Allow the creation of a skia::PlatformCanvas from a CGContextRef.

webkit/glue/webmediaplayer_impl.cc

Index: webkit/glue/webmediaplayer_impl.cc
diff --git a/webkit/glue/webmediaplayer_impl.cc b/webkit/glue/webmediaplayer_impl.cc
index 4a64b0f71b693404e74fc461ca840a4725767f47..ff0160f8cb326b94ef439cb6e562e99bc9eae69b 100644
--- a/webkit/glue/webmediaplayer_impl.cc
+++ b/webkit/glue/webmediaplayer_impl.cc
@@ -563,55 +563,80 @@ void WebMediaPlayerImpl::paint(WebCanvas* canvas,
 #if WEBKIT_USING_SKIA
   proxy_->Paint(canvas, rect);
 #elif WEBKIT_USING_CG
-  // Get the current scaling in X and Y.
-  CGAffineTransform mat = CGContextGetCTM(canvas);
-  float scale_x = sqrt(mat.a * mat.a + mat.b * mat.b);
-  float scale_y = sqrt(mat.c * mat.c + mat.d * mat.d);
-  float inverse_scale_x = SkScalarNearlyZero(scale_x) ? 0.0f : 1.0f / scale_x;
-  float inverse_scale_y = SkScalarNearlyZero(scale_y) ? 0.0f : 1.0f / scale_y;
-  int scaled_width = static_cast<int>(rect.width * fabs(scale_x));
-  int scaled_height = static_cast<int>(rect.height * fabs(scale_y));
-
-  // Make sure we don't create a huge canvas.
-  // TODO(hclam): Respect the aspect ratio.
-  if (scaled_width > static_cast<int>(media::Limits::kMaxCanvas))
-    scaled_width = media::Limits::kMaxCanvas;
-  if (scaled_height > static_cast<int>(media::Limits::kMaxCanvas))
-    scaled_height = media::Limits::kMaxCanvas;
-
-  // If there is no preexisting platform canvas, or if the size has
-  // changed, recreate the canvas.  This is to avoid recreating the bitmap
-  // buffer over and over for each frame of video.
-  if (!skia_canvas_.get() ||
-      skia_canvas_->getDevice()->width() != scaled_width ||
-      skia_canvas_->getDevice()->height() != scaled_height) {
-    skia_canvas_.reset(
-        new skia::PlatformCanvas(scaled_width, scaled_height, true));
-  }
+  if (CGBitmapContextGetData(canvas)) {
+    int width = CGBitmapContextGetWidth(canvas);
+    int height = CGBitmapContextGetHeight(canvas);
+    DCHECK(width != 0 && height != 0);
+    skia::PlatformCanvas skia_canvas(width, height, true, canvas);
+
+    // Copy the transformation matrix from the context.
+    CGAffineTransform cgMat = CGContextGetCTM(canvas);
+    SkMatrix skMat;
+    skMat.reset();
+    skMat[SkMatrix::kMScaleX] = cgMat.a;
+    skMat[SkMatrix::kMScaleY] = -cgMat.d;
+    skMat[SkMatrix::kMSkewX] = cgMat.b;
+    skMat[SkMatrix::kMSkewY] = -cgMat.c;
+    skMat[SkMatrix::kMTransX] = cgMat.tx;
+    skMat[SkMatrix::kMTransY] = height - cgMat.ty;
+    skia_canvas.setMatrix(skMat);
+
+    proxy_->Paint(&skia_canvas, rect);
+  } else {
+    // No bitmap context available, so we need to proxy via a bitmap.
+    // TODO(sjl): Can this ever happen?

[brettw, 2010/12/29 21:03:52]

I was wondering the same thing as this todo says. Looking quickly at the
documentation, it's my (possibly incorrect) understanding that this will happen
if the context is created in a way where the storage is unspecified. Is that
your understanding as well?

If we never hit this, I think it would be better to assert instead of keeping
this (kind of a lot of) code around, which may have bugs and will bitrot.

[sjl, 2010/12/31 05:55:49]

That's my understanding too.
Good idea. Done.

+
+    // Get the current scaling in X and Y.
+    CGAffineTransform mat = CGContextGetCTM(canvas);
+    float scale_x = sqrt(mat.a * mat.a + mat.b * mat.b);
+    float scale_y = sqrt(mat.c * mat.c + mat.d * mat.d);
+    float inverse_scale_x = SkScalarNearlyZero(scale_x) ? 0.0f : 1.0f / scale_x;
+    float inverse_scale_y = SkScalarNearlyZero(scale_y) ? 0.0f : 1.0f / scale_y;
+    int scaled_width = static_cast<int>(rect.width * fabs(scale_x));
+    int scaled_height = static_cast<int>(rect.height * fabs(scale_y));
+
+    // Make sure we don't create a huge canvas.
+    // TODO(hclam): Respect the aspect ratio.
+    if (scaled_width > static_cast<int>(media::Limits::kMaxCanvas))
+      scaled_width = media::Limits::kMaxCanvas;
+    if (scaled_height > static_cast<int>(media::Limits::kMaxCanvas))
+      scaled_height = media::Limits::kMaxCanvas;
+
+    // If there is no preexisting platform canvas, or if the size has
+    // changed, recreate the canvas.  This is to avoid recreating the bitmap
+    // buffer over and over for each frame of video.
+    if (!skia_canvas_.get() ||
+        skia_canvas_->getDevice()->width() != scaled_width ||
+        skia_canvas_->getDevice()->height() != scaled_height) {
+      skia_canvas_.reset(
+          new skia::PlatformCanvas(scaled_width, scaled_height, true));
+    }
+
+    // Draw to our temporary skia canvas.
+    gfx::Rect normalized_rect(scaled_width, scaled_height);
+    proxy_->Paint(skia_canvas_.get(), normalized_rect);
+
+    // The mac coordinate system is flipped vertical from the normal skia
+    // coordinates.  During painting of the frame, flip the coordinates
+    // system and, for simplicity, also translate the clip rectangle to
+    // start at 0,0.
+    CGContextSaveGState(canvas);
+    CGContextTranslateCTM(canvas, rect.x, rect.height + rect.y);
+    CGContextScaleCTM(canvas, inverse_scale_x, -inverse_scale_y);
 
-  // Draw to our temporary skia canvas.
-  gfx::Rect normalized_rect(scaled_width, scaled_height);
-  proxy_->Paint(skia_canvas_.get(), normalized_rect);
-
-  // The mac coordinate system is flipped vertical from the normal skia
-  // coordinates.  During painting of the frame, flip the coordinates
-  // system and, for simplicity, also translate the clip rectangle to
-  // start at 0,0.
-  CGContextSaveGState(canvas);
-  CGContextTranslateCTM(canvas, rect.x, rect.height + rect.y);
-  CGContextScaleCTM(canvas, inverse_scale_x, -inverse_scale_y);
-
-  // We need a local variable CGRect version for DrawToContext.
-  CGRect normalized_cgrect =
-      CGRectMake(normalized_rect.x(), normalized_rect.y(),
-                 normalized_rect.width(), normalized_rect.height());
-
-  // Copy the frame rendered to our temporary skia canvas onto the passed in
-  // canvas.
-  skia_canvas_->getTopPlatformDevice().DrawToContext(canvas, 0, 0,
-                                                     &normalized_cgrect);
-
-  CGContextRestoreGState(canvas);
+    // We need a local variable CGRect version for DrawToContext.
+    CGRect normalized_cgrect =
+        CGRectMake(normalized_rect.x(), normalized_rect.y(),
+                   normalized_rect.width(), normalized_rect.height());
+
+    // Copy the frame rendered to our temporary skia canvas onto the passed in
+    // canvas.
+
+    skia_canvas_->getTopPlatformDevice().DrawToContext(canvas, 0, 0,
+                                                       &normalized_cgrect);
+
+    CGContextRestoreGState(canvas);
+  }
 #else
   NOTIMPLEMENTED() << "We only support rendering to skia or CG";
 #endif