#1277 Color font for Windows 8.1 and above in Direct2D mode

[Zufu Liu]

https://docs.microsoft.com/en-us/windows/desktop/api/d2d1/ne-d2d1-d2d1_draw_text_options
D2D1_DRAW_TEXT_OPTIONS_ENABLE_COLOR_FONT is available for Windows 8.1 and above ( not available in Win7 SDK and MinGW-w64 before 2019-02-12).

Using this option crashed on early systems.
The patch is just an outline, need portable version checking (versionhelpers.h only usable for _WIN32_WINNT >= 0x0501 and not available in MinGW-w64 before 2015-03-09. call GetVersion() may got deprecated warnings).

[Neil Hodgson]

Versionhelpers have an unchecked version dependency themselves since VerifyVersionInfo is only from Windows 2000 or later. Not that Windows NT 4 has been checked recently.
https://docs.microsoft.com/en-us/windows/desktop/api/Winbase/nf-winbase-verifyversioninfoa

Attempting to dynamically load and use VerifyVersionInfo is complex.
https://walbourn.github.io/whats-in-a-version-number/

Its unclear just which call 'crashed on early systems' and its possible the crash can be avoided by checking the results from some test calls with coloured characters.

kD2D1DrawTextOptions isn't a constant and Scintilla doesn't use 'k' prefixes for constants. Its also inside the Scintilla namespace so doesn't need to be static.

Perhaps its better to have a more direct check. The coloured text support arrived with the dwrite_2.h file and IDWriteFactory2.
https://docs.microsoft.com/en-us/windows/desktop/api/dwrite_2/nn-dwrite_2-idwritefactory2
So, the code could ask for IDWriteFactory2, and set D2D1_DRAW_TEXT_OPTIONS_ENABLE_COLOR_FONT if that worked. If it fails, ask for IDWriteFactory. Something like:

DWriteCFSig fnDWCF = reinterpret_cast<DWriteCFSig>(::GetProcAddress(hDLLDWrite, "DWriteCreateFactory"));
if (fnDWCF) {
    const HRESULT hr = fnDWCF(DWRITE_FACTORY_TYPE_SHARED,
        __uuidof(IDWriteFactory2),
        reinterpret_cast<IUnknown**>(&pIDWriteFactory));
    if (SUCCEEDED(hr)) {
        // D2D1_DRAW_TEXT_OPTIONS_ENABLE_COLOR_FONT
        drawTextOptions = static_cast<D2D1_DRAW_TEXT_OPTIONS>(0x00000004);
    } else {
        fnDWCF(DWRITE_FACTORY_TYPE_SHARED,
            __uuidof(IDWriteFactory),
            reinterpret_cast<IUnknown**>(&pIDWriteFactory));
    }
}

Including dwrite_2.h could have its own problems with older SDKs or MinGW distributions.

[Zufu Liu]

Your code works.
the patch replaced __uuidof(IDWriteFactory2) with hard-coded UUID (which not changes), no dependency on dwrite_2.h.

[Zufu Liu]

'crashed on early systems': application (i.e. SciTE) not crashed, but draws nothing when open files, only got a black editor window, no caret, no text.

[Neil Hodgson]

Change committed as [76fcbb].