History

Bartosz Taudul 6469b94304 Silence memset warning. (#3505 ) Compiling the code as-is results in the following warning: -->8-- imgui_freetype.cpp:341:72: warning: ‘void* memset(void, int, size_t)’ clearing an object of type ‘struct ImFontBuildSrcDataFT’ with no trivial copy-assignment; use assignment or value-initialization instead [-Wclass-memaccess] 341 \| memset(src_tmp_array.Data, 0, (size_t)src_tmp_array.size_in_bytes()); \| ^ imgui_freetype.cpp:302:8: note: ‘struct ImFontBuildSrcDataFT’ declared here 302 \| struct ImFontBuildSrcDataFT \| ^~~~~~~~~~~~~~~~~~~~ --8<-- This is caused by presence of ImVector<> directly in ImFontBuildSrcDataFT data structure, as well as in the child ImBitVector. Since ImVector<> has a constructor, the compiler infers that initialization by memset is not valid. Such initialization is not a bug, however, as the default ImVector<> ctor just sets the structure data members to 0, which is exactly what the memset does. Casting the data structure address to void pointer silences this warning.		2020-10-02 19:12:53 +02:00
..
README.md	Internals: Renamed ImBoolVector to ImBitVector, added low-level loose function to replicate the behavior include a help SetBitRange() function.	2020-03-13 18:50:02 +01:00
imgui_freetype.cpp	Silence memset warning. (#3505 )	2020-10-02 19:12:53 +02:00
imgui_freetype.h	Fixed stray end of line blanks, added comments in .editorconfig, tweaked some headers.	2020-04-07 14:46:46 +02:00

README.md

imgui_freetype

Build font atlases using FreeType instead of stb_truetype (which is the default font rasterizer in Dear ImGui).
by @vuhdo, @mikesart, @ocornut.

Usage

Get latest FreeType binaries or build yourself (under Windows you may use vcpkg with vcpkg install freetype, vcpkg integrate install).
Add imgui_freetype.h/cpp alongside your imgui sources.
Include imgui_freetype.h after imgui.h.
Call ImGuiFreeType::BuildFontAtlas() BEFORE calling ImFontAtlas::GetTexDataAsRGBA32() or ImFontAtlas::Build() (so normal Build() won't be called):

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

Gamma Correct Blending

FreeType assumes blending in linear space rather than gamma space. See FreeType note for FT_Render_Glyph. For correct results you need to be using sRGB and convert to linear space in the pixel shader output. The default Dear ImGui styles will be impacted by this change (alpha values will need tweaking).

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
      ImGui_ImplXXX_DestroyDeviceObjects();
      ImGui_ImplXXX_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;
    int           FontsPadding;
    unsigned int  FontsFlags;

    FreeTypeTest()
    {
        BuildMode = FontBuildMode_FreeType;
        WantRebuild = true;
        FontsMultiply = 1.0f;
        FontsPadding = 1;
        FontsFlags = 0;
    }

    // Call _BEFORE_ NewFrame()
    bool UpdateRebuild()
    {
        if (!WantRebuild)
            return false;
        ImGuiIO& io = ImGui::GetIO();
        io.Fonts->TexGlyphPadding = FontsPadding;
        for (int n = 0; n < io.Fonts->ConfigData.Size; n++)
        {
            ImFontConfig* font_config = (ImFontConfig*)&io.Fonts->ConfigData[n];
            font_config->RasterizerMultiply = FontsMultiply;
            font_config->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);
        WantRebuild |= ImGui::DragInt("Padding", &FontsPadding, 0.1f, 0, 16);
        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);
            WantRebuild |= ImGui::CheckboxFlags("Monochrome",    &FontsFlags, ImGuiFreeType::Monochrome);
        }
        ImGui::End();
    }
};

Known issues

cfg.OversampleH, OversampleV are ignored (but perhaps not so necessary with this rasterizer).