[core][Qt] Use Qt for UTF16, since codecvt is not always available

platform/android/config.cmake

@@ -79,6 +79,7 @@ macro(mbgl_platform_core)
         PRIVATE platform/android/src/logging_android.cpp
         PRIVATE platform/default/string_stdlib.cpp
         PRIVATE platform/default/bidi.cpp
+        PRIVATE platform/default/utf.cpp
 
         # Image handling
         PRIVATE platform/default/image.cpp

platform/default/utf.cpp

@@ -0,0 +1,16 @@
+#include <mbgl/util/utf.hpp>
+
+#include <memory>
+#include <locale>
+#include <codecvt>
+
+namespace mbgl {
+namespace util {
+
+std::u16string utf8_to_utf16::convert(std::string const& utf8) {
+    std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> converter;
+    return converter.from_bytes(utf8);
+}
+
+} // namespace util
+} // namespace mbgl

platform/ios/config.cmake

@@ -41,6 +41,7 @@ macro(mbgl_platform_core)
         PRIVATE platform/darwin/src/nsthread.mm
         PRIVATE platform/darwin/src/string_nsstring.mm
         PRIVATE platform/default/bidi.cpp
+        PRIVATE platform/default/utf.cpp
 
         # Image handling
         PRIVATE platform/darwin/src/image.mm

platform/linux/config.cmake

@@ -72,6 +72,7 @@ macro(mbgl_platform_core)
         PRIVATE platform/default/string_stdlib.cpp
         PRIVATE platform/default/thread.cpp
         PRIVATE platform/default/bidi.cpp
+        PRIVATE platform/default/utf.cpp
 
         # Image handling
         PRIVATE platform/default/image.cpp

platform/macos/config.cmake

@@ -37,6 +37,7 @@ macro(mbgl_platform_core)
         PRIVATE platform/darwin/src/nsthread.mm
         PRIVATE platform/darwin/src/string_nsstring.mm
         PRIVATE platform/default/bidi.cpp
+        PRIVATE platform/default/utf.cpp
 
         # Image handling
         PRIVATE platform/darwin/src/image.mm

platform/qt/qt.cmake

@@ -48,6 +48,7 @@ set(MBGL_QT_FILES
     PRIVATE platform/qt/src/string_stdlib.cpp
     PRIVATE platform/qt/src/timer.cpp
     PRIVATE platform/qt/src/timer_impl.hpp
+    PRIVATE platform/qt/src/utf.cpp
 )
 
 include_directories(

platform/qt/src/utf.cpp

@@ -0,0 +1,17 @@
+#include <mbgl/util/utf.hpp>
+
+#include <QString>
+
+namespace mbgl {
+namespace util {
+
+std::u16string utf8_to_utf16::convert(std::string const& utf8) {
+    auto utf16 = QString::fromUtf8(utf8.data(), utf8.length());
+
+    // Newers Qt have QString::toStdU16String(), but this is how it is
+    // implemented. Do it here to keep compatibility with older versions.
+    return std::u16string(reinterpret_cast<const char16_t*>(utf16.utf16()), utf16.length());
+}
+
+} // namespace util
+} // namespace mbgl

src/mbgl/util/utf.hpp

@@ -1,19 +1,13 @@
 #pragma once
 
-#include <memory>
-
-#include <locale>
-#include <codecvt>
+#include <string>
 
 namespace mbgl {
 namespace util {
 
 class utf8_to_utf16 {
 public:
-    static std::u16string convert(std::string const& utf8) {
-        std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> converter;
-        return converter.from_bytes(utf8);
-    }
+    static std::u16string convert(std::string const&);
 };
 
 } // namespace util