Pass the missing strut half leading flag over to skia paragraph builder (#50385)

Not sure how this can be tested. Part of flutter/flutter#142969

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: LongCatIsLooong

third_party/txt/BUILD.gn

@@ -147,6 +147,7 @@ if (enable_unittests) {
 
     sources = [
       "tests/font_collection_tests.cc",
+      "tests/paragraph_builder_skia_tests.cc",
       "tests/paragraph_unittests.cc",
       "tests/txt_run_all_unittests.cc",
     ]

third_party/txt/src/skia/paragraph_builder_skia.cc

@@ -119,6 +119,7 @@ skt::ParagraphStyle ParagraphBuilderSkia::TxtToSkia(const ParagraphStyle& txt) {
   strut_style.setFontSize(SkDoubleToScalar(txt.strut_font_size));
   strut_style.setHeight(SkDoubleToScalar(txt.strut_height));
   strut_style.setHeightOverride(txt.strut_has_height_override);
+  strut_style.setHalfLeading(txt.strut_half_leading);
 
   std::vector<SkString> strut_fonts;
   std::transform(txt.strut_font_families.begin(), txt.strut_font_families.end(),

third_party/txt/src/skia/paragraph_builder_skia.h

@@ -45,6 +45,8 @@ class ParagraphBuilderSkia : public ParagraphBuilder {
   virtual std::unique_ptr<Paragraph> Build() override;
 
  private:
+  friend class SkiaParagraphBuilderTests_ParagraphStrutStyle_Test;
+
   skia::textlayout::ParagraphPainter::PaintID CreatePaintID(
       const flutter::DlPaint& dl_paint);
   skia::textlayout::ParagraphStyle TxtToSkia(const ParagraphStyle& txt);

third_party/txt/tests/paragraph_builder_skia_tests.cc

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2017 Google, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "gtest/gtest.h"
+
+#include <sstream>
+
+#include "skia/paragraph_builder_skia.h"
+#include "txt/paragraph_style.h"
+
+namespace txt {
+
+class SkiaParagraphBuilderTests : public ::testing::Test {
+ public:
+  SkiaParagraphBuilderTests() {}
+
+  void SetUp() override {}
+};
+
+TEST_F(SkiaParagraphBuilderTests, ParagraphStrutStyle) {
+  ParagraphStyle style = ParagraphStyle();
+  auto collection = std::make_shared<FontCollection>();
+  auto builder = ParagraphBuilderSkia(style, collection, false);
+
+  auto strut_style = builder.TxtToSkia(style).getStrutStyle();
+  ASSERT_FALSE(strut_style.getHalfLeading());
+
+  style.strut_half_leading = true;
+  strut_style = builder.TxtToSkia(style).getStrutStyle();
+  ASSERT_TRUE(strut_style.getHalfLeading());
+}
+}  // namespace txt