ui/lib/src/engine/platform_dispatcher.dart

@@ -727,8 +727,9 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
     scheduleFrameCallback!();
   }
 
-  /// Updates the application's rendering on the GPU with the newly provided
-  /// [Scene]. This function must be called within the scope of the
+  /// Updates the [view]'s rendering on the GPU with the newly provided [scene] of physical [size].
+  ///
+  /// This function must be called within the scope of the
   /// [onBeginFrame] or [onDrawFrame] callbacks being invoked. If this function
   /// is called a second time during a single [onBeginFrame]/[onDrawFrame]
   /// callback sequence or called outside the scope of those callbacks, the call
@@ -751,15 +752,18 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
   ///    scheduling of frames.
   ///  * [RendererBinding], the Flutter framework class which manages layout and
   ///    painting.
-  @override
-  void render(ui.Scene scene, [ui.FlutterView? view]) {
-    assert(view != null || implicitView != null,
-        'Calling render without a FlutterView');
-    if (view == null && implicitView == null) {
+  void render(ui.Scene scene, { ui.FlutterView? view, ui.Size? size }) {
+    final ui.FlutterView? target = view ?? implicitView;
+    assert(target != null, 'Calling render without a FlutterView');
+    if (target == null) {
       // If there is no view to render into, then this is a no-op.
       return;
     }
-    renderer.renderScene(scene, view ?? implicitView!);
+
+    if (size != null && view is EngineFlutterView) {
+      view.dom.resize(size / view.devicePixelRatio);
+    }
+    renderer.renderScene(scene, target, size: size);
   }
 
   /// Additional accessibility features that may be enabled by the platform.

lib/web_ui/lib/src/engine/renderer.dart

@@ -222,5 +222,5 @@ abstract class Renderer {
 
   ui.ParagraphBuilder createParagraphBuilder(ui.ParagraphStyle style);
 
-  FutureOr<void> renderScene(ui.Scene scene, ui.FlutterView view);
+  FutureOr<void> renderScene(ui.Scene scene, ui.FlutterView view, { ui.Size? size });
 }

lib/web_ui/lib/src/engine/skwasm/skwasm_impl/renderer.dart

@@ -401,7 +401,7 @@ class SkwasmRenderer implements Renderer {
   // TODO(harryterkelsen): Add multiview support,
   // https://github.com/flutter/flutter/issues/137073.
   @override
-  Future<void> renderScene(ui.Scene scene, ui.FlutterView view) =>
+  Future<void> renderScene(ui.Scene scene, ui.FlutterView view, { ui.Size? size }) =>
       sceneView.renderScene(scene as EngineScene);
 
   @override

lib/web_ui/lib/src/engine/skwasm/skwasm_stub/renderer.dart

@@ -150,7 +150,7 @@ class SkwasmRenderer implements Renderer {
   }
 
   @override
-  void renderScene(ui.Scene scene, ui.FlutterView view) {
+  void renderScene(ui.Scene scene, ui.FlutterView view, { ui.Size? size }) {
     throw UnimplementedError('Skwasm not implemented on this platform.');
   }
 

lib/web_ui/lib/src/engine/view_embedder/dimensions_provider/custom_element_dimensions_provider.dart

@@ -48,8 +48,13 @@ class CustomElementDimensionsProvider extends DimensionsProvider {
   final StreamController<ui.Size> _onResizeStreamController =
       StreamController<ui.Size>.broadcast();
 
+  // A cache of the last Size reported by the browser for hostElement, so this
+  // never has to hit the clientWidth/Height metrics from the DOM.
+  ui.Size? _lastObservedSize;
+
   // Broadcasts the last seen `Size`.
   void _broadcastSize(ui.Size size) {
+    _lastObservedSize = size;
     _onResizeStreamController.add(size);
   }
 
@@ -68,10 +73,10 @@ class CustomElementDimensionsProvider extends DimensionsProvider {
   ui.Size computePhysicalSize() {
     final double devicePixelRatio = getDevicePixelRatio();
 
-    return ui.Size(
-      _hostElement.clientWidth * devicePixelRatio,
-      _hostElement.clientHeight * devicePixelRatio,
-    );
+    final ui.Size size = _lastObservedSize ??
+        ui.Size(_hostElement.clientWidth, _hostElement.clientHeight);
+
+    return size * devicePixelRatio;
   }
 
   @override

lib/web_ui/lib/src/engine/view_embedder/dom_manager.dart

@@ -204,6 +204,13 @@ class DomManager {
       sceneHost.append(sceneElement);
     }
   }
+
+  /// Resizes the [rootElement] to [logicalSize] (in px) via CSS.
+  void resize(ui.Size logicalSize) {
+    rootElement.style
+      ..width = '${logicalSize.width}px'
+      ..height = '${logicalSize.height}px';
+  }
 }
 
 DomShadowRoot _attachShadowRoot(DomElement element) {

lib/web_ui/lib/src/engine/view_embedder/flutter_view_manager.dart

@@ -39,8 +39,11 @@ class FlutterViewManager {
   EngineFlutterView createAndRegisterView(
     JsFlutterViewOptions jsViewOptions,
   ) {
-    final EngineFlutterView view =
-        EngineFlutterView(_dispatcher, jsViewOptions.hostElement);
+    final EngineFlutterView view = EngineFlutterView(
+      _dispatcher,
+      jsViewOptions.hostElement,
+      viewConstraints: jsViewOptions.viewConstraints,
+    );
     registerView(view, jsViewOptions: jsViewOptions);
     return view;
   }

lib/web_ui/lib/src/engine/window.dart

@@ -13,6 +13,7 @@ import '../engine.dart' show DimensionsProvider, registerHotRestartListener, ren
 import 'browser_detection.dart';
 import 'display.dart';
 import 'dom.dart';
+import 'js_interop/js_app.dart' show JsViewConstraints, JsViewConstraintsExtension;
 import 'mouse/context_menu.dart';
 import 'mouse/cursor.dart';
 import 'navigation/history.dart';
@@ -48,17 +49,26 @@ base class EngineFlutterView implements ui.FlutterView {
   /// the Flutter view will be rendered.
   factory EngineFlutterView(
     EnginePlatformDispatcher platformDispatcher,
-    DomElement hostElement,
+    DomElement hostElement, {
+      JsViewConstraints? viewConstraints,
+    }
   ) = _EngineFlutterViewImpl;
 
   EngineFlutterView._(
-    this.viewId,
     this.platformDispatcher,
-    // This is nullable to accommodate the legacy `EngineFlutterWindow`. In
-    // multi-view mode, the host element is required for each view (as reflected
-    // by the public `EngineFlutterView` constructor).
-    DomElement? hostElement,
-  )   : embeddingStrategy = EmbeddingStrategy.create(hostElement: hostElement),
+    {
+      // This is configurable for the implicit view that sets it to a specific
+      // kImplicitViewId value. Otherwise, this could be auto-incremental and
+      // not configurable.
+      required this.viewId,
+      // This is nullable to accommodate the legacy `EngineFlutterWindow`. In
+      // multi-view mode, the host element is required for each view (as reflected
+      // by the public `EngineFlutterView` constructor).
+      DomElement? hostElement,
+      JsViewConstraints? viewConstraints,
+    }
+  )   : _jsViewConstraints = viewConstraints,
+        embeddingStrategy = EmbeddingStrategy.create(hostElement: hostElement),
         dimensionsProvider = DimensionsProvider.create(hostElement: hostElement) {
     // The embeddingStrategy will take care of cleaning up the rootElement on
     // hot restart.
@@ -107,10 +117,9 @@ base class EngineFlutterView implements ui.FlutterView {
   }
 
   @override
-  void render(ui.Scene scene, {ui.Size? size}) {
+  void render(ui.Scene scene, { ui.Size? size }) {
     assert(!isDisposed, 'Trying to render a disposed EngineFlutterView.');
-    // TODO(goderbauer): Respect the provided size when "physicalConstraints" are not always tight. See TODO on "physicalConstraints".
-    platformDispatcher.render(scene, this);
+    platformDispatcher.render(scene, view: this, size: size);
   }
 
   @override
@@ -135,9 +144,13 @@ base class EngineFlutterView implements ui.FlutterView {
 
   late final PointerBinding pointerBinding;
 
-  // TODO(goderbauer): Provide API to configure constraints. See also TODO in "render".
   @override
-  ViewConstraints get physicalConstraints => ViewConstraints.tight(physicalSize);
+  ViewConstraints get physicalConstraints {
+    _computePhysicalSize();
+    return ViewConstraints.fromJsOptions(_jsViewConstraints, physicalSize);
+  }
+  // The configured constraints used to compute the actual physicalConstraints.
+  final JsViewConstraints? _jsViewConstraints;
 
   late final EngineSemanticsOwner semantics = EngineSemanticsOwner(dom.semanticsHost);
 
@@ -267,17 +280,19 @@ base class EngineFlutterView implements ui.FlutterView {
 
 final class _EngineFlutterViewImpl extends EngineFlutterView {
   _EngineFlutterViewImpl(
-    EnginePlatformDispatcher platformDispatcher,
-    DomElement hostElement,
-  ) : super._(_nextViewId++, platformDispatcher, hostElement);
+    super.platformDispatcher,
+    DomElement hostElement, {
+      super.viewConstraints,
+    }
+  ) : super._(viewId: _nextViewId++, hostElement: hostElement);
 }
 
 /// The Web implementation of [ui.SingletonFlutterWindow].
 final class EngineFlutterWindow extends EngineFlutterView implements ui.SingletonFlutterWindow {
   EngineFlutterWindow._(
-    EnginePlatformDispatcher platformDispatcher,
+    super.platformDispatcher,
     DomElement? hostElement,
-  ) : super._(kImplicitViewId, platformDispatcher, hostElement) {
+  ) : super._(viewId: kImplicitViewId, hostElement: hostElement) {
     if (ui_web.isCustomUrlStrategySet) {
       _browserHistory = createHistoryForExistingState(ui_web.urlStrategy);
     }
@@ -643,7 +658,7 @@ final class EngineFlutterWindow extends EngineFlutterView implements ui.Singleto
 EngineFlutterWindow get window {
   assert(
     _window != null,
-    'Trying to access the implicit FlutterView, but it is not available.\n'
+    'Trying to access the implicit FlutterView, but it is not available.'
     'Note: the implicit FlutterView is not available in multi-view mode.',
   );
   return _window!;
@@ -692,12 +707,52 @@ class ViewConstraints implements ui.ViewConstraints {
     this.maxHeight = double.infinity,
   });
 
+  factory ViewConstraints.fromJsOptions(JsViewConstraints? constraints, ui.Size? size) {
+    if (size == null) {
+      return const ViewConstraints();
+    }
+    if (constraints == null) {
+      return ViewConstraints.tight(size);
+    }
+    return ViewConstraints(
+      minWidth: _computeMinValue(constraints.minWidth, size.width),
+      minHeight: _computeMinValue(constraints.minHeight, size.height),
+      maxWidth: _computeMaxValue(constraints.maxWidth, size.width),
+      maxHeight: _computeMaxValue(constraints.maxHeight, size.height),
+    );
+  }
+
   ViewConstraints.tight(ui.Size size)
     : minWidth = size.width,
       maxWidth = size.width,
       minHeight = size.height,
       maxHeight = size.height;
 
+  // Computes the "min" value for a constraint that takes into account user configuration
+  // and the actual available size.
+  //
+  // Returns the configured userValue, unless it's null (not passed) in which it returns
+  // the actual physicalSize.
+  static double _computeMinValue(double? userValue, double physicalSize) {
+    assert(userValue == null || userValue >= 0, 'Minimum constraint cannot be less than 0');
+    return userValue ?? physicalSize;
+  }
+
+  // Computes the "max" value for a constraint that takes into account user configuration
+  // and the available size.
+  //
+  // Returns the configured userValue unless:
+  //  * It is null, in which case it returns the physicalSize
+  //  * It is `-1`, in which case it returns "infinity" / unconstrained.
+  static double _computeMaxValue(double? userValue, double physicalSize) {
+    assert(userValue == null || userValue >= -1, 'Maximum constraint must be greater than 0 (or -1 for unconstrained)');
+    return switch (userValue) {
+      null => physicalSize,
+      -1 => double.infinity,
+      _ => userValue,
+    };
+  }
+
   @override
   final double minWidth;
   @override