Add perspective support to SkMatrix44 initializers.

I noticed SkMatrix <-> SkMatrix44 conversions were dropping the
perspective values on the floor.  As we use SkMatrix44 heavily in
Chromium, I'm concerned this missing code will cause a bug eventually.
It should be correct to simply use the bottom row of the 4x4 matrix
excluding the third column.

Previously committed and reverted, second attempt with fix for
incorrect use of SkMScalar/SkScalar.

BUG=
R=reed@google.com, caryclark@google.com

Author: aelias@chromium.org

Review URL: https://codereview.chromium.org/25484006

git-svn-id: http://skia.googlecode.com/svn/trunk@11624 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 54 insertions, 3 deletions

diff --git a/tests/Matrix44Test.cpp b/tests/Matrix44Test.cpp
index 67af60df90..849f355489 100644
--- a/tests/Matrix44Test.cpp
+++ b/tests/Matrix44Test.cpp
@@ -16,7 +16,13 @@ static bool nearly_equal_double(double a, double b) {
     return diff <= tolerance;
 }
 
-static bool nearly_equal_scalar(SkMScalar a, SkMScalar b) {
+static bool nearly_equal_mscalar(SkMScalar a, SkMScalar b) {
+    const SkMScalar tolerance = SK_MScalar1 / 200000;
+
+    return SkTAbs<SkMScalar>(a - b) <= tolerance;
+}
+
+static bool nearly_equal_scalar(SkScalar a, SkScalar b) {
     // Note that we get more compounded error for multiple operations when
     // SK_SCALAR_IS_FIXED.
 #ifdef SK_SCALAR_IS_FLOAT
@@ -25,7 +31,7 @@ static bool nearly_equal_scalar(SkMScalar a, SkMScalar b) {
     const SkScalar tolerance = SK_Scalar1 / 1024;
 #endif
 
-    return SkTAbs<SkMScalar>(a - b) <= tolerance;
+    return SkScalarAbs(a - b) <= tolerance;
 }
 
 template <typename T> void assert16(skiatest::Reporter* reporter, const T data[],
@@ -57,7 +63,7 @@ template <typename T> void assert16(skiatest::Reporter* reporter, const T data[]
 static bool nearly_equal(const SkMatrix44& a, const SkMatrix44& b) {
     for (int i = 0; i < 4; ++i) {
         for (int j = 0; j < 4; ++j) {
-            if (!nearly_equal_scalar(a.get(i, j), b.get(i, j))) {
+            if (!nearly_equal_mscalar(a.get(i, j), b.get(i, j))) {
                 printf("not equal %g %g\n", a.get(i, j), b.get(i, j));
                 return false;
             }
@@ -471,6 +477,50 @@ static void test_set_row_col_major(skiatest::Reporter* reporter) {
     REPORTER_ASSERT(reporter, nearly_equal(a, b));
 }
 
+static void test_3x3_conversion(skiatest::Reporter* reporter) {
+    SkMScalar values4x4[16] = { 1, 2, 3, 4,
+                                5, 6, 7, 8,
+                                9, 10, 11, 12,
+                                13, 14, 15, 16 };
+    SkScalar values3x3[9] = { 1, 2, 4,
+                              5, 6, 8,
+                              13, 14, 16 };
+    SkMScalar values4x4flattened[16] = { 1, 2, 0, 4,
+                                         5, 6, 0, 8,
+                                         0, 0, 1, 0,
+                                         13, 14, 0, 16 };
+    SkMatrix44 a44;
+    a44.setRowMajor(values4x4);
+
+    SkMatrix a33 = a44;
+    SkMatrix expected33;
+    for (int i = 0; i < 9; i++) expected33[i] = values3x3[i];
+    REPORTER_ASSERT(reporter, expected33 == a33);
+
+    SkMatrix44 a44flattened = a33;
+    SkMatrix44 expected44flattened;
+    expected44flattened.setRowMajor(values4x4flattened);
+    REPORTER_ASSERT(reporter, nearly_equal(a44flattened, expected44flattened));
+
+    // Test that a point with a Z value of 0 is transformed the same way.
+    SkScalar vec4[4] = { 2, 4, 0, 8 };
+    SkScalar vec3[3] = { 2, 4, 8 };
+
+    SkScalar vec4transformed[4];
+    SkScalar vec3transformed[3];
+    SkScalar vec4transformed2[4];
+    a44.mapScalars(vec4, vec4transformed);
+    a33.mapHomogeneousPoints(vec3transformed, vec3, 1);
+    a44flattened.mapScalars(vec4, vec4transformed2);
+    REPORTER_ASSERT(reporter, nearly_equal_scalar(vec4transformed[0], vec3transformed[0]));
+    REPORTER_ASSERT(reporter, nearly_equal_scalar(vec4transformed[1], vec3transformed[1]));
+    REPORTER_ASSERT(reporter, nearly_equal_scalar(vec4transformed[3], vec3transformed[2]));
+    REPORTER_ASSERT(reporter, nearly_equal_scalar(vec4transformed[0], vec4transformed2[0]));
+    REPORTER_ASSERT(reporter, nearly_equal_scalar(vec4transformed[1], vec4transformed2[1]));
+    REPORTER_ASSERT(reporter, !nearly_equal_scalar(vec4transformed[2], vec4transformed2[2]));
+    REPORTER_ASSERT(reporter, nearly_equal_scalar(vec4transformed[3], vec4transformed2[3]));
+}
+
 static void TestMatrix44(skiatest::Reporter* reporter) {
     SkMatrix44 mat, inverse, iden1, iden2, rot;
 
@@ -572,6 +622,7 @@ static void TestMatrix44(skiatest::Reporter* reporter) {
     test_translate(reporter);
     test_scale(reporter);
     test_map2(reporter);
+    test_3x3_conversion(reporter);
 }
 
 #include "TestClassDef.h"