Adds DefaultSvgTheme (#964)

packages/flutter_svg/CHANGELOG.md

@@ -1,5 +1,9 @@
 # CHANGES
 
+## 2.0.8
+
+- Adds back `DefaultSvgTheme`.
+
 ## 2.0.7
 
 - Fix broken `matchTextDirection`.

packages/flutter_svg/lib/src/default_theme.dart

@@ -0,0 +1,42 @@
+import 'package:flutter/widgets.dart';
+
+import 'loaders.dart';
+
+/// The SVG theme to apply to descendant [SvgPicture] widgets
+/// which don't have explicit theme values.
+class DefaultSvgTheme extends InheritedTheme {
+  /// Creates a default SVG theme for the given subtree
+  /// using the provided [theme].
+  const DefaultSvgTheme({
+    Key? key,
+    required Widget child,
+    required this.theme,
+  }) : super(key: key, child: child);
+
+  /// The SVG theme to apply.
+  final SvgTheme theme;
+
+  /// The closest instance of this class that encloses the given context.
+  ///
+  /// Typical usage is as follows:
+  ///
+  /// ```dart
+  /// DefaultSvgTheme theme = DefaultSvgTheme.of(context);
+  /// ```
+  static DefaultSvgTheme? of(BuildContext context) {
+    return context.dependOnInheritedWidgetOfExactType<DefaultSvgTheme>();
+  }
+
+  @override
+  bool updateShouldNotify(DefaultSvgTheme oldWidget) {
+    return theme != oldWidget.theme;
+  }
+
+  @override
+  Widget wrap(BuildContext context, Widget child) {
+    return DefaultSvgTheme(
+      theme: theme,
+      child: child,
+    );
+  }
+}

packages/flutter_svg/lib/src/loaders.dart

@@ -3,13 +3,14 @@ import 'dart:convert' show utf8;
 import 'package:flutter/foundation.dart' hide compute;
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
-import 'package:flutter_svg/src/utilities/http.dart';
 import 'package:vector_graphics/vector_graphics.dart';
 import 'package:vector_graphics_compiler/vector_graphics_compiler.dart' as vg;
 
 import '../svg.dart' show svg;
+import 'default_theme.dart';
 import 'utilities/compute.dart';
 import 'utilities/file.dart';
+import 'utilities/http.dart';
 
 /// A theme used when decoding an SVG picture.
 @immutable
@@ -111,12 +112,12 @@ class _DelegateVgColorMapper extends vg.ColorMapper {
 abstract class SvgLoader<T> extends BytesLoader {
   /// See class doc.
   const SvgLoader({
-    this.theme = const SvgTheme(),
+    this.theme,
     this.colorMapper,
   });
 
   /// The theme to determine currentColor and font sizing attributes.
-  final SvgTheme theme;
+  final SvgTheme? theme;
 
   /// The [ColorMapper] used to transform colors from the SVG, if any.
   final ColorMapper? colorMapper;
@@ -130,7 +131,24 @@ abstract class SvgLoader<T> extends BytesLoader {
   Future<T?> prepareMessage(BuildContext? context) =>
       SynchronousFuture<T?>(null);
 
+  /// Returns the svg theme.
+  @visibleForTesting
+  @protected
+  SvgTheme getTheme(BuildContext? context) {
+    if (theme != null) {
+      return theme!;
+    }
+    if (context != null) {
+      final SvgTheme? defaultTheme = DefaultSvgTheme.of(context)?.theme;
+      if (defaultTheme != null) {
+        return defaultTheme;
+      }
+    }
+    return const SvgTheme();
+  }
+
   Future<ByteData> _load(BuildContext? context) {
+    final SvgTheme theme = getTheme(context);
     return prepareMessage(context).then((T? message) {
       return compute((T? message) {
         return vg
@@ -160,6 +178,7 @@ abstract class SvgLoader<T> extends BytesLoader {
 
   @override
   SvgCacheKey cacheKey(BuildContext? context) {
+    final SvgTheme theme = getTheme(context);
     return SvgCacheKey(keyData: this, theme: theme, colorMapper: colorMapper);
   }
 }
@@ -172,13 +191,13 @@ abstract class SvgLoader<T> extends BytesLoader {
 class SvgCacheKey {
   /// See [SvgCacheKey].
   const SvgCacheKey({
-    required this.theme,
     required this.keyData,
     required this.colorMapper,
+    this.theme,
   });
 
   /// The theme for this cached SVG.
-  final SvgTheme theme;
+  final SvgTheme? theme;
 
   /// The other key data for the SVG.
   ///
@@ -365,6 +384,7 @@ class SvgAssetLoader extends SvgLoader<ByteData> {
 
   @override
   SvgCacheKey cacheKey(BuildContext? context) {
+    final SvgTheme theme = getTheme(context);
     return SvgCacheKey(
       theme: theme,
       colorMapper: colorMapper,

packages/flutter_svg/lib/svg.dart

@@ -12,6 +12,7 @@ export 'package:vector_graphics/vector_graphics.dart'
     show BytesLoader, vg, VectorGraphicUtilities, PictureInfo;
 
 export 'src/cache.dart';
+export 'src/default_theme.dart';
 export 'src/loaders.dart';
 
 /// Instance for [Svg]'s utility methods, which can produce a [DrawableRoot]
@@ -84,7 +85,6 @@ class SvgPicture extends StatelessWidget {
     this.semanticsLabel,
     this.excludeFromSemantics = false,
     this.clipBehavior = Clip.hardEdge,
-    this.theme = const SvgTheme(),
     @deprecated bool cacheColorFilter = false,
   }) : super(key: key);
 
@@ -179,7 +179,7 @@ class SvgPicture extends StatelessWidget {
     this.semanticsLabel,
     this.excludeFromSemantics = false,
     this.clipBehavior = Clip.hardEdge,
-    this.theme = const SvgTheme(),
+    SvgTheme? theme,
     ui.ColorFilter? colorFilter,
     @deprecated ui.Color? color,
     @deprecated ui.BlendMode colorBlendMode = ui.BlendMode.srcIn,
@@ -243,7 +243,7 @@ class SvgPicture extends StatelessWidget {
     this.excludeFromSemantics = false,
     this.clipBehavior = Clip.hardEdge,
     @deprecated bool cacheColorFilter = false,
-    this.theme = const SvgTheme(),
+    SvgTheme? theme,
   })  : bytesLoader = SvgNetworkLoader(url, headers: headers, theme: theme),
         colorFilter = colorFilter ?? _getColorFilter(color, colorBlendMode),
         super(key: key);
@@ -294,7 +294,7 @@ class SvgPicture extends StatelessWidget {
     this.semanticsLabel,
     this.excludeFromSemantics = false,
     this.clipBehavior = Clip.hardEdge,
-    this.theme = const SvgTheme(),
+    SvgTheme? theme,
     @deprecated bool cacheColorFilter = false,
   })  : bytesLoader = SvgFileLoader(file, theme: theme),
         colorFilter = colorFilter ?? _getColorFilter(color, colorBlendMode),
@@ -343,7 +343,7 @@ class SvgPicture extends StatelessWidget {
     this.semanticsLabel,
     this.excludeFromSemantics = false,
     this.clipBehavior = Clip.hardEdge,
-    this.theme = const SvgTheme(),
+    SvgTheme? theme,
     @deprecated bool cacheColorFilter = false,
   })  : bytesLoader = SvgBytesLoader(bytes, theme: theme),
         colorFilter = colorFilter ?? _getColorFilter(color, colorBlendMode),
@@ -392,7 +392,7 @@ class SvgPicture extends StatelessWidget {
     this.semanticsLabel,
     this.excludeFromSemantics = false,
     this.clipBehavior = Clip.hardEdge,
-    this.theme = const SvgTheme(),
+    SvgTheme? theme,
     @deprecated bool cacheColorFilter = false,
   })  : bytesLoader = SvgStringLoader(string, theme: theme),
         colorFilter = colorFilter ?? _getColorFilter(color, colorBlendMode),
@@ -479,9 +479,6 @@ class SvgPicture extends StatelessWidget {
   /// The color filter, if any, to apply to this widget.
   final ColorFilter? colorFilter;
 
-  /// The theme used when parsing SVG elements.
-  final SvgTheme theme;
-
   @override
   Widget build(BuildContext context) {
     return createCompatVectorGraphic(