Handle different x, y scales in drawLines AA path

bug:7114630

Fixes different x, y scales, and fixes boundaryWidthProportion to be from
center, not edge.

Also adds drawLine tests that previously drew blurry.

Change-Id: I2b648a60361ad3931eac67647b9b27909525ee1e

Author: ChrisCraik

libs/hwui/OpenGLRenderer.cpp

@@ -1978,6 +1978,10 @@ status_t OpenGLRenderer::drawLines(float* points, int count, SkPaint* paint) {
 
         // Find the normal to the line
         vec2 n = (b - a).copyNormalized() * halfStrokeWidth;
+        float x = n.x;
+        n.x = -n.y;
+        n.y = x;
+
         if (isHairLine) {
             if (isAA) {
                 float wideningFactor;
@@ -2002,14 +2006,10 @@ status_t OpenGLRenderer::drawLines(float* points, int count, SkPaint* paint) {
 
             float extendedNLength = extendedN.length();
             // We need to set this value on the shader prior to drawing
-            boundaryWidthProportion = extendedNLength / (halfStrokeWidth + extendedNLength);
+            boundaryWidthProportion = .5 - extendedNLength / (halfStrokeWidth + extendedNLength);
             n += extendedN;
         }
 
-        float x = n.x;
-        n.x = -n.y;
-        n.y = x;
-
         // aa lines expand the endpoint vertices to encompass the AA boundary
         if (isAA) {
             vec2 abVector = (b - a);

tests/HwAccelerationTest/src/com/android/test/hwui/LinesActivity.java

@@ -153,6 +153,14 @@ protected void onDraw(Canvas canvas) {
             canvas.drawLine(10.0f, 45.0f, 20.0f, 55.0f, mSmallPaint);
             canvas.drawLine(10.0f, 60.0f, 50.0f, 60.0f, mHairLinePaint);
             canvas.restore();
+
+            canvas.save();
+            canvas.scale(10.0f, 50.0f);
+            mSmallPaint.setStrokeWidth(0.0f);
+            canvas.drawLine(20.0f, 9.0f, 30.0f, 11.0f, mSmallPaint);
+            mSmallPaint.setStrokeWidth(1.0f);
+            canvas.drawLine(30.0f, 9.0f, 40.0f, 11.0f, mSmallPaint);
+            canvas.restore();
         }
     }
 }