skia/ext/platform_device.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 SKIA_EXT_PLATFORM_DEVICE_H_
#define SKIA_EXT_PLATFORM_DEVICE_H_
#pragma once

#include "build/build_config.h"

#if defined(OS_WIN)
#include <windows.h>
#include <vector>
#endif

#include "third_party/skia/include/core/SkPreConfig.h"
#include "third_party/skia/include/core/SkDevice.h"
#include "third_party/skia/include/core/SkColor.h"

class SkMatrix;
class SkMetaData;
class SkPath;
class SkRegion;

struct SkIRect;

#if defined(OS_LINUX) || defined(OS_OPENBSD) || defined(OS_FREEBSD) \
    || defined(OS_SUN)
typedef struct _cairo cairo_t;
typedef struct _cairo_rectangle cairo_rectangle_t;
#elif defined(OS_MACOSX)
typedef struct CGContext* CGContextRef;
typedef struct CGRect CGRect;
#endif

namespace skia {

class PlatformDevice;

#if defined(OS_WIN)
typedef HDC PlatformSurface;
typedef RECT PlatformRect;
#elif defined(OS_LINUX) || defined(OS_OPENBSD) || defined(OS_FREEBSD) \
    || defined(OS_SUN)
typedef cairo_t* PlatformSurface;
typedef cairo_rectangle_t PlatformRect;
#elif defined(OS_MACOSX)
typedef CGContextRef PlatformSurface;
typedef CGRect PlatformRect;
#elif defined(ANDROID)
// TODO(tonyg): FIX TYPES!
typedef void* PlatformSurface;
typedef void* PlatformRect;
#endif

// The following routines provide accessor points for the functionality
// exported by the various PlatformDevice ports.  The PlatformDevice, and
// BitmapPlatformDevice classes inherit directly from SkDevice, which is no
// longer a supported usage-pattern for skia.  In preparation of the removal of
// these classes, all calls to PlatformDevice::* should be routed through these
// helper functions.

// Bind a PlatformDevice instance, |platform_device| to |device|.  Subsequent
// calls to the functions exported below will forward the request to the
// corresponding method on the bound PlatformDevice instance.    If no
// PlatformDevice has been bound to the SkDevice passed, then the routines are
// NOPS.
SK_API void SetPlatformDevice(SkDevice* device,
                              PlatformDevice* platform_device);
SK_API PlatformDevice* GetPlatformDevice(SkDevice* device);


#if defined(OS_WIN)
// Initializes the default settings and colors in a device context.
SK_API void InitializeDC(HDC context);
#elif defined (OS_MACOSX)
// Returns the CGContext that backing the SkDevice.  Forwards to the bound
// PlatformDevice.  Returns NULL if no PlatformDevice is bound.
SK_API CGContextRef GetBitmapContext(SkDevice* device);
#endif

// Following routines are used in print preview workflow to mark the draft mode
// metafile and preview metafile.
SK_API SkMetaData& getMetaData(const SkCanvas& canvas);
SK_API void SetIsDraftMode(const SkCanvas& canvas, bool draft_mode);
SK_API bool IsDraftMode(const SkCanvas& canvas);

#if defined(OS_MACOSX) || defined(OS_WIN)
SK_API void SetIsPreviewMetafile(const SkCanvas& canvas, bool is_preview);
SK_API bool IsPreviewMetafile(const SkCanvas& canvas);
#endif

// A SkDevice is basically a wrapper around SkBitmap that provides a surface for
// SkCanvas to draw into. PlatformDevice provides a surface Windows can also
// write to. It also provides functionality to play well with GDI drawing
// functions. This class is abstract and must be subclassed. It provides the
// basic interface to implement it either with or without a bitmap backend.
//
// PlatformDevice provides an interface which sub-classes of SkDevice can also
// provide to allow for drawing by the native platform into the device.
class SK_API PlatformDevice {
 public:
  virtual ~PlatformDevice() {}

#if defined(OS_MACOSX)
  // The CGContext that corresponds to the bitmap, used for CoreGraphics
  // operations drawing into the bitmap. This is possibly heavyweight, so it
  // should exist only during one pass of rendering.
  virtual CGContextRef GetBitmapContext() = 0;
#endif

  // The DC that corresponds to the bitmap, used for GDI operations drawing
  // into the bitmap. This is possibly heavyweight, so it should be existant
  // only during one pass of rendering.
  virtual PlatformSurface BeginPlatformPaint();

  // Finish a previous call to beginPlatformPaint.
  virtual void EndPlatformPaint();

  // Draws to the given screen DC, if the bitmap DC doesn't exist, this will
  // temporarily create it. However, if you have created the bitmap DC, it will
  // be more efficient if you don't free it until after this call so it doesn't
  // have to be created twice.  If src_rect is null, then the entirety of the
  // source device will be copied.
  virtual void DrawToNativeContext(PlatformSurface surface, int x, int y,
                                   const PlatformRect* src_rect) = 0;

  // Returns if GDI is allowed to render text to this device.
  virtual bool IsNativeFontRenderingAllowed();

  // True if AlphaBlend() was called during a
  // BeginPlatformPaint()/EndPlatformPaint() pair.
  // Used by the printing subclasses.  See |VectorPlatformDeviceEmf|.
  virtual bool AlphaBlendUsed() const;

#if defined(OS_WIN)
  // Loads a SkPath into the GDI context. The path can there after be used for
  // clipping or as a stroke. Returns false if the path failed to be loaded.
  static bool LoadPathToDC(HDC context, const SkPath& path);

  // Loads a SkRegion into the GDI context.
  static void LoadClippingRegionToDC(HDC context, const SkRegion& region,
                                     const SkMatrix& transformation);
#elif defined(OS_MACOSX)
  // Loads a SkPath into the CG context. The path can there after be used for
  // clipping or as a stroke.
  static void LoadPathToCGContext(CGContextRef context, const SkPath& path);

  // Initializes the default settings and colors in a device context.
  static void InitializeCGContext(CGContextRef context);

  // Loads a SkRegion into the CG context.
  static void LoadClippingRegionToCGContext(CGContextRef context,
                                            const SkRegion& region,
                                            const SkMatrix& transformation);
#endif

 protected:
#if defined(OS_WIN)
  // Arrays must be inside structures.
  struct CubicPoints {
    SkPoint p[4];
  };
  typedef std::vector<CubicPoints> CubicPath;
  typedef std::vector<CubicPath> CubicPaths;

  // Loads the specified Skia transform into the device context, excluding
  // perspective (which GDI doesn't support).
  static void LoadTransformToDC(HDC dc, const SkMatrix& matrix);

  // Transforms SkPath's paths into a series of cubic path.
  static bool SkPathToCubicPaths(CubicPaths* paths, const SkPath& skpath);
#elif defined(OS_MACOSX)
  // Loads the specified Skia transform into the device context
  static void LoadTransformToCGContext(CGContextRef context,
                                       const SkMatrix& matrix);
#endif
};

}  // namespace skia

#endif