imgui_freetype: Documentation, tweaks. (#618)
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# imgui_freetype
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This is an attempt to replace stb_truetype (the default imgui's font rasterizer) with FreeType.
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Currently not optimal and probably has some limitations or bugs.
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By [Vuhdo](https://github.com/Vuhdo) (Aleksei Skriabin). Improvements by @mikesart. Maintained by @ocornut.
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**Usage**
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1. Get latest FreeType binaries or build yourself.
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2. Add imgui_freetype.h/cpp alongside your imgui sources.
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3. Include imgui_freetype.h after imgui.h.
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4. Call ImGuiFreeType::BuildFontAtlas() *BEFORE* calling ImFontAtlas::GetTexDataAsRGBA32() or ImFontAtlas::Build() (so normal Build() won't be called):
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```cpp
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// See ImGuiFreeType::RasterizationFlags
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unsigned int flags = ImGuiFreeType::DisableHinting;
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ImGuiFreeType::BuildFontAtlas(io.Fonts, flags);
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io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);
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```
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**Test code Usage**
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```cpp
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#include "misc/freetype/imgui_freetype.h"
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#include "misc/freetype/imgui_freetype.cpp"
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// Load various small fonts
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ImGuiIO& io = ImGui::GetIO();
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io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 13.0f);
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io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 13.0f);
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io.Fonts->AddFontDefault();
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FreeTypeTest freetype_test;
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// Main Loop
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while (true)
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{
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if (freetype_test.UpdateRebuild())
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{
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// REUPLOAD FONT TEXTURE TO GPU
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// e.g ImGui_ImplGlfwGL3_InvalidateDeviceObjects() + ImGui_ImplGlfwGL3_CreateDeviceObjects()
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}
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ImGui::NewFrame();
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freetype_test.ShowFreetypeOptionsWindow();
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...
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}
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}
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```
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**Test code**
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```cpp
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#include "misc/freetype/imgui_freetype.h"
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#include "misc/freetype/imgui_freetype.cpp"
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struct FreeTypeTest
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{
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enum FontBuildMode
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{
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FontBuildMode_FreeType,
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FontBuildMode_Stb,
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};
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FontBuildMode BuildMode;
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bool WantRebuild;
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float FontsMultiply;
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unsigned int FontsFlags;
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FreeTypeTest()
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{
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BuildMode = FontBuildMode_FreeType;
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WantRebuild = true;
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FontsMultiply = 1.0f;
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FontsFlags = 0;
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}
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// Call _BEFORE_ NewFrame()
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bool UpdateRebuild()
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{
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if (!WantRebuild)
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return false;
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ImGuiIO& io = ImGui::GetIO();
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for (int n = 0; n < io.Fonts->Fonts.Size; n++)
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{
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io.Fonts->Fonts[n]->ConfigData->RasterizerMultiply = FontsMultiply;
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io.Fonts->Fonts[n]->ConfigData->RasterizerFlags = (BuildMode == FontBuildMode_FreeType) ? FontsFlags : 0x00;
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}
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if (BuildMode == FontBuildMode_FreeType)
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ImGuiFreeType::BuildFontAtlas(io.Fonts, FontsFlags);
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else if (BuildMode == FontBuildMode_Stb)
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io.Fonts->Build();
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WantRebuild = false;
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return true;
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}
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// Call to draw interface
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void ShowFreetypeOptionsWindow()
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{
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ImGui::Begin("FreeType Options");
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ImGui::ShowFontSelector("Fonts");
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WantRebuild |= ImGui::RadioButton("FreeType", (int*)&BuildMode, FontBuildMode_FreeType);
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ImGui::SameLine();
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WantRebuild |= ImGui::RadioButton("Stb (Default)", (int*)&BuildMode, FontBuildMode_Stb);
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WantRebuild |= ImGui::DragFloat("Multiply", &FontsMultiply, 0.001f, 0.0f, 2.0f);
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if (BuildMode == FontBuildMode_FreeType)
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{
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WantRebuild |= ImGui::CheckboxFlags("NoHinting", &FontsFlags, ImGuiFreeType::NoHinting);
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WantRebuild |= ImGui::CheckboxFlags("NoAutoHint", &FontsFlags, ImGuiFreeType::NoAutoHint);
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WantRebuild |= ImGui::CheckboxFlags("ForceAutoHint", &FontsFlags, ImGuiFreeType::ForceAutoHint);
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WantRebuild |= ImGui::CheckboxFlags("LightHinting", &FontsFlags, ImGuiFreeType::LightHinting);
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WantRebuild |= ImGui::CheckboxFlags("MonoHinting", &FontsFlags, ImGuiFreeType::MonoHinting);
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WantRebuild |= ImGui::CheckboxFlags("Bold", &FontsFlags, ImGuiFreeType::Bold);
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WantRebuild |= ImGui::CheckboxFlags("Oblique", &FontsFlags, ImGuiFreeType::Oblique);
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}
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ImGui::End();
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}
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};
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```
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**Known issues**
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- Output texture has excessive resolution (lots of vertical waste)
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- FreeType's memory allocator is not overridden.
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**Obligatory comparison screenshots**
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Using Windows built-in segoeui.ttf font. Open in new browser tabs, view at 1080p+.
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![freetype rasterizer](https://raw.githubusercontent.com/wiki/ocornut/imgui_club/images/freetype_20170817.png)
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