Add support for custom fonts in SVGs.

This adds the interface `SvgCustomFonts` and a corresponding parameter
to the SvgImage widget. This provides a mechanism to support SVGs that
have known fonts referenced in them.

Closes #1731.

 # Changelog
 
+## 3.11.2
+
+- Add support for custom fonts in SVGs. [Tyler Denniston]
+
 ## 3.11.1
 
 - Fixed display problems with textfields [ilaurillard]

@@ -16,6 +16,7 @@
 
 import '../../pdf.dart';
 import '../widgets/font.dart';
+import '../widgets/svg.dart';
 import 'brush.dart';
 import 'color.dart';
 import 'group.dart';
@@ -26,8 +27,9 @@ class SvgPainter {
     this.parser,
     this._canvas,
     this.document,
-    this.boundingBox,
-  );
+    this.boundingBox, {
+    this.customFontLookup,
+  });
 
   final SvgParser parser;
 
@@ -37,6 +39,8 @@ class SvgPainter {
 
   final PdfRect boundingBox;
 
+  final SvgCustomFontLookup? customFontLookup;
+
   void paint() {
     final brush = parser.colorFilter == null
         ? SvgBrush.defaultContext
@@ -59,6 +63,12 @@ class SvgPainter {
   }
 
   Font getFont(String fontFamily, String fontStyle, String fontWeight) {
+    final customFont =
+        customFontLookup?.call(fontFamily, fontStyle, fontWeight);
+    if (customFont != null) {
+      return customFont;
+    }
+
     switch (fontFamily) {
       case 'serif':
         switch (fontStyle) {

@@ -32,6 +32,7 @@ class SvgImage extends Widget {
     double? width,
     double? height,
     PdfColor? colorFilter,
+    SvgCustomFontLookup? customFontLookup,
   }) {
     final xml = XmlDocument.parse(svg);
     final parser = SvgParser(
@@ -46,6 +47,7 @@ class SvgImage extends Widget {
       clip,
       width,
       height,
+      customFontLookup,
     );
   }
 
@@ -56,6 +58,7 @@ class SvgImage extends Widget {
     this.clip,
     this.width,
     this.height,
+    this.customFontLookup,
   );
 
   final SvgParser _svgParser;
@@ -70,6 +73,8 @@ class SvgImage extends Widget {
 
   final double? height;
 
+  final SvgCustomFontLookup? customFontLookup;
+
   late FittedSizes sizes;
 
   @override
@@ -126,6 +131,7 @@ class SvgImage extends Widget {
         context.page.pageFormat.width,
         context.page.pageFormat.height,
       ),
+      customFontLookup: customFontLookup,
     );
     painter.paint();
     context.canvas.restoreContext();
@@ -154,3 +160,6 @@ class DecorationSvgImage extends DecorationGraphic {
     );
   }
 }
+
+typedef SvgCustomFontLookup = Font? Function(
+    String fontFamily, String fontStyle, String fontWeight);

@@ -12,7 +12,7 @@ topics:
   - print
   - printing
   - report
-version: 3.11.1
+version: 3.11.2
 
 environment:
   sdk: ">=2.19.0 <4.0.0"

@@ -20,6 +20,8 @@ import 'package:pdf/pdf.dart';
 import 'package:pdf/widgets.dart';
 import 'package:test/test.dart';
 
+import 'utils.dart';
+
 late Document pdf;
 
 void main() {
@@ -195,6 +197,31 @@ void main() {
     );
   });
 
+  test('SVG Widgets Text custom fonts', () {
+    const customFamilyName1 = 'Test-Font-Family1';
+    const customFamilyName2 = 'Test-Font-Family2';
+    final customFont1 = loadFont('open-sans-bold.ttf');
+    final customFont2 = loadFont('genyomintw.ttf');
+    pdf.addPage(
+      Page(
+        build: (context) => SvgImage(
+            svg:
+                '<?xml version="1.0" standalone="no"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg viewBox="0 0 1000 300" xmlns="http://www.w3.org/2000/svg" version="1.1"><text x="367.055" y="168.954" font-size="55" fill="darkgreen" font-family="$customFamilyName1" >Custom <tspan font-family="$customFamilyName2">fonts</tspan></text><rect x="1" y="1" width="998" height="298" fill="none" stroke="purple" stroke-width="2" /></svg>',
+            customFontLookup:
+                (String fontFamily, String fontStyle, String fontWeight) {
+              switch (fontFamily) {
+                case customFamilyName1:
+                  return customFont1;
+                case customFamilyName2:
+                  return customFont2;
+                default:
+                  return null;
+              }
+            }),
+      ),
+    );
+  });
+
   tearDownAll(() async {
     final file = File('widgets-svg.pdf');
     await file.writeAsBytes(await pdf.save());