Fix tessellation bounds computation

bug:17401066

Now correctly accounts for scale, both in hairline case (where scale
needs to be accounted for), and in standard case (where scale
shouldn't be applied, since bounds are in local space)

Change-Id: I597a20834dce42ddb741b46e4c1a4f3169a48ccc

1 files changed, 12 insertions, 5 deletions

diff --git a/libs/hwui/PathTessellator.cpp b/libs/hwui/PathTessellator.cpp
index e30ac19..281ca02 100644
--- a/libs/hwui/PathTessellator.cpp
+++ b/libs/hwui/PathTessellator.cpp
@@ -162,14 +162,21 @@ public:
     }
 
     /**
-     * Outset the bounds of point data (for line endpoints or points) to account for AA stroke
+     * Outset the bounds of point data (for line endpoints or points) to account for stroke
      * geometry.
+     *
+     * bounds are in pre-scaled space.
      */
     void expandBoundsForStroke(Rect* bounds) const {
-        float outset = halfStrokeWidth;
-        if (outset == 0) outset = 0.5f;
-        bounds->outset(outset * inverseScaleX + Vertex::GeometryFudgeFactor(),
-                outset * inverseScaleY + Vertex::GeometryFudgeFactor());
+        if (halfStrokeWidth == 0) {
+            // hairline, outset by (0.5f + fudge factor) in post-scaling space
+            bounds->outset(fabs(inverseScaleX) * (0.5f + Vertex::GeometryFudgeFactor()),
+                    fabs(inverseScaleY) * (0.5f + Vertex::GeometryFudgeFactor()));
+        } else {
+            // non hairline, outset by half stroke width pre-scaled, and fudge factor post scaled
+            bounds->outset(halfStrokeWidth + fabs(inverseScaleX) * Vertex::GeometryFudgeFactor(),
+                    halfStrokeWidth + fabs(inverseScaleY) * Vertex::GeometryFudgeFactor());
+        }
     }
 };