Update PDF accessibility when zoom level changes

components/pdf/renderer/pdf_accessibility_tree.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <algorithm>
 
 #include "base/memory/ptr_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversion_utils.h"
 #include "components/pdf/renderer/pdf_accessibility_tree.h"
 #include "content/public/renderer/render_accessibility.h"
 #include "content/public/renderer/render_frame.h"
 #include "content/public/renderer/render_view.h"
 #include "content/public/renderer/renderer_ppapi_host.h"
 #include "grit/components_strings.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/gfx/geometry/rect_conversions.h"
+#include "ui/gfx/transform.h"
 
 namespace pdf {
 
 namespace {
 
 // Don't try to apply font size thresholds to automatically identify headings
 // if the median font size is not at least this many points.
 const double kMinimumFontSize = 5;
 
 // Don't try to apply line break thresholds to automatically identify
@@ skipping 26 matching lines @@
 }
 
 void PdfAccessibilityTree::SetAccessibilityViewportInfo(
     const PP_PrivateAccessibilityViewportInfo& viewport_info) {
   zoom_ = viewport_info.zoom;
   CHECK_GT(zoom_, 0);
   scroll_ = ToVector2dF(viewport_info.scroll);
   scroll_.Scale(1.0 / zoom_);
   offset_ = ToVector2dF(viewport_info.offset);
   offset_.Scale(1.0 / zoom_);
+
+  content::RenderAccessibility* render_accessibility = GetRenderAccessibility();
+  if (render_accessibility && tree_.size() > 1) {
+    ui::AXNode* root = tree_.root();
+    ui::AXNodeData root_data = root->data();
+    root_data.transform = base::WrapUnique(MakeTransformFromViewInfo());
+    root->SetData(root_data);
+    render_accessibility->OnPdfRootNodeUpdated();
+  }
 }
 
 void PdfAccessibilityTree::SetAccessibilityDocInfo(
     const PP_PrivateAccessibilityDocInfo& doc_info) {
   if (!GetRenderAccessibility())
     return;
 
   doc_info_ = doc_info;
   doc_node_ = CreateNode(ui::AX_ROLE_GROUP);
+
+  // Because all of the coordinates are expressed relative to the
+  // doc's coordinates, the origin of the doc must be (0, 0). Its
+  // width and height will be updated as we add each page so that the
+  // doc's bounding box surrounds all pages.
+  doc_node_->location = gfx::RectF(0, 0, 1, 1);
 }
 
 void PdfAccessibilityTree::SetAccessibilityPageInfo(
     const PP_PrivateAccessibilityPageInfo& page_info,
     const std::vector<PP_PrivateAccessibilityTextRunInfo>& text_runs,
     const std::vector<PP_PrivateAccessibilityCharInfo>& chars) {
   content::RenderAccessibility* render_accessibility = GetRenderAccessibility();
   if (!render_accessibility)
     return;
 
   uint32_t page_index = page_info.page_index;
   CHECK_GE(page_index, 0U);
   CHECK_LT(page_index, doc_info_.page_count);
 
   ui::AXNodeData* page_node = CreateNode(ui::AX_ROLE_REGION);
   page_node->AddStringAttribute(
       ui::AX_ATTR_NAME,
       l10n_util::GetPluralStringFUTF8(
           IDS_PDF_PAGE_INDEX, page_index + 1));
 
   gfx::RectF page_bounds = ToRectF(page_info.bounds);
-  page_bounds += offset_;
-  page_bounds -= scroll_;
-  page_bounds.Scale(zoom_ / GetDeviceScaleFactor());
   page_node->location = page_bounds;
   doc_node_->location.Union(page_node->location);
   doc_node_->child_ids.push_back(page_node->id);
 
   double heading_font_size_threshold = 0;
   double line_spacing_threshold = 0;
   ComputeParagraphAndHeadingThresholds(text_runs,
                                        &heading_font_size_threshold,
                                        &line_spacing_threshold);
 
@@ skipping 28 matching lines @@
       para_node->child_ids.push_back(static_text_node->id);
     }
 
     // Add this text run to the current static text node.
     ui::AXNodeData* inline_text_box_node = CreateNode(
         ui::AX_ROLE_INLINE_TEXT_BOX);
     static_text_node->child_ids.push_back(inline_text_box_node->id);
 
     inline_text_box_node->AddStringAttribute(ui::AX_ATTR_NAME, chars_utf8);
     gfx::RectF text_run_bounds = ToGfxRectF(text_run.bounds);
-    text_run_bounds.Scale(zoom_ / GetDeviceScaleFactor());
     text_run_bounds += page_bounds.OffsetFromOrigin();
     inline_text_box_node->location = text_run_bounds;
     inline_text_box_node->AddIntListAttribute(ui::AX_ATTR_CHARACTER_OFFSETS,
                                               char_offsets);
 
     para_node->location.Union(inline_text_box_node->location);
     static_text_node->location.Union(inline_text_box_node->location);
 
     if (i == text_runs.size() - 1) {
       static_text_node->AddStringAttribute(ui::AX_ATTR_NAME, static_text);
@@ skipping 10 matching lines @@
       static_text_node = nullptr;
       static_text.clear();
     }
   }
 
   if (page_index == doc_info_.page_count - 1)
     Finish();
 }
 
 void PdfAccessibilityTree::Finish() {
+  doc_node_->transform = base::WrapUnique(MakeTransformFromViewInfo());
+
   ui::AXTreeUpdate update;
   update.root_id = doc_node_->id;
   for (const auto& node : nodes_)
     update.nodes.push_back(*node);
 
   CHECK(tree_.Unserialize(update)) << update.ToString() << tree_.error();
   content::RenderAccessibility* render_accessibility = GetRenderAccessibility();
   if (render_accessibility)
     render_accessibility->SetPdfTreeSource(this);
 }
@@ skipping 48 matching lines @@
 }
 
 std::vector<int32_t> PdfAccessibilityTree::GetTextRunCharOffsets(
     const PP_PrivateAccessibilityTextRunInfo& text_run,
     const std::vector<PP_PrivateAccessibilityCharInfo>& chars,
     int char_index) {
   std::vector<int32_t> char_offsets(text_run.len);
   double offset = 0.0;
   for (uint32_t j = 0; j < text_run.len; ++j) {
     offset += chars[char_index + j].char_width;
-    char_offsets[j] = floor(offset * zoom_ / GetDeviceScaleFactor());
+    char_offsets[j] = floor(offset);
   }
   return char_offsets;
 }
 
 gfx::Vector2dF PdfAccessibilityTree::ToVector2dF(const PP_Point& p) {
   return gfx::Vector2dF(p.x, p.y);
 }
 
 gfx::RectF PdfAccessibilityTree::ToRectF(const PP_Rect& r) {
   return gfx::RectF(r.point.x, r.point.y, r.size.width, r.size.height);
 }
 
 ui::AXNodeData* PdfAccessibilityTree::CreateNode(ui::AXRole role) {
   content::RenderAccessibility* render_accessibility = GetRenderAccessibility();
   DCHECK(render_accessibility);
 
   ui::AXNodeData* node = new ui::AXNodeData();
   node->id = render_accessibility->GenerateAXID();
   node->role = role;
   node->state = 1 << ui::AX_STATE_READ_ONLY;
+
+  // All nodes other than the first one have coordinates relative to
+  // the first node.
+  if (nodes_.size() > 0)
+    node->offset_container_id = nodes_[0]->id;
+
   nodes_.push_back(base::WrapUnique(node));
+
   return node;
 }
 
 float PdfAccessibilityTree::GetDeviceScaleFactor() const {
   content::RenderFrame* render_frame =
       host_->GetRenderFrameForInstance(instance_);
   DCHECK(render_frame);
   return render_frame->GetRenderView()->GetDeviceScaleFactor();
 }
 
 content::RenderAccessibility* PdfAccessibilityTree::GetRenderAccessibility() {
   content::RenderFrame* render_frame =
       host_->GetRenderFrameForInstance(instance_);
   return render_frame ? render_frame->GetRenderAccessibility() : nullptr;
 }
 
+gfx::Transform* PdfAccessibilityTree::MakeTransformFromViewInfo() {
+  gfx::Transform* transform = new gfx::Transform();
+  float scale_factor = zoom_ / GetDeviceScaleFactor();
+  transform->Scale(scale_factor, scale_factor);
+  transform->Translate(offset_);
+  transform->Translate(-scroll_);
+  return transform;
+}
+
 //
 // AXTreeSource implementation.
 //
 
 bool PdfAccessibilityTree::GetTreeData(ui::AXTreeData* tree_data) const {
   return false;
 }
 
 ui::AXNode* PdfAccessibilityTree::GetRoot() const {
   return tree_.root();
@@ skipping 30 matching lines @@
 const ui::AXNode* PdfAccessibilityTree::GetNull() const {
   return nullptr;
 }
 
 void PdfAccessibilityTree::SerializeNode(
     const ui::AXNode* node, ui::AXNodeData* out_data) const {
   *out_data = node->data();
 }
 
 }  // namespace pdf