SkCanvas interface for drawing a patch.

src/core/SkDevice.cpp

Index: src/core/SkDevice.cpp
diff --git a/src/core/SkDevice.cpp b/src/core/SkDevice.cpp
index e71c889451df139dd8e92ed28d9e4a2b57ebf084..153913453e621a4580c7d70f5253ac06b231ba0e 100644
--- a/src/core/SkDevice.cpp
+++ b/src/core/SkDevice.cpp
@@ -6,6 +6,7 @@
  */
 
 #include "SkDevice.h"
+#include "SkDraw.h"
 #include "SkMetaData.h"
 
 SkBaseDevice::SkBaseDevice()
@@ -77,6 +78,28 @@ void SkBaseDevice::drawDRRect(const SkDraw& draw, const SkRRect& outer,
     this->drawPath(draw, path, paint, preMatrix, pathIsMutable);
 }
 
+void SkBaseDevice::drawPatch(const SkDraw& draw, const SkPatch& patch, const SkPaint& paint) {
+    SkPatch::VertexData data;
+    
+    SkPoint corners[4];
+    patch.getCornerPoints(corners);
+    draw.fMatrix->mapPoints(corners, 4);
+    
+    // size in pixels of each partition per axis, adjust this knob
+    int partitionSize = 25;

[bsalomon, 2014/07/31 17:39:06]

static const int kPartitionSize?

[dandov, 2014/07/31 21:35:40]

Done.

+    
+    // level of detail per axis, based on the larger side between top and bottom or left and right
+    int lodX = SkMaxScalar(SkScalarAbs(corners[0].x() - corners[1].x()),

[bsalomon, 2014/07/31 17:39:06]

Doesn't this need to be

SkScalarSqrt(SkMaxScalar(corners[0].distanceToSqd(corners[1]),
corners[3].distanceToSqd(corners[2])));

?

It doesn't seem right to look at just the x coords after you've transformed the
patch into the dst space.

[dandov, 2014/07/31 21:35:40]

Completed using an approximate arc length based on the distances between the
points already mapped to the 
transformation matrix of the canvas. 

+                            SkScalarAbs(corners[3].x() - corners[2].x())) / partitionSize;
+    int lodY = SkMaxScalar(SkScalarAbs(corners[0].y() - corners[3].y()),
+                            SkScalarAbs(corners[1].y() - corners[2].y())) / partitionSize;
+
+    // It automatically adjusts lodX and lodY in case it exceeds the number of indices.
+    patch.getVertexData(&data, SkMax32(2, lodX), SkMax32(2, lodY));
+    this->drawVertices(draw, SkCanvas::kTriangles_VertexMode, data.fVertexCount, data.fPoints,
+                       data.fTexCoords, data.fColors, NULL, data.fIndices, data.fIndexCount, paint);
+}
+
 bool SkBaseDevice::readPixels(const SkImageInfo& info, void* dstP, size_t rowBytes, int x, int y) {
 #ifdef SK_DEBUG
     SkASSERT(info.width() > 0 && info.height() > 0);