Add private PPAPI interfaces for PDFium accessibility.

pdf/pdfium/pdfium_engine.cc

 // Copyright (c) 2012 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 "pdf/pdfium/pdfium_engine.h"
 
 #include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 2285 matching lines @@
   if (index < 0 || static_cast<size_t>(index) > pages_.size() - 1)
     return "{}";
 
   std::unique_ptr<base::Value> node(
       pages_[index]->GetAccessibleContentAsValue(current_rotation_));
   std::string page_json;
   base::JSONWriter::Write(*node, &page_json);
   return page_json;
 }
 
+void PDFiumEngine::EnableAccessibility() {
+  PP_PrivateAccessibilityDocInfo doc_info;
+  doc_info.page_count = pages_.size();
+  doc_info.text_accessible = PP_FromBool(
+      HasPermission(PERMISSION_COPY_ACCESSIBLE));
+  doc_info.text_copyable = PP_FromBool(HasPermission(PERMISSION_COPY));
+  pp::PDF::SetAccessibilityDocInfo(GetPluginInstance(), &doc_info);
+
+  // If the document contents isn't accessible, don't send anything more.
+  if (!(HasPermission(PERMISSION_COPY) ||
+        HasPermission(PERMISSION_COPY_ACCESSIBLE))) {
+    return;
+  }
+
+  PP_PrivateAccessibilityViewportInfo viewport_info;
+  viewport_info.scroll.x = 0;
+  viewport_info.scroll.y = -client_->GetToolbarHeight();
+  viewport_info.offset = page_offset_;
+  viewport_info.zoom = current_zoom_;
+  pp::PDF::SetAccessibilityViewportInfo(GetPluginInstance(), &viewport_info);

[raymes, 2016/05/17 20:38:40]

Does the viewport info need to be updated as the viewport changes?

[raymes, 2016/05/17 20:40:12]

Also, is the viewport information important for accessibility (I'm guessing so
since you're sending it but I wanted to double check :)

[dmazzoni, 2016/05/17 20:56:58]

Yes, I just haven't implemented that yet.

[dmazzoni, 2016/05/17 20:56:58]

Yes, it's important to expose the on-screen location of all of the text - it's
not just for totally blind users, there are tools using accessibility APIs for
low-vision users, etc.

+
+  for (size_t page_index = 0; page_index < pages_.size(); ++page_index) {
+    FPDF_TEXTPAGE text_page = pages_[page_index]->GetTextPage();
+    int char_count = FPDFText_CountChars(text_page);
+    PP_PrivateAccessibilityPageInfo page_info;
+    page_info.bounds = pages_[page_index]->rect();
+    page_info.char_count = char_count;
+    pp::PDF::SetAccessibilityPageInfo(
+        GetPluginInstance(), page_index, &page_info);
+
+    int char_index = 0;
+    int text_run_index = 0;
+    while (char_index < char_count) {
+      PP_PrivateAccessibilityTextRunInfo text_run_info;

[raymes, 2016/05/17 20:38:40]

Could getting all this data be slow for large docs? If so it might hang the
plugin. I'd suggest breaking up the function by posting tasks with a delay. You
can take a look in OutOfProcessInstance::NotifyNumberOfFindResultsChanged for an
example.

An even better approach might be to only send the data that is visible in the
current viewport. That only works if we update on viewport changes though. I'm
not sure if you were planning to do this.

[dmazzoni, 2016/05/17 20:56:58]

I think I'd prefer to do this, maybe one page at a time.
Screen readers like to buffer the whole document. I think I'd like to try
posting
tasks and see how that works, at a minimum try to buffer more than just the
visible
portion, if not the whole doc.

+      pp::FloatRect bounds;
+      pages_[page_index]->GetTextRunInfo(
+          char_index, &text_run_info.len, &text_run_info.font_size, &bounds);
+      text_run_info.direction = PP_PRIVATEDIRECTION_LTR;
+      text_run_info.bounds = bounds;
+      std::vector<PP_PrivateAccessibilityCharInfo> chars(text_run_info.len);
+      for (uint32_t i = 0; i < text_run_info.len; ++i) {
+        chars[i].unicode_character = FPDFText_GetUnicode(text_page, i);
+        chars[i].char_width = pages_[page_index]->GetCharWidth(i);
+      }
+
+      pp::PDF::SetAccessibilityTextRunInfo(GetPluginInstance(),
+                                           page_index,
+                                           text_run_index,
+                                           &text_run_info,
+                                           chars.data());
+      text_run_index++;
+      char_index += text_run_info.len;
+    }
+  }

[raymes, 2016/05/17 20:38:40]

Could this code live in out_of_process_instance.cc (by exposing the necessary
information through the PDFEngine API)? I'd rather not expose the toolbar height
offset to the engine because it's more of a UI detail.

[dmazzoni, 2016/05/17 20:56:58]

Sure. That's one of the reasons I wanted to stop and get this reviewed before
I did things like updating the viewport.

+}
+
 bool PDFiumEngine::GetPrintScaling() {
   return !!FPDF_VIEWERREF_GetPrintScaling(doc_);
 }
 
 int PDFiumEngine::GetCopiesToPrint() {
   return FPDF_VIEWERREF_GetNumCopies(doc_);
 }
 
 int PDFiumEngine::GetDuplexType() {
   return static_cast<int>(FPDF_VIEWERREF_GetDuplex(doc_));
@@ skipping 1557 matching lines @@
   FPDF_DOCUMENT doc =
       FPDF_LoadMemDocument(pdf_buffer, pdf_buffer_size, nullptr);
   if (!doc)
     return false;
   bool success = FPDF_GetPageSizeByIndex(doc, page_number, width, height) != 0;
   FPDF_CloseDocument(doc);
   return success;
 }
 
 }  // namespace chrome_pdf