Crate dear_imgui_sys

Expand description

Low-level FFI bindings for Dear ImGui (via cimgui C API) with docking support

This crate provides raw, unsafe bindings to Dear ImGui using the cimgui C API, specifically targeting the docking branch (multi-viewport capable).

§Features

docking: Always enabled in this crate
freetype: Enable FreeType font rasterizer support
wasm: Enable the wasm32-unknown-unknown browser import-provider ABI
stack-layout: Enable the native patched core artifact used by blueprint-style layouts
prebuilt: Allow downloading a compatible native prebuilt artifact
build-from-source: Force compilation of the native artifact from vendored sources
test-engine: Enable native test engine hooks and force a source build
backend-shim-*: Expose selected repository-owned backend shim modules for low-level integrations

§WebAssembly Support

On wasm32-unknown-unknown, the explicit wasm feature selects bindings that import cimgui functions from the fixed imgui-sys-v1 provider. Build the matching Emscripten provider and share its memory with the Rust application. WASI and Rust’s Emscripten targets are unsupported. Enabling this feature on a native target leaves the native ABI selected. Native shims, prebuilts, and Test Engine cannot be used on the browser target.

§Safety

This crate provides raw FFI bindings and is inherently unsafe. Users should prefer the high-level dear-imgui-rs crate for safe Rust bindings.

§Usage

This crate is typically not used directly. Instead, use the dear-imgui-rs crate which provides safe, idiomatic Rust bindings built on top of these FFI bindings.

§Backend Shim Modules

For downstream backend crates, engine integrations, and platform-specific application glue, dear-imgui-sys can expose selected official backend pieces through backend_shim::*.

Important boundary:

these modules expose the repository-owned C shim ABI
they do not expose upstream imgui_impl_* C++ symbol names as a stable Rust-facing contract
enabling backend-shim-* features does not imply that dear-imgui-rs already owns a safe wrapper for those backends

Typical feature gates:

backend-shim-opengl3
backend-shim-android
backend-shim-win32
backend-shim-dx11
backend-shim-dx12
backend-shim-metal (macOS / iOS)
backend-shim-osx (macOS)

SDLRenderer3 and SDLGPU3 renderer shims are owned by dear-imgui-sdl3.

§Android Direction

The current Android story is intentionally low-level but supported.

[dependencies]
dear-imgui-sys = { version = "0.20", features = ["backend-shim-android", "backend-shim-opengl3"] }

Recommended split of responsibilities:

dear-imgui-sys owns the raw context and frame API; the official OpenGL3 backend owns native texture updates
dear-imgui-sys::backend_shim::{android, opengl3} exposes the low-level official backend pieces
the Android application still owns lifecycle glue, input translation strategy, EGL / GLES context creation, and packaging

The repository’s concrete reference for this path is examples-android/dear-imgui-android-smoke/, which now carries a minimal NativeActivity + EGL / GLES3 render loop proving that downstream users can build Android support on top of dear-imgui-sys before a dedicated first-party Android convenience crate exists. A safe dear-imgui-rs route needs a renderer implementing its managed texture protocol; the raw OpenGL3 shim is not such an adapter.