- add FadeInImage.placeholderFit (#90739)

packages/flutter/lib/src/widgets/fade_in_image.dart

@@ -67,6 +67,9 @@ class FadeInImage extends StatefulWidget {
   /// The [placeholder] and [image] may be composed in a [ResizeImage] to provide
   /// a custom decode/cache size.
   ///
+  /// The [placeholder] and [image] may be have their own BoxFit settings via [fit]
+  /// and [placeholderFit].
+  ///
   /// The [placeholder], [image], [fadeOutDuration], [fadeOutCurve],
   /// [fadeInDuration], [fadeInCurve], [alignment], [repeat], and
   /// [matchTextDirection] arguments must not be null.
@@ -87,6 +90,7 @@ class FadeInImage extends StatefulWidget {
     this.width,
     this.height,
     this.fit,
+    this.placeholderFit,
     this.alignment = Alignment.center,
     this.repeat = ImageRepeat.noRepeat,
     this.matchTextDirection = false,
@@ -146,6 +150,7 @@ class FadeInImage extends StatefulWidget {
     this.width,
     this.height,
     this.fit,
+    this.placeholderFit,
     this.alignment = Alignment.center,
     this.repeat = ImageRepeat.noRepeat,
     this.matchTextDirection = false,
@@ -217,6 +222,7 @@ class FadeInImage extends StatefulWidget {
     this.width,
     this.height,
     this.fit,
+    this.placeholderFit,
     this.alignment = Alignment.center,
     this.repeat = ImageRepeat.noRepeat,
     this.matchTextDirection = false,
@@ -295,6 +301,11 @@ class FadeInImage extends StatefulWidget {
   /// [paintImage].
   final BoxFit? fit;
 
+  /// How to inscribe the placeholder image into the space allocated during layout.
+  ///
+  /// If not value set, it will fallback to [fit].
+  final BoxFit? placeholderFit;
+
   /// How to align the image within its bounds.
   ///
   /// The alignment aligns the given position in the image to the given position
@@ -376,6 +387,7 @@ class _FadeInImageState extends State<FadeInImage> {
     required ImageProvider image,
     ImageErrorWidgetBuilder? errorBuilder,
     ImageFrameBuilder? frameBuilder,
+    BoxFit? fit,
     required Animation<double> opacity,
   }) {
     assert(image != null);
@@ -386,7 +398,7 @@ class _FadeInImageState extends State<FadeInImage> {
       opacity: opacity,
       width: widget.width,
       height: widget.height,
-      fit: widget.fit,
+      fit: fit,
       alignment: widget.alignment,
       repeat: widget.repeat,
       matchTextDirection: widget.matchTextDirection,
@@ -401,6 +413,7 @@ class _FadeInImageState extends State<FadeInImage> {
       image: widget.image,
       errorBuilder: widget.imageErrorBuilder,
       opacity: _imageAnimation,
+      fit: widget.fit,
       frameBuilder: (BuildContext context, Widget child, int? frame, bool wasSynchronouslyLoaded) {
         if (wasSynchronouslyLoaded) {
           _resetAnimations();
@@ -413,6 +426,7 @@ class _FadeInImageState extends State<FadeInImage> {
             image: widget.placeholder,
             errorBuilder: widget.placeholderErrorBuilder,
             opacity: _placeholderAnimation,
+            fit: widget.placeholderFit ?? widget.fit,
           ),
           placeholderProxyAnimation: _placeholderAnimation,
           isTargetLoaded: frame != null,

packages/flutter/test/widgets/fade_in_image_test.dart

@@ -49,6 +49,7 @@ class FadeInImageElements {
 
   RawImage get rawImage => rawImageElement.widget as RawImage;
   double get opacity => rawImage.opacity?.value ?? 1.0;
+  BoxFit? get fit => rawImage.fit;
 }
 
 class LoadTestImageProvider extends ImageProvider<Object> {
@@ -435,5 +436,36 @@ Future<void> main() async {
         });
       });
     });
+
+    group("placeholder's BoxFit", () {
+      testWidgets("should be the image's BoxFit when not set", (WidgetTester tester) async {
+        final TestImageProvider placeholderProvider = TestImageProvider(placeholderImage);
+        final TestImageProvider imageProvider = TestImageProvider(targetImage);
+
+        await tester.pumpWidget(FadeInImage(
+          placeholder: placeholderProvider,
+          image: imageProvider,
+          fit: BoxFit.cover,
+        ));
+
+        expect(findFadeInImage(tester).placeholder!.fit, equals(findFadeInImage(tester).target.fit));
+        expect(findFadeInImage(tester).placeholder!.fit, equals(BoxFit.cover));
+      });
+
+      testWidgets('should be the given value when set', (WidgetTester tester) async {
+        final TestImageProvider placeholderProvider = TestImageProvider(placeholderImage);
+        final TestImageProvider imageProvider = TestImageProvider(targetImage);
+
+        await tester.pumpWidget(FadeInImage(
+          placeholder: placeholderProvider,
+          image: imageProvider,
+          fit: BoxFit.cover,
+          placeholderFit: BoxFit.fill,
+        ));
+
+        expect(findFadeInImage(tester).target.fit, equals(BoxFit.cover));
+        expect(findFadeInImage(tester).placeholder!.fit, equals(BoxFit.fill));
+      });
+    });
   });
 }