From 047ea1efd4e799af617e5f5e5ed1825cde3585ab Mon Sep 17 00:00:00 2001
From: Jackson Gardner <jacksongardner@google.com>
Date: Fri, 22 Mar 2024 14:56:53 -0700
Subject: [PATCH] [skwasm] Use test fonts while in
 debugEmulateFlutterTesterEnvironment mode (flutter/engine#51630)

This brings the behavior in line with the other renderers. The framework sets this bit to make sure we render only using the Ahem font.
---
 .../engine/skwasm/skwasm_impl/paragraph.dart  | 12 ++++++++++--
 .../lib/web_ui/test/ui/line_metrics_test.dart | 19 +++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/engine/src/flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/paragraph.dart b/engine/src/flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/paragraph.dart
index 97c5b173b1b..7b036779059 100644
--- a/engine/src/flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/paragraph.dart
+++ b/engine/src/flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/paragraph.dart
@@ -9,10 +9,18 @@ import 'dart:js_interop';
 import 'package:ui/src/engine.dart';
 import 'package:ui/src/engine/skwasm/skwasm_impl.dart';
 import 'package:ui/ui.dart' as ui;
+import 'package:ui/ui_web/src/ui_web.dart' as ui_web;
 
 const int _kSoftLineBreak = 0;
 const int _kHardLineBreak = 100;
 
+final List<String> _testFonts = <String>['FlutterTest', 'Ahem'];
+String _computeEffectiveFontFamily(String fontFamily) {
+  return ui_web.debugEmulateFlutterTesterEnvironment && !_testFonts.contains(fontFamily)
+    ? _testFonts.first
+    : fontFamily;
+}
+
 class SkwasmLineMetrics extends SkwasmObjectWrapper<RawLineMetrics> implements ui.LineMetrics {
   factory SkwasmLineMetrics({
     required bool hardBreak,
@@ -430,8 +438,8 @@ class SkwasmTextStyle implements ui.TextStyle {
   }
 
   List<String> get fontFamilies => <String>[
-    if (fontFamily != null) fontFamily!,
-    if (fontFamilyFallback != null) ...fontFamilyFallback!,
+    if (fontFamily != null) _computeEffectiveFontFamily(fontFamily!),
+    if (fontFamilyFallback != null) ...fontFamilyFallback!.map(_computeEffectiveFontFamily),
   ];
 
   final ui.Color? color;
diff --git a/engine/src/flutter/lib/web_ui/test/ui/line_metrics_test.dart b/engine/src/flutter/lib/web_ui/test/ui/line_metrics_test.dart
index 9feb049a481..b356c4c8d48 100644
--- a/engine/src/flutter/lib/web_ui/test/ui/line_metrics_test.dart
+++ b/engine/src/flutter/lib/web_ui/test/ui/line_metrics_test.dart
@@ -116,4 +116,23 @@ Future<void> testMain() async {
         expect(metrics, hasLength(1));
     }
   }, skip: isHtml); // The rounding hack doesn't apply to the html renderer
+
+  test('uses flutter test fonts when debugEmulateFlutterTesterEnvironment is enabled', () {
+    final ui.ParagraphBuilder builder = ui.ParagraphBuilder(ui.ParagraphStyle());
+    builder.pushStyle(ui.TextStyle(
+      fontSize: 10.0,
+      fontFamily: 'SomeOtherFontFamily',
+    ));
+    builder.addText('XXXX');
+    final ui.Paragraph paragraph = builder.build();
+    paragraph.layout(const ui.ParagraphConstraints(width: 400));
+
+    expect(paragraph.numberOfLines, 1);
+
+    final ui.LineMetrics? metrics = paragraph.getLineMetricsAt(0);
+    expect(metrics, isNotNull);
+
+    // FlutterTest font's 'X' character is a square, so it's the font size (10.0) * 4 characters.
+    expect(metrics!.width, 40.0);
+  });
 }