Create a Factory for NativeMetafile.

printing/native_metafile_win.h

+// Copyright (c) 2011 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 PRINTING_NATIVE_METAFILE_WIN_H_
+#define PRINTING_NATIVE_METAFILE_WIN_H_
+
+#include <windows.h>
+#include <vector>
+
+#include "base/basictypes.h"
+
+class FilePath;
+
+namespace gfx {
+class Rect;
+}
+
+namespace printing {
+
+// Simple wrapper class that manage an EMF data stream and its virtual HDC.
+class NativeMetafile {
+ public:
+  virtual ~NativeMetafile() {};
+
+  // Initializes the Emf with the data in |src_buffer|. Returns true on success.
+  virtual bool Init(const void* src_buffer, uint32 src_buffer_size) = 0;
+
+  // Generates a virtual HDC that will record every GDI commands and compile it
+  // in a EMF data stream.
+  // hdc is used to setup the default DPI and color settings. hdc is optional.
+  // rect specifies the dimensions (in .01-millimeter units) of the EMF. rect is
+  // optional.
+  virtual bool CreateDc(HDC sibling, const RECT* rect) = 0;
+
+  // Similar to the above method but the metafile is backed by a file.
+  virtual bool CreateFileBackedDc(HDC sibling,
+                                  const RECT* rect,
+                                  const FilePath& path) = 0;
+
+  // Load an EMF file.
+  virtual bool CreateFromFile(const FilePath& metafile_path) = 0;
+
+  // TODO(maruel): CreateFromFile(). If ever used. Maybe users would like to
+  // have the ability to save web pages to an EMF file? Afterward, it is easy to
+  // convert to PDF or PS.
+
+  // Closes the HDC created by CreateDc() and generates the compiled EMF
+  // data.
+  virtual bool CloseDc() = 0;
+
+  // Closes the EMF data handle when it is not needed anymore.
+  virtual void CloseEmf() = 0;
+
+  // "Plays" the EMF buffer in a HDC. It is the same effect as calling the
+  // original GDI function that were called when recording the EMF. |rect| is in
+  // "logical units" and is optional. If |rect| is NULL, the natural EMF bounds
+  // are used.
+  // Note: Windows has been known to have stack buffer overflow in its GDI
+  // functions, whether used directly or indirectly through precompiled EMF
+  // data. We have to accept the risk here. Since it is used only for printing,
+  // it requires user intervention.
+  virtual bool Playback(HDC hdc, const RECT* rect) const = 0;
+
+  // The slow version of Playback(). It enumerates all the records and play them
+  // back in the HDC. The trick is that it skip over the records known to have
+  // issue with some printers. See Emf::Record::SafePlayback implementation for
+  // details.
+  virtual bool SafePlayback(HDC hdc) const = 0;
+
+  // Retrieves the bounds of the painted area by this EMF buffer. This value
+  // should be passed to Playback to keep the exact same size.
+  virtual gfx::Rect GetBounds() const = 0;
+
+  // Retrieves the EMF stream size.
+  virtual uint32 GetDataSize() const = 0;
+
+  // Retrieves the EMF stream.
+  virtual bool GetData(void* buffer, uint32 size) const = 0;
+
+  // Retrieves the EMF stream. It is an helper function.
+  virtual bool GetData(std::vector<uint8>* buffer) const = 0;
+
+  virtual HENHMETAFILE emf() const = 0;
+
+  virtual HDC hdc() const = 0;
+
+  // Inserts a custom GDICOMMENT records indicating StartPage/EndPage calls
+  // (since StartPage and EndPage do not work in a metafile DC). Only valid
+  // when hdc_ is non-NULL.
+  virtual bool StartPage() = 0;
+  virtual bool EndPage() = 0;
+
+  // Saves the EMF data to a file as-is. It is recommended to use the .emf file
+  // extension but it is not enforced. This function synchronously writes to the
+  // file. For testing only.
+  virtual bool SaveTo(const std::wstring& filename) const = 0;
+};
+
+}  // namespace printing
+
+#endif  // PRINTING_NATIVE_METAFILE_WIN_H_