browser/printing/print_job_worker.h

// 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.

#ifndef CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_H_
#define CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_H_

#include "base/memory/ref_counted.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/weak_ptr.h"
#include "base/threading/thread.h"
#include "printing/page_number.h"
#include "printing/print_destination_interface.h"
#include "printing/printing_context.h"
#include "printing/print_job_constants.h"

namespace base {
class DictionaryValue;
}

namespace printing {

class PrintJob;
class PrintJobWorkerOwner;
class PrintedDocument;
class PrintedPage;
class PrintingUIWebContentsObserver;

// Worker thread code. It manages the PrintingContext, which can be blocking
// and/or run a message loop. This is the object that generates most
// NOTIFY_PRINT_JOB_EVENT notifications, but they are generated through a
// NotificationTask task to be executed from the right thread, the UI thread.
// PrintJob always outlives its worker instance.
class PrintJobWorker {
 public:
  explicit PrintJobWorker(PrintJobWorkerOwner* owner);
  virtual ~PrintJobWorker();

  void SetNewOwner(PrintJobWorkerOwner* new_owner);

  // Set a destination for print.
  // This supersedes the document's rendering destination.
  void SetPrintDestination(PrintDestinationInterface* destination);

  // Initializes the print settings. If |ask_user_for_settings| is true, a
  // Print... dialog box will be shown to ask the user his preference.
  void GetSettings(
      bool ask_user_for_settings,
      scoped_ptr<PrintingUIWebContentsObserver> web_contents_observer,
      int document_page_count,
      bool has_selection,
      MarginType margin_type);

  // Set the new print settings.
  void SetSettings(
      scoped_ptr<base::DictionaryValue> new_settings);

  // Starts the printing loop. Every pages are printed as soon as the data is
  // available. Makes sure the new_document is the right one.
  void StartPrinting(PrintedDocument* new_document);

  // Updates the printed document.
  void OnDocumentChanged(PrintedDocument* new_document);

  // Dequeues waiting pages. Called when PrintJob receives a
  // NOTIFY_PRINTED_DOCUMENT_UPDATED notification. It's time to look again if
  // the next page can be printed.
  void OnNewPage();

  // This is the only function that can be called in a thread.
  void Cancel();

  // Returns true if the thread has been started, and not yet stopped.
  bool IsRunning() const;

  // Posts the given task to be run.
  bool PostTask(const tracked_objects::Location& from_here,
                const base::Closure& task);

  // Signals the thread to exit in the near future.
  void StopSoon();

  // Signals the thread to exit and returns once the thread has exited.
  void Stop();

  // Starts the thread.
  bool Start();

 protected:
  // Retrieves the context for testing only.
  PrintingContext* printing_context() { return printing_context_.get(); }

 private:
  // The shared NotificationService service can only be accessed from the UI
  // thread, so this class encloses the necessary information to send the
  // notification from the right thread. Most NOTIFY_PRINT_JOB_EVENT
  // notifications are sent this way, except USER_INIT_DONE, USER_INIT_CANCELED
  // and DEFAULT_INIT_DONE. These three are sent through PrintJob::InitDone().
  class NotificationTask;

  // Renders a page in the printer.
  void SpoolPage(PrintedPage* page);

  // Closes the job since spooling is done.
  void OnDocumentDone();

  // Discards the current document, the current page and cancels the printing
  // context.
  void OnFailure();

  // Asks the user for print settings. Must be called on the UI thread.
  // Required on Mac and Linux. Windows can display UI from non-main threads,
  // but sticks with this for consistency.
  void GetSettingsWithUI(
      scoped_ptr<PrintingUIWebContentsObserver> web_contents_observer,
      int document_page_count,
      bool has_selection);

  // The callback used by PrintingContext::GetSettingsWithUI() to notify this
  // object that the print settings are set.  This is needed in order to bounce
  // back into the IO thread for GetSettingsDone().
  void GetSettingsWithUIDone(PrintingContext::Result result);

  // Called on the UI thread to update the print settings.
  void UpdatePrintSettings(scoped_ptr<base::DictionaryValue> new_settings);

  // Reports settings back to owner_.
  void GetSettingsDone(PrintingContext::Result result);

  // Use the default settings. When using GTK+ or Mac, this can still end up
  // displaying a dialog. So this needs to happen from the UI thread on these
  // systems.
  void UseDefaultSettings();

  // Information about the printer setting.
  scoped_ptr<PrintingContext> printing_context_;

  // The printed document. Only has read-only access.
  scoped_refptr<PrintedDocument> document_;

  // The print destination, may be NULL.
  scoped_refptr<PrintDestinationInterface> destination_;

  // The print job owning this worker thread. It is guaranteed to outlive this
  // object.
  PrintJobWorkerOwner* owner_;

  // Current page number to print.
  PageNumber page_number_;

  // Thread to run worker tasks.
  base::Thread thread_;

  // Tread-safe pointer to task runner of the |thread_|.
  scoped_refptr<base::SequencedTaskRunner> task_runner_;

  // Used to generate a WeakPtr for callbacks.
  base::WeakPtrFactory<PrintJobWorker> weak_factory_;

  DISALLOW_COPY_AND_ASSIGN(PrintJobWorker);
};

}  // namespace printing

#endif  // CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_H_