376e3bd8ec added the new class for Qt 6.1,
but during header review we concluded that using a class introduces
complexity wrt instance ownership and API design that can be avoided by
using a std::function instead.
The functionality is tied to QTextDocument, so the type definition and
the default provider API is added there.
Since std::function is not trivially copyable, the atomicity of the
previous implementation is not maintained, and concurrent modifications
of and access to the global default provider from multiple threads is
not allowed. The relevant use case can be supported by implementing a
resource provider that is thread safe.
Task-number: QTBUG-90211
Fixes: QTBUG-92208
Pick-to: 6.1
Change-Id: I39215c5e51c7bd27f1dd29e1d9d908aecf754fb7
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
ccf1a1a953