1 files changed, 106 insertions, 0 deletions
diff --git a/widget/windows/WindowsEMF.h b/widget/windows/WindowsEMF.h
new file mode 100644
index 0000000000..3a7a20173c
--- /dev/null
+++ b/widget/windows/WindowsEMF.h
@@ -0,0 +1,106 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZILLA_WIDGET_WINDOWSEMF_H
+#define MOZILLA_WIDGET_WINDOWSEMF_H
+
+/* include windows.h for the HDC definitions that we need. */
+#include <windows.h>
+
+namespace mozilla {
+namespace widget {
+
+/**
+ * Windows Enhance Metafile: https://en.wikipedia.org/wiki/Windows_Metafile
+ * A metafile, also called a vector image, is an image that is stored as a
+ * sequence of drawing commands and settings. The commands and settings
+ * recorded in a Metafile object can be stored in memory or saved to a file.
+ *
+ * The metafile device context is used for all drawing operations required to
+ * create the picture. When the system processes a GDI function associated with
+ * a metafile DC, it converts the function into the appropriate data and stores
+ * this data in a record appended to the metafile.
+ */
+class WindowsEMF {
+ public:
+  WindowsEMF();
+  ~WindowsEMF();
+
+  /**
+   * Initializes the object with the path of a file where the EMF data stream
+   * should be stored. Callers are then expected to call GetDC() to draw output
+   * before going on to call Playback() or SaveToFile() to generate the EMF
+   * output.
+   */
+  bool InitForDrawing(const wchar_t* aMetafilePath = nullptr);
+
+  /**
+   * Initializes the object with an existing EMF file. Consumers cannot use
+   * GetDC() to obtain an HDC to modify the file. They can only use Playback().
+   */
+  bool InitFromFileContents(const wchar_t* aMetafilePath);
+
+  /**
+   * Creates the EMF from the specified data
+   *
+   * @param aByte Pointer to a buffer that contains EMF data.
+   * @param aSize Specifies the size, in bytes, of aByte.
+   */
+  bool InitFromFileContents(PBYTE aBytes, UINT aSize);
+
+  /**
+   * If this object was initiaziled using InitForDrawing() then this function
+   * returns an HDC that can be drawn to generate the EMF output. Otherwise it
+   * returns null. After finishing with the HDC, consumers could call Playback()
+   * to draw EMF onto the given DC or call SaveToFile() to finish writing the
+   * EMF file.
+   */
+  HDC GetDC() const {
+    MOZ_ASSERT(mDC,
+               "GetDC can be used only after "
+               "InitForDrawing/ InitFromFileContents and before"
+               "Playback/ SaveToFile");
+    return mDC;
+  }
+
+  /**
+   * Play the EMF's drawing commands onto the given DC.
+   */
+  bool Playback(HDC aDeviceContext, const RECT& aRect);
+
+  /**
+   * Called to generate the EMF file once a consumer has finished drawing to
+   * the HDC returned by GetDC(), if initializes the object with the path of a
+   * file.
+   */
+  bool SaveToFile();
+
+  /**
+   * Return the size of the enhanced metafile, in bytes.
+   */
+  UINT GetEMFContentSize();
+
+  /**
+   * Retrieves the contents of the EMF and copies them into a buffer.
+   *
+   * @param aByte the buffer to receive the data.
+   */
+  bool GetEMFContentBits(PBYTE aBytes);
+
+ private:
+  WindowsEMF(const WindowsEMF& aEMF) = delete;
+  bool FinishDocument();
+  void ReleaseEMFHandle();
+  void ReleaseAllResource();
+
+  /* Compiled EMF data handle. */
+  HENHMETAFILE mEmf;
+  HDC mDC;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* MOZILLA_WIDGET_WINDOWSEMF_H */