Request for implementations of From/Into to convert between PWSTR/PCWSTR and String/&str

[wravery]

Most COM and Win32 apps #define UNICODE and prefer the W APIs which take PWSTR or PCWSTR. Rust has built-in String::encode_utf16 and String::from_utf16 methods, it would be great if PWSTR and PCWSTR could implement From/Into traits to encapsulate that.

It's tricky since it needs extra storage, but maybe the tuple could be extended with an , Option<Vec<u16>> to hold the extra allocation, and the .0 could point to that when this is used.

[kennykerr]

This already works for input parameters. You can pass a string to any function expecting a PSTR or PWSTR and it will create the null-terminated string of the appropriate encoding. For example, the following just works today:

 SetWindowTextA(handle, "Hello A");
 SetWindowTextW(handle, "Hello W");

I'm still working on making it easier for PWSTR and PSTR output parameters. That is tracked by #595.