Add drawRegion() API to SkCanvas

src/core/SkDevice.cpp

Index: src/core/SkDevice.cpp
diff --git a/src/core/SkDevice.cpp b/src/core/SkDevice.cpp
index a90076d44216d98cac3f41056b5e8fd0f35ac328..3e1064018c7bef9768988d489aa92f116c783361 100644
--- a/src/core/SkDevice.cpp
+++ b/src/core/SkDevice.cpp
@@ -72,6 +72,22 @@ SkPixelGeometry SkBaseDevice::CreateInfo::AdjustGeometry(const SkImageInfo& info
     return geo;
 }
 
+void SkBaseDevice::drawRegion(const SkDraw& draw, const SkRegion& region, const SkPaint& paint) {
+    bool complexMatrix = !draw.fMatrix->isScaleTranslate();
+    bool complexPaint = paint.isAntiAlias() || paint.getImageFilter() || paint.getMaskFilter();
+    if (complexMatrix && complexPaint) {

[msarett, 2016/08/25 13:02:32]

Hwui also checks that the paint must be kFill_Style before choosing "simple
rects".  Is this something that we also need to worry about?

[bsalomon, 2016/08/25 13:58:20]

To me a clear definition of drawRegion(region, paint) is that it draws the same
as drawPath(region.getBoundaryPath(), paint).

If we accept that definition then a path effect or non-fill style would also
throw us out of the rect-at-a-time implementation.

[msarett, 2016/08/25 15:07:35]

Agreed.

New checks should catch everything I think:
(1) Default to path if non-translate.
(2) Default to path if non-fill, mask filter, or path effect.
(3) Default to path if anti-alias AND we'll actually have non-integer pixels.

We'll miss the fast path on the case where we have a scale matrix with integer
scales - I think that's ok.

Image filters should work fine on the fast path.

+        SkPath path;
+        region.getBoundaryPath(&path);
+        return this->drawPath(draw, path, paint, nullptr, false);
+    }
+
+    SkRegion::Iterator it(region);
+    while (!it.done()) {
+        this->drawRect(draw, SkRect::Make(it.rect()), paint);
+        it.next();
+    }
+}
+
 void SkBaseDevice::drawArc(const SkDraw& draw, const SkRect& oval, SkScalar startAngle,
                            SkScalar sweepAngle, bool useCenter, const SkPaint& paint) {
     SkASSERT(SkScalarAbs(sweepAngle) >= 0.f && SkScalarAbs(sweepAngle) < 360.f);