The code in imgui.cpp embeds a copy of 'ProggyClean.ttf' that you can use without any external files.
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EXTRA FONTS FOR IMGUI
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DroidSans.ttf
Copyright (c) Steve Matteson
Apache License, version 2.0
http://www.google.com/fonts/specimen/Droid+Sans
ProggyClean.ttf
Copyright (c) 2004, 2005 Tristan Grimmer
MIT License
recommended loading setting in ImGui: Size = 13.0, DisplayOffset.Y = +1
ProggyTiny.ttf
Copyright (c) 2004, 2005 Tristan Grimmer
MIT License
recommended loading setting in ImGui: Size = 10.0, DisplayOffset.Y = +1
Karla-Regular
Copyright (c) 2012, Jonathan Pinhorn
SIL OPEN FONT LICENSE Version 1.1
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OTHER FONTS
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For Japanese:
M+ fonts by Coji Morishita are free and include most useful Kanjis you would need.
mplus-fonts.sourceforge.jp/mplus-outline-fonts/index-en.html
For Japanese, Chinese, Korean:
You can use Arial Unicode or other Unicode fonts provided with Windows (not sure of their license).
Other suggestions?
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LOADING INSTRUCTIONS
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Load .TTF file with:
ImGuiIO& io = ImGui::GetIO();
io.Fonts->AddFontFromFileTTF("myfontfile.ttf", size_pixels);
Add a third parameter to bake specific font ranges:
io.Fonts->LoadFromFileTTF("myfontfile.ttf", size_pixels, io.Fonts->GetGlyphRangesDefault()); // Basic Latin, Extended Latin
io.Fonts->LoadFromFileTTF("myfontfile.ttf", size_pixels, io.Fonts->GetGlyphRangesJapanese()); // Default + Hiragana, Katakana, Half-Width, Selection of 1946 Ideographs
io.Fonts->LoadFromFileTTF("myfontfile.ttf", size_pixels, io.Fonts->GetGlyphRangesChinese()); // Include full set of about 21000 CJK Unified Ideographs
Offset font by altering the io.Font->DisplayOffset value:
ImFont* font = io.Fonts->AddFontFromFileTTF("myfontfile.ttf", size_pixels);
font->DisplayOffset.y += 1; // Render 1 pixel down
