Handle special angles with care in SkMatrix44

tests/Matrix44Test.cpp

Index: tests/Matrix44Test.cpp 
=================================================================== 
--- tests/Matrix44Test.cpp	(revision 1698) 
+++ tests/Matrix44Test.cpp	(working copy) 
@@ -1,5 +1,6 @@ 
 #include "Test.h" 
 #include "SkMatrix44.h" 
+#include "SkRect.h" 
 
 static bool nearly_equal_scalar(SkMScalar a, SkMScalar b) { 
 // Note that we get more compounded error for multiple operations when 
@@ -83,6 +84,7 @@ 
 SkIntToScalar(0), 
 SkIntToScalar(-1), 
 SkIntToScalar(90)); 
+ 
 mat.postConcat(rot); 
 REPORTER_ASSERT(reporter, mat.invert(NULL)); 
 mat.invert(&inverse); 
@@ -96,7 +98,7 @@ 
 mat.setTranslate(2, 3, 4); 
 float dataf[16]; 
 double datad[16]; 
- 
+ 
 mat.asColMajorf(dataf); 
 assert16<float>(reporter, dataf, 
 1, 0, 0, 0, 
@@ -119,6 +121,19 @@ 
 0, 0, 1, 4, 
 0, 0, 0, 1); 
 } 
+ 
+ // Test precision of rotation in common cases 
+ int common_angles[] = { 0, 90, -90, 180, -180, 270, -270, 360, -360 }; 
+ for (int i = 0; i < 9; ++i) { 
+ rot.setRotateDegreesAbout( 
+ SkIntToScalar(0), 
+ SkIntToScalar(0), 
+ SkIntToScalar(-1), 
+ SkIntToScalar(common_angles[i])); 
+ 
+ SkMatrix rot3x3 = rot; 
+ REPORTER_ASSERT(reporter, rot3x3.rectStaysRect()); 
+ } 
 #endif 
 }