Unifying NativeMetafile class interface (as much as possible) for Linux, Mac, Win

printing/native_metafile.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_H_
 #define PRINTING_NATIVE_METAFILE_H_
 
 #include "base/basictypes.h"
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
-#include "printing/native_metafile_win.h"
+#include <windows.h>
+#include <vector>
 #elif defined(OS_MACOSX)
-#include "printing/native_metafile_mac.h"
-#elif defined(OS_POSIX)
-#include "printing/native_metafile_linux.h"
+#include <ApplicationServices/ApplicationServices.h>
+#include <CoreFoundation/CoreFoundation.h>
+#include "base/mac/scoped_cftyperef.h"
 #endif
 
+namespace gfx {
+class Rect;
+class Size;
+class Point;
+}
+
+#if defined(OS_WIN)
+typedef HDC PlatformContext;
+#elif defined(OS_MACOSX)
+typedef CGContextRef PlatformContext;
+#elif defined(OS_POSIX)
+typedef struct _cairo PlatformContext;
+#endif
+
+class FilePath;
+
+namespace printing {
+
+// This class creates a graphics context that renders into a data stream.
+class NativeMetafile {
+ public:
+  virtual ~NativeMetafile() {}
+
+  // Initializes a fresh new metafile for rendering. Returns false on failure.
+  // Note: It should only be called from within the renderer process to allocate
+  // rendering resources.
+  virtual bool Init() = 0;
+
+  // Initializes the metafile with the data in |src_buffer|. Returns true
+  // on success.
+  // Note: It should only be called from within the browser process.
+  virtual bool Init(const void* src_buffer, uint32 src_buffer_size) = 0;
+
+  // Returns the size of the underlying data stream. Only valid after Close()
+  // has been called.
+  virtual uint32 GetDataSize() const = 0;
+
+  // Copies the first |dst_buffer_size| bytes of the underlying data stream into
+  // |dst_buffer|. This function should ONLY be called after Close() is invoked.
+  // Returns true if the copy succeeds.
+  virtual bool GetData(void* dst_buffer, uint32 dst_buffer_size) const = 0;
+
+  // Closes the current page and destroys the context used in rendering that
+  // page. The results of current page will be appended into the underlying
+  // data stream. Returns true on success.
+  virtual bool FinishPage() = 0;
+
+  // Closes the metafile. No further rendering is allowed (the current page
+  // is implicitly closed).
+  virtual void Close() = 0;
+
+  // Saves the underlying data to the given file. This function should ONLY be
+  // called after the metafile is closed. Returns true if writing succeeded.
+  virtual bool SaveTo(const FilePath& file_path) const = 0;
+
+  // Returns the bounds of the given page. Pages use a 1-based index.
+  virtual gfx::Rect GetPageBounds(unsigned int page_number) const = 0;
+  virtual unsigned int GetPageCount() const = 0;
+
+#if defined(OS_WIN)
+  // 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;
+#elif defined(OS_MACOSX)
+  // Prepares a new pdf page at specified |content_origin| with the given
+  // |page_size| and a |scale_factor| to use for the drawing.
+  virtual PlatformContext StartPage(const gfx::Size& page_size,
+                                    const gfx::Point& content_origin,
+                                    const float& scale_factor) = 0;
+#elif defined(OS_POSIX)
+  // Prepares a new cairo surface/context for rendering a new page.
+  // The unit is in point (=1/72 in).
+  // Returns NULL when failed.
+  virtual PlatformContext* StartPage(const gfx::Size& page_sixe,
+                                     double margin_top_in_points,
+                                     double margin_right_in_points,
+                                     double margin_bottom_in_points,
+                                     double margin_left_in_points) = 0;
+#endif
+
+#if defined(OS_WIN)
+  // 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(PlatformContext sibling, const RECT* rect) = 0;
+
+  // Similar to the above method but the metafile is backed by a file.
+  virtual bool CreateFileBackedDc(PlatformContex sibling,
+                                  const RECT* rect,
+                                  const FilePath& path) = 0;
+
+  // Closes the HDC created by CreateDc() and generates the compiled EMF
+  // data.
+  virtual bool CloseDc() = 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(PlatformContext 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(PlatformContext hdc) const = 0;
+
+  // Retrieves the EMF stream. It is a helper function.
+  virtual bool GetData(std::vector<uint8>* buffer) const = 0;
+
+  virtual HENHMETAFILE emf() const = 0;
+  virtual PlatformContext hdc() const = 0;
+#elif defined(OS_MACOSX)
+  // Renders the given page into |rect| in the given context.
+  // Pages use a 1-based index. The rendering uses the following arguments
+  // to determine scaling and translation factors.
+  // |shrink_to_fit| specifies whether the output should be shrunk to fit the
+  // supplied |rect| if the page size is larger than |rect| in any dimension.
+  // If this is false, parts of the PDF page that lie outside the bounds will be
+  // clipped.
+  // |stretch_to_fit| specifies whether the output should be stretched to fit
+  // the supplied bounds if the page size is smaller than |rect| in all
+  // dimensions.
+  // |center_horizontally| specifies whether the final image (after any scaling
+  // is done) should be centered horizontally within the given |rect|.
+  // |center_vertically| specifies whether the final image (after any scaling
+  // is done) should be centered vertically within the given |rect|.
+  // Note that all scaling preserves the original aspect ratio of the page.
+  virtual bool RenderPage(unsigned int page_number,
+                          PlatformContext context,
+                          const CGRect rect,
+                          bool shrink_to_fit,
+                          bool stretch_to_fit,
+                          bool center_horizontally,
+                          bool center_vertically) const = 0;
+
+  // Get the context for rendering to the PDF.
+  virtual PlatformContext context() = 0;
+#elif defined(OS_POSIX)
+  // Sets raw PDF data for the document. This is used when a cairo drawing
+  // surface has already been created. This method will cause all subsequent
+  // drawing on the surface to be discarded (in Close()). If Init() has not yet
+  // been called this method simply calls the second version of Init.
+  virtual bool SetRawData(const void* src_buffer, uint32 src_buffer_size) = 0;
+#endif
+};
+
+}  // namespace printing
+
 #endif  // PRINTING_NATIVE_METAFILE_H_