Use SDF path miplevels based on the original path's size.

Should produce sharper results than arbitrary fixed sizes.
Adds a new test to pathfill GM.

BUG=chromium:682918

Change-Id: I5a394098665d01e995a244fde278236f1471e6c9
Reviewed-on: https://skia-review.googlesource.com/8328
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/core/SkMathPriv.h b/src/core/SkMathPriv.h
index 14ebeb17b7..5ef0cb25e4 100644
--- a/src/core/SkMathPriv.h
+++ b/src/core/SkMathPriv.h
@@ -132,6 +132,16 @@ static inline int SkNextPow2(int value) {
 }
 
 /**
+*  Returns the largest power-of-2 that is <= the specified value. If value
+*  is already a power of 2, then it is returned unchanged. It is undefined
+*  if value is <= 0.
+*/
+static inline int SkPrevPow2(int value) {
+    SkASSERT(value > 0);
+    return 1 << (32 - SkCLZ(value >> 1));
+}
+
+/**
  *  Returns the log2 of the specified value, were that value to be rounded up
  *  to the next power of 2. It is undefined to pass 0. Examples:
  *  SkNextLog2(1) -> 0
@@ -145,6 +155,20 @@ static inline int SkNextLog2(uint32_t value) {
     return 32 - SkCLZ(value - 1);
 }
 
+/**
+*  Returns the log2 of the specified value, were that value to be rounded down
+*  to the previous power of 2. It is undefined to pass 0. Examples:
+*  SkPrevLog2(1) -> 0
+*  SkPrevLog2(2) -> 1
+*  SkPrevLog2(3) -> 1
+*  SkPrevLog2(4) -> 2
+*  SkPrevLog2(5) -> 2
+*/
+static inline int SkPrevLog2(uint32_t value) {
+    SkASSERT(value != 0);
+    return 32 - SkCLZ(value >> 1);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 /**