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imgui/misc/freetype/README.md

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# imgui_freetype
2019-06-11 14:11:19 +00:00
Build font atlases using FreeType instead of stb_truetype (which is the default font rasterizer in Dear ImGui).
<br>by @vuhdo, @mikesart, @ocornut.
### Usage
1. Get latest FreeType binaries or build yourself (under Windows you may use vcpkg with `vcpkg install freetype`).
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):
```cpp
// See ImGuiFreeType::RasterizationFlags
2018-05-30 08:28:27 +00:00
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](https://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#FT_Render_Glyph).
For correct results you need to be using sRGB and convert to linear space in the pixel shader output.
2019-06-11 14:11:19 +00:00
The default Dear ImGui styles will be impacted by this change (alpha values will need tweaking).
### Test code Usage
```cpp
#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
```cpp
#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).