imgui-mirror/misc/dwrite

imgui_dwrite

This implements font rasterization using DirectWrite instead of stb_truetype (otherwise the default).
by @lhecker.

The minimum requirement is Windows 10 1709 (build 16299).

Usage

1. Add imgui_dwrite.h/cpp alongside your project files.
2. Either set #define IMGUI_ENABLE_DWRITE in your imconfig.h file or call ImGui::GetIO().Fonts->SetFontLoader(ImGuiDWrite::GetFontLoader()).
3. Add fonts using ImGui::GetIO().Fonts->AddFontFromFamily("Segoe UI").

The Good

• An improved rasterization over stb_truetype (particularly at small font sizes).
• You can use system fonts.
• It supports font fallback.

The Bad

• Loads font families using regular weight, normal stretch, and normal style only.
• Not all ImFontConfig rasterizer options are implemented.
• IMGUI_USE_WCHAR32 is required to render codepoints above U+FFFF, such as emoji. Multi-codepoint glyphs are not supported.
• ProggyForever.ttf will not look good. If you're curious: This is because the font does not set USE_TYPO_METRICS, which causes DirectWrite to correctly use the OS/2 usWinAscent/Descent fields instead of sTypoAscender/Descender. stb_truetype on the other hand uses the hhea table (OpenType is an old standard and has competing metrics tables) whose values coincide with the latter. This causes the glyphs to be nice and large with stb_truetype and small and squished with DirectWrite.

...and most importantly: Gamma correct text blending is not supported. DirectWrite relies on gamma correction being applied by a shader during composition. A variant of this can be found at https://github.com/lhecker/dwrite-hlsl but this cannot be trivially integrated into ImGui.