Rebuilding the ImGui library

The bindings in libs/imgui are not a pure Odin implementation. They wrap the C++ API of dear imgui and link against a static library. That library has to be compiled once, per platform, and dropped next to the bindings. Both versions are committed in the repo - imgui_windows_x64.lib and libimgui_linux_x64.a - so day to day you never need this page. You need it only when you bump the ImGui version, or when a library goes missing and has to be regenerated.

This page walks through the rebuild for Windows and Linux, with the exact versions the project uses.

The version pairing

The Odin binding and the C library must be built from the same ImGui version, otherwise the app fails fast at startup. The binding stores the version it was generated for:

VERSION :: "1.92.8"

(libs/imgui/imgui.odin:49)

CHECKVERSION (libs/imgui/imgui.odin:35) compares that string against the compiled library’s IMGUI_VERSION, plus the size of its core structs. If they disagree you get an assert at initialization, not a compile or link error. So when you rebuild the library, rebuild it from the same version the bindings were generated from.

This project uses:

  • dear imgui: v1.92.8-docking
  • dear_bindings: DearBindings_v0.21_ImGui_v1.92.8-docking
  • GLFW headers: 3.3 (why this exact pin? see the pitfalls at the bottom)

Prerequisites

  • premake5 - the odin-imgui repository ships one at its root, or install it from premake.github.io.
  • git - premake clones the ImGui, dear_bindings, GLFW and Vulkan-Headers sources into build/deps.
  • Python 3 with the venv and pip modules (dear_bindings needs them). On Linux: 
    sudo apt install python3-venv python3-pip
  • Windows: MSVC - Visual Studio 2022 or the Build Tools. The build script needs vcvars64.bat to be reachable.
  • Linux: make and a C++ compiler (the build-essential package).

Get the odin-imgui repository

The bindings and the build tooling come from Capati/odin-imgui. Clone it once:

git clone https://github.com/Capati/odin-imgui
cd odin-imgui

The rest of this page assumes you are working from that folder.

Generate the build files

From the repository root, generate the project files with the pinned versions and the backends the project uses.

On Linux:

premake5 --backends=glfw,vulkan --imgui-version=v1.92.8-docking --dear-bindings-version=DearBindings_v0.21_ImGui_v1.92.8-docking --glfw-version=3.3 gmake

On Windows:

premake5 --backends=glfw,vulkan --imgui-version=v1.92.8-docking --dear-bindings-version=DearBindings_v0.21_ImGui_v1.92.8-docking --glfw-version=3.3 vs2022

premake clones the dependencies if needed, runs dear_bindings (the Python step, which generates the dcimgui C wrapper in build/generated) and writes the build files.

Build on Windows

Open a Visual Studio developer prompt - so vcvars64.bat is on the PATH - go to the build folder and run:

build.bat

The script compiles the ImGui sources and the generated wrapper, then archives them into imgui_windows_x64.lib at the repository root.

Build on Linux

Go to the generated make directory and build with make:

cd build/make/linux
make config=release_x86_64

The result, libimgui_linux_x64.a, lands at the repository root.

Copy the result

Move the archive into the project, next to the binding:

  • Windows: imgui_windows_x64.lib -> libs/imgui/imgui_windows_x64.lib
  • Linux: libimgui_linux_x64.a -> libs/imgui/libimgui_linux_x64.a

That is where the foreign import in libs/imgui/imgui.odin looks for it - line 12 on Windows, line 20 on Linux. No other file needs to change, since the committed bindings already match the pinned version.

Pitfalls

premake does not re-checkout existing dependencies

premake only clones a repository if its folder under build/deps/ does not exist yet. Running it again with different version flags on an existing checkout changes nothing. To switch versions, delete build/deps/imgui, build/deps/dear_bindings and build/deps/glfw first (or check the tags out manually inside those folders), then re-run premake.

premake’s default GLFW version is 3.4. With those headers, imgui_impl_glfw.cpp calls glfwGetPlatform(), a GLFW 3.4-only function. On Linux the Odin program links against the system GLFW, which on Ubuntu 24.04 is 3.3.10, so the link fails with:

undefined reference to glfwGetPlatform

The Odin binding dodges this because it declares GetPlatform with weak linkage on Linux (vendor/glfw/bindings/bindings.odin:216), so the app itself links fine and the error only shows up through the static library. Pinning --glfw-version=3.3 makes the ImGui backend compile against the 3.3 headers, which do not reference the function at all.

A version mismatch shows up at runtime

If the library and the bindings disagree, the failure is not a link error but an assert during initialization:

unsatisfied ensure: DebugCheckVersionAndDataLayout(...)

That means the library was built from a different ImGui version than imgui.odin. Check the --imgui-version you passed to premake against VERSION in libs/imgui/imgui.odin.

The generated bindings use spaces, the project wants tabs

The .odin binding files generated by dear_bindings indent with spaces, but the project compiles with -vet-tabs. The copies committed in libs/imgui were converted. If you regenerate the bindings - as opposed to only rebuilding the C library - convert the indentation to tabs before copying them in.