From 3959a76ab086a4adbdb9d48977fa276ce0213cb1 Mon Sep 17 00:00:00 2001
From: "vollick@chromium.org"
 <vollick@chromium.org@2bbb7eff-a529-9590-31e7-b0007b416f81>
Date: Tue, 13 Nov 2012 15:08:22 +0000
Subject: [PATCH] Changing the visibility of SkMatrix44::determinant().

Review URL: https://codereview.appspot.com/6819080

git-svn-id: http://skia.googlecode.com/svn/trunk@6395 2bbb7eff-a529-9590-31e7-b0007b416f81
---
 include/utils/SkMatrix44.h |  4 ++--
 tests/Matrix44Test.cpp     | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/include/utils/SkMatrix44.h b/include/utils/SkMatrix44.h
index cff0d04a3d..8c6d0350dd 100644
--- a/include/utils/SkMatrix44.h
+++ b/include/utils/SkMatrix44.h
@@ -219,6 +219,8 @@ public:
 
     void dump() const;
 
+    double determinant() const;
+
 private:
     /*  Stored in the same order as opengl:
          [3][0] = tx
@@ -226,8 +228,6 @@ private:
          [3][2] = tz
      */
     SkMScalar fMat[4][4];
-
-    double determinant() const;
 };
 
 #endif
diff --git a/tests/Matrix44Test.cpp b/tests/Matrix44Test.cpp
index 086321c1cf..af10e00d71 100644
--- a/tests/Matrix44Test.cpp
+++ b/tests/Matrix44Test.cpp
@@ -8,6 +8,14 @@
 #include "Test.h"
 #include "SkMatrix44.h"
 
+static bool nearly_equal_double(double a, double b) {
+    const double tolerance = 1e-7;
+    double diff = a - b;
+    if (diff < 0)
+        diff = -diff;
+    return diff <= tolerance;
+}
+
 static bool nearly_equal_scalar(SkMScalar a, SkMScalar b) {
     // Note that we get more compounded error for multiple operations when
     // SK_SCALAR_IS_FIXED.
@@ -114,6 +122,31 @@ static void test_concat(skiatest::Reporter* reporter) {
     }
 }
 
+static void test_determinant(skiatest::Reporter* reporter) {
+  SkMatrix44 a;
+  REPORTER_ASSERT(reporter, nearly_equal_double(1, a.determinant()));
+  a.set(1, 1, SkFloatToMScalar(2));
+  REPORTER_ASSERT(reporter, nearly_equal_double(2, a.determinant()));
+  SkMatrix44 b;
+  REPORTER_ASSERT(reporter, a.invert(&b));
+  REPORTER_ASSERT(reporter, nearly_equal_double(0.5, b.determinant()));
+  SkMatrix44 c = b = a;
+  c.set(0, 1, SkFloatToMScalar(4));
+  b.set(1, 0, SkFloatToMScalar(4));
+  REPORTER_ASSERT(reporter,
+                  nearly_equal_double(a.determinant(),
+                                      b.determinant()));
+  SkMatrix44 d = a;
+  d.set(0, 0, SkFloatToMScalar(8));
+  REPORTER_ASSERT(reporter, nearly_equal_double(16, d.determinant()));
+
+  SkMatrix44 e = a;
+  e.postConcat(d);
+  REPORTER_ASSERT(reporter, nearly_equal_double(32, e.determinant()));
+  e.set(0, 0, SkFloatToMScalar(0));
+  REPORTER_ASSERT(reporter, nearly_equal_double(0, e.determinant()));
+}
+
 static void TestMatrix44(skiatest::Reporter* reporter) {
 #ifdef SK_SCALAR_IS_FLOAT
     SkMatrix44 mat, inverse, iden1, iden2, rot;
@@ -182,6 +215,8 @@ static void TestMatrix44(skiatest::Reporter* reporter) {
     if (false) { // avoid bit rot, suppress warning (working on making this pass)
         test_common_angles(reporter);
     }
+
+    test_determinant(reporter);
 #endif
 }