Clean up quick rejection, especially surrounding points + lines.

bug:4351353

quickReject and quickRejectNoScissor have been renamed and refactored:
- to make the scissor side effect clear and explicit
- dangerous methods no longer public
- to make the simple quick reject check logic const
- simple quick reject is now conservative

This CL also fixes several issues with line and point quickRejection -
sub-pixel and hairline lines are much less likely to be incorrectly
rejected, especially at small canvas scale.

Additionally, alpha modulation for AA points < 1px in size is now
correct, dumplicating SW behavior (similar to lines and stroked
shapes work).

Change-Id: Ibb0710c721b9fb415d05acf54dd3d2b4d602156a

1 files changed, 6 insertions, 3 deletions

diff --git a/libs/hwui/DisplayListOp.h b/libs/hwui/DisplayListOp.h
index 5816872..88077d4 100644
--- a/libs/hwui/DisplayListOp.h
+++ b/libs/hwui/DisplayListOp.h
@@ -182,9 +182,12 @@ public:
     }
 
     inline float strokeWidthOutset() {
-        float width = mPaint->getStrokeWidth();
-        if (width == 0) return 0.5f; // account for hairline
-        return width * 0.5f;
+        // since anything AA stroke with less than 1.0 pixel width is drawn with an alpha-reduced
+        // 1.0 stroke, treat 1.0 as minimum.
+
+        // TODO: it would be nice if this could take scale into account, but scale isn't stable
+        // since higher levels of the view hierarchy can change scale out from underneath it.
+        return fmaxf(mPaint->getStrokeWidth(), 1) * 0.5f;
     }
 
 protected: