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 #elif defined(__APPLE__)
  47   SK_API SkCanvas* CreatePlatformCanvas(CGContextRef context,
  48                                         int width,
  49                                         int height,
  50                                         bool is_opaque,
  51                                         OnFailureType failure_type);
  52
  53   SK_API SkCanvas* CreatePlatformCanvas(int width,
  54                                         int height,
  55                                         bool is_opaque,
  56                                         uint8_t* context,
  57                                         OnFailureType failure_type);
  58 #elif defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || \
  59       defined(__sun) || defined(ANDROID)
  60   // Linux ---------------------------------------------------------------------
  61
  62   // Construct a canvas from the given memory region. The memory is not cleared
  63   // first. @data must be, at least, @height * StrideForWidth(@width) bytes.
  64   SK_API SkCanvas* CreatePlatformCanvas(int width,
  65                                         int height,
  66                                         bool is_opaque,
  67                                         uint8_t* data,
  68                                         OnFailureType failure_type);
  69 #endif
  70
  71 static inline SkCanvas* CreatePlatformCanvas(int width,
  72                                              int height,
  73                                              bool is_opaque) {
  74   return CreatePlatformCanvas(width, height, is_opaque, 0, CRASH_ON_FAILURE);
  75 }
  76
  77 SK_API SkCanvas* CreateCanvas(const skia::RefPtr<SkDevice>& device,
  78                               OnFailureType failure_type);
  79
  80 static inline SkCanvas* CreateBitmapCanvas(int width,
  81                                            int height,
  82                                            bool is_opaque) {
  83   return CreatePlatformCanvas(width, height, is_opaque, 0, CRASH_ON_FAILURE);
  84 }
  85
  86 static inline SkCanvas* TryCreateBitmapCanvas(int width,
  87                                               int height,
  88                                               bool is_opaque) {
  89   return CreatePlatformCanvas(width, height, is_opaque, 0,
  90                               RETURN_NULL_ON_FAILURE);
  91 }
  92
  93 // Return the stride (length of a line in bytes) for the given width. Because
  94 // we use 32-bits per pixel, this will be roughly 4*width. However, for
  95 // alignment reasons we may wish to increase that.
  96 SK_API size_t PlatformCanvasStrideForWidth(unsigned width);
  97
  98 // Returns the SkDevice pointer of the topmost rect with a non-empty
  99 // clip. In practice, this is usually either the top layer or nothing, since
 100 // we usually set the clip to new layers when we make them.
 101 //
 102 // If there is no layer that is not all clipped out, this will return a
 103 // dummy device so callers do not have to check. If you are concerned about
 104 // performance, check the clip before doing any painting.
 105 //
 106 // This is different than SkCanvas' getDevice, because that returns the
 107 // bottommost device.
 108 //
 109 // Danger: the resulting device should not be saved. It will be invalidated
 110 // by the next call to save() or restore().
 111 SK_API SkDevice* GetTopDevice(const SkCanvas& canvas);
 112
 113 // Returns true if native platform routines can be used to draw on the
 114 // given canvas. If this function returns false, BeginPlatformPaint will
 115 // return NULL PlatformSurface.
 116 SK_API bool SupportsPlatformPaint(const SkCanvas* canvas);
 117
 118 // Draws into the a native platform surface, |context|.  Forwards to
 119 // DrawToNativeContext on a PlatformDevice instance bound to the top device.
 120 // If no PlatformDevice instance is bound, is a no-operation.
 121 SK_API void DrawToNativeContext(SkCanvas* canvas,
 122                                 PlatformSurface context,
 123                                 int x,
 124                                 int y,
 125                                 const PlatformRect* src_rect);
 126
 127 // Sets the opacity of each pixel in the specified region to be opaque.
 128 SK_API void MakeOpaque(SkCanvas* canvas, int x, int y, int width, int height);
 129
 130 // These calls should surround calls to platform drawing routines, the
 131 // surface returned here can be used with the native platform routines.
 132 //
 133 // Call EndPlatformPaint when you are done and want to use skia operations
 134 // after calling the platform-specific BeginPlatformPaint; this will
 135 // synchronize the bitmap to OS if necessary.
 136 SK_API PlatformSurface BeginPlatformPaint(SkCanvas* canvas);
 137 SK_API void EndPlatformPaint(SkCanvas* canvas);
 138
 139 // Helper class for pairing calls to BeginPlatformPaint and EndPlatformPaint.
 140 // Upon construction invokes BeginPlatformPaint, and upon destruction invokes
 141 // EndPlatformPaint.
 142 class SK_API ScopedPlatformPaint {
 143  public:
 144   explicit ScopedPlatformPaint(SkCanvas* canvas) : canvas_(canvas) {
 145     platform_surface_ = BeginPlatformPaint(canvas);
 146   }
 147   ~ScopedPlatformPaint() { EndPlatformPaint(canvas_); }
 148
 149   // Returns the PlatformSurface to use for native platform drawing calls.
 150   PlatformSurface GetPlatformSurface() { return platform_surface_; }
 151  private:
 152   SkCanvas* canvas_;
 153   PlatformSurface platform_surface_;
 154
 155   // Disallow copy and assign
 156   ScopedPlatformPaint(const ScopedPlatformPaint&);
 157   ScopedPlatformPaint& operator=(const ScopedPlatformPaint&);
 158 };
 159
 160 // PlatformBitmap holds a PlatformSurface that can also be used as an SkBitmap.
 161 class SK_API PlatformBitmap {
 162  public:
 163   PlatformBitmap();
 164   ~PlatformBitmap();
 165
 166   // Returns true if the bitmap was able to allocate its surface.
 167   bool Allocate(int width, int height, bool is_opaque);
 168
 169   // Returns the platform surface, or 0 if Allocate() did not return true.
 170   PlatformSurface GetSurface() { return surface_; }
 171
 172   // Return the skia bitmap, which will be empty if Allocate() did not
 173   // return true.
 174   //
 175   // The resulting SkBitmap holds a refcount on the underlying platform surface,
 176   // so the surface will remain allocated so long as the SkBitmap or its copies
 177   // stay around.
 178   const SkBitmap& GetBitmap() { return bitmap_; }
 179
 180  private:
 181   SkBitmap bitmap_;
 182   PlatformSurface surface_;  // initialized to 0
 183   intptr_t platform_extra_;  // platform specific, initialized to 0
 184
 185   DISALLOW_COPY_AND_ASSIGN(PlatformBitmap);
 186 };
 187
 188 }  // namespace skia
 189
 190 #endif  // SKIA_EXT_PLATFORM_CANVAS_H_