converting D's string to use with C API with unicode

[Jack]

On Sunday, 6 December 2020 at 04:41:56 UTC, Виталий Фадеев wrote:
> On Saturday, 5 December 2020 at 19:51:14 UTC, Jack wrote:
>> So in D I have a struct like this:
>>
>>>struct ProcessResult
>>>{
>>>	string[] output;
>>>	bool ok;
>>>}
>>
>> in order to use output from C WINAPI with unicode, I need to 
>> convert each string to wchar* so that i can acess it from C 
>> with wchar_t*. Is that right or am I missing anything?
>>
>>
>>>struct ProcessResult
>>>{
>>>	string[] output;
>>>	bool ok;
>>>
>>>	C_ProcessResult toCResult()
>>>	{
>>>		auto r = C_ProcessResult();
>>>		r.ok = this.ok; // just copy, no conversion needed
>>>		foreach(s; this.output)
>>>			r.output ~= cast(wchar*)s.ptr;
>>>		return r;
>>>	}
>>>}
>>
>>>version(Windows) extern(C) export
>>>struct C_ProcessResult
>>>{
>>>	wchar*[] output;
>>>	bool ok;
>>>}
>
> Drawing string via WinAPI. As example.
>
> // UTF-16. wchar*
> wstring ws = "Abc"w;
> ExtTextOutW( hdc, x, y, 0, &clipRect, cast( LPCWSTR ) ws.ptr, 
> cast( uint ) ws.length, NULL );
>
> // UTF-8. char*
> string s = "Abc";
> import std.utf : toUTF16;
> string ws = s.toUTF16;
> ExtTextOutW( hdc, x, y, 0, &clipRect, cast( LPCWSTR ) ws.ptr, 
> cast( uint ) ws.length, NULL );
>
> // UTF-32. dchar*
> dstring ds = "Abc"d;
> import std.utf : toUTF16;
> string ws = ds.toUTF16;
> ExtTextOutW( hdc, x, y, 0, &clipRect, cast( LPCWSTR ) ws.ptr, 
> cast( uint ) ws.length, NULL );
>
> One char.
> // UTF-16. wchar
> wchar wc = 'A';
> ExtTextOutW( hdc, x, y, 0, &clipRect, cast( LPCWSTR ) &wc, 1, 
> NULL );
>
> // UTF-32. dchar
> dchar dc = 'A';
> import std.utf : encode;
> wchar[ 2 ] ws;
> auto l = encode( ws, dc );
> ExtTextOutW( hdc, x, y, 0, &clipRect, cast( LPCWSTR ) &ws.ptr, 
> cast( uint ) l, NULL );
>
> //
> // Font API
> string face = "Arial";
> LOGFONT lf;
> import std.utf : toUTF16;
> lf.lfFaceName[ 0 .. face.length ] = face.toUTF16;
> HFONT hfont = CreateFontIndirect( &lf );
>
> // Common case
> LPWSTR toLPWSTR( string s ) nothrow // wchar_t*. UTF-16
> {
>     import std.utf : toUTFz, toUTF16z, UTFException;
>     try                        { return toUTFz!( LPWSTR )( s ); 
> }
>     catch ( UTFException e )   { return cast( LPWSTR ) 
> "ERR"w.ptr; }
>     catch ( Exception e )      { return cast( LPWSTR ) 
> "ERR"w.ptr; }
> }

didn't know about toUTFz!( LPWSTR ), I'll save everything else 
for futher reference, I'll be using WINAPI for a while. Thanks

> alias toLPWSTR toPWSTR;
> alias toLPWSTR toLPOLESTR;
> alias toLPWSTR toPOLESTR;

that's interesting, I didn't about using multiples alias.

> // WinAPI
> string windowName = "Abc";
> HWND hwnd =
>     CreateWindowEx(
>         ...
>         windowName.toLPWSTR,
>         ...
>     );