add SkRect::joinNonEmptyArg for faster unioning

include/core/SkRect.h

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkRect_DEFINED
@@ skipping 684 matching lines @@
      */
     void join(SkScalar left, SkScalar top, SkScalar right, SkScalar bottom);
 
     /** Update this rectangle to enclose itself and the specified rectangle.
         If this rectangle is empty, just set it to the specified rectangle. If the specified
         rectangle is empty, do nothing.
     */
     void join(const SkRect& r) {
         this->join(r.fLeft, r.fTop, r.fRight, r.fBottom);
     }
-    // alias for join()
-    void growToInclude(const SkRect& r) { this->join(r); }
+
+    void joinNonEmptyArg(const SkRect& r) {
+        SkASSERT(!r.isEmpty());
+        // if we are empty, just assign
+        if (fLeft >= fRight || fTop >= fBottom) {
+            *this = r;
+        } else {
+            fLeft   = SkMinScalar(fLeft, r.left());
+            fTop    = SkMinScalar(fTop, r.top());
+            fRight  = SkMaxScalar(fRight, r.right());
+            fBottom = SkMaxScalar(fBottom, r.bottom());
+        }
+    }
 
     /**
      *  Grow the rect to include the specified (x,y). After this call, the
      *  following will be true: fLeft <= x <= fRight && fTop <= y <= fBottom.
      *
      *  This is close, but not quite the same contract as contains(), since
      *  contains() treats the left and top different from the right and bottom.
      *  contains(x,y) -> fLeft <= x < fRight && fTop <= y < fBottom. Also note
      *  that contains(x,y) always returns false if the rect is empty.
      */
@@ skipping 121 matching lines @@
      * rely on the existence of this function or the formatting of its output.
      */
     void dump() const {
         SkDebugf("{ l: %f, t: %f, r: %f, b: %f }", fLeft, fTop, fRight, fBottom);
     }
 #endif
 
 };
 
 #endif