skia/ext/bitmap_platform_device_win.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef SKIA_EXT_BITMAP_PLATFORM_DEVICE_WIN_H_
   6 #define SKIA_EXT_BITMAP_PLATFORM_DEVICE_WIN_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/compiler_specific.h"
  10 #include "skia/ext/platform_device.h"
  11 #include "skia/ext/refptr.h"
  12
  13 namespace skia {
  14
  15 // A device is basically a wrapper around SkBitmap that provides a surface for
  16 // SkCanvas to draw into. Our device provides a surface Windows can also write
  17 // to. BitmapPlatformDevice creates a bitmap using CreateDIBSection() in a
  18 // format that Skia supports and can then use this to draw ClearType into, etc.
  19 // This pixel data is provided to the bitmap that the device contains so that it
  20 // can be shared.
  21 //
  22 // The GDI bitmap created for drawing is actually owned by a
  23 // PlatformBitmapPixelRef, and stored in an SkBitmap via the normal skia
  24 // SkPixelRef refcounting mechanism. In this way, the GDI bitmap can outlive
  25 // the device created to draw into it. So it is safe to call accessBitmap() on
  26 // the device, and retain the returned SkBitmap.
  27 class SK_API BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice {
  28  public:
  29   // Factory function. is_opaque should be set if the caller knows the bitmap
  30   // will be completely opaque and allows some optimizations.
  31   //
  32   // The |shared_section| parameter is optional (pass NULL for default
  33   // behavior). If |shared_section| is non-null, then it must be a handle to a
  34   // file-mapping object returned by CreateFileMapping.  See CreateDIBSection
  35   // for details. If |shared_section| is null, the bitmap backing store is not
  36   // initialized.
  37   static BitmapPlatformDevice* Create(int width, int height,
  38                                       bool is_opaque, HANDLE shared_section);
  39
  40   // Create a BitmapPlatformDevice with no shared section. The bitmap is not
  41   // initialized to 0.
  42   static BitmapPlatformDevice* Create(int width, int height, bool is_opaque);
  43
  44   // Creates a BitmapPlatformDevice instance respecting the parameters as above.
  45   // If |is_opaque| is false, then the bitmap is initialzed to 0.
  46   static BitmapPlatformDevice* CreateAndClear(int width, int height,
  47                                               bool is_opaque);
  48
  49   virtual ~BitmapPlatformDevice();
  50
  51   // PlatformDevice overrides
  52   // Retrieves the bitmap DC, which is the memory DC for our bitmap data. The
  53   // bitmap DC is lazy created.
  54   virtual PlatformSurface BeginPlatformPaint() OVERRIDE;
  55   virtual void EndPlatformPaint() OVERRIDE;
  56
  57   virtual void DrawToNativeContext(HDC dc, int x, int y,
  58                                    const RECT* src_rect) OVERRIDE;
  59
  60   // Loads the given transform and clipping region into the HDC. This is
  61   // overridden from SkBaseDevice.
  62   virtual void setMatrixClip(const SkMatrix& transform, const SkRegion& region,
  63                              const SkClipStack&) OVERRIDE;
  64
  65  protected:
  66   // Flushes the Windows device context so that the pixel data can be accessed
  67   // directly by Skia. Overridden from SkBaseDevice, this is called when Skia
  68   // starts accessing pixel data.
  69   virtual const SkBitmap& onAccessBitmap() OVERRIDE;
  70
  71   virtual SkBaseDevice* onCreateDevice(const SkImageInfo& info,
  72                                        Usage usage) OVERRIDE;
  73
  74  private:
  75   // Private constructor.
  76   BitmapPlatformDevice(HBITMAP hbitmap, const SkBitmap& bitmap);
  77
  78   // Bitmap into which the drawing will be done. This bitmap not owned by this
  79   // class, but by the BitmapPlatformPixelRef inside the device's SkBitmap.
  80   // It's only stored here in order to lazy-create the DC (below).
  81   HBITMAP hbitmap_;
  82
  83   // Previous bitmap held by the DC. This will be selected back before the
  84   // DC is destroyed.
  85   HBITMAP old_hbitmap_;
  86
  87   // Lazily-created DC used to draw into the bitmap; see GetBitmapDC().
  88   HDC hdc_;
  89
  90   // True when there is a transform or clip that has not been set to the
  91   // context.  The context is retrieved for every text operation, and the
  92   // transform and clip do not change as much. We can save time by not loading
  93   // the clip and transform for every one.
  94   bool config_dirty_;
  95
  96   // Translation assigned to the context: we need to keep track of this
  97   // separately so it can be updated even if the context isn't created yet.
  98   SkMatrix transform_;
  99
 100   // The current clipping region.
 101   SkRegion clip_region_;
 102
 103   // Create/destroy hdc_, which is the memory DC for our bitmap data.
 104   HDC GetBitmapDC();
 105   void ReleaseBitmapDC();
 106   bool IsBitmapDCCreated() const;
 107
 108   // Sets the transform and clip operations. This will not update the DC,
 109   // but will mark the config as dirty. The next call of LoadConfig will
 110   // pick up these changes.
 111   void SetMatrixClip(const SkMatrix& transform, const SkRegion& region);
 112
 113   // Loads the current transform and clip into the context. Can be called even
 114   // when |hbitmap_| is NULL (will be a NOP).
 115   void LoadConfig();
 116
 117 #ifdef SK_DEBUG
 118   int begin_paint_count_;
 119 #endif
 120
 121   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
 122 };
 123
 124 }  // namespace skia
 125
 126 #endif  // SKIA_EXT_BITMAP_PLATFORM_DEVICE_WIN_H_