does pdfium expose its api to javascript? i want to get the number of current page, but how to do this?

Question

as we all know pdfium is now part of chrome, and this is a nice pdf render, but i am confronted with some problem.

the code is as follows, the default page is 12 as

Answer 1

2019 update: While looking at the PDFium engine source code and header files (link here). I filtered out these API calls definitions:

  virtual bool New(const char* url);
  virtual bool New(const char* url,
  virtual void PageOffsetUpdated(const pp::Point& page_offset);
  virtual void PluginSizeUpdated(const pp::Size& size);
  virtual void ScrolledToXPosition(int position);
  virtual void ScrolledToYPosition(int position);
  virtual void PrePaint();
  virtual void Paint(const pp::Rect& rect,
  virtual void PostPaint();
  virtual bool HandleDocumentLoad(const pp::URLLoader& loader);
  virtual bool HandleEvent(const pp::InputEvent& event);
  virtual uint32_t QuerySupportedPrintOutputFormats();
  virtual void PrintBegin();
  virtual pp::Resource PrintPages(
  virtual void PrintEnd();
  virtual void StartFind(const char* text, bool case_sensitive);
  virtual bool SelectFindResult(bool forward);
  virtual void StopFind();
  virtual void ZoomUpdated(double new_zoom_level);
  virtual void RotateClockwise();
  virtual void RotateCounterclockwise();
  virtual std::string GetSelectedText();
  virtual std::string GetLinkAtPosition(const pp::Point& point);
  virtual bool IsSelecting();
  virtual bool HasPermission(DocumentPermission permission) const;
  virtual void SelectAll();
  virtual int GetNumberOfPages();
  virtual int GetNamedDestinationPage(const std::string& destination);
  virtual int GetFirstVisiblePage();
  virtual int GetMostVisiblePage();
  virtual pp::Rect GetPageRect(int index);
  virtual pp::Rect GetPageContentsRect(int index);
  virtual int GetVerticalScrollbarYPosition() { return position_.y(); }
  virtual void PaintThumbnail(pp::ImageData* image_data, int index);
  virtual void SetGrayscale(bool grayscale);
  virtual void OnCallback(int id);
  virtual std::string GetPageAsJSON(int index);
  virtual bool GetPrintScaling();
  virtual void AppendBlankPages(int num_pages);
  virtual void AppendPage(PDFEngine* engine, int index);
  virtual pp::Point GetScrollPosition();
  virtual void SetScrollPosition(const pp::Point& position);
  virtual bool IsProgressiveLoad();
  virtual pp::Instance* GetPluginInstance();
  virtual pp::URLLoader CreateURLLoader();
  virtual void OnPartialDocumentLoaded();
  virtual void OnPendingRequestComplete();
  virtual void OnNewDataAvailable();
  virtual void OnDocumentComplete();
  void UnsupportedFeature(int type);
    void GetVisibleSelectionsScreenRects(std::vector* rects);
  static int GetBlock(void* param, unsigned long position,
  static bool IsDataAvail(FX_FILEAVAIL* param,
  static void AddSegment(FX_DOWNLOADHINTS* param,
  void LoadDocument();
  bool TryLoadingDoc(bool with_password,
                     bool* needs_password);
  void GetPasswordAndLoad();
  void OnGetPasswordComplete(int32_t result,
  void ContinueLoadingDocument(bool has_password,
  void FinishLoadingDocument();
  void LoadPageInfo(bool reload);
  void CalculateVisiblePages();
  bool IsPageVisible(int index) const;
  bool CheckPageAvailable(int index, std::vector* pending);
  void UpdateTickMarks();
  void ContinueFind(int32_t result);
  void AddFindResult(const PDFiumRange& result);
  void SearchUsingPDFium(const base::string16& term,
                         bool case_sensitive,
                         bool first_search,
                         int character_to_start_searching_from,
                         int current_page);
  void SearchUsingICU(const base::string16& term,
                      bool case_sensitive,
                      bool first_search,
                      int character_to_start_searching_from,
                      int current_page);
  bool OnMouseDown(const pp::MouseInputEvent& event);
  bool OnMouseUp(const pp::MouseInputEvent& event);
  bool OnMouseMove(const pp::MouseInputEvent& event);
  bool OnKeyDown(const pp::KeyboardInputEvent& event);
  bool OnKeyUp(const pp::KeyboardInputEvent& event);
  bool OnChar(const pp::KeyboardInputEvent& event);
  void FitContentsToPrintableAreaIfRequired(
  void SaveSelectedFormForPrint();
                                int* page_index,
                                int* char_index,
                                int* page_index,
                                int* char_index,
  void OnSingleClick(int page_index, int char_index);
  void OnMultipleClick(int click_count, int page_index, int char_index);
  int StartPaint(int page_index, const pp::Rect& dirty);
  bool ContinuePaint(int progressive_index, pp::ImageData* image_data);
  void FinishPaint(int progressive_index, pp::ImageData* image_data);
  void CancelPaints();
  void InvalidateAllPages();
  void FillPageSides(int progressive_index);
  void PaintPageShadow(int progressive_index, pp::ImageData* image_data);
  void DrawSelections(int progressive_index, pp::ImageData* image_data);
  void PaintUnavailablePage(int page_index,
  int GetProgressiveIndex(int page_index) const;
  void GetPDFiumRect(int page_index, const pp::Rect& rect, int* start_x,
                     int* start_y, int* size_x, int* size_y) const;
  int GetRenderingFlags() const;
  void Highlight(void* buffer,
                 int stride,
  void DeviceToPage(int page_index,
  int GetVisiblePageIndex(FPDF_PAGE page);
  void SetCurrentPage(int index);
  void TransformPDFPageForPrinting(FPDF_PAGE page,
  void DrawPageShadow(const pp::Rect& page_rect,
  void GetRegion(const pp::Point& location,
                 void** region,
                 int* stride) const;
  void OnSelectionChanged();
  static void Form_Invalidate(FPDF_FORMFILLINFO* param,
  static void Form_OutputSelectedRect(FPDF_FORMFILLINFO* param,
  static void Form_SetCursor(FPDF_FORMFILLINFO* param, int cursor_type);
  static int Form_SetTimer(FPDF_FORMFILLINFO* param,
                           int elapse,
  static void Form_KillTimer(FPDF_FORMFILLINFO* param, int timer_id);
  static FPDF_SYSTEMTIME Form_GetLocalTime(FPDF_FORMFILLINFO* param);
  static void Form_OnChange(FPDF_FORMFILLINFO* param);
  static FPDF_PAGE Form_GetPage(FPDF_FORMFILLINFO* param,
                                int page_index);
  static FPDF_PAGE Form_GetCurrentPage(FPDF_FORMFILLINFO* param,
  static int Form_GetRotation(FPDF_FORMFILLINFO* param, FPDF_PAGE page);
  static void Form_ExecuteNamedAction(FPDF_FORMFILLINFO* param,
  static void Form_SetTextFieldFocus(FPDF_FORMFILLINFO* param,
  static void Form_DoURIAction(FPDF_FORMFILLINFO* param, FPDF_BYTESTRING uri);
  static void Form_DoGoToAction(FPDF_FORMFILLINFO* param,
                                int page_index,
                                int zoom_mode,
                                int size_of_array);
  static int Form_Alert(IPDF_JSPLATFORM* param,
                        int type,
                        int icon);
  static void Form_Beep(IPDF_JSPLATFORM* param, int type);
  static int Form_Response(IPDF_JSPLATFORM* param,
                           void* response,
                           int length);
  static int Form_GetFilePath(IPDF_JSPLATFORM* param,
                              void* file_path,
                              int length);
  static void Form_Mail(IPDF_JSPLATFORM* param,
                        void* mail_data,
                        int length,
  static void Form_Print(IPDF_JSPLATFORM* param,
                         int start,
                         int end,
  static void Form_SubmitForm(IPDF_JSPLATFORM* param,
                              void* form_data,
                              int length,
  static void Form_GotoPage(IPDF_JSPLATFORM* param, int page_number);
  static int Form_Browse(IPDF_JSPLATFORM* param, void* file_path, int length);
  static FPDF_BOOL Pause_NeedToPauseNow(IFSDK_PAUSE* param);
  int32_t password_tries_remaining_;
  bool defer_page_unload_;
  bool selecting_;
  int next_page_to_search_;
  int last_page_to_search_;
  int last_character_index_to_search_;  // -1 if search until end of page.
  int current_find_index_;
  int next_timer_id_;
  int last_page_mouse_down_;
  int first_visible_page_;
  int most_visible_page_;
  bool called_do_document_action_;
  bool render_grayscale_;
    int page_index;
    int painted_;
  int progressive_paint_timeout_;
  bool getting_password_;
  virtual bool RenderPDFPageToDC(const void* pdf_buffer,
                                 int buffer_size,
                                 int page_number,
  virtual bool RenderPDFPageToBitmap(const void* pdf_buffer,
                                     int pdf_buffer_size,
                                     int page_number,
                                     void* bitmap_buffer);
  virtual bool GetPDFDocInfo(const void* pdf_buffer,
                             int buffer_size,
                             int* page_count,
  virtual bool GetPDFPageSizeByIndex(const void* pdf_buffer,
                                     int pdf_buffer_size, int page_number,