Fixing SkTileGrid to clamp rather than clip content and querries that are outside the bounds of the…

include/core/SkMath.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 SkMath_DEFINED
@@ skipping 37 matching lines @@
     #define SkCLZ(x)    SkCLZ_portable(x)
 #endif
 
 /**
  *  Returns (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)
  */
 static inline int SkClampPos(int value) {
     return value & ~(value >> 31);
 }
 
+/** Given an integer and an integer range, return the value
+ *  pinned against min and max, inclusive.
+ *  @param value    The value we want returned pinned between [min...max]

[Tom Hudson, 2013/04/09 10:10:50]

Nit: Skia doesn't usually use @param when it's completely redundant, as here.

+ *  @param min      The min value
+ *  @param max      The max value
+ *  @return min if value < min, max if value > max, else value
+ */
+static inline int SkClampMinMax(int value, int min, int max) {

[Tom Hudson, 2013/04/09 10:10:50]

Given that SkClampMax doesn't use the trinary operator, you could follow this up
by checking generated assembly, or just comparing performance? Maybe it doesn't
make a difference...

[Justin Novosad, 2013/04/09 14:47:50]

Ternary operators are actually more likely to trigger optimizations (e.g. the MS
compiler avoids branching by using conditional assignment x86 instruction) 

Anyways, I agree. This should be micro-benched and tuned. skbug.com/1215

+    return (value < min ? min : (value > max ? max : value));
+}
+
 /** Given an integer and a positive (max) integer, return the value
  *  pinned against 0 and max, inclusive.
  *  @param value    The value we want returned pinned between [0...max]
  *  @param max      The positive max value
  *  @return 0 if value < 0, max if value > max, else value
  */
 static inline int SkClampMax(int value, int max) {
     // ensure that max is positive
     SkASSERT(max >= 0);
     if (value < 0) {
@@ skipping 84 matching lines @@
  *  a and b are 0..255
  */
 static inline U8CPU SkMulDiv255Round(U8CPU a, U8CPU b) {
     SkASSERT((uint8_t)a == a);
     SkASSERT((uint8_t)b == b);
     unsigned prod = SkMulS16(a, b) + 128;
     return (prod + (prod >> 8)) >> 8;
 }
 
 #endif