windows-sys doesn't distinguish between LPCWSTR and LPWSTR

[maroider]

Crate version: 0.32.0

This is similar to #1490, but perhaps a bit more specific.

windows-sys doesn't distinguish between mutable and immutable string pointers, so all functions get whatever LPWSTR is aliased to (used to be *mut u16, now it's *const u16). With type LPWSTR = *const u16, APIs like GetWindowTextW now take a *const u16 where they should take a *mut u16, which is a problem.

There's a similar issue with ImmSetCompositionWindow, where the function is documented on MSDN as taking an LPCOMPOSITIONFORM (*mut COMPOSITIONFORM), but windows-sys says it takes a *const COMPOSITIONFORM.

[kennykerr]

This is the same signature issue as #1496.

[kennykerr]

Note that this applies to GetWindowTextW (same as #1496). It's less clear to me that there's anything wrong with the way ImmSetCompositionWindow is defined. The docs and metadata say that it has input parameters and I don't see anything that could be used to infer that it needs to be mutable.

[kennykerr]

#1550 adds first-class types for PCSTR and PCWSTR.