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                                       bool do_clear = false);
  40
  41   // Create a BitmapPlatformDevice with no shared section. The bitmap is not
  42   // initialized to 0.
  43   static BitmapPlatformDevice* Create(int width, int height, bool is_opaque);
  44
  45   virtual ~BitmapPlatformDevice();
  46
  47   // PlatformDevice overrides
  48   // Retrieves the bitmap DC, which is the memory DC for our bitmap data. The
  49   // bitmap DC is lazy created.
  50   virtual PlatformSurface BeginPlatformPaint() override;
  51   virtual void EndPlatformPaint() override;
  52
  53   // Loads the given transform and clipping region into the HDC. This is
  54   // overridden from SkBaseDevice.
  55   virtual void setMatrixClip(const SkMatrix& transform, const SkRegion& region,
  56                              const SkClipStack&) override;
  57
  58   void DrawToHDC(HDC dc, int x, int y, const RECT* src_rect) override;
  59
  60  protected:
  61   // Flushes the Windows device context so that the pixel data can be accessed
  62   // directly by Skia. Overridden from SkBaseDevice, this is called when Skia
  63   // starts accessing pixel data.
  64   virtual const SkBitmap& onAccessBitmap() override;
  65
  66   virtual SkBaseDevice* onCreateCompatibleDevice(const CreateInfo& info)
  67     override;
  68
  69  private:
  70   // Private constructor.
  71   BitmapPlatformDevice(HBITMAP hbitmap, const SkBitmap& bitmap);
  72
  73   // Bitmap into which the drawing will be done. This bitmap not owned by this
  74   // class, but by the BitmapPlatformPixelRef inside the device's SkBitmap.
  75   // It's only stored here in order to lazy-create the DC (below).
  76   HBITMAP hbitmap_;
  77
  78   // Previous bitmap held by the DC. This will be selected back before the
  79   // DC is destroyed.
  80   HBITMAP old_hbitmap_;
  81
  82   // Lazily-created DC used to draw into the bitmap; see GetBitmapDC().
  83   HDC hdc_;
  84
  85   // True when there is a transform or clip that has not been set to the
  86   // context.  The context is retrieved for every text operation, and the
  87   // transform and clip do not change as much. We can save time by not loading
  88   // the clip and transform for every one.
  89   bool config_dirty_;
  90
  91   // Translation assigned to the context: we need to keep track of this
  92   // separately so it can be updated even if the context isn't created yet.
  93   SkMatrix transform_;
  94
  95   // The current clipping region.
  96   SkRegion clip_region_;
  97
  98   // Create/destroy hdc_, which is the memory DC for our bitmap data.
  99   HDC GetBitmapDC();
 100   void ReleaseBitmapDC();
 101   bool IsBitmapDCCreated() const;
 102
 103   // Sets the transform and clip operations. This will not update the DC,
 104   // but will mark the config as dirty. The next call of LoadConfig will
 105   // pick up these changes.
 106   void SetMatrixClip(const SkMatrix& transform, const SkRegion& region);
 107
 108   // Loads the current transform and clip into the context. Can be called even
 109   // when |hbitmap_| is NULL (will be a NOP).
 110   void LoadConfig();
 111
 112 #ifdef SK_DEBUG
 113   int begin_paint_count_;
 114 #endif
 115
 116   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
 117 };
 118
 119 }  // namespace skia
 120
 121 #endif  // SKIA_EXT_BITMAP_PLATFORM_DEVICE_WIN_H_