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      1 
      2 /*
      3  * Copyright 2011 Google Inc.
      4  *
      5  * Use of this source code is governed by a BSD-style license that can be
      6  * found in the LICENSE file.
      7  */
      8 // Unit tests for src/core/SkPoint.cpp and its header
      9 
     10 #include "SkPoint.h"
     11 #include "SkRect.h"
     12 #include "Test.h"
     13 
     14 static void test_casts(skiatest::Reporter* reporter) {
     15     SkPoint p = { 0, 0 };
     16     SkRect  r = { 0, 0, 0, 0 };
     17 
     18     const SkScalar* pPtr = SkTCast<const SkScalar*>(&p);
     19     const SkScalar* rPtr = SkTCast<const SkScalar*>(&r);
     20 
     21     REPORTER_ASSERT(reporter, p.asScalars() == pPtr);
     22     REPORTER_ASSERT(reporter, r.asScalars() == rPtr);
     23 }
     24 
     25 // Tests SkPoint::Normalize() for this (x,y)
     26 static void test_Normalize(skiatest::Reporter* reporter,
     27                            SkScalar x, SkScalar y) {
     28     SkPoint point;
     29     point.set(x, y);
     30     SkScalar oldLength = point.length();
     31     SkScalar returned = SkPoint::Normalize(&point);
     32     SkScalar newLength = point.length();
     33     REPORTER_ASSERT(reporter, SkScalarNearlyEqual(returned, oldLength));
     34     REPORTER_ASSERT(reporter, SkScalarNearlyEqual(newLength, SK_Scalar1));
     35 }
     36 
     37 // Tests that SkPoint::length() and SkPoint::Length() both return
     38 // approximately expectedLength for this (x,y).
     39 static void test_length(skiatest::Reporter* reporter, SkScalar x, SkScalar y,
     40                         SkScalar expectedLength) {
     41     SkPoint point;
     42     point.set(x, y);
     43     SkScalar s1 = point.length();
     44     SkScalar s2 = SkPoint::Length(x, y);
     45     //The following should be exactly the same, but need not be.
     46     //See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=323
     47     REPORTER_ASSERT(reporter, SkScalarNearlyEqual(s1, s2));
     48     REPORTER_ASSERT(reporter, SkScalarNearlyEqual(s1, expectedLength));
     49 
     50     test_Normalize(reporter, x, y);
     51 }
     52 
     53 // Ugh. Windows compiler can dive into other .cpp files, and sometimes
     54 // notices that I will generate an overflow... which is exactly the point
     55 // of this test!
     56 //
     57 // To avoid this warning, I need to convince the compiler that I might not
     58 // use that big value, hence this hacky helper function: reporter is
     59 // ALWAYS non-null. (shhhhhh, don't tell the compiler that).
     60 template <typename T> T get_value(skiatest::Reporter* reporter, T value) {
     61     return reporter ? value : 0;
     62 }
     63 
     64 // On linux gcc, 32bit, we are seeing the compiler propagate up the value
     65 // of SkPoint::length() as a double (which we use sometimes to avoid overflow
     66 // during the computation), even though the signature says float (SkScalar).
     67 //
     68 // force_as_float is meant to capture our latest technique (horrible as
     69 // it is) to force the value to be a float, so we can test whether it was
     70 // finite or not.
     71 static float force_as_float(skiatest::Reporter* reporter, float value) {
     72     uint32_t storage;
     73     memcpy(&storage, &value, 4);
     74     // even the pair of memcpy calls are not sufficient, since those seem to
     75     // be no-op'd, so we add a runtime tests (just like get_value) to force
     76     // the compiler to give us an actual float.
     77     if (NULL == reporter) {
     78         storage = ~storage;
     79     }
     80     memcpy(&value, &storage, 4);
     81     return value;
     82 }
     83 
     84 // test that we handle very large values correctly. i.e. that we can
     85 // successfully normalize something whose mag overflows a float.
     86 static void test_overflow(skiatest::Reporter* reporter) {
     87     SkScalar bigFloat = get_value(reporter, 3.4e38f);
     88     SkPoint pt = { bigFloat, bigFloat };
     89 
     90     SkScalar length = pt.length();
     91     length = force_as_float(reporter, length);
     92 
     93     // expect this to be non-finite, but dump the results if not.
     94     if (SkScalarIsFinite(length)) {
     95         SkDebugf("length(%g, %g) == %g\n", pt.fX, pt.fY, length);
     96         REPORTER_ASSERT(reporter, !SkScalarIsFinite(length));
     97     }
     98 
     99     // this should succeed, even though we can't represent length
    100     REPORTER_ASSERT(reporter, pt.setLength(SK_Scalar1));
    101 
    102     // now that pt is normalized, we check its length
    103     length = pt.length();
    104     REPORTER_ASSERT(reporter, SkScalarNearlyEqual(length, SK_Scalar1));
    105 }
    106 
    107 // test that we handle very small values correctly. i.e. that we can
    108 // report failure if we try to normalize them.
    109 static void test_underflow(skiatest::Reporter* reporter) {
    110     SkPoint pt = { 1.0e-37f, 1.0e-37f };
    111     SkPoint copy = pt;
    112 
    113     REPORTER_ASSERT(reporter, 0 == SkPoint::Normalize(&pt));
    114     REPORTER_ASSERT(reporter, pt == copy);  // pt is unchanged
    115 
    116     REPORTER_ASSERT(reporter, !pt.setLength(SK_Scalar1));
    117     REPORTER_ASSERT(reporter, pt == copy);  // pt is unchanged
    118 }
    119 
    120 DEF_TEST(Point, reporter) {
    121     test_casts(reporter);
    122 
    123     static const struct {
    124         SkScalar fX;
    125         SkScalar fY;
    126         SkScalar fLength;
    127     } gRec[] = {
    128         { SkIntToScalar(3), SkIntToScalar(4), SkIntToScalar(5) },
    129         { 0.6f, 0.8f, SK_Scalar1 },
    130     };
    131 
    132     for (size_t i = 0; i < SK_ARRAY_COUNT(gRec); ++i) {
    133         test_length(reporter, gRec[i].fX, gRec[i].fY, gRec[i].fLength);
    134     }
    135 
    136     test_underflow(reporter);
    137     test_overflow(reporter);
    138 }
    139 
    140 DEF_TEST(Point_setLengthFast, reporter) {
    141     // Scale a (1,1) point to a bunch of different lengths,
    142     // making sure the slow and fast paths are within 0.1%.
    143     const float tests[] = { 1.0f, 0.0f, 1.0e-37f, 3.4e38f, 42.0f, 0.00012f };
    144 
    145     const SkPoint kOne = {1.0f, 1.0f};
    146     for (unsigned i = 0; i < SK_ARRAY_COUNT(tests); i++) {
    147         SkPoint slow = kOne, fast = kOne;
    148 
    149         slow.setLength(tests[i]);
    150         fast.setLengthFast(tests[i]);
    151 
    152         if (slow.length() < FLT_MIN && fast.length() < FLT_MIN) continue;
    153 
    154         SkScalar ratio = slow.length() / fast.length();
    155         REPORTER_ASSERT(reporter, ratio > 0.999f);
    156         REPORTER_ASSERT(reporter, ratio < 1.001f);
    157     }
    158 }
    159