Windows has shipped a (limited) subset of ICU for quite a while: https://learn.microsoft.com/en-us/windows/win32/intl/international-components-for-unicode--icu- The C API for this subset uses non-standard names for headers and lib though, and is therefore not picked up by the ICU configure logic in CMake. This patch adds a separate configure test that enables the use of this ICU API, specifically for text codec support in QStringConverter. If a 'proper' ICU is enabled by the user, this still takes precedence. Also, note that MinGW-w64 misses the respective Windows API, and will therefore still use the old fallback. [ChangeLog][QtCore][Text] Qt on Windows now uses the ICU API of the Windows SDK for text codec support (if available and no 'full' ICU is configured). This greatly enhances the list of supported text codecs available. Fixes: QTBUG-132056 Change-Id: Id02ae9f8cf56dee8c34795c0e60d2113f319bfd9 Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io> Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>