Partial implementation of TextLayoutManager::measureLines

change/react-native-windows-6ffd41f8-bf53-4629-9917-3c2349d77112.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Partial implementation of TextLayoutManager::measureLines",
+  "packageName": "react-native-windows",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

vnext/Microsoft.ReactNative/Fabric/platform/react/renderer/textlayoutmanager/TextLayoutManager.cpp

@@ -17,14 +17,11 @@
 namespace facebook::react {
 
 void TextLayoutManager::GetTextLayout(
-    AttributedStringBox attributedStringBox,
-    ParagraphAttributes paragraphAttributes,
-    LayoutConstraints layoutConstraints,
+    const AttributedString &attributedString,
+    const ParagraphAttributes &paragraphAttributes,
+    Size size,
     winrt::com_ptr<IDWriteTextLayout> &spTextLayout) noexcept {
-  if (attributedStringBox.getValue().isEmpty())
-    return;
-
-  auto fragments = attributedStringBox.getValue().getFragments();
+  auto fragments = attributedString.getFragments();
   auto outerFragment = fragments[0];
 
   DWRITE_FONT_STYLE style = DWRITE_FONT_STYLE_NORMAL;
@@ -86,14 +83,14 @@ void TextLayoutManager::GetTextLayout(
   }
   winrt::check_hresult(spTextFormat->SetTextAlignment(alignment));
 
-  auto str = GetTransformedText(attributedStringBox);
+  auto str = GetTransformedText(attributedString);
 
   winrt::check_hresult(Microsoft::ReactNative::DWriteFactory()->CreateTextLayout(
       str.c_str(), // The string to be laid out and formatted.
       static_cast<UINT32>(str.size()), // The length of the string.
       spTextFormat.get(), // The text format to apply to the string (contains font information, etc).
-      layoutConstraints.maximumSize.width, // The width of the layout box.
-      layoutConstraints.maximumSize.height, // The height of the layout box.
+      size.width, // The width of the layout box.
+      size.height, // The height of the layout box.
       spTextLayout.put() // The IDWriteTextLayout interface pointer.
       ));
 
@@ -129,9 +126,20 @@ void TextLayoutManager::GetTextLayout(
   }
 }
 
+void TextLayoutManager::GetTextLayout(
+    const AttributedStringBox &attributedStringBox,
+    const ParagraphAttributes &paragraphAttributes,
+    LayoutConstraints layoutConstraints,
+    winrt::com_ptr<IDWriteTextLayout> &spTextLayout) noexcept {
+  if (attributedStringBox.getValue().isEmpty())
+    return;
+
+  GetTextLayout(attributedStringBox.getValue(), paragraphAttributes, layoutConstraints.maximumSize, spTextLayout);
+}
+
 TextMeasurement TextLayoutManager::measure(
-    AttributedStringBox attributedStringBox,
-    ParagraphAttributes paragraphAttributes,
+    const AttributedStringBox &attributedStringBox,
+    const ParagraphAttributes &paragraphAttributes,
     const TextLayoutContext &layoutContext,
     LayoutConstraints layoutConstraints,
     std::shared_ptr<void> /* hostTextStorage */) const {
@@ -185,31 +193,12 @@ TextMeasurement TextLayoutManager::measure(
  */
 TextMeasurement TextLayoutManager::measureCachedSpannableById(
     int64_t cacheId,
-    ParagraphAttributes const &paragraphAttributes,
+    const ParagraphAttributes &paragraphAttributes,
     LayoutConstraints layoutConstraints) const {
   assert(false);
   return {};
 }
 
-LinesMeasurements TextLayoutManager::measureLines(
-    AttributedString attributedString,
-    ParagraphAttributes paragraphAttributes,
-    Size size) const {
-  assert(false);
-  return {};
-}
-
-std::shared_ptr<void> TextLayoutManager::getHostTextStorage(
-    AttributedString attributedString,
-    ParagraphAttributes paragraphAttributes,
-    LayoutConstraints layoutConstraints) const {
-  return nullptr;
-}
-
-void *TextLayoutManager::getNativeTextLayoutManager() const {
-  return (void *)this;
-}
-
 Microsoft::ReactNative::TextTransform ConvertTextTransform(std::optional<TextTransform> const &transform) {
   if (transform) {
     switch (transform.value()) {
@@ -229,9 +218,92 @@ Microsoft::ReactNative::TextTransform ConvertTextTransform(std::optional<TextTra
   return Microsoft::ReactNative::TextTransform::Undefined;
 }
 
-winrt::hstring TextLayoutManager::GetTransformedText(AttributedStringBox const &attributedStringBox) {
+LinesMeasurements TextLayoutManager::measureLines(
+    const AttributedString &attributedString,
+    const ParagraphAttributes &paragraphAttributes,
+    Size size) const {
+  LinesMeasurements lineMeasurements{};
+
+  winrt::com_ptr<IDWriteTextLayout> spTextLayout;
+
+  GetTextLayout(attributedString, paragraphAttributes, size, spTextLayout);
+
+  if (spTextLayout) {
+    std::vector<DWRITE_LINE_METRICS> lineMetrics;
+    uint32_t actualLineCount;
+    spTextLayout->GetLineMetrics(nullptr, 0, &actualLineCount);
+    lineMetrics.resize(static_cast<size_t>(actualLineCount));
+    winrt::check_hresult(spTextLayout->GetLineMetrics(lineMetrics.data(), actualLineCount, &actualLineCount));
+    uint32_t startRange = 0;
+    const auto count = (paragraphAttributes.maximumNumberOfLines > 0)
+        ? std::min(static_cast<uint32_t>(paragraphAttributes.maximumNumberOfLines), actualLineCount)
+        : actualLineCount;
+    for (uint32_t i = 0; i < count; ++i) {
+      UINT32 actualHitTestCount = 0;
+      spTextLayout->HitTestTextRange(
+          startRange,
+          lineMetrics[i].length,
+          0, // x
+          0, // y
+          NULL,
+          0, // metrics count
+          &actualHitTestCount);
+
+      // Allocate enough room to return all hit-test metrics.
+      std::vector<DWRITE_HIT_TEST_METRICS> hitTestMetrics(actualHitTestCount);
+      spTextLayout->HitTestTextRange(
+          startRange,
+          lineMetrics[i].length,
+          0, // x
+          0, // y
+          &hitTestMetrics[0],
+          static_cast<UINT32>(hitTestMetrics.size()),
+          &actualHitTestCount);
+
+      float width = 0;
+      for (auto tm : hitTestMetrics) {
+        width += tm.width;
+      }
+
+      std::string str;
+      for (const auto &fragment : attributedString.getFragments()) {
+        str = str +
+            winrt::to_string(Microsoft::ReactNative::TransformableText::TransformText(
+                winrt::hstring{Microsoft::Common::Unicode::Utf8ToUtf16(fragment.string)},
+                ConvertTextTransform(fragment.textAttributes.textTransform)));
+      }
+
+      lineMeasurements.emplace_back(LineMeasurement(
+          str.substr(startRange, lineMetrics[i].length),
+          {{hitTestMetrics[0].left, hitTestMetrics[0].top}, // origin
+           {width, lineMetrics[i].height}},
+          0.0f, // TODO descender
+          0.0f, // TODO: capHeight
+          0.0f, // TODO ascender
+          0.0f // TODO: xHeight
+          ));
+
+      startRange += lineMetrics[i].length;
+    }
+  }
+
+  return lineMeasurements;
+}
+
+std::shared_ptr<void> TextLayoutManager::getHostTextStorage(
+    const AttributedString &attributedString,
+    const ParagraphAttributes &paragraphAttributes,
+    LayoutConstraints layoutConstraints) const {
+  return nullptr;
+}
+
+void *TextLayoutManager::getNativeTextLayoutManager() const {
+  return (void *)this;
+}
+
+winrt::hstring TextLayoutManager::GetTransformedText(const AttributedString &attributedString) {
   winrt::hstring result{};
-  for (const auto &fragment : attributedStringBox.getValue().getFragments()) {
+  for (const auto &fragment : attributedString.getFragments()) {
     result = result +
         Microsoft::ReactNative::TransformableText::TransformText(
                  winrt::hstring{Microsoft::Common::Unicode::Utf8ToUtf16(fragment.string)},

vnext/Microsoft.ReactNative/Fabric/platform/react/renderer/textlayoutmanager/TextLayoutManager.h

@@ -35,8 +35,8 @@ class TextLayoutManager {
    * Measures `attributedStringBox` using native text rendering infrastructure.
    */
   TextMeasurement measure(
-      AttributedStringBox attributedStringBox,
-      ParagraphAttributes paragraphAttributes,
+      const AttributedStringBox &attributedStringBox,
+      const ParagraphAttributes &paragraphAttributes,
       const TextLayoutContext &layoutContext,
       LayoutConstraints layoutConstraints,
       std::shared_ptr<void> /* hostTextStorage */) const;
@@ -45,12 +45,14 @@ class TextLayoutManager {
    * Measures lines of `attributedString` using native text rendering
    * infrastructure.
    */
-  LinesMeasurements measureLines(AttributedString attributedString, ParagraphAttributes paragraphAttributes, Size size)
-      const;
+  LinesMeasurements measureLines(
+      const AttributedString &attributedString,
+      const ParagraphAttributes &paragraphAttributes,
+      Size size) const;
 
   std::shared_ptr<void> getHostTextStorage(
-      AttributedString attributedString,
-      ParagraphAttributes paragraphAttributes,
+      const AttributedString &attributedString,
+      const ParagraphAttributes &paragraphAttributes,
       LayoutConstraints layoutConstraints) const;
 
   /**
@@ -59,7 +61,7 @@ class TextLayoutManager {
    */
   TextMeasurement measureCachedSpannableById(
       int64_t cacheId,
-      ParagraphAttributes const &paragraphAttributes,
+      const ParagraphAttributes &paragraphAttributes,
       LayoutConstraints layoutConstraints) const;
 
   /*
@@ -69,15 +71,20 @@ class TextLayoutManager {
   void *getNativeTextLayoutManager() const;
 
   static void GetTextLayout(
-      AttributedStringBox attributedStringBox,
-      ParagraphAttributes paragraphAttributes,
+      const AttributedStringBox &attributedStringBox,
+      const ParagraphAttributes &paragraphAttributes,
       LayoutConstraints layoutConstraints,
       winrt::com_ptr<IDWriteTextLayout> &spTextLayout) noexcept;
 
 #pragma endregion
 
  private:
-  static winrt::hstring GetTransformedText(AttributedStringBox const &attributedStringBox);
+  static winrt::hstring GetTransformedText(const AttributedString &attributedString);
+  static void GetTextLayout(
+      const AttributedString &attributedString,
+      const ParagraphAttributes &paragraphAttributes,
+      Size size,
+      winrt::com_ptr<IDWriteTextLayout> &spTextLayout) noexcept;
 
   ContextContainer::Shared m_contextContainer;
 #pragma warning(push)