widget/windows/WindowsEMF.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef MOZILLA_WIDGET_WINDOWSEMF_H
   7 #define MOZILLA_WIDGET_WINDOWSEMF_H
   8
   9 /* include windows.h for the HDC definitions that we need. */
  10 #include <windows.h>
  11
  12 namespace mozilla {
  13 namespace widget {
  14
  15 /**
  16  * Windows Enhance Metafile: https://en.wikipedia.org/wiki/Windows_Metafile
  17  * A metafile, also called a vector image, is an image that is stored as a
  18  * sequence of drawing commands and settings. The commands and settings
  19  * recorded in a Metafile object can be stored in memory or saved to a file.
  20  *
  21  * The metafile device context is used for all drawing operations required to
  22  * create the picture. When the system processes a GDI function associated with
  23  * a metafile DC, it converts the function into the appropriate data and stores
  24  * this data in a record appended to the metafile.
  25  */
  26 class WindowsEMF {
  27  public:
  28   WindowsEMF();
  29   ~WindowsEMF();
  30
  31   /**
  32    * Initializes the object with the path of a file where the EMF data stream
  33    * should be stored. Callers are then expected to call GetDC() to draw output
  34    * before going on to call Playback() or SaveToFile() to generate the EMF
  35    * output.
  36    */
  37   bool InitForDrawing(const wchar_t* aMetafilePath = nullptr);
  38
  39   /**
  40    * Initializes the object with an existing EMF file. Consumers cannot use
  41    * GetDC() to obtain an HDC to modify the file. They can only use Playback().
  42    */
  43   bool InitFromFileContents(const wchar_t* aMetafilePath);
  44
  45   /**
  46    * Creates the EMF from the specified data
  47    *
  48    * @param aByte Pointer to a buffer that contains EMF data.
  49    * @param aSize Specifies the size, in bytes, of aByte.
  50    */
  51   bool InitFromFileContents(PBYTE aBytes, UINT aSize);
  52
  53   /**
  54    * If this object was initiaziled using InitForDrawing() then this function
  55    * returns an HDC that can be drawn to generate the EMF output. Otherwise it
  56    * returns null. After finishing with the HDC, consumers could call Playback()
  57    * to draw EMF onto the given DC or call SaveToFile() to finish writing the
  58    * EMF file.
  59    */
  60   HDC GetDC() const {
  61     MOZ_ASSERT(mDC,
  62                "GetDC can be used only after "
  63                "InitForDrawing/ InitFromFileContents and before"
  64                "Playback/ SaveToFile");
  65     return mDC;
  66   }
  67
  68   /**
  69    * Play the EMF's drawing commands onto the given DC.
  70    */
  71   bool Playback(HDC aDeviceContext, const RECT& aRect);
  72
  73   /**
  74    * Called to generate the EMF file once a consumer has finished drawing to
  75    * the HDC returned by GetDC(), if initializes the object with the path of a
  76    * file.
  77    */
  78   bool SaveToFile();
  79
  80   /**
  81    * Return the size of the enhanced metafile, in bytes.
  82    */
  83   UINT GetEMFContentSize();
  84
  85   /**
  86    * Retrieves the contents of the EMF and copies them into a buffer.
  87    *
  88    * @param aByte the buffer to receive the data.
  89    */
  90   bool GetEMFContentBits(PBYTE aBytes);
  91
  92  private:
  93   WindowsEMF(const WindowsEMF& aEMF) = delete;
  94   bool FinishDocument();
  95   void ReleaseEMFHandle();
  96   void ReleaseAllResource();
  97
  98   /* Compiled EMF data handle. */
  99   HENHMETAFILE mEmf;
 100   HDC mDC;
 101 };
 102
 103 }  // namespace widget
 104 }  // namespace mozilla
 105
 106 #endif /* MOZILLA_WIDGET_WINDOWSEMF_H */