Implement native metafile for printing on Linux.

printing/pdf_ps_metafile_linux.h

+// Copyright (c) 2009 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_PDF_PS_METAFILE_LINUX_H_
+#define PRINTING_PDF_PS_METAFILE_LINUX_H_
+
+#include <cairo.h>
+
+#include <string>
+
+#include "base/basictypes.h"
+
+class FilePath;
+
+namespace printing {
+
+// This class uses Cairo graphics library to generate PostScript/PDF stream
+// and stores rendering results in a string buffer.
+class PdfPsMetafile {
+ public:
+  enum FileFormat {
+    PDF,
+    PS,
+  };
+
+  // The constructor we should use in the renderer process.
+  explicit PdfPsMetafile(const FileFormat& format);
+
+  // The constructor we should use in the browser process.
+  // |src_buffer| should point to the shared memory which stores PDF/PS
+  // contents generated in the renderer.
+  PdfPsMetafile(const FileFormat& format,
+                const void* src_buffer,
+                size_t src_buffer_size);
+
+  ~PdfPsMetafile();
+
+  FileFormat GetFileFormat() { return format_; }
+
+  // Prepares a new cairo surface/context for rendering a new page.
+  bool StartPage(double width, double height);  // The unit is pt (=1/72 in).
+
+  // Returns the Cairo context for rendering current page.
+  cairo_t* GetPageContext() const { return page_context_; }
+
+  // Destroys the surface and the context used in rendering current page.
+  // The results of current page will be appended into buffer |all_pages_|.
+  // TODO(myhuang): I plan to also do page setup here (margins, the header
+  // and the footer). At this moment, only pre-defined margins for US letter
+  // paper are hard-coded here.
+  // |shrink| decides the scaling factor to fit raw printing results into
+  // printable area.
+  void FinishPage(float shrink);
+
+  // Closes resulting PDF/PS file. No further rendering is allowed.
+  void Close();
+
+  // Returns size of PDF/PS contents stored in buffer |all_pages_|.
+  // This function should ONLY be called after PDF/PS file is closed.
+  unsigned int GetDataSize() const;
+
+  // Copies PDF/PS contents stored in buffer |all_pages_| into |dst_buffer|.
+  // This function should ONLY be called after PDF/PS file is closed.
+  void GetData(void* dst_buffer, size_t dst_buffer_size) const;
+
+  // Saves PDF/PS contents stored in buffer |all_pages_| into |filename| on
+  // the disk.
+  // This function should ONLY be called after PDF/PS file is closed.
+  bool SaveTo(const FilePath& filename) const;
+
+ private:
+  // Callback function for Cairo to write PDF/PS stream.
+  // |dst_buffer| is actually a pointer of type `std::string*`.
+  static cairo_status_t WriteCairoStream(void* dst_buffer,
+                                         const unsigned char* src_data,
+                                         unsigned int src_data_length);
+
+  // Convenient function to test if |surface| is valid.
+  bool IsSurfaceValid(cairo_surface_t* surface) const;
+
+  // Convenient function to test if |context| is valid.
+  bool IsContextValid(cairo_t* context) const;
+
+  FileFormat format_;
+
+  // Cairo surface and context for entire PDF/PS file.
+  cairo_surface_t* surface_;
+  cairo_t* context_;
+
+  // Cairo surface and context for current page only.
+  cairo_surface_t* page_surface_;
+  cairo_t* page_context_;
+
+  // Buffer stores PDF/PS contents for entire PDF/PS file.
+  std::string all_pages_;
+
+  // Buffer stores PDF/PS contents for current page only.
+  std::string current_page_;
+
+  DISALLOW_COPY_AND_ASSIGN(PdfPsMetafile);
+};
+
+}  // namespace printing
+
+#endif  // PRINTING_PDF_PS_METAFILE_LINUX_H_
+