Dear ImGui: Using Fonts

(You may browse this document at https://github.com/ocornut/imgui/blob/master/docs/FONTS.md or view this file with any Markdown viewer.)

The code in imgui.cpp embeds a copy of ‘ProggyClean.ttf’ (by Tristan Grimmer), a 13 pixels high, pixel-perfect font used by default. We embed it font in source code so you can use Dear ImGui without any file system access.

You may also load external .TTF/.OTF files. In the misc/fonts/ folder you can find a few suggested fonts, provided as a convenience.

Also read the FAQ: https://www.dearimgui.org/faq

Please use the Discord server: http://discord.dearimgui.org and not the Github issue tracker for basic font loading questions.

Index
Readme First
Fonts Loading Instructions
Using Icons
Using the FreeType Rasterizer
Building Custom Glyph Ranges
Using Custom Colorful Icons
Embedding Fonts In Source Code
Credits/Licenses For Fonts Included In Repository
Font Links

Readme First

  • All loaded fonts glyphs are rendered into a single texture atlas at the time of calling either of io.Fonts->GetTexDataAsAlpha8(), io.Fonts->GetTexDataAsRGBA32() or io.Fonts->Build().
  • You can use the style editor ImGui::ShowStyleEditor() in the “Fonts” section to browse your fonts and understand what's going on if you have an issue.
  • Make sure your font ranges data are persistent (available during the call to GetTexDataAsAlpha8()/GetTexDataAsRGBA32()/Build().
  • Use C++11 u8“my text” syntax to encode literal strings as UTF-8. e.g.:
u8"hello"
u8"こんにちは"   // this will be encoded as UTF-8
  • If you want to include a backslash \ character in your string literal, you need to double them e.g. "folder\\filename".
  • Please use the Discord forum and not the Github issue tracker for basic font loading questions.

Font Loading Instructions

Load default font:

  ImGuiIO& io = ImGui::GetIO();
  io.Fonts->AddFontDefault();

Load .TTF/.OTF file with:

ImGuiIO& io = ImGui::GetIO();
ImFont* font1 = io.Fonts->AddFontFromFileTTF("font.ttf", size_pixels);
ImFont* font2 = io.Fonts->AddFontFromFileTTF("anotherfont.otf", size_pixels);

// Select font at runtime
ImGui::Text("Hello");	// use the default font (which is the first loaded font)
ImGui::PushFont(font2);
ImGui::Text("Hello with another font");
ImGui::PopFont();

For advanced options create a ImFontConfig structure and pass it to the AddFont function (it will be copied internally):

ImFontConfig config;
config.OversampleH = 2;
config.OversampleV = 1;
config.GlyphExtraSpacing.x = 1.0f;
ImFont* font = io.Fonts->AddFontFromFileTTF("font.ttf", size_pixels, &config);

Combine two fonts into one:

// Load a first font
ImFont* font = io.Fonts->AddFontDefault();

// Add character ranges and merge into the previous font
// The ranges array is not copied by the AddFont* functions and is used lazily
// so ensure it is available at the time of building or calling GetTexDataAsRGBA32().
static const ImWchar icons_ranges[] = { 0xf000, 0xf3ff, 0 }; // Will not be copied by AddFont* so keep in scope.
ImFontConfig config;
config.MergeMode = true;
io.Fonts->AddFontFromFileTTF("DroidSans.ttf", 18.0f, &config, io.Fonts->GetGlyphRangesJapanese());
io.Fonts->AddFontFromFileTTF("fontawesome-webfont.ttf", 18.0f, &config, icons_ranges);
io.Fonts->Build();

Add a fourth parameter to bake specific font ranges only:

// Basic Latin, Extended Latin
io.Fonts->AddFontFromFileTTF("font.ttf", size_pixels, NULL, io.Fonts->GetGlyphRangesDefault());

// Default + Selection of 2500 Ideographs used by Simplified Chinese
io.Fonts->AddFontFromFileTTF("font.ttf", size_pixels, NULL, io.Fonts->GetGlyphRangesChineseSimplifiedCommon());

// Default + Hiragana, Katakana, Half-Width, Selection of 1946 Ideographs
io.Fonts->AddFontFromFileTTF("font.ttf", size_pixels, NULL, io.Fonts->GetGlyphRangesJapanese());

See Building Custom Glyph Ranges section to create your own ranges. Offset font vertically by altering the io.Font->DisplayOffset value:

ImFont* font = io.Fonts->AddFontFromFileTTF("font.ttf", size_pixels);
font->DisplayOffset.y = 1;   // Render 1 pixel down

Font Atlas too large?

  • If you have very large number of glyphs or multiple fonts, the texture may become too big for your graphics API. The typical result of failing to upload a texture is if every glyphs appears as white rectangles.
  • In particular, using a large range such as GetGlyphRangesChineseSimplifiedCommon() is not recommended unless you set OversampleH/OversampleV to 1 and use a small font size.
  • Mind the fact that some graphics drivers have texture size limitation.
  • If you are building a PC application, mind the fact that your users may use hardware with lower limitations than yours.

Some solutions:

  1. Reduce glyphs ranges by calculating them from source localization data. You can use the ImFontGlyphRangesBuilder for this purpose, this will be the biggest win!
  2. You may reduce oversampling, e.g. font_config.OversampleH = font_config.OversampleV = 1, this will largely reduce your texture size.
  3. Set io.Fonts.TexDesiredWidth to specify a texture width to minimize texture height (see comment in ImFontAtlas::Build() function).
  4. Set io.Fonts.Flags |= ImFontAtlasFlags_NoPowerOfTwoHeight; to disable rounding the texture height to the next power of two.
  5. Read about oversampling here.

Using Icons

  • Using an icon font (such as FontAwesome or OpenFontIcons) is an easy and practical way to use icons in your Dear ImGui application.
  • A common pattern is to merge the icon font within your main font, so you can embed icons directly from your strings without having to change fonts back and forth.
  • To refer to the icon UTF-8 codepoints from your C++ code, you may use those headers files created by Juliette Foucaut: https://github.com/juliettef/IconFontCppHeaders

The C++11 version of those files uses the u8"" UTF-8 encoding syntax:

#define ICON_FA_SEARCH u8"\uf002"

The pre-C++11 version has the values manually encoded as UTF-8:

#define ICON_FA_SEARCH "\xEF\x80\x82"

Example Setup:

  // Merge icons into default tool font
  #include "IconsFontAwesome.h"
  ImGuiIO& io = ImGui::GetIO();
  io.Fonts->AddFontDefault();

  ImFontConfig config;
  config.MergeMode = true;
  config.GlyphMinAdvanceX = 13.0f; // Use if you want to make the icon monospaced
  static const ImWchar icon_ranges[] = { ICON_MIN_FA, ICON_MAX_FA, 0 };
  io.Fonts->AddFontFromFileTTF("fonts/fontawesome-webfont.ttf", 13.0f, &config, icon_ranges);

Example Usage:

  // Usage, e.g.
  ImGui::Text("%s among %d items", ICON_FA_SEARCH, count);
  ImGui::Button(ICON_FA_SEARCH " Search");
  // C string _literals_ can be concatenated at compilation time, e.g. "hello" " world"
  // ICON_FA_SEARCH is defined as a string literal so this is the same as "A" "B" becoming "AB"

See Links below for other icons fonts and related tools.

Using the FreeType Rasterizer

  • Dear ImGui uses imstb_truetype.h to rasterize fonts (with optional oversampling). This technique and its implementation are not ideal for fonts rendered at small sizes, which may appear a little blurry or hard to read.
  • There is an implementation of the ImFontAtlas builder using FreeType that you can use in the misc/freetype/ folder.
  • FreeType supports auto-hinting which tends to improve the readability of small fonts.

Note

  • This code currently creates textures that are unoptimally too large (could be fixed with some work).
  • Also note that correct sRGB space blending will have an important effect on your font rendering quality.

Building Custom Glyph Ranges

You can use the ImFontGlyphRangesBuilder helper to create glyph ranges based on text input. For example: for a game where your script is known, if you can feed your entire script to it and only build the characters the game needs.

  ImVector<ImWchar> ranges;
  ImFontGlyphRangesBuilder builder;
  builder.AddText("Hello world");                        // Add a string (here "Hello world" contains 7 unique characters)
  builder.AddChar(0x7262);                               // Add a specific character
  builder.AddRanges(io.Fonts->GetGlyphRangesJapanese()); // Add one of the default ranges
  builder.BuildRanges(&ranges);                          // Build the final result (ordered ranges with all the unique characters submitted)

  io.Fonts->AddFontFromFileTTF("myfontfile.ttf", size_in_pixels, NULL, ranges.Data);
  io.Fonts->Build();                                     // Build the atlas while 'ranges' is still in scope and not deleted.

Using Custom Colorful Icons

(This is a BETA api, use if you are familiar with dear imgui and with your rendering back-end)

  • You can use the ImFontAtlas::AddCustomRect() and ImFontAtlas::AddCustomRectFontGlyph() api to register rectangles that will be packed into the font atlas texture. Register them before building the atlas, then call Build()`.
  • You can then use ImFontAtlas::GetCustomRectByIndex(int) to query the position/size of your rectangle within the texture, and blit/copy any graphics data of your choice into those rectangles.

Pseudo-code:

  // Add font, then register two custom 13x13 rectangles mapped to glyph 'a' and 'b' of this font
  ImFont* font = io.Fonts->AddFontDefault();
  int rect_ids[2];
  rect_ids[0] = io.Fonts->AddCustomRectFontGlyph(font, 'a', 13, 13, 13+1);
  rect_ids[1] = io.Fonts->AddCustomRectFontGlyph(font, 'b', 13, 13, 13+1);

  // Build atlas
  io.Fonts->Build();

  // Retrieve texture in RGBA format
  unsigned char* tex_pixels = NULL;
  int tex_width, tex_height;
  io.Fonts->GetTexDataAsRGBA32(&tex_pixels, &tex_width, &tex_height);

  for (int rect_n = 0; rect_n < IM_ARRAYSIZE(rect_ids); rect_n++)
  {
      int rect_id = rects_ids[rect_n];
      if (const ImFontAtlas::CustomRect* rect = io.Fonts->GetCustomRectByIndex(rect_id))
      {
          // Fill the custom rectangle with red pixels (in reality you would draw/copy your bitmap data here!)
          for (int y = 0; y < rect->Height; y++)
          {
              ImU32* p = (ImU32*)tex_pixels + (rect->Y + y) * tex_width + (rect->X);
              for (int x = rect->Width; x > 0; x--)
                  *p++ = IM_COL32(255, 0, 0, 255);
          }
      }
  }

Embedding Fonts In Source Code

  • Compile and use ‘binary_to_compressed_c.cpp’ to create a compressed C style array that you can embed in source code.
  • See the documentation in binary_to_compressed_c.cpp for instruction on how to use the tool.
  • You may find a precompiled version binary_to_compressed_c.exe for Windows instead of demo binaries package (see README).
  • The tool can optionally output Base85 encoding to reduce the size of source code but the read-only arrays in the actual binary will be about 20% bigger.

Then load the font with: ImFont* font = io.Fonts->AddFontFromMemoryCompressedTTF(compressed_data, compressed_data_size, size_pixels, ...); or ImFont* font = io.Fonts- AddFontFromMemoryCompressedBase85TTF(compressed_data_base85, size_pixels, ...);

Credits/Licenses For Fonts Included In Repository

Some fonts files are available in the misc/fonts/ folder.

Roboto-Medium.ttf

Apache License 2.0 by Christian Robertson https://fonts.google.com/specimen/Roboto

Cousine-Regular.ttf

by Steve Matteson Digitized data copyright (c) 2010 Google Corporation. Licensed under the SIL Open Font License, Version 1.1 https://fonts.google.com/specimen/Cousine

DroidSans.ttf

Copyright (c) Steve Matteson Apache License, version 2.0 https://www.fontsquirrel.com/fonts/droid-sans

ProggyClean.ttf

Copyright (c) 2004, 2005 Tristan Grimmer MIT License recommended loading setting: Size = 13.0, DisplayOffset.Y = +1 http://www.proggyfonts.net/

ProggyTiny.ttf Copyright (c) 2004, 2005 Tristan Grimmer MIT License recommended loading setting: Size = 10.0, DisplayOffset.Y = +1 http://www.proggyfonts.net/

Karla-Regular.ttf Copyright (c) 2012, Jonathan Pinhorn SIL OPEN FONT LICENSE Version 1.1

Font Links

ICON FONTS

REGULAR FONTS

MONOSPACE FONTS

Pixel Perfect:

Regular:

Or use Arial Unicode or other Unicode fonts provided with Windows for full characters coverage (not sure of their licensing).