[Windows] Fix signed/unsigned int comparison (#142341)

Previously, we were comparing the signed int `target_length` (returned by WideCharToMultiByte) to a size_t string length, resulting in a signed/unsigned comparison warning as follows:

```
windows\runner\utils.cpp(54,43): warning C4018:  '>': signed/unsigned mismatch
```

WideCharToMultiByte returns:
* 0 on error
* the number of bytes written to the buffer pointed to by its fifth parameter, lpMultiByteStr, on success.

As a result it's safe to store the return value in an unsigned int, which eliminates the warning.

No changes to tests since this is dependent on end-user project settings/modifications and does not trigger a warning with default project settings.

Fixes: https://github.com/flutter/flutter/issues/134227

dev/a11y_assessments/windows/runner/utils.cpp

@@ -49,13 +49,13 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   int input_length = (int)wcslen(utf16_string);
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

dev/benchmarks/complex_layout/windows/runner/utils.cpp

@@ -49,12 +49,12 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

dev/integration_tests/flutter_gallery/windows/runner/utils.cpp

@@ -49,13 +49,13 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   int input_length = (int)wcslen(utf16_string);
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

dev/integration_tests/ui/windows/runner/utils.cpp

@@ -49,13 +49,13 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   int input_length = (int)wcslen(utf16_string);
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

dev/integration_tests/windows_startup_test/windows/runner/utils.cpp

@@ -49,13 +49,13 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   int input_length = (int)wcslen(utf16_string);
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

dev/manual_tests/windows/runner/utils.cpp

@@ -49,12 +49,12 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

examples/api/windows/runner/utils.cpp

@@ -49,12 +49,12 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

examples/flutter_view/windows/runner/utils.cpp

@@ -49,12 +49,12 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

examples/hello_world/windows/runner/utils.cpp

@@ -49,12 +49,12 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

examples/layers/windows/runner/utils.cpp

@@ -49,13 +49,13 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   int input_length = (int)wcslen(utf16_string);
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

examples/platform_channel/windows/runner/utils.cpp

@@ -49,12 +49,12 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

examples/platform_view/windows/runner/utils.cpp

@@ -49,12 +49,12 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);

packages/flutter_tools/templates/app_shared/windows.tmpl/runner/utils.cpp

@@ -45,13 +45,13 @@ std::string Utf8FromUtf16(const wchar_t* utf16_string) {
   if (utf16_string == nullptr) {
     return std::string();
   }
-  int target_length = ::WideCharToMultiByte(
+  unsigned int target_length = ::WideCharToMultiByte(
       CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
       -1, nullptr, 0, nullptr, nullptr)
     -1; // remove the trailing null character
   int input_length = (int)wcslen(utf16_string);
   std::string utf8_string;
-  if (target_length <= 0 || target_length > utf8_string.max_size()) {
+  if (target_length == 0 || target_length > utf8_string.max_size()) {
     return utf8_string;
   }
   utf8_string.resize(target_length);