Limit manual control of platform painting

Platform painting should be through skia::ScopedPlatformPaint.
(Only one compositor callsite was calling Begin/End directly.)

Remove skia::EndPlatformPaint() and all device-specific implementations,
which were effectively noops.

Remove skia::BeginPlatformPaint(), and make all device-specific impls
protected.

BUG=598695
R=fmalita@chromium.org
TBR=danakj@chromium.org

Review URL: https://codereview.chromium.org/1839113002

Cr-Commit-Position: refs/heads/master@{#383820}

content/browser/compositor/software_output_device_win.cc

@@ -180,10 +180,10 @@ void SoftwareOutputDeviceWin::EndPaint() {
     style |= WS_EX_LAYERED;
     SetWindowLong(hwnd_, GWL_EXSTYLE, style);
 
-    HDC dib_dc = skia::BeginPlatformPaint(contents_.get());
+    skia::ScopedPlatformPaint spp(contents_.get());
+    HDC dib_dc = spp.GetPlatformSurface();
     ::UpdateLayeredWindow(hwnd_, NULL, &position, &size, dib_dc, &zero,
                           RGB(0xFF, 0xFF, 0xFF), &blend, ULW_ALPHA);
-    skia::EndPlatformPaint(contents_.get());
   } else {
     HDC hdc = ::GetDC(hwnd_);
     RECT src_rect = rect.ToRECT();

skia/ext/bitmap_platform_device_cairo.h

@@ -46,6 +46,8 @@ typedef struct _cairo_surface cairo_surface_t;
 
 namespace skia {
 
+class ScopedPlatformPaint;
+
 // -----------------------------------------------------------------------------
 // This is the Linux bitmap backing for Skia. We create a Cairo image surface
 // to store the backing buffer. This buffer is BGRA in memory (on little-endian
@@ -84,13 +86,13 @@ class BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice {
                      const SkRegion& region,
                      const SkClipStack&) override;
 
-  // Overridden from PlatformDevice:
-  cairo_t* BeginPlatformPaint() override;
-
  protected:
   SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;
 
  private:
+  // Overridden from PlatformDevice:
+  cairo_t* BeginPlatformPaint() override;
+
   static BitmapPlatformDevice* Create(int width, int height, bool is_opaque,
                                       cairo_surface_t* surface);
 
@@ -119,6 +121,7 @@ class BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice {
   SkRegion clip_region_;
 
   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
+  friend class ScopedPlatformPaint;
 };
 
 }  // namespace skia

skia/ext/bitmap_platform_device_skia.h

@@ -14,6 +14,8 @@
 
 namespace skia {
 
+class ScopedPlatformPaint;
+
 // -----------------------------------------------------------------------------
 // For now we just use SkBitmap for SkBitmapDevice
 //
@@ -40,13 +42,15 @@ class BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice {
   explicit BitmapPlatformDevice(const SkBitmap& other);
   ~BitmapPlatformDevice() override;
 
-  PlatformSurface BeginPlatformPaint() override;
-
  protected:
   SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;
 
  private:
+  PlatformSurface BeginPlatformPaint() override;
+
   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
+
+  friend class ScopedPlatformPaint;
 };
 
 }  // namespace skia

skia/ext/bitmap_platform_device_win.cc

@@ -200,7 +200,6 @@ BitmapPlatformDevice::BitmapPlatformDevice(
       config_dirty_(true),  // Want to load the config next time.
       transform_(SkMatrix::I()) {
   // The data object is already ref'ed for us by create().
-  SkDEBUGCODE(begin_paint_count_ = 0);
   if (hbitmap) {
     SetPlatformDevice(this, this);
     // Initialize the clip region to the entire bitmap.
@@ -214,21 +213,14 @@ BitmapPlatformDevice::BitmapPlatformDevice(
 }
 
 BitmapPlatformDevice::~BitmapPlatformDevice() {
-  SkASSERT(begin_paint_count_ == 0);
   if (hdc_)
     ReleaseBitmapDC();
 }
 
 HDC BitmapPlatformDevice::BeginPlatformPaint() {
-  SkDEBUGCODE(begin_paint_count_++);
   return GetBitmapDC();
 }
 
-void BitmapPlatformDevice::EndPlatformPaint() {
-  SkASSERT(begin_paint_count_--);
-  PlatformDevice::EndPlatformPaint();
-}
-
 void BitmapPlatformDevice::setMatrixClip(const SkMatrix& transform,
                                          const SkRegion& region,
                                          const SkClipStack&) {
@@ -285,7 +277,6 @@ void BitmapPlatformDevice::DrawToHDC(HDC dc, int x, int y,
   }
   LoadTransformToDC(source_dc, transform_);
 
-  EndPlatformPaint();
   if (created_dc)
     ReleaseBitmapDC();
 }

skia/ext/bitmap_platform_device_win.h

@@ -12,6 +12,8 @@
 
 namespace skia {
 
+class ScopedPlatformPaint;
+
 // A device is basically a wrapper around SkBitmap that provides a surface for
 // SkCanvas to draw into. Our device provides a surface Windows can also write
 // to. BitmapPlatformDevice creates a bitmap using CreateDIBSection() in a
@@ -38,14 +40,8 @@ class SK_API BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice
 
   ~BitmapPlatformDevice() override;
 
-  // PlatformDevice overrides
-  // Retrieves the bitmap DC, which is the memory DC for our bitmap data. The
-  // bitmap DC is lazy created.
-  PlatformSurface BeginPlatformPaint() override;
-  void EndPlatformPaint() override;
-
-  // Loads the given transform and clipping region into the HDC. This is
-  // overridden from SkBaseDevice.
+  // Loads (lazily) the given transform and clipping region into the HDC. This
+  // is overridden from SkBaseDevice, where it is deprecated.
   void setMatrixClip(const SkMatrix& transform,
                      const SkRegion& region,
                      const SkClipStack&) override;
@@ -61,6 +57,11 @@ class SK_API BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice
   SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;
 
  private:
+  // PlatformDevice override
+  // Retrieves the bitmap DC, which is the memory DC for our bitmap data. The
+  // bitmap DC may be lazily created.
+  PlatformSurface BeginPlatformPaint() override;
+
   // Private constructor.
   BitmapPlatformDevice(HBITMAP hbitmap, const SkBitmap& bitmap);
 
@@ -103,11 +104,8 @@ class SK_API BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice
   // when |hbitmap_| is NULL (will be a NOP).
   void LoadConfig();
 
-#ifdef SK_DEBUG
-  int begin_paint_count_;
-#endif
-
   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
+  friend class ScopedPlatformPaint;
 };
 
 }  // namespace skia

skia/ext/platform_canvas.cc

@@ -65,20 +65,6 @@ bool SupportsPlatformPaint(const SkCanvas* canvas) {
   return GetPlatformDevice(GetTopDevice(*canvas)) != nullptr;
 }
 
-PlatformSurface BeginPlatformPaint(SkCanvas* canvas) {
-  PlatformDevice* platform_device = GetPlatformDevice(GetTopDevice(*canvas));
-  if (platform_device)
-    return platform_device->BeginPlatformPaint();
-
-  return 0;
-}
-
-void EndPlatformPaint(SkCanvas* canvas) {
-  PlatformDevice* platform_device = GetPlatformDevice(GetTopDevice(*canvas));
-  if (platform_device)
-    platform_device->EndPlatformPaint();
-}
-
 size_t PlatformCanvasStrideForWidth(unsigned width) {
   return 4 * width;
 }
@@ -116,5 +102,12 @@ CGContextRef GetBitmapContext(const SkCanvas& canvas) {
 
 #endif
 
+ScopedPlatformPaint::ScopedPlatformPaint(SkCanvas* canvas) :
+    canvas_(canvas),
+    platform_surface_(nullptr) {
+  PlatformDevice* platform_device = GetPlatformDevice(GetTopDevice(*canvas));
+  if (platform_device)
+    platform_surface_ = platform_device->BeginPlatformPaint();
+}
 
 }  // namespace skia

skia/ext/platform_canvas.h

@@ -145,27 +145,16 @@ SK_API bool GetWritablePixels(SkCanvas* canvas, SkPixmap* pixmap);
 // return NULL PlatformSurface.
 SK_API bool SupportsPlatformPaint(const SkCanvas* canvas);
 
-// These calls should surround calls to platform drawing routines, the
-// surface returned here can be used with the native platform routines.
-//
-// Call EndPlatformPaint when you are done and want to use skia operations
-// after calling the platform-specific BeginPlatformPaint; this will
-// synchronize the bitmap to OS if necessary.
-SK_API PlatformSurface BeginPlatformPaint(SkCanvas* canvas);
-SK_API void EndPlatformPaint(SkCanvas* canvas);
-
-// Helper class for pairing calls to BeginPlatformPaint and EndPlatformPaint.
-// Upon construction invokes BeginPlatformPaint, and upon destruction invokes
-// EndPlatformPaint.
+// This object guards calls to platform drawing routines. The surface
+// returned from GetPlatformSurface() can be used with the native platform
+// routines.
 class SK_API ScopedPlatformPaint {
  public:
-  explicit ScopedPlatformPaint(SkCanvas* canvas) : canvas_(canvas) {
-    platform_surface_ = BeginPlatformPaint(canvas);
-  }
-  ~ScopedPlatformPaint() { EndPlatformPaint(canvas_); }
+  explicit ScopedPlatformPaint(SkCanvas* canvas);
 
   // Returns the PlatformSurface to use for native platform drawing calls.
   PlatformSurface GetPlatformSurface() { return platform_surface_; }
+
  private:
   SkCanvas* canvas_;
   PlatformSurface platform_surface_;

skia/ext/platform_device.h

@@ -23,6 +23,7 @@ class SkRegion;
 namespace skia {
 
 class PlatformDevice;
+class ScopedPlatformPaint;
 
 // The following routines provide accessor points for the functionality
 // exported by the various PlatformDevice ports.  
@@ -61,14 +62,6 @@ class SK_API PlatformDevice {
   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();
-
 #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.
@@ -87,6 +80,7 @@ class SK_API PlatformDevice {
 #endif
 
  protected:
+
 #if defined(OS_WIN)
   // Arrays must be inside structures.
   struct CubicPoints {
@@ -102,6 +96,14 @@ class SK_API PlatformDevice {
   // Transforms SkPath's paths into a series of cubic path.
   static bool SkPathToCubicPaths(CubicPaths* paths, const SkPath& skpath);
 #endif
+
+ private:
+  // 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();
+
+  friend class ScopedPlatformPaint;
 };
 
 }  // namespace skia

skia/ext/platform_device_linux.cc

@@ -10,8 +10,4 @@ PlatformSurface PlatformDevice::BeginPlatformPaint() {
   return NULL;
 }
 
-void PlatformDevice::EndPlatformPaint() {
-  // We don't need to do anything on Linux here.
-}
-
 }  // namespace skia

skia/ext/platform_device_mac.cc

@@ -10,8 +10,4 @@ CGContextRef PlatformDevice::BeginPlatformPaint() {
   return GetBitmapContext();
 }
 
-void PlatformDevice::EndPlatformPaint() {
-  // Flushing will be done in onAccessBitmap.
-}
-
 }  // namespace skia

skia/ext/platform_device_win.cc

@@ -15,11 +15,6 @@ PlatformSurface PlatformDevice::BeginPlatformPaint() {
   return 0;
 }
 
-void PlatformDevice::EndPlatformPaint() {
-  // We don't clear the DC here since it will be likely to be used again.
-  // Flushing will be done in onAccessBitmap.
-}
-
 // static
 bool PlatformDevice::LoadPathToDC(HDC context, const SkPath& path) {
   switch (path.getFillType()) {