No longer using non-antialiased fast path for lines when antialiasing is on.

src/gpu/SkGpuDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGpuDevice.h"
 
 #include "GrBlurUtils.h"
@@ skipping 378 matching lines @@
     fDrawContext->drawPaint(fRenderTarget, fClip, grPaint, *draw.fMatrix);
 }
 
 // must be in SkCanvas::PointMode order
 static const GrPrimitiveType gPointMode2PrimtiveType[] = {
     kPoints_GrPrimitiveType,
     kLines_GrPrimitiveType,
     kLineStrip_GrPrimitiveType
 };
 
+// suppress antialiasing on axis-aligned integer-coordinate lines
+static bool needs_antialiasing(SkCanvas::PointMode mode, size_t count, const SkPoint pts[]) {
+    if (mode == SkCanvas::PointMode::kPoints_PointMode) {
+        return false;
+    }
+    if (count == 2) {
+        // We do not antialias as long as the primary axis of the line is integer-aligned, even if
+        // the other coordinates are not. This does mean the two end pixels of the line will be
+        // sharp even when they shouldn't be, but turning antialiasing on (as things stand 
+        // currently) means that the line will turn into a two-pixel-wide blur. While obviously a
+        // more complete fix is possible down the road, for the time being we accept the error on 
+        // the two end pixels as being the lesser of two evils.
+        if (pts[0].fX == pts[1].fX) {
+            return ((int) pts[0].fX) != pts[0].fX;
+        }
+        if (pts[0].fY == pts[1].fY) {
+            return ((int) pts[0].fY) != pts[0].fY;
+        }
+    }
+    return true;
+}
+
 void SkGpuDevice::drawPoints(const SkDraw& draw, SkCanvas::PointMode mode,
                              size_t count, const SkPoint pts[], const SkPaint& paint) {
     CHECK_FOR_ANNOTATION(paint);
     CHECK_SHOULD_DRAW(draw);
 
     SkScalar width = paint.getStrokeWidth();
     if (width < 0) {
         return;
     }
 
     if (paint.getPathEffect() && 2 == count && SkCanvas::kLines_PointMode == mode) {
         GrStrokeInfo strokeInfo(paint, SkPaint::kStroke_Style);
         GrPaint grPaint;
         if (!SkPaint2GrPaint(this->context(), fRenderTarget, paint, *draw.fMatrix, true,
                              &grPaint)) {
             return;
         }
         SkPath path;
         path.setIsVolatile(true);
         path.moveTo(pts[0]);
         path.lineTo(pts[1]);
         fDrawContext->drawPath(fRenderTarget, fClip, grPaint, *draw.fMatrix, path, strokeInfo);
         return;
     }
 
-    // we only handle hairlines and paints without path effects or mask filters,
+    // we only handle non-antialiased hairlines and paints without path effects or mask filters,
     // else we let the SkDraw call our drawPath()
-    if (width > 0 || paint.getPathEffect() || paint.getMaskFilter()) {
+    if (width > 0 || paint.getPathEffect() || paint.getMaskFilter() || 
+        (paint.isAntiAlias() && needs_antialiasing(mode, count, pts))) {
         draw.drawPoints(mode, count, pts, paint, true);
         return;
     }
 
     GrPaint grPaint;
     if (!SkPaint2GrPaint(this->context(), fRenderTarget, paint, *draw.fMatrix, true, &grPaint)) {
         return;
     }
 
     fDrawContext->drawVertices(fRenderTarget,
@@ skipping 1416 matching lines @@
 #endif
 }
 
 SkImageFilter::Cache* SkGpuDevice::getImageFilterCache() {
     // We always return a transient cache, so it is freed after each
     // filter traversal.
     return SkImageFilter::Cache::Create(kDefaultImageFilterCacheSize);
 }
 
 #endif