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 in the source code so you can use Dear ImGui without any file system access. ProggyClean does not scale smoothly, therefore it is recommended that you load your own file when using Dear ImGui in an application aiming to look nice and wanting to support multiple resolutions.

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

Read the FAQ: https://www.dearimgui.org/faq (there is a Fonts section!)

Use the Discord server: http://discord.dearimgui.org and not the GitHub issue tracker for basic font loading questions.

Index

Readme First

  • All loaded fonts glyphs are rendered into a single texture atlas ahead of time. Calling either of io.Fonts->GetTexDataAsAlpha8(), io.Fonts->GetTexDataAsRGBA32() or io.Fonts->Build() will build the atlas.

  • 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. You can also reach it in Demo->Tools->Style Editor->Fonts:

imgui_capture_0008

  • Make sure your font ranges data are persistent (available during the calls 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
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How should I handle DPI in my application?

See FAQ entry.

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Font Loading Instructions

Load default font:

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

Load .TTF/.OTF file with:

ImGuiIO& io = ImGui::GetIO();
io.Fonts->AddFontFromFileTTF("font.ttf", size_pixels);

If you get an assert stating “Could not load font file!”, your font filename is likely incorrect. Read “About filenames” carefully.

Load multiple fonts:

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 multiple 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()); // Merge into first font
io.Fonts->AddFontFromFileTTF("fontawesome-webfont.ttf", 18.0f, &config, icons_ranges);             // Merge into first font
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 Using Custom Glyph Ranges section to create your own ranges.

Example loading and using a Japanese font:

ImGuiIO& io = ImGui::GetIO();
io.Fonts->AddFontFromFileTTF("NotoSansCJKjp-Medium.otf", 20.0f, NULL, io.Fonts->GetGlyphRangesJapanese());

ImGui::Text(u8"こんにちは！テスト %d", 123);
if (ImGui::Button(u8"ロード"))
{
    // do stuff
}
ImGui::InputText("string", buf, IM_ARRAYSIZE(buf));
ImGui::SliderFloat("float", &f, 0.0f, 1.0f);

sample code output
(settings: Dark style (left), Light style (right) / Font: NotoSansCJKjp-Medium, 20px / Rounding: 5)

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.
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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.

So you can use ICON_FA_SEARCH as a string that will render as a “Search” icon.

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.

Here's an application using icons (“Avoyd”, https://www.avoyd.com): avoyd

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Using 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.
  • Read documentation in the misc/freetype/ folder.
  • Correct sRGB space blending will have an important effect on your font rendering quality.
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Using 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.
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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.
  • This API is beta because it is likely to change in order to support multi-dpi (multiple viewports on multiple monitors with varying DPI scale).

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);
        }
    }
}
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Using Font Data Embedded 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, ...);
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About filenames

Please note that many new C/C++ users have issues their files because the filename they provide is wrong.

Two things to watch for:

  • Make sure your IDE/debugger settings starts your executable from the right working directory. In Visual Studio you can change your working directory in project Properties > General > Debugging > Working Directory. People assume that their execution will start from the root folder of the project, where by default it oftens start from the folder where object or executable files are stored.
// Relative filename depends on your Working Directory when running your program!
io.Fonts->AddFontFromFileTTF("MyImage01.jpg", ...);

// Load from the parent folder of your Working Directory
io.Fonts->AddFontFromFileTTF("../MyImage01.jpg", ...);
  • In C/C++ and most programming languages if you want to use a backslash \ within a string literal, you need to write it double backslash \\. At it happens, Windows uses backslashes as a path separator, so be mindful.
io.Fonts->AddFontFromFileTTF("MyFiles\MyImage01.jpg", ...);   // This is INCORRECT!!
io.Fonts->AddFontFromFileTTF("MyFiles\\MyImage01.jpg", ...);  // This is CORRECT

In some situations, you may also use / path separator under Windows.

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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 Robetson
  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
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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).

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