Tagged PDFs: Consolidate code for retrieving text & image info into PDFiumPage class

Follow up to https://crrev.com/c/5980169

AX-Relnotes: n/a.
Bug: 40707542
Change-Id: Ia0dc2d3223a8d8b6fff3a3c36d472d8554868caa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6053970
Reviewed-by: Lei Zhang <thestig@chromium.org>
Auto-Submit: Nektarios Paisios <nektar@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1425200}

pdf/accessibility.cc

@@ -39,7 +39,6 @@ void GetAccessibilityInfo(PDFiumEngine* engine,
   CHECK(page);
 
   const int raw_char_count = page->GetCharCount();
-
   // Treat a char count of -1 (error) as 0 (an empty page), since
   // other pages might have valid content.
   const uint32_t char_count = std::max<uint32_t>(raw_char_count, 0);
@@ -48,70 +47,9 @@ void GetAccessibilityInfo(PDFiumEngine* engine,
   page_info.bounds = page->rect();
   page_info.char_count = char_count;
   page_info.is_searchified = page->IsPageSearchified();
-
-  chars.resize(page_info.char_count);
-  for (uint32_t i = 0; i < char_count; ++i) {
-    chars[i].unicode_character = page->GetCharUnicode(i);
-  }
-
-  // TODO(crbug.com/40707542): Move the entire logic present in the following
-  // while loop to `PDFiumPage` class.
-  uint32_t char_index = 0;
-  while (char_index < char_count) {
-    std::optional<AccessibilityTextRunInfo> text_run_info_result =
-        page->GetTextRunInfo(char_index);
-    CHECK(text_run_info_result.has_value());
-    const auto& text_run_info = text_run_info_result.value();
-    uint32_t text_run_end = char_index + text_run_info.len;
-    CHECK_LE(text_run_end, char_count);
-    text_runs.push_back(text_run_info);
-
-    // We need to provide enough information to draw a bounding box
-    // around any arbitrary text range, but the bounding boxes of characters
-    // we get from PDFium don't necessarily "line up".
-    // Example for LTR text direction: walk through the
-    // characters in each text run and let the width of each character be
-    // the difference between the x coordinate of one character and the
-    // x coordinate of the next. The rest of the bounds of each character
-    // can be computed from the bounds of the text run.
-    // The same idea is used for RTL, TTB and BTT text direction.
-    gfx::RectF char_bounds = page->GetCharBounds(char_index);
-    for (uint32_t i = char_index; i < text_run_end - 1; i++) {
-      CHECK_LT(i + 1, char_count);
-      gfx::RectF next_char_bounds = page->GetCharBounds(i + 1);
-      double& char_width = chars[i].char_width;
-      switch (text_run_info.direction) {
-        case AccessibilityTextDirection::kNone:
-        case AccessibilityTextDirection::kLeftToRight:
-          char_width = next_char_bounds.x() - char_bounds.x();
-          break;
-        case AccessibilityTextDirection::kTopToBottom:
-          char_width = next_char_bounds.y() - char_bounds.y();
-          break;
-        case AccessibilityTextDirection::kRightToLeft:
-          char_width = char_bounds.right() - next_char_bounds.right();
-          break;
-        case AccessibilityTextDirection::kBottomToTop:
-          char_width = char_bounds.bottom() - next_char_bounds.bottom();
-          break;
-      }
-      char_bounds = next_char_bounds;
-    }
-    double& char_width = chars[text_run_end - 1].char_width;
-    if (text_run_info.direction == AccessibilityTextDirection::kBottomToTop ||
-        text_run_info.direction == AccessibilityTextDirection::kTopToBottom) {
-      char_width = char_bounds.height();
-    } else {
-      char_width = char_bounds.width();
-    }
-
-    char_index += text_run_info.len;
-  }
-
-  page->PopulateTextRunTypeAndImageAltText(text_runs);
+  page->GetTextAndImageInfo(text_runs, chars, page_objects.images);
   page_info.text_run_count = text_runs.size();
   page_objects.links = page->GetLinkInfo(text_runs);
-  page_objects.images = page->GetImageInfo(page_info.text_run_count);
   page_objects.highlights = page->GetHighlightInfo(text_runs);
   page_objects.form_fields =
       GetAccessibilityFormFieldInfo(page, page_info.text_run_count);

pdf/pdfium/pdfium_page.cc

@@ -541,6 +541,76 @@ int PDFiumPage::GetCharCount() {
   return FPDFText_CountChars(GetTextPage());
 }
 
+void PDFiumPage::GetTextAndImageInfo(
+    std::vector<AccessibilityTextRunInfo>& text_runs,
+    std::vector<AccessibilityCharInfo>& chars,
+    std::vector<AccessibilityImageInfo>& images) {
+  const int raw_char_count = GetCharCount();
+  // Treat a char count of -1 (error) as 0 (an empty page), since
+  // other pages might have valid content.
+  const uint32_t char_count = std::max<uint32_t>(raw_char_count, 0);
+
+  chars.resize(char_count);
+  for (uint32_t i = 0; i < char_count; ++i) {
+    chars[i].unicode_character = GetCharUnicode(i);
+  }
+
+  uint32_t char_index = 0;
+  while (char_index < char_count) {
+    std::optional<AccessibilityTextRunInfo> text_run_info_result =
+        GetTextRunInfo(char_index);
+    CHECK(text_run_info_result.has_value());
+    AccessibilityTextRunInfo& text_run_info = *text_run_info_result;
+    uint32_t text_run_end = char_index + text_run_info.len;
+    CHECK_LE(text_run_end, char_count);
+    text_runs.push_back(text_run_info);
+
+    // We need to provide enough information to draw a bounding box
+    // around any arbitrary text range, but the bounding boxes of characters
+    // we get from PDFium don't necessarily "line up".
+    // Example for LTR text direction: walk through the
+    // characters in each text run and let the width of each character be
+    // the difference between the x coordinate of one character and the
+    // x coordinate of the next. The rest of the bounds of each character
+    // can be computed from the bounds of the text run.
+    // The same idea is used for RTL, TTB and BTT text direction.
+    gfx::RectF char_bounds = GetCharBounds(char_index);
+    for (uint32_t i = char_index; i < text_run_end - 1; i++) {
+      CHECK_LT(i + 1, char_count);
+      gfx::RectF next_char_bounds = GetCharBounds(i + 1);
+      double& char_width = chars[i].char_width;
+      switch (text_run_info.direction) {
+        case AccessibilityTextDirection::kNone:
+        case AccessibilityTextDirection::kLeftToRight:
+          char_width = next_char_bounds.x() - char_bounds.x();
+          break;
+        case AccessibilityTextDirection::kTopToBottom:
+          char_width = next_char_bounds.y() - char_bounds.y();
+          break;
+        case AccessibilityTextDirection::kRightToLeft:
+          char_width = char_bounds.right() - next_char_bounds.right();
+          break;
+        case AccessibilityTextDirection::kBottomToTop:
+          char_width = char_bounds.bottom() - next_char_bounds.bottom();
+          break;
+      }
+      char_bounds = next_char_bounds;
+    }
+    double& char_width = chars[text_run_end - 1].char_width;
+    if (text_run_info.direction == AccessibilityTextDirection::kBottomToTop ||
+        text_run_info.direction == AccessibilityTextDirection::kTopToBottom) {
+      char_width = char_bounds.height();
+    } else {
+      char_width = char_bounds.width();
+    }
+
+    char_index += text_run_info.len;
+  }
+
+  PopulateTextRunTypeAndImageAltText(text_runs);
+  images = GetImageInfo(text_runs.size());
+}
+
 std::optional<AccessibilityTextRunInfo> PDFiumPage::GetTextRunInfo(
     int start_char_index) {
   FPDF_PAGE page = GetPage();
@@ -999,49 +1069,6 @@ std::vector<AccessibilityTextFieldInfo> PDFiumPage::GetTextFieldInfo(
   return text_field_info;
 }
 
-void PDFiumPage::PopulateTextRunTypeAndImageAltText(
-    std::vector<AccessibilityTextRunInfo>& text_runs) {
-  CalculateImages();
-  ScopedFPDFStructTree struct_tree(FPDF_StructTree_GetForPage(GetPage()));
-  if (!struct_tree) {
-    return;
-  }
-
-  // TODO(crbug.com/40707542): Consolidate `Accessibility"TextRunInfo` building
-  // logic into this class and remove the following block.
-  MarkedContentIdToTextRunInfoMap marked_content_id_text_run_info_map;
-  if (base::FeatureList::IsEnabled(chrome_pdf::features::kPdfTags)) {
-    FPDF_TEXTPAGE text_page = GetTextPage();
-    uint32_t char_index = 0;
-    for (auto& text_run : text_runs) {
-      FPDF_PAGEOBJECT text_object =
-          FPDFText_GetTextObject(text_page, char_index);
-      int marked_content_id = FPDFPageObj_GetMarkedContentID(text_object);
-      if (marked_content_id == -1) {
-        continue;
-      }
-      auto [iter, _] = marked_content_id_text_run_info_map.emplace(
-          marked_content_id, std::vector<raw_ptr<AccessibilityTextRunInfo>>());
-      iter->second.push_back(&text_run);
-      char_index += text_run.len;
-    }
-  }
-
-  if (marked_content_id_text_run_info_map.empty() &&
-      marked_content_id_image_map_.empty()) {
-    return;
-  }
-
-  std::set<FPDF_STRUCTELEMENT> visited_elements;
-  int tree_children_count = FPDF_StructTree_CountChildren(struct_tree.get());
-  for (int i = 0; i < tree_children_count; ++i) {
-    FPDF_STRUCTELEMENT current_element =
-        FPDF_StructTree_GetChildAtIndex(struct_tree.get(), i);
-    PopulateTextRunTypeAndImageAltTextForStructElement(
-        current_element, visited_elements, marked_content_id_text_run_info_map);
-  }
-}
-
 PDFiumPage::Area PDFiumPage::GetLinkTargetAtIndex(int link_index,
                                                   LinkTarget* target) {
   if (!available_ || link_index < 0)
@@ -1465,6 +1492,50 @@ void PDFiumPage::CalculateImages() {
   }
 }
 
+void PDFiumPage::PopulateTextRunTypeAndImageAltText(
+    std::vector<AccessibilityTextRunInfo>& text_runs) {
+  CalculateImages();
+
+  ScopedFPDFStructTree struct_tree(FPDF_StructTree_GetForPage(GetPage()));
+  if (!struct_tree) {
+    return;
+  }
+
+  // TODO(crbug.com/40707542): Consolidate `Accessibility"TextRunInfo` building
+  // logic into this class and remove the following block.
+  MarkedContentIdToTextRunInfoMap marked_content_id_text_run_info_map;
+  if (base::FeatureList::IsEnabled(chrome_pdf::features::kPdfTags)) {
+    FPDF_TEXTPAGE text_page = GetTextPage();
+    uint32_t char_index = 0;
+    for (auto& text_run : text_runs) {
+      FPDF_PAGEOBJECT text_object =
+          FPDFText_GetTextObject(text_page, char_index);
+      int marked_content_id = FPDFPageObj_GetMarkedContentID(text_object);
+      if (marked_content_id == -1) {
+        continue;
+      }
+      auto [iter, _] = marked_content_id_text_run_info_map.emplace(
+          marked_content_id, std::vector<raw_ptr<AccessibilityTextRunInfo>>());
+      iter->second.push_back(&text_run);
+      char_index += text_run.len;
+    }
+  }
+
+  if (marked_content_id_text_run_info_map.empty() &&
+      marked_content_id_image_map_.empty()) {
+    return;
+  }
+
+  std::set<FPDF_STRUCTELEMENT> visited_elements;
+  int tree_children_count = FPDF_StructTree_CountChildren(struct_tree.get());
+  for (int i = 0; i < tree_children_count; ++i) {
+    FPDF_STRUCTELEMENT current_element =
+        FPDF_StructTree_GetChildAtIndex(struct_tree.get(), i);
+    PopulateTextRunTypeAndImageAltTextForStructElement(
+        current_element, visited_elements, marked_content_id_text_run_info_map);
+  }
+}
+
 void PDFiumPage::PopulateTextRunTypeAndImageAltTextForStructElement(
     FPDF_STRUCTELEMENT current_element,
     std::set<FPDF_STRUCTELEMENT>& visited_elements,

pdf/pdfium/pdfium_page.h

@@ -41,6 +41,7 @@ namespace chrome_pdf {
 
 class PDFiumEngine;
 class Thumbnail;
+struct AccessibilityCharInfo;
 struct AccessibilityHighlightInfo;
 struct AccessibilityImageInfo;
 struct AccessibilityLinkInfo;
@@ -69,6 +70,7 @@ class PDFiumPage {
 
   // Unloads the PDFium data for this page from memory.
   void Unload();
+
   // Gets the FPDF_PAGE for this page, loading and parsing it if necessary.
   FPDF_PAGE GetPage();
 
@@ -81,6 +83,11 @@ class PDFiumPage {
   // Resets loaded text and loads it again.
   void ReloadTextPage();
 
+  // Get all the chars, text runs and images from the page.
+  void GetTextAndImageInfo(std::vector<AccessibilityTextRunInfo>& text_runs,
+                           std::vector<AccessibilityCharInfo>& chars,
+                           std::vector<AccessibilityImageInfo>& images);
+
   // Given a start char index, find the longest continuous run of text that's
   // in a single direction and with the same text style. Return a filled out
   // AccessibilityTextRunInfo on success or std::nullopt on failure. e.g. When
@@ -109,6 +116,7 @@ class PDFiumPage {
   // bounding boxes.
   std::vector<AccessibilityLinkInfo> GetLinkInfo(
       const std::vector<AccessibilityTextRunInfo>& text_runs);
+
   // For all the images on the page, get their alt texts and bounding boxes. If
   // the alt text is empty or unavailable, and if the user has requested that
   // the OCR service tag the PDF so that it is made accessible, transfer the raw
@@ -143,13 +151,6 @@ class PDFiumPage {
   std::vector<AccessibilityTextFieldInfo> GetTextFieldInfo(
       uint32_t text_run_count);
 
-  // Traverses the entire struct tree of the page recursively and extracts the
-  // text run type or the alt text from struct tree elements corresponding to
-  // the marked content IDs associated with `text_runs` or present in
-  // `marked_content_id_image_map_` respectively.
-  void PopulateTextRunTypeAndImageAltText(
-      std::vector<AccessibilityTextRunInfo>& text_runs);
-
   enum Area {
     NONSELECTABLE_AREA,
     TEXT_AREA,       // Area contains regular, selectable text not
@@ -447,6 +448,13 @@ class PDFiumPage {
   // Value  :  Index of the image in the `images_` vector.
   using MarkedContentIdToImageMap = std::map<int, size_t>;
 
+  // Traverses the entire struct tree of the page recursively and extracts the
+  // text run type or the alt text from struct tree elements corresponding to
+  // the marked content IDs associated with `text_runs` or present in
+  // `marked_content_id_image_map_` respectively.
+  void PopulateTextRunTypeAndImageAltText(
+      std::vector<AccessibilityTextRunInfo>& text_runs);
+
   // Traverses a struct element and its sub-tree recursively and extracts the
   // text run type or the alt text from struct elements corresponding to the
   // marked content IDs present in `marked_content_id_text_run_info_map` or