How to create an IDWriteFontFile - delphi

Question

I would like to create a Direct2D path geometry from text. As I understood, I'll need to create an IDWriteFontFace, from which I'll have to call GetGlyphRunOutline.
Unfortunately, I cannot figure out how to create that font face. So far, I stumble on even creating a font file reference, which I think I have to use to create the font face.
procedure CreateFontFace;
var
hr: HRESULT;
FontDir: string;
FontPath: string;
ft: _FILETIME;
FontFile: IDWriteFontFile;
FontFace: IDWriteFontFace;
begin
FontDir := GetSpecialFolder(CSIDL_FONTS);
FontPath := IncludeTrailingPathDelimiter(FontDir) + 'Arial.ttf';
// Here, FontPath contains 'C:\Windows\Fonts\Arial.ttf'
// (which exists on my machine)
ft.dwLowDateTime := 0;
ft.dwHighDateTime := 0;
hr := DWriteFactory.CreateFontFileReference(
FontPath, // DOES NOT COMPILE
ft,
FontFile);
if Succeeded(hr) then begin
hr := DWriteFactory.CreateFontFace(
DWRITE_FONT_FACE_TYPE_TRUETYPE,
1,
#FontFile,
0,
DWRITE_FONT_SIMULATIONS_NONE,
FontFace);
end;
end;
The prototype of CreateFontFileReference in Winapi.D2D1 is as follow:
function CreateFontFileReference(var filePath: WCHAR;
var lastWriteTime: FILETIME;
out fontFile: IDWriteFontFile): HResult; stdcall;
I understand that putting a string instead of a WCHAR can bother the compiler, but how should this be written? I'm also interested if there is another, simpler way...
UPDATE:
As stated by Remy Lebeau, there are other similar buggy declarations in the Winapi.D2D1 unit. The second one that I encountered is even in CreateFontFileReference too: parameter lastWriteTime should be a pointer, so to make my code work, I had to change my use of the ft variable as follows:
var
...
ft: ^_FILETIME;
...
begin
...
ft := nil;
hr := DWriteFactory.CreateFontFileReference(
PChar(FontPath)^,
ft^, // Yes, I am dereferencing nil, and it's working!
FontFile);
...
end;

Answer 1

If you are using Delphi 2009 or later, where String is Unicode, you need to typecast your String to PChar when passing it to CreateFontFileReference():
hr := DWriteFactory.CreateFontFileReference(
PChar(FontPath),
ft,
FontFile);
If you are using Delphi 2007 or earlier, where String is Ansi, you need to convert your String to a WideString first and then typecast that to PWideChar:
hr := DWriteFactory.CreateFontFileReference(
PWideChar(WideString(FontPath)),
ft,
FontFile);
Update: turns out there is a bug in the declaration of the first parameter of CreateFontFileReference(). Embarcadero declares it as var filePath: WCHAR, but it should have been declared as const filePath: PWCHAR instead. So you will have to account for that bug by dereferencing the PChar/PWideChar pointer, eg:
hr := DWriteFactory.CreateFontFileReference(
PChar(FontPath)^,
...);
hr := DWriteFactory.CreateFontFileReference(
PWideChar(WideString(FontPath))^,
...);