CL removing inheritance of SkDevice from PlatformDevice. Flavours of PlatformDevice classes now ...

skia/ext/platform_device.h

Index: skia/ext/platform_device.h
===================================================================
--- skia/ext/platform_device.h	(revision 97852)
+++ skia/ext/platform_device.h	(working copy)
@@ -6,24 +6,27 @@
 #define SKIA_EXT_PLATFORM_DEVICE_H_
 #pragma once
 
-// This file provides an easy way to include the appropriate PlatformDevice
-// header file for your platform.
+#include "build/build_config.h"
 
-#if defined(WIN32)
+#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 SkPath;
+class SkRegion;
 
-class SkDevice;
 struct SkIRect;
 
-#if defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__sun)
+#if defined(OS_LINUX)
 typedef struct _cairo cairo_t;
 typedef struct _cairo_rectangle cairo_rectangle_t;
-#elif defined(__APPLE__)
+#elif defined(OS_MACOSX)
 typedef struct CGContext* CGContextRef;
 typedef struct CGRect CGRect;
 #endif
@@ -32,13 +35,13 @@
 
 class PlatformDevice;
 
-#if defined(WIN32)
+#if defined(OS_WIN)
 typedef HDC PlatformSurface;
 typedef RECT PlatformRect;
-#elif defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__sun)
+#elif defined(OS_LINUX)
 typedef cairo_t* PlatformSurface;
 typedef cairo_rectangle_t PlatformRect;
-#elif defined(__APPLE__)
+#elif defined(OS_MACOSX)
 typedef CGContextRef PlatformSurface;
 typedef CGRect PlatformRect;
 #endif
@@ -59,15 +62,114 @@
                               PlatformDevice* platform_device);
 SK_API PlatformDevice* GetPlatformDevice(SkDevice* device);
 
-}  // namespace skia
 
-#if defined(WIN32)
-#include "skia/ext/platform_device_win.h"
-#elif defined(__APPLE__)
-#include "skia/ext/platform_device_mac.h"
-#elif defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || \
-      defined(__sun)
-#include "skia/ext/platform_device_linux.h"
+#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
 
+// 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 {

[alokp, 2011/08/24 17:03:02]

This is OK for now. Medium term I would like to get rid of this hierarchy.
PlatformDevice should be replaced by a set of helper functions.

[Jeff Timanus, 2011/08/24 22:09:58]

This change is a good step in that direction.

I'm wondering if I'm being thick-headed, but if all of these routines were
helper functions, taking a SkDevice as an argument, wouldn't we have to roll our
own type-inference?

A struct that contains the union of all of the fields used by all of the
different types of platform device implementations could be created, and stashed
in the devices meta-data.  However, for any of the calls, we would have to
switch on the type of device being serviced to take the appropriate action.

Isn't having a class heirarchy cleaner than switching on the type of class?

+ public:
+#if defined(OS_WIN)
+  typedef HDC PlatformSurface;

[alokp, 2011/08/24 17:03:02]

definition of PlatformSurface is duplicated here.

[Jeff Timanus, 2011/08/24 22:09:58]

Done.

+#elif defined(OS_MACOSX)
+  typedef CGContextRef PlatformSurface;
+#elif defined(OS_LINUX)

[vandebo (ex-Chrome), 2011/08/23 21:16:43]

There are OS_ defines for the BSD's and Sun, if you feel like adding them.

[Jeff Timanus, 2011/08/24 22:09:58]

Done.

+  typedef cairo_t* PlatformSurface;
 #endif
+
+  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;
+
+  // Sets the opacity of each pixel in the specified region to be opaque.
+  virtual void MakeOpaque(int x, int y, int width, int height) { }
+
+  // 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