如何在 DirectWrite 中使用默认 UI 字体绘制文本？

Question

CreateTextFormat 方法需要一个 fontFamilyName 参数。如何创建使用默认 UI 字体的 IDWriteTextFormat？

Answer 1

请注意，这里的所有代码都是在没有任何检查的情况下完成的（这里返回 HRESULT 的方法太多，会炸毁这个示例！）。

要获取系统范围的字体，您应该使用：

（这是来自另一个stackoverflow问题！）

NONCLIENTMETRICS ncm;
ncm.cbSize = sizeof(ncm);
SystemParametersInfo(SPI_GETNONCLIENTMETRICS, ncm.cbSize, &ncm, 0);
HFONT hFont = CreateFontIndirect(&(ncm.lfMessageFont)); //

现在用这个来作画：

HDC hdc = BeginPaint(...); //Creates a device context
SelectObject(hdc, hFont);
//Your font is now set for the current device context
//do something

DeleteObject(hFont); //Don't forget to do this at the end!

与this问题有点不同！

这个解决方案真的很原始，在我看来很难看。

替代解决方案确实获得 IDWriteFont（看起来很丑但很好）：

//just the same as above except the hfont, instead use
NONCLIENTMETRICS ncm;

ncm.cbSize = sizeof(ncm);
SystemParametersInfo(SPI_GETNONCLIENTMETRICS, ncm.cbSize, &ncm, 0);

IDWriteFactory *dwriteFactory_;
DWriteCreateFactory(
    DWRITE_FACTORY_TYPE_SHARED,
    __uuidof(IDWriteFactory),
    reinterpret_cast<IUnknown**>(&dwriteFactory_)
);

IDWriteGdiInterop* gdiInterop = NULL;
dwriteFactory_->GetGdiInterop(&gdiInterop);

IDWriteFont* sys_font = nullptr;
gdiInterop->CreateFontFromLOGFONT(&ncm.lfMessageFont, &sys_font); //Now we have it!

//The text format can now be aquired like this
//We need the font family of our font
IDWriteFontFamily* family = nullptr;
sys_font->GetFontFamily(&family);

//Now we have to get the "localized" name of our family
IDWriteLocalizedStrings* font_family_name = nullptr;
family->GetFamilyNames(&font_family_name);
UINT32 index = 0;
UINT32 length = 0;
BOOL exists = false;
font_family_name->FindLocaleName(L"en-us", &index, &exists);
font_family_name->GetStringLength(index, &length);
wchar_t* name = new wchar_t[length + 1];
font_family_name->GetString(index, name, length + 1);
wprintf(L"%s\n", name);

//Some user defined stuff
DWRITE_FONT_WEIGHT font_weight = DWRITE_FONT_WEIGHT_BLACK;
DWRITE_FONT_STYLE font_style = DWRITE_FONT_STYLE_ITALIC;
DWRITE_FONT_STRETCH font_stretch = DWRITE_FONT_STRETCH_EXPANDED;

IDWriteTextFormat* text_format = nullptr;
dwriteFactory_->CreateTextFormat(name, nullptr, font_weight, font_style, font_stretch, 10.0, L"en-us", &text_format);

即使没有检查，代码在我的计算机上运行也没有任何问题，并给我与第一个解决方案相同的结果（Windows 10，字体系列名称是 Segoe UI）。

来源： General Microsoft DirectWrite API documentation

CreateIndirectFont Documentation

How to enumerate font families, Microsoft documentation