imgui/misc/freetype/README.md

imgui_freetype

This is an attempt to replace stb_truetype (the default imgui's font rasterizer) with FreeType. Currently not optimal and probably has some limitations or bugs. By Vuhdo (Aleksei Skriabin). Improvements by @mikesart. Maintained by @ocornut.

Usage

1. Get latest FreeType binaries or build yourself.
2. Add imgui_freetype.h/cpp alongside your imgui sources.
3. Include imgui_freetype.h after imgui.h.
4. Call ImGuiFreeType::BuildFontAtlas() BEFORE calling ImFontAtlas::GetTexDataAsRGBA32() or ImFontAtlas::Build() (so normal Build() won't be called):

// See ImGuiFreeType::RasterizationFlags
unsigned int flags = ImGuiFreeType::DisableHinting;
ImGuiFreeType::BuildFontAtlas(io.Fonts, flags);
io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);

Test code Usage

#include "misc/freetype/imgui_freetype.h"
#include "misc/freetype/imgui_freetype.cpp"

// Load various small fonts
ImGuiIO& io = ImGui::GetIO();
io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 13.0f);
io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 13.0f);
io.Fonts->AddFontDefault();

FreeTypeTest freetype_test;

// Main Loop
while (true)
{
   if (freetype_test.UpdateRebuild())
   {
      // REUPLOAD FONT TEXTURE TO GPU
      // e.g ImGui_ImplGlfwGL3_InvalidateDeviceObjects() + ImGui_ImplGlfwGL3_CreateDeviceObjects()
   }
   ImGui::NewFrame();
   freetype_test.ShowFreetypeOptionsWindow();
   ...
   }
}

Test code

#include "misc/freetype/imgui_freetype.h"
#include "misc/freetype/imgui_freetype.cpp"

struct FreeTypeTest
{
    enum FontBuildMode
    {
        FontBuildMode_FreeType,
        FontBuildMode_Stb,
    };

    FontBuildMode BuildMode;
    bool          WantRebuild;
    float         FontsMultiply;
    unsigned int  FontsFlags;

    FreeTypeTest()
    {
        BuildMode = FontBuildMode_FreeType;
        WantRebuild = true;
        FontsMultiply = 1.0f;
        FontsFlags = 0;
    }

    // Call _BEFORE_ NewFrame()
    bool UpdateRebuild()
    {
        if (!WantRebuild)
            return false;
        ImGuiIO& io = ImGui::GetIO();
        for (int n = 0; n < io.Fonts->Fonts.Size; n++)
        {
            io.Fonts->Fonts[n]->ConfigData->RasterizerMultiply = FontsMultiply;
            io.Fonts->Fonts[n]->ConfigData->RasterizerFlags = (BuildMode == FontBuildMode_FreeType) ? FontsFlags : 0x00;
        }
        if (BuildMode == FontBuildMode_FreeType)
            ImGuiFreeType::BuildFontAtlas(io.Fonts, FontsFlags);
        else if (BuildMode == FontBuildMode_Stb)
            io.Fonts->Build();
        WantRebuild = false;
        return true;
    }

    // Call to draw interface
    void ShowFreetypeOptionsWindow()
    {
        ImGui::Begin("FreeType Options");
        ImGui::ShowFontSelector("Fonts");
        WantRebuild |= ImGui::RadioButton("FreeType", (int*)&BuildMode, FontBuildMode_FreeType);
        ImGui::SameLine();
        WantRebuild |= ImGui::RadioButton("Stb (Default)", (int*)&BuildMode, FontBuildMode_Stb);
        WantRebuild |= ImGui::DragFloat("Multiply", &FontsMultiply, 0.001f, 0.0f, 2.0f);
        if (BuildMode == FontBuildMode_FreeType)
        {
            WantRebuild |= ImGui::CheckboxFlags("NoHinting",     &FontsFlags, ImGuiFreeType::NoHinting);
            WantRebuild |= ImGui::CheckboxFlags("NoAutoHint",    &FontsFlags, ImGuiFreeType::NoAutoHint);
            WantRebuild |= ImGui::CheckboxFlags("ForceAutoHint", &FontsFlags, ImGuiFreeType::ForceAutoHint);
            WantRebuild |= ImGui::CheckboxFlags("LightHinting",  &FontsFlags, ImGuiFreeType::LightHinting);
            WantRebuild |= ImGui::CheckboxFlags("MonoHinting",   &FontsFlags, ImGuiFreeType::MonoHinting);
            WantRebuild |= ImGui::CheckboxFlags("Bold",          &FontsFlags, ImGuiFreeType::Bold);
            WantRebuild |= ImGui::CheckboxFlags("Oblique",       &FontsFlags, ImGuiFreeType::Oblique);
        }
        ImGui::End();
    }
};

Known issues

• Output texture has excessive resolution (lots of vertical waste)
• FreeType's memory allocator is not overridden.

Obligatory comparison screenshots

Using Windows built-in segoeui.ttf font. Open in new browser tabs, view at 1080p+.