Extract WideToUTF16String/UTF16StringToWide to FML (flutter#39006)

* Extract WideToUTF16String/UTF16StringToWide to FML

In third_party/accessibility, for string conversion, we use a mix of:
* FML
* third_party/accessibility base string utility functions
* static functions local to the translation unit itself

This moves all conversions between UTF16 and wide strings to FML. Note
that this implementation is only safe on platforms where:
  * the size of wchar_t and char16_t are the same
  * the encoding of wchar_t and char16_t are both UTF-16
which is the case for Windows, hence why these functions are implemented
in a Windows-specific translation unit (wstring_conversion).

Issue: flutter/flutter#118811

* Migrate UTF16ToWide as well

fml/platform/win/wstring_conversion.cc

@@ -23,4 +23,16 @@ std::wstring Utf8ToWideString(const std::string_view str) {
   return converter.from_bytes(str.data());
 }
 
+std::u16string WideStringToUtf16(const std::wstring_view str) {
+  static_assert(sizeof(std::wstring::value_type) ==
+                sizeof(std::u16string::value_type));
+  return {begin(str), end(str)};
+}
+
+std::wstring Utf16ToWideString(const std::u16string_view str) {
+  static_assert(sizeof(std::wstring::value_type) ==
+                sizeof(std::u16string::value_type));
+  return {begin(str), end(str)};
+}
+
 }  // namespace fml

fml/platform/win/wstring_conversion.h

@@ -16,6 +16,12 @@ std::string WideStringToUtf8(const std::wstring_view str);
 // string.
 std::wstring Utf8ToWideString(const std::string_view str);
 
+// Returns a UTF-16 encoded equivalent of a UTF-16 encoded wide string.
+std::u16string WideStringToUtf16(const std::wstring_view str);
+
+// Returns a UTF-16 encoded wide string equivalent of a UTF-16 string.
+std::wstring Utf16ToWideString(const std::u16string_view str);
+
 }  // namespace fml
 
 #endif  // FLUTTER_FML_PLATFORM_WIN_WSTRING_CONVERSION_H_

fml/platform/win/wstring_conversion_unittests.cc

@@ -9,7 +9,7 @@
 namespace fml {
 namespace testing {
 
-TEST(StringConversion, Utf16ToWideStringEmpty) {
+TEST(StringConversion, Utf8ToWideStringEmpty) {
   EXPECT_EQ(Utf8ToWideString(""), L"");
 }
 
@@ -33,5 +33,29 @@ TEST(StringConversion, WideStringToUtf8Unicode) {
   EXPECT_EQ(WideStringToUtf8(L"\x2603"), "\xe2\x98\x83");
 }
 
+TEST(StringConversion, WideStringToUtf16Empty) {
+  EXPECT_EQ(WideStringToUtf16(L""), u"");
+}
+
+TEST(StringConversion, WideStringToUtf16Ascii) {
+  EXPECT_EQ(WideStringToUtf16(L"abc123"), u"abc123");
+}
+
+TEST(StringConversion, WideStringToUtf16Unicode) {
+  EXPECT_EQ(WideStringToUtf16(L"\xe2\x98\x83"), u"\xe2\x98\x83");
+}
+
+TEST(StringConversion, Utf16ToWideStringEmpty) {
+  EXPECT_EQ(Utf16ToWideString(u""), L"");
+}
+
+TEST(StringConversion, Utf16ToWideStringAscii) {
+  EXPECT_EQ(Utf16ToWideString(u"abc123"), L"abc123");
+}
+
+TEST(StringConversion, Utf16ToWideStringUtf8Unicode) {
+  EXPECT_EQ(Utf16ToWideString(u"\xe2\x98\x83"), L"\xe2\x98\x83");
+}
+
 }  // namespace testing
 }  // namespace fml

third_party/accessibility/ax/BUILD.gn

@@ -106,6 +106,7 @@ source_set("ax") {
       "oleacc.lib",
       "uiautomationcore.lib",
     ]
+    deps = [ "//flutter/fml:string_conversion" ]
   }
 
   public_deps = [

third_party/accessibility/ax/ax_node_position_unittest.cc

@@ -19,6 +19,7 @@
 #include "ax/ax_tree_id.h"
 #include "ax/ax_tree_update.h"
 #include "ax/test_ax_tree_manager.h"
+#include "flutter/fml/platform/win/wstring_conversion.h"
 #include "gtest/gtest.h"
 
 namespace ui {
@@ -28,10 +29,6 @@ using TestPositionRange = AXRange<AXPosition<AXNodePosition, AXNode>>;
 
 namespace {
 
-std::u16string WideToUTF16(const std::wstring wide) {
-  return std::u16string(wide.begin(), wide.end());
-}
-
 constexpr AXNode::AXID ROOT_ID = 1;
 constexpr AXNode::AXID BUTTON_ID = 2;
 constexpr AXNode::AXID CHECK_BOX_ID = 3;
@@ -43,20 +40,20 @@ constexpr AXNode::AXID STATIC_TEXT2_ID = 8;
 constexpr AXNode::AXID INLINE_BOX2_ID = 9;
 
 // A group of basic and extended characters.
-constexpr const wchar_t* kGraphemeClusters[] = {
+constexpr const char16_t* kGraphemeClusters[] = {
     // The English word "hey" consisting of four ASCII characters.
-    L"h",
-    L"e",
-    L"y",
+    u"h",
+    u"e",
+    u"y",
     // A Hindi word (which means "Hindi") consisting of two Devanagari
     // grapheme clusters.
-    L"\x0939\x093F",
-    L"\x0928\x094D\x0926\x0940",
+    u"\x0939\x093F",
+    u"\x0928\x094D\x0926\x0940",
     // A Thai word (which means "feel") consisting of three Thai grapheme
     // clusters.
-    L"\x0E23\x0E39\x0E49",
-    L"\x0E2A\x0E36",
-    L"\x0E01",
+    u"\x0E23\x0E39\x0E49",
+    u"\x0E2A\x0E36",
+    u"\x0E01",
 };
 
 class AXPositionTest : public testing::Test, public TestAXTreeManager {
@@ -419,7 +416,7 @@ std::unique_ptr<AXTree> AXPositionTest::CreateMultilingualDocument(
 
   std::u16string english_text;
   for (int i = 0; i < 3; ++i) {
-    std::u16string grapheme = WideToUTF16(kGraphemeClusters[i]);
+    std::u16string grapheme = kGraphemeClusters[i];
     EXPECT_EQ(1u, grapheme.length())
         << "All English characters should be one UTF16 code unit in length.";
     text_offsets->push_back(text_offsets->back() +
@@ -429,7 +426,7 @@ std::unique_ptr<AXTree> AXPositionTest::CreateMultilingualDocument(
 
   std::u16string hindi_text;
   for (int i = 3; i < 5; ++i) {
-    std::u16string grapheme = WideToUTF16(kGraphemeClusters[i]);
+    std::u16string grapheme = kGraphemeClusters[i];
     EXPECT_LE(2u, grapheme.length()) << "All Hindi characters should be two "
                                         "or more UTF16 code units in length.";
     text_offsets->push_back(text_offsets->back() +
@@ -439,7 +436,7 @@ std::unique_ptr<AXTree> AXPositionTest::CreateMultilingualDocument(
 
   std::u16string thai_text;
   for (int i = 5; i < 8; ++i) {
-    std::u16string grapheme = WideToUTF16(kGraphemeClusters[i]);
+    std::u16string grapheme = kGraphemeClusters[i];
     EXPECT_LT(0u, grapheme.length())
         << "One of the Thai characters should be one UTF16 code unit, "
            "whilst others should be two or more.";
@@ -618,7 +615,7 @@ TEST_F(AXPositionTest, ToString) {
   AXNodeData static_text_data_2;
   static_text_data_2.id = 3;
   static_text_data_2.role = ax::mojom::Role::kStaticText;
-  static_text_data_2.SetName(WideToUTF16(L"\xfffc"));
+  static_text_data_2.SetName(u"\xfffc");
 
   AXNodeData static_text_data_3;
   static_text_data_3.id = 4;
@@ -876,7 +873,7 @@ TEST_F(AXPositionTest, GetTextFromNullPosition) {
   TestPositionType text_position = AXNodePosition::CreateNullPosition();
   ASSERT_NE(nullptr, text_position);
   ASSERT_TRUE(text_position->IsNullPosition());
-  ASSERT_EQ(WideToUTF16(L""), text_position->GetText());
+  ASSERT_EQ(u"", text_position->GetText());
 }
 
 TEST_F(AXPositionTest, GetTextFromRoot) {
@@ -885,7 +882,7 @@ TEST_F(AXPositionTest, GetTextFromRoot) {
       ax::mojom::TextAffinity::kUpstream);
   ASSERT_NE(nullptr, text_position);
   ASSERT_TRUE(text_position->IsTextPosition());
-  ASSERT_EQ(WideToUTF16(L"Line 1\nLine 2"), text_position->GetText());
+  ASSERT_EQ(u"Line 1\nLine 2", text_position->GetText());
 }
 
 TEST_F(AXPositionTest, GetTextFromButton) {
@@ -894,7 +891,7 @@ TEST_F(AXPositionTest, GetTextFromButton) {
       ax::mojom::TextAffinity::kUpstream);
   ASSERT_NE(nullptr, text_position);
   ASSERT_TRUE(text_position->IsTextPosition());
-  ASSERT_EQ(WideToUTF16(L""), text_position->GetText());
+  ASSERT_EQ(u"", text_position->GetText());
 }
 
 TEST_F(AXPositionTest, GetTextFromCheckbox) {
@@ -903,7 +900,7 @@ TEST_F(AXPositionTest, GetTextFromCheckbox) {
       ax::mojom::TextAffinity::kUpstream);
   ASSERT_NE(nullptr, text_position);
   ASSERT_TRUE(text_position->IsTextPosition());
-  ASSERT_EQ(WideToUTF16(L""), text_position->GetText());
+  ASSERT_EQ(u"", text_position->GetText());
 }
 
 TEST_F(AXPositionTest, GetTextFromTextField) {
@@ -912,7 +909,7 @@ TEST_F(AXPositionTest, GetTextFromTextField) {
       ax::mojom::TextAffinity::kUpstream);
   ASSERT_NE(nullptr, text_position);
   ASSERT_TRUE(text_position->IsTextPosition());
-  ASSERT_EQ(WideToUTF16(L"Line 1\nLine 2"), text_position->GetText());
+  ASSERT_EQ(u"Line 1\nLine 2", text_position->GetText());
 }
 
 TEST_F(AXPositionTest, GetTextFromStaticText) {
@@ -921,7 +918,7 @@ TEST_F(AXPositionTest, GetTextFromStaticText) {
       ax::mojom::TextAffinity::kUpstream);
   ASSERT_NE(nullptr, text_position);
   ASSERT_TRUE(text_position->IsTextPosition());
-  ASSERT_EQ(WideToUTF16(L"Line 1"), text_position->GetText());
+  ASSERT_EQ(u"Line 1", text_position->GetText());
 }
 
 TEST_F(AXPositionTest, GetTextFromInlineTextBox) {
@@ -930,7 +927,7 @@ TEST_F(AXPositionTest, GetTextFromInlineTextBox) {
       ax::mojom::TextAffinity::kUpstream);
   ASSERT_NE(nullptr, text_position);
   ASSERT_TRUE(text_position->IsTextPosition());
-  ASSERT_EQ(WideToUTF16(L"Line 1"), text_position->GetText());
+  ASSERT_EQ(u"Line 1", text_position->GetText());
 }
 
 TEST_F(AXPositionTest, GetTextFromLineBreak) {
@@ -939,7 +936,7 @@ TEST_F(AXPositionTest, GetTextFromLineBreak) {
       ax::mojom::TextAffinity::kUpstream);
   ASSERT_NE(nullptr, text_position);
   ASSERT_TRUE(text_position->IsTextPosition());
-  ASSERT_EQ(WideToUTF16(L"\n"), text_position->GetText());
+  ASSERT_EQ(u"\n", text_position->GetText());
 }
 
 TEST_F(AXPositionTest, GetMaxTextOffsetFromNullPosition) {
@@ -1106,7 +1103,7 @@ TEST_F(AXPositionTest, GetMaxTextOffsetAndGetTextWithGeneratedContent) {
   ASSERT_NE(nullptr, text_position);
   EXPECT_TRUE(text_position->IsTextPosition());
   EXPECT_EQ(38, text_position->MaxTextOffset());
-  EXPECT_EQ(WideToUTF16(L"Placeholder from generated content3.14"),
+  EXPECT_EQ(u"Placeholder from generated content3.14",
             text_position->GetText());
 }
 
@@ -7712,10 +7709,10 @@ TEST_F(AXPositionTest, EmptyObjectReplacedByCharacterTextNavigation) {
       GetTreeID(), root_1.id, 0 /* text_offset */,
       ax::mojom::TextAffinity::kDownstream);
 
-  expected_text = WideToUTF16(L"Hello ") + AXNodePosition::kEmbeddedCharacter +
-                  WideToUTF16(L" world3.14") +
-                  AXNodePosition::kEmbeddedCharacter + WideToUTF16(L"hey") +
-                  AXNodePosition::kEmbeddedCharacter;
+  expected_text =
+      std::u16string(u"Hello ") + AXNodePosition::kEmbeddedCharacter +
+      std::u16string(u" world3.14") + AXNodePosition::kEmbeddedCharacter +
+      std::u16string(u"hey") + AXNodePosition::kEmbeddedCharacter;
   ASSERT_EQ(expected_text, position->GetText());
 
   // MaxTextOffset() with an embedded object replacement character.

third_party/accessibility/ax/platform/ax_platform_node_textprovider_win_unittest.cc

@@ -349,7 +349,7 @@ TEST_F(AXPlatformNodeTextProviderTest,
   base::win::ScopedBstr text_content;
   EXPECT_HRESULT_SUCCEEDED(
       text_range_provider->GetText(-1, text_content.Receive()));
-  EXPECT_EQ(base::WideToUTF16(text_content.Get()),
+  EXPECT_EQ(fml::WideStringToUtf16(text_content.Get()),
             u"Dialog label.Dialog description." + kEmbeddedCharacterAsString +
                 u"ok.Some more detail " + u"about dialog.");
 

third_party/accessibility/ax/platform/ax_platform_node_textrangeprovider_win.cc

@@ -13,6 +13,7 @@
 #include "ax/platform/ax_platform_node_win.h"
 #include "ax/platform/ax_platform_tree_manager.h"
 #include "base/win/variant_vector.h"
+#include "flutter/fml/platform/win/wstring_conversion.h"
 
 #define UIA_VALIDATE_TEXTRANGEPROVIDER_CALL()                  \
   if (!GetOwner() || !GetOwner()->GetDelegate() || !start() || \
@@ -483,7 +484,7 @@ HRESULT AXPlatformNodeTextRangeProviderWin::FindText(
   ScopedAXEmbeddedObjectBehaviorSetter ax_embedded_object_behavior(
       AXEmbeddedObjectBehavior::kSuppressCharacter);
 
-  std::u16string search_string = base::WideToUTF16(string);
+  std::u16string search_string = fml::WideStringToUtf16(string);
   if (search_string.length() <= 0)
     return E_INVALIDARG;
 
@@ -703,7 +704,7 @@ HRESULT AXPlatformNodeTextRangeProviderWin::GetText(int max_count, BSTR* text) {
   if (max_count < -1)
     return E_INVALIDARG;
 
-  std::wstring full_text = base::UTF16ToWide(GetString(max_count));
+  std::wstring full_text = fml::Utf16ToWideString(GetString(max_count));
   if (!full_text.empty()) {
     size_t length = full_text.length();