Accessibility number formatting improvements for Windows

third_party/accessibility/base/BUILD.gn

@@ -53,5 +53,6 @@ source_set("base") {
   public_deps = [
     "numerics",
     "//flutter/third_party/accessibility/ax_build",
+    "//third_party/dart/runtime/third_party/double-conversion/src:libdouble_conversion",
   ]
 }

third_party/accessibility/base/string_utils.cc

@@ -4,12 +4,15 @@
 
 #include "string_utils.h"
 
+#include <array>
 #include <cctype>
 #include <codecvt>
 #include <locale>
 #include <regex>
 #include <sstream>
 
+#include "third_party/dart/runtime/third_party/double-conversion/src/double-conversion.h"
+
 #if defined(_WIN32)
 #include "base/win/string_conversion.h"
 #endif
@@ -18,6 +21,48 @@
 
 namespace base {
 
+using double_conversion::DoubleToStringConverter;
+using double_conversion::StringBuilder;
+
+namespace {
+constexpr char kExponentChar = 'e';
+constexpr char kInfinitySymbol[] = "Infinity";
+constexpr char kNaNSymbol[] = "NaN";
+
+// The number of digits after the decimal we allow before switching to
+// exponential representation.
+constexpr int kDecimalInShortestLow = -6;
+// The number of digits before the decimal we allow before switching to
+// exponential representation.
+constexpr int kDecimalInShortestHigh = 12;
+constexpr int kConversionFlags =
+    DoubleToStringConverter::EMIT_POSITIVE_EXPONENT_SIGN;
+
+const DoubleToStringConverter& GetDoubleToStringConverter() {
+  static DoubleToStringConverter converter(
+      kConversionFlags, kInfinitySymbol, kNaNSymbol, kExponentChar,
+      kDecimalInShortestLow, kDecimalInShortestHigh, 0, 0);
+  return converter;
+}
+
+std::string NumberToStringImpl(double number, bool is_single_precision) {
+  if (number == 0.0) {
+    return "0";
+  }
+
+  constexpr int kBufferSize = 128;
+  std::array<char, kBufferSize> char_buffer;
+  StringBuilder builder(char_buffer.data(), char_buffer.size());
+  if (is_single_precision) {
+    GetDoubleToStringConverter().ToShortestSingle(static_cast<float>(number),
+                                                  &builder);
+  } else {
+    GetDoubleToStringConverter().ToShortest(number, &builder);
+  }
+  return std::string(char_buffer.data(), builder.position());
+}
+}  // namespace
+
 std::u16string ASCIIToUTF16(std::string src) {
   return std::u16string(src.begin(), src.end());
 }
@@ -73,15 +118,11 @@ std::string NumberToString(unsigned int number) {
 }
 
 std::string NumberToString(float number) {
-  // TODO(gw280): Format decimals to the shortest reasonable representation.
-  // See: https://github.com/flutter/flutter/issues/78460
-  return std::to_string(number);
+  return NumberToStringImpl(number, true);
 }
 
 std::string NumberToString(double number) {
-  // TODO(gw280): Format decimals to the shortest reasonable representation.
-  // See: https://github.com/flutter/flutter/issues/78460
-  return std::to_string(number);
+  return NumberToStringImpl(number, false);
 }
 
 std::string JoinString(std::vector<std::string> tokens, std::string delimiter) {

third_party/accessibility/base/string_utils.h

@@ -29,9 +29,9 @@ std::string UTF16ToUTF8(std::u16string src);
 std::u16string WideToUTF16(const std::wstring& src);
 std::wstring UTF16ToWide(const std::u16string& src);
 
-std::u16string NumberToString16(float number);
 std::u16string NumberToString16(unsigned int number);
 std::u16string NumberToString16(int32_t number);
+std::u16string NumberToString16(float number);
 std::u16string NumberToString16(double number);
 
 std::string NumberToString(unsigned int number);

third_party/accessibility/base/string_utils_unittest.cc

@@ -6,6 +6,7 @@
 
 #include <cerrno>
 #include <cstddef>
+#include <string>
 
 #include "base/logging.h"
 #include "gtest/gtest.h"
@@ -42,17 +43,38 @@ TEST(StringUtilsTest, canUTF16ToUTF8) {
 }
 
 TEST(StringUtilsTest, canNumberToString16) {
-  float number = 1.123;
-  EXPECT_EQ(NumberToString16(number).compare(u"1.123000"), 0);
+  EXPECT_EQ(NumberToString16(1.123f), std::u16string(u"1.123"));
 }
 
-TEST(StringUtilsTest, canNumberToString) {
-  float f = 1.123;
-  EXPECT_EQ(NumberToString(f).compare("1.123000"), 0);
-  unsigned int s = 11;
-  EXPECT_EQ(NumberToString(s).compare("11"), 0);
-  int32_t i = -23;
-  EXPECT_EQ(NumberToString(i).compare("-23"), 0);
+TEST(StringUtilsTest, numberToStringSimplifiesOutput) {
+  EXPECT_STREQ(NumberToString(0.0).c_str(), "0");
+  EXPECT_STREQ(NumberToString(0.0f).c_str(), "0");
+  EXPECT_STREQ(NumberToString(1.123).c_str(), "1.123");
+  EXPECT_STREQ(NumberToString(1.123f).c_str(), "1.123");
+  EXPECT_STREQ(NumberToString(-1.123).c_str(), "-1.123");
+  EXPECT_STREQ(NumberToString(-1.123f).c_str(), "-1.123");
+  EXPECT_STREQ(NumberToString(1.00001).c_str(), "1.00001");
+  EXPECT_STREQ(NumberToString(1.00001f).c_str(), "1.00001");
+  EXPECT_STREQ(NumberToString(1000.000001).c_str(), "1000.000001");
+  EXPECT_STREQ(NumberToString(10.00001f).c_str(), "10.00001");
+  EXPECT_STREQ(NumberToString(1.0 + 1e-8).c_str(), "1.00000001");
+  EXPECT_STREQ(NumberToString(1.0f + 1e-8f).c_str(), "1");
+  EXPECT_STREQ(NumberToString(1e-6).c_str(), "0.000001");
+  EXPECT_STREQ(NumberToString(1e-6f).c_str(), "0.000001");
+  EXPECT_STREQ(NumberToString(1e-8).c_str(), "1e-8");
+  EXPECT_STREQ(NumberToString(1e-8f).c_str(), "1e-8");
+  EXPECT_STREQ(NumberToString(100.0).c_str(), "100");
+  EXPECT_STREQ(NumberToString(100.0f).c_str(), "100");
+  EXPECT_STREQ(NumberToString(-1.0 - 1e-7).c_str(), "-1.0000001");
+  EXPECT_STREQ(NumberToString(-1.0f - 1e-7f).c_str(), "-1.0000001");
+  EXPECT_STREQ(NumberToString(0.00000012345678).c_str(), "1.2345678e-7");
+  // Difference in output is due to differences in double and float precision.
+  EXPECT_STREQ(NumberToString(0.00000012345678f).c_str(), "1.2345679e-7");
+  EXPECT_STREQ(NumberToString(-0.00000012345678).c_str(), "-1.2345678e-7");
+  // Difference in output is due to differences in double and float precision.
+  EXPECT_STREQ(NumberToString(-0.00000012345678f).c_str(), "-1.2345679e-7");
+  EXPECT_STREQ(NumberToString(static_cast<unsigned int>(11)).c_str(), "11");
+  EXPECT_STREQ(NumberToString(static_cast<int32_t>(-23)).c_str(), "-23");
 }
 
 }  // namespace base