SkPDF: re-work SkPDFUtils::FloatToDecimal

tests/PDFPrimitivesTest.cpp

 /*
  * Copyright 2010 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.
  */
 
 #include "Resources.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
@@ skipping 192 matching lines @@
     SkPDFUnion realHalf = SkPDFUnion::Scalar(SK_ScalarHalf);
     ASSERT_EMIT_EQ(reporter, realHalf, ".5");
 
     SkPDFUnion bigScalar = SkPDFUnion::Scalar(110999.75f);
     ASSERT_EMIT_EQ(reporter, bigScalar, "110999.75");
 
     SkPDFUnion biggerScalar = SkPDFUnion::Scalar(50000000.1f);
     ASSERT_EMIT_EQ(reporter, biggerScalar, "50000000");
 
     SkPDFUnion smallestScalar = SkPDFUnion::Scalar(1.0f / 65536);
-    ASSERT_EMIT_EQ(reporter, smallestScalar, ".0000152587890");
+    ASSERT_EMIT_EQ(reporter, smallestScalar, ".0000152587891");

[tomhudson, 2016/07/15 20:45:42]

One digit change? How did this ever work? Or is there something subtle here that
isn't obvious from reading the code?

[hal.canary, 2016/07/17 02:33:42]

Both values round back to the original float value, which is somewhere in
between them:
    Before: .0000152587890
    After:  .0000152587891
    Exact:  .0000152587890625

    assert(1.0f / 65536 == (float)atof(".0000152587890"));
    assert(1.0f / 65536 == (float)atof(".0000152587891"));

 
     SkPDFUnion stringSimple = SkPDFUnion::String("test ) string ( foo");
     ASSERT_EMIT_EQ(reporter, stringSimple, "(test \\) string \\( foo)");
 
     SkString stringComplexInput("\ttest ) string ( foo");
     SkPDFUnion stringComplex = SkPDFUnion::String(stringComplexInput);
     ASSERT_EMIT_EQ(reporter, stringComplex, "(\\011test \\) string \\( foo)");
 
     SkString binaryStringInput("\1\2\3\4\5\6\7\10\11\12\13\14\15\16\17\20");
     SkPDFUnion binaryString = SkPDFUnion::String(binaryStringInput);
@@ skipping 260 matching lines @@
     float alwaysCheck[] = {
         0.0f, -0.0f, 1.0f, -1.0f, SK_ScalarPI, 0.1f, FLT_MIN, FLT_MAX,
         -FLT_MIN, -FLT_MAX, FLT_MIN / 16.0f, -FLT_MIN / 16.0f,
         SK_FloatNaN, SK_FloatInfinity, SK_FloatNegativeInfinity,
         -FLT_MIN / 8388608.0
     };
     for (float inputFloat: alwaysCheck) {
         check_pdf_scalar_serialization(reporter, inputFloat);
     }
 }