fix bounds for BW lines, AA Hairlines

src/gpu/GrContext.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 "GrContext.h"
 
@@ skipping 504 matching lines @@
 
         fBatch.fHairline = geometry.fStrokeWidth == 0;
 
         fGeoData.push_back(geometry);
 
         // setup bounds
         fBounds = geometry.fRect;
         SkScalar rad = SkScalarHalf(geometry.fStrokeWidth);
         fBounds.outset(rad, rad);
         geometry.fViewMatrix.mapRect(&fBounds);
+

[robertphillips, 2015/05/07 14:42:02]

For this case, BW hairline rect draw, I believe we just force the lines to pixel
centers.

[bsalomon, 2015/05/07 14:47:45]

Correct. This is an unfortunate case of coupling where the user of this batch
did the snapping rather than the batch itself, but the batch has to know about
it.

+        // This is conservative but, b.c. the hardware can employ somewhat arbitrary
+        // snapping rules to BW lines, it is the best we can do.
+        if (fBatch.fHairline) {
+            fBounds.outset(0.5f, 0.5f);
+        }
     }
 
     /*  create a triangle strip that strokes the specified rect. There are 8
      unique vertices, but we repeat the last 2 to close up. Alternatively we
      could use an indices array, and then only send 8 verts, but not sure that
      would be faster.
      */
     void setStrokeRectStrip(SkPoint verts[10], const SkRect& rect, SkScalar width) {
         const SkScalar rad = SkScalarHalf(width);
         // TODO we should be able to enable this assert, but we'd have to filter these draws
@@ skipping 479 matching lines @@
 
     // TODO clients should give us bounds
     SkRect bounds;
     if (!bounds.setBoundsCheck(positions, vertexCount)) {
         SkDebugf("drawVertices call empty bounds\n");
         return;
     }
 
     viewMatrix.mapRect(&bounds);
 
+    // If we don't have AA then we outset for a half pixel in each direction to account for
+    // snapping
+    if (!paint.isAntiAlias()) {
+        bounds.outset(0.5f, 0.5f);
+    }
+
     DrawVerticesBatch::Geometry geometry;
     geometry.fColor = paint.getColor();
     SkAutoTUnref<GrBatch> batch(DrawVerticesBatch::Create(geometry, primitiveType, viewMatrix,
                                                           positions, vertexCount, indices,
                                                           indexCount, colors, texCoords,
                                                           bounds));
 
     target->drawBatch(&pipelineBuilder, batch);
 }
 
@@ skipping 858 matching lines @@
         fDrawBuffer->addGpuTraceMarker(marker);
     }
 }
 
 void GrContext::removeGpuTraceMarker(const GrGpuTraceMarker* marker) {
     fGpu->removeGpuTraceMarker(marker);
     if (fDrawBuffer) {
         fDrawBuffer->removeGpuTraceMarker(marker);
     }
 }