[flutter] Fit and alignment support.

spine-flutter/example/lib/main.dart

@@ -50,17 +50,13 @@ class SimpleAnimation extends StatelessWidget {
     reportLeaks();
     final controller = SpineWidgetController((controller) {
       // Set the walk animation on track 0, let it loop
-      controller.animationState?.setAnimationByName(0, "walk", true);
-
-      print("Skeleton name: ${controller.skeletonData?.getName()}");
-      print("Skeleton version: ${controller.skeletonData?.getVersion()}");
-      print("Skeleton hash: ${controller.skeletonData?.getHash()}");
-      print("Bones: ${controller.skeletonData!.getBones()}");
+      // controller.animationState?.setAnimationByName(0, "walk", true);
     });
 
     return Scaffold(
       appBar: AppBar(title: const Text('Spineboy')),
-      body: SpineWidget.asset("assets/spineboy-pro.skel", "assets/spineboy.atlas", controller),
+      // body: SpineWidget.asset("assets/skeleton.json", "assets/skeleton.atlas", controller, alignment: Alignment.center, fit: BoxFit.none),
+      body: SpineWidget.asset("assets/spineboy-pro.skel", "assets/spineboy.atlas", controller)
       // body: SpineWidget.file("/Users/badlogic/workspaces/spine-runtimes/examples/spineboy/export/spineboy-pro.skel", "/Users/badlogic/workspaces/spine-runtimes/examples/spineboy/export/spineboy.atlas", controller),
       // body: const SpineWidget.http("https://marioslab.io/dump/spineboy/spineboy-pro.json", "https://marioslab.io/dump/spineboy/spineboy.atlas"),
     );
@@ -84,7 +80,8 @@ class AnimationStateEvents extends StatelessWidget {
       controller.animationState?.setAnimationByName(0, "walk", true)?.setListener((type, trackEntry, event) {
         print("Walk animation event ${type}");
       });
-      controller.animationState?.addAnimationByName(0, "run", true, 2)?.setListener((type, trackEntry, event) {
+      controller.animationState?.addAnimationByName(0, "jump", false, 2);
+      controller.animationState?.addAnimationByName(0, "run", true, 0)?.setListener((type, trackEntry, event) {
         print("Run animation event ${type}");
       });
       controller.animationState?.setListener((type, trackEntry, event) {

spine-flutter/lib/spine_widget.dart

@@ -1,5 +1,6 @@
 import 'dart:convert';
 import 'dart:io';
+import 'dart:math';
 
 import 'package:flutter/rendering.dart' as rendering;
 import 'package:flutter/scheduler.dart';
@@ -47,24 +48,26 @@ class SpineWidget extends StatefulWidget {
   final SkeletonData? skeletonData;
   final Atlas? atlas;
   final SpineWidgetController controller;
+  final BoxFit? fit;
+  final Alignment? alignment;
   final AssetType _assetType;
 
-  const SpineWidget.asset(this.skeletonFile, this.atlasFile, this.controller, {super.key})
+  const SpineWidget.asset(this.skeletonFile, this.atlasFile, this.controller, {this.fit, this.alignment, super.key})
       : _assetType = AssetType.Asset,
         atlas = null,
         skeletonData = null;
 
-  const SpineWidget.file(this.skeletonFile, this.atlasFile, this.controller, {super.key})
+  const SpineWidget.file(this.skeletonFile, this.atlasFile, this.controller, {this.fit, this.alignment, super.key})
       : _assetType = AssetType.File,
         atlas = null,
         skeletonData = null;
 
-  const SpineWidget.http(this.skeletonFile, this.atlasFile, this.controller, {super.key})
+  const SpineWidget.http(this.skeletonFile, this.atlasFile, this.controller, {this.fit, this.alignment, super.key})
       : _assetType = AssetType.Http,
         atlas = null,
         skeletonData = null;
 
-  const SpineWidget.raw(this.skeletonData, this.atlas, this.controller, {super.key})
+  const SpineWidget.raw(this.skeletonData, this.atlas, this.controller, {this.fit, this.alignment, super.key})
       : _assetType = AssetType.Raw,
         atlasFile = null,
         skeletonFile = null;
@@ -88,7 +91,7 @@ class _SpineWidgetState extends State<SpineWidget> {
 
   void loadRaw(SkeletonData skeletonData, Atlas atlas) {
     skeletonDrawable = SkeletonDrawable(atlas, skeletonData, false);
-    skeletonDrawable?.update(0.016);
+    skeletonDrawable?.update(0);
   }
 
   void loadFromAsset(String skeletonFile, String atlasFile, AssetType assetType) async {
@@ -114,6 +117,8 @@ class _SpineWidgetState extends State<SpineWidget> {
             ? SkeletonData.fromJson(atlas, utf8.decode((await http.get(Uri.parse(skeletonFile))).bodyBytes))
             : SkeletonData.fromBinary(atlas, (await http.get(Uri.parse(skeletonFile))).bodyBytes);
         break;
+      case AssetType.Raw:
+        throw Exception("Raw assets can not be loaded via loadFromAsset().");
     }
 
     skeletonDrawable = SkeletonDrawable(atlas, skeletonData, true);
@@ -126,10 +131,10 @@ class _SpineWidgetState extends State<SpineWidget> {
   Widget build(BuildContext context) {
     if (skeletonDrawable != null) {
       print("Skeleton loaded, rebuilding painter");
-      return _SpineRenderObjectWidget(skeletonDrawable!, widget.controller);
+      return _SpineRenderObjectWidget(skeletonDrawable!, widget.controller, widget.fit, widget.alignment);
     } else {
       print("Skeleton not loaded yet");
-      return SizedBox();
+      return const SizedBox();
     }
   }
 
@@ -143,12 +148,16 @@ class _SpineWidgetState extends State<SpineWidget> {
 class _SpineRenderObjectWidget extends LeafRenderObjectWidget {
   final SkeletonDrawable _skeletonDrawable;
   final SpineWidgetController _controller;
+  final BoxFit _fit;
+  final Alignment _alignment;
 
-  _SpineRenderObjectWidget(this._skeletonDrawable, this._controller);
+  _SpineRenderObjectWidget(this._skeletonDrawable, this._controller, BoxFit? fit, Alignment? alignment) :
+        _fit = fit ?? BoxFit.contain,
+        _alignment = alignment ?? Alignment.center;
 
   @override
   RenderObject createRenderObject(BuildContext context) {
-    return _SpineRenderObject(_skeletonDrawable, _controller);
+    return _SpineRenderObject(_skeletonDrawable, _controller, _fit, _alignment);
   }
 
   @override
@@ -162,13 +171,39 @@ class _SpineRenderObject extends RenderBox {
   SpineWidgetController _controller;
   double _deltaTime = 0;
   final Stopwatch _stopwatch = Stopwatch();
+  BoxFit _fit;
+  Alignment _alignment;
+  Bounds _bounds;
 
-  _SpineRenderObject(this._skeletonDrawable, this._controller);
+  _SpineRenderObject(this._skeletonDrawable, this._controller, this._fit, this._alignment): _bounds = _computeBounds(_skeletonDrawable);
+
+  static Bounds _computeBounds(SkeletonDrawable drawable) {
+    return drawable.skeleton.getBounds();
+  }
+
+  BoxFit get fit => _fit;
+
+  set fit(BoxFit fit) {
+    if (fit != _fit) {
+      _fit = fit;
+      markNeedsPaint();
+    }
+  }
+
+  Alignment get alignment => _alignment;
+
+  set alignment(Alignment alignment) {
+    if (alignment != _alignment) {
+      _alignment = alignment;
+      markNeedsPaint();
+    }
+  }
 
   set skeletonDrawable(SkeletonDrawable skeletonDrawable) {
     if (_skeletonDrawable == skeletonDrawable) return;
 
     _skeletonDrawable = skeletonDrawable;
+    _bounds = _computeBounds(_skeletonDrawable);
     markNeedsPaint();
   }
 
@@ -181,11 +216,42 @@ class _SpineRenderObject extends RenderBox {
   @override
   bool hitTestSelf(Offset position) => true;
 
+  @override
+  double computeMinIntrinsicWidth(double height) {
+    return _computeConstrainedSize(BoxConstraints.tightForFinite(height: height)).width;
+  }
+
+  @override
+  double computeMaxIntrinsicWidth(double height) {
+    return _computeConstrainedSize(BoxConstraints.tightForFinite(height: height)).width;
+  }
+
+  @override
+  double computeMinIntrinsicHeight(double width) {
+    return _computeConstrainedSize(BoxConstraints.tightForFinite(width: width)).height;
+  }
+
+  @override
+  double computeMaxIntrinsicHeight(double width) {
+    return _computeConstrainedSize(BoxConstraints.tightForFinite(width: width)).height;
+  }
+
+  // Called when not sizedByParent, uses the intrinsic width/height for sizing, while trying to retain aspect ratio.
+  @override
+  void performLayout() {
+    if (!sizedByParent) size = _computeConstrainedSize(constraints);
+  }
+
+  // Called when sizedByParent, we want to go as big as possible.
   @override
   void performResize() {
     size = constraints.biggest;
   }
 
+  Size _computeConstrainedSize(BoxConstraints constraints) {
+    return sizedByParent ? constraints.smallest : constraints.constrainSizeAndAttemptToPreserveAspectRatio(Size(_bounds.width, _bounds.height));
+  }
+
   @override
   void attach(rendering.PipelineOwner owner) {
     super.attach(owner);
@@ -206,6 +272,45 @@ class _SpineRenderObject extends RenderBox {
     markNeedsPaint();
   }
 
+  void _setCanvasTransform(Canvas canvas, Offset offset) {
+    final double x = -_bounds.x - _bounds.width / 2.0 - (_alignment.x * _bounds.width / 2.0);
+    final double y = -_bounds.y - _bounds.height / 2.0 + (_alignment.y * _bounds.height / 2.0);
+    double scaleX = 1.0, scaleY = 1.0;
+
+    switch (_fit) {
+      case BoxFit.fill:
+        scaleX = size.width / _bounds.width;
+        scaleY = size.height / _bounds.height;
+        break;
+      case BoxFit.contain:
+        scaleX = scaleY = min(size.width / _bounds.width, size.height / _bounds.height);
+        break;
+      case BoxFit.cover:
+        scaleX = scaleY = max(size.width / _bounds.width, size.height / _bounds.height);
+        break;
+      case BoxFit.fitHeight:
+        scaleX = scaleY = size.height / _bounds.height;
+        break;
+      case BoxFit.fitWidth:
+        scaleX = scaleY = size.width / _bounds.width;
+        break;
+      case BoxFit.none:
+        scaleX = scaleY = 1.0;
+        break;
+      case BoxFit.scaleDown:
+        final double scale = min(size.width / _bounds.width, size.height / _bounds.height);
+        scaleX = scaleY = scale < 1.0 ? scale : 1.0;
+        break;
+    }
+
+    canvas
+      ..translate(
+          offset.dx + size.width / 2.0 + (_alignment.x * size.width / 2.0),
+          offset.dy + size.height / 2.0 + (_alignment.y * size.height / 2.0))
+      ..scale(scaleX, scaleY)
+      ..translate(x, y);
+  }
+
   @override
   void paint(PaintingContext context, Offset offset) {
     final Canvas canvas = context.canvas
@@ -213,7 +318,7 @@ class _SpineRenderObject extends RenderBox {
       ..clipRect(offset & size);
 
     canvas.save();
-    canvas.translate(offset.dx + size.width / 2, offset.dy + size.height);
+    _setCanvasTransform(canvas, offset);
 
     final commands = _skeletonDrawable.render();
     for (final cmd in commands) {