skia/ext/platform_canvas.h

   1 // Copyright (c) 2011 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_PLATFORM_CANVAS_H_
   6 #define SKIA_EXT_PLATFORM_CANVAS_H_
   7
   8 // The platform-specific device will include the necessary platform headers
   9 // to get the surface type.
  10 #include "base/basictypes.h"
  11 #include "skia/ext/platform_device.h"
  12 #include "skia/ext/refptr.h"
  13 #include "third_party/skia/include/core/SkBitmap.h"
  14 #include "third_party/skia/include/core/SkCanvas.h"
  15 #include "third_party/skia/include/core/SkPixelRef.h"
  16
  17 namespace skia {
  18
  19 typedef SkCanvas PlatformCanvas;
  20
  21 //
  22 //  Note about error handling.
  23 //
  24 //  Creating a canvas can fail at times, most often because we fail to allocate
  25 //  the backing-store (pixels). This can be from out-of-memory, or something
  26 //  more opaque, like GDI or cairo reported a failure.
  27 //
  28 //  To allow the caller to handle the failure, every Create... factory takes an
  29 //  enum as its last parameter. The default value is kCrashOnFailure. If the
  30 //  caller passes kReturnNullOnFailure, then the caller is responsible to check
  31 //  the return result.
  32 //
  33 enum OnFailureType {
  34   CRASH_ON_FAILURE,
  35   RETURN_NULL_ON_FAILURE
  36 };
  37
  38 #if defined(WIN32)
  39   // The shared_section parameter is passed to gfx::PlatformDevice::create.
  40   // See it for details.
  41   SK_API SkCanvas* CreatePlatformCanvas(int width,
  42                                         int height,
  43                                         bool is_opaque,
  44                                         HANDLE shared_section,
  45                                         OnFailureType failure_type);
  46
  47   // Draws the top layer of the canvas into the specified HDC. Only works
  48   // with a PlatformCanvas with a BitmapPlatformDevice.
  49   SK_API void DrawToNativeContext(SkCanvas* canvas,
  50                                   HDC hdc,
  51                                   int x,
  52                                   int y,
  53                                   const RECT* src_rect);
  54 #elif defined(__APPLE__)
  55   SK_API SkCanvas* CreatePlatformCanvas(CGContextRef context,
  56                                         int width,
  57                                         int height,
  58                                         bool is_opaque,
  59                                         OnFailureType failure_type);
  60
  61   SK_API SkCanvas* CreatePlatformCanvas(int width,
  62                                         int height,
  63                                         bool is_opaque,
  64                                         uint8_t* context,
  65                                         OnFailureType failure_type);
  66 #elif defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || \
  67       defined(__sun) || defined(ANDROID)
  68   // Linux ---------------------------------------------------------------------
  69
  70   // Construct a canvas from the given memory region. The memory is not cleared
  71   // first. @data must be, at least, @height * StrideForWidth(@width) bytes.
  72   SK_API SkCanvas* CreatePlatformCanvas(int width,
  73                                         int height,
  74                                         bool is_opaque,
  75                                         uint8_t* data,
  76                                         OnFailureType failure_type);
  77 #endif
  78
  79 static inline SkCanvas* CreatePlatformCanvas(int width,
  80                                              int height,
  81                                              bool is_opaque) {
  82   return CreatePlatformCanvas(width, height, is_opaque, 0, CRASH_ON_FAILURE);
  83 }
  84
  85 SK_API SkCanvas* CreateCanvas(const skia::RefPtr<SkBaseDevice>& device,
  86                               OnFailureType failure_type);
  87
  88 static inline SkCanvas* CreateBitmapCanvas(int width,
  89                                            int height,
  90                                            bool is_opaque) {
  91   return CreatePlatformCanvas(width, height, is_opaque, 0, CRASH_ON_FAILURE);
  92 }
  93
  94 static inline SkCanvas* TryCreateBitmapCanvas(int width,
  95                                               int height,
  96                                               bool is_opaque) {
  97   return CreatePlatformCanvas(width, height, is_opaque, 0,
  98                               RETURN_NULL_ON_FAILURE);
  99 }
 100
 101 // Return the stride (length of a line in bytes) for the given width. Because
 102 // we use 32-bits per pixel, this will be roughly 4*width. However, for
 103 // alignment reasons we may wish to increase that.
 104 SK_API size_t PlatformCanvasStrideForWidth(unsigned width);
 105
 106 // Returns the SkBaseDevice pointer of the topmost rect with a non-empty
 107 // clip. In practice, this is usually either the top layer or nothing, since
 108 // we usually set the clip to new layers when we make them.
 109 //
 110 // This may return NULL, so callers need to check.
 111 //
 112 // This is different than SkCanvas' getDevice, because that returns the
 113 // bottommost device.
 114 //
 115 // Danger: the resulting device should not be saved. It will be invalidated
 116 // by the next call to save() or restore().
 117 SK_API SkBaseDevice* GetTopDevice(const SkCanvas& canvas);
 118
 119 // Returns true if native platform routines can be used to draw on the
 120 // given canvas. If this function returns false, BeginPlatformPaint will
 121 // return NULL PlatformSurface.
 122 SK_API bool SupportsPlatformPaint(const SkCanvas* canvas);
 123
 124 // Sets the opacity of each pixel in the specified region to be opaque.
 125 SK_API void MakeOpaque(SkCanvas* canvas, int x, int y, int width, int height);
 126
 127 // These calls should surround calls to platform drawing routines, the
 128 // surface returned here can be used with the native platform routines.
 129 //
 130 // Call EndPlatformPaint when you are done and want to use skia operations
 131 // after calling the platform-specific BeginPlatformPaint; this will
 132 // synchronize the bitmap to OS if necessary.
 133 SK_API PlatformSurface BeginPlatformPaint(SkCanvas* canvas);
 134 SK_API void EndPlatformPaint(SkCanvas* canvas);
 135
 136 // Helper class for pairing calls to BeginPlatformPaint and EndPlatformPaint.
 137 // Upon construction invokes BeginPlatformPaint, and upon destruction invokes
 138 // EndPlatformPaint.
 139 class SK_API ScopedPlatformPaint {
 140  public:
 141   explicit ScopedPlatformPaint(SkCanvas* canvas) : canvas_(canvas) {
 142     platform_surface_ = BeginPlatformPaint(canvas);
 143   }
 144   ~ScopedPlatformPaint() { EndPlatformPaint(canvas_); }
 145
 146   // Returns the PlatformSurface to use for native platform drawing calls.
 147   PlatformSurface GetPlatformSurface() { return platform_surface_; }
 148  private:
 149   SkCanvas* canvas_;
 150   PlatformSurface platform_surface_;
 151
 152   // Disallow copy and assign
 153   ScopedPlatformPaint(const ScopedPlatformPaint&);
 154   ScopedPlatformPaint& operator=(const ScopedPlatformPaint&);
 155 };
 156
 157 // PlatformBitmap holds a PlatformSurface that can also be used as an SkBitmap.
 158 class SK_API PlatformBitmap {
 159  public:
 160   PlatformBitmap();
 161   ~PlatformBitmap();
 162
 163   // Returns true if the bitmap was able to allocate its surface.
 164   bool Allocate(int width, int height, bool is_opaque);
 165
 166   // Returns the platform surface, or 0 if Allocate() did not return true.
 167   PlatformSurface GetSurface() { return surface_; }
 168
 169   // Return the skia bitmap, which will be empty if Allocate() did not
 170   // return true.
 171   //
 172   // The resulting SkBitmap holds a refcount on the underlying platform surface,
 173   // so the surface will remain allocated so long as the SkBitmap or its copies
 174   // stay around.
 175   const SkBitmap& GetBitmap() { return bitmap_; }
 176
 177  private:
 178   SkBitmap bitmap_;
 179   PlatformSurface surface_;  // initialized to 0
 180   intptr_t platform_extra_;  // platform specific, initialized to 0
 181
 182   DISALLOW_COPY_AND_ASSIGN(PlatformBitmap);
 183 };
 184
 185 }  // namespace skia
 186
 187 #endif  // SKIA_EXT_PLATFORM_CANVAS_H_