- [Writing your own Backend](#writing-your-own-backend)
- [Using a custom engine?](#using-a-custom-engine)
- [Platform: Implementing your Platform Backend](#platform-implementing-your-platform-backend)
- [Rendering: Implementing your RenderDrawData function](#rendering-implementing-your-renderdrawdata-function)
- [Rendering: Adding support for `ImGuiBackendFlags_RendererHasTextures` (1.92+)](#rendering-adding-support-for-imguibackendflags_rendererhastextures-192)
💡 The **[Getting Started](https://github.com/ocornut/imgui/wiki/Getting-Started) wiki guide** has examples of how to integrate Dear ImGui into an existing application.
<BR> The [EXAMPLES.MD](https://github.com/ocornut/imgui/blob/master/docs/EXAMPLES.md) documentation may also be worth a read.
This is essentially what each backend is doing + obligatory portability cruft. Using standard backends ensure you can get all those features including the ones that would be harder to implement on your side (e.g. multi-viewports support).
**The [backends/](https://github.com/ocornut/imgui/blob/master/backends) folder contains backends for popular platforms/graphics API, which you can use in
your application or engine to easily integrate Dear ImGui.** Each backend is typically self-contained in a pair of files: imgui_impl_XXXX.cpp + imgui_impl_XXXX.h.
- The 'Platform' backends are in charge of: mouse/keyboard/gamepad inputs, cursor shape, timing, and windowing.<BR>
e.g. Windows ([imgui_impl_win32.cpp](https://github.com/ocornut/imgui/blob/master/backends/imgui_impl_win32.cpp)), SDL3 ([imgui_impl_sdl3.cpp](https://github.com/ocornut/imgui/blob/master/backends/imgui_impl_sdl3.cpp)), GLFW ([imgui_impl_glfw.cpp](https://github.com/ocornut/imgui/blob/master/backends/imgui_impl_glfw.cpp)), etc.
- The 'Renderer' backends are in charge of: creating atlas texture, and rendering imgui draw data.<BR>
e.g. DirectX11 ([imgui_impl_dx11.cpp](https://github.com/ocornut/imgui/blob/master/backends/imgui_impl_dx11.cpp)), OpenGL/WebGL ([imgui_impl_opengl3.cpp](https://github.com/ocornut/imgui/blob/master/backends/imgui_impl_opengl3.cpp)), Vulkan ([imgui_impl_vulkan.cpp](https://github.com/ocornut/imgui/blob/master/backends/imgui_impl_vulkan.cpp)), etc.
- For some high-level frameworks, a single backend usually handles both 'Platform' and 'Renderer' parts.<BR>
e.g. Allegro 5 ([imgui_impl_allegro5.cpp](https://github.com/ocornut/imgui/blob/master/backends/imgui_impl_allegro5.cpp)). If you end up creating a custom backend for your engine, you may want to do the same.
An application usually combines one Platform backend + one Renderer backend + main Dear ImGui sources.
For example, the [example_win32_directx11](https://github.com/ocornut/imgui/tree/master/examples/example_win32_directx11) application combines imgui_impl_win32.cpp + imgui_impl_dx11.cpp. There are 20+ examples in the [examples/](https://github.com/ocornut/imgui/blob/master/examples/) folder. See [EXAMPLES.MD](https://github.com/ocornut/imgui/blob/master/docs/EXAMPLES.md) for details.
**Once Dear ImGui is setup and running, run and refer to `ImGui::ShowDemoWindow()` in imgui_demo.cpp for usage of the end-user API.**
If your application runs on Windows or if you are using multi-viewport, the win32 backend handles some details a little better than other backends.
## Using third-party Backends
See https://github.com/ocornut/imgui/wiki/Bindings for the full list (e.g. Adventure Game Studio, Cinder, Cocos2d-x, Game Maker Studio2, Godot, LÖVE+LUA, Magnum, Monogame, Ogre, openFrameworks, OpenSceneGraph, SFML, Sokol, Unity, Unreal Engine and many others).
window", but some things are more difficult "find OS window under mouse position BUT with some windows marked as passthrough". See 'ImGuiPlatformIO' for details.
The Platform backends in impl_impl_XXX.cpp files contain many implementations.
**In your `ImGui_ImplXXX_Init()` function:**
- You can allocate your backend data and use `io.BackendPlatformUserData` to store/retrieve it later.
- Set `io.BackendPlatformName` to a name `"imgui_impl_xxxx"` which will be available in e.g. About box.
- Set `io.BackendPlatformUserData` to your backend data.
- Set `io.BackendFlags` with supported optional features:
-`ImGuiBackendFlags_HasGamepad`: supports gamepad and currently has one connected.
-`ImGuiBackendFlags_HasMouseCursors`: supports honoring GetMouseCursor() value to change the OS cursor shape.
-`ImGuiBackendFlags_HasSetMousePos`: supports io.WantSetMousePos requests to reposition the OS mouse position (only used if io.ConfigNavMoveSetMousePos is set).
-`ImGuiBackendFlags_HasMouseHoveredViewport` supports calling io.AddMouseViewportEvent() with the viewport under the mouse. IF POSSIBLE, ignore viewports with the ImGuiViewportFlags_NoInputs flag. If this cannot be done, Dear ImGui needs to use a flawed heuristic to find the viewport under mouse position, as it doesn't know about foreign windows. (multi-viewports only)
**In your `ImGui_ImplXXX_NewFrame()` function:**
- Set `io.DeltaTime` to the time elapsed (in seconds) since last frame.
- Set `io.DisplaySize` to your window size.
- Set `io.DisplayFrameBufferSize` to your window pixel density (macOS/iOS only).
- Update mouse cursor shape is supported.
**In your `ImGui_ImplXXX_NewFrame()` function or event handlers:**
- **Mouse Support**
- Use `io.AddMousePosEvent()`, `io.AddMouseButtonEvent()`, `io.AddMouseWheelEvent()` to pass mouse events.
- Use `io.AddMouseSourceEvent()` if you are able to distinguish Mouse from TouchScreen from Pen inputs. TouchScreen and Pen inputs requires different logic for some Dear ImGui features.
- Use `io.AddMouseViewportEvent()` to specify which viewport/OS window is being hovered by the mouse. Read instructions carefully as this is not as simple as it seems! (multi-viewports only)
- **Keyboard Support**
- Use `io.AddKeyEvent()` to pass key events.
- Use `io.AddInputCharacter()` to pass text/character events.
- **Gamepad Support**
- Use `io.AddKeyEvent()` and `io.AddKeyAnalogEvent()` to pass gamepad events, using `ImGuiKey_GamepadXXX` values.
- **Miscellaneous**
- Clipboard Support: setup `Platform_GetClipboardTextFn()`, `Platform_SetClipboardTextFn()` handlers in `ImGuiPlatformIO`.
- Open in Shell support: setup `Platform_OpenInShellFn()` handler in `ImGuiPlatformIO`.
- IME Support: setup `Platform_SetImeDataFn()` handler in `ImGuiPlatformIO`.
- Use `io.AddFocusEvent()` to notify when application window gets focused/unfocused.
- **Multi-viewport Support**
- Update monitor list if supported.
- Setup all required handlers in `ImGuiPlatformIO` to create/destroy/move/resize/title/focus/etc. windows.
### Rendering: Implementing your RenderDrawData function
Note: set `ImGuiBackendFlags_RendererHasVtxOffset` to signify your backend can handle rendering with a vertex offset (`ImDrawCmd::VtxOffset` field).
Otherwise, rendering will be limited to 64K vertices per window, which may be limiting for advanced plot.
As an alternative, you may also use `#define ImDrawIdx unsigned int` in your `imconfig.h` file to support 32-bit indices.
if (pcmd->UserCallback == ImDrawCallback_ResetRenderState)
MyEngineSetupenderState();
else
pcmd->UserCallback(cmd_list, pcmd);
}
else
{
// Project scissor/clipping rectangles into framebuffer space
// - Clipping coordinates are provided in imgui coordinates space:
// - For a given viewport, draw_data->DisplayPos == viewport->Pos and draw_data->DisplaySize == viewport->Size
// - In a single viewport application, draw_data->DisplayPos == (0,0) and draw_data->DisplaySize == io.DisplaySize, but always use GetMainViewport()->Pos/Size instead of hardcoding those values.
// - In the interest of supporting multi-viewport applications (see 'docking' branch on github),
// always subtract draw_data->DisplayPos from clipping bounds to convert them to your viewport space.
// - Note that pcmd->ClipRect contains Min+Max bounds. Some graphics API may use Min+Max, other may use Min+Size (size being Max-Min)
### Rendering: Adding support for `ImGuiBackendFlags_RendererHasTextures` (1.92+)
Version [1.92.0](https://github.com/ocornut/imgui/releases/tag/v1.92.0) (June 2025), added texture support in Rendering Backends, which is the backbone for supporting dynamic font scaling among other things.
**In order to move forward and take advantage of all new features, support for `ImGuiBackendFlags_RendererHasTextures` will likely be REQUIRED for all backends before June 2026.**
`ImFontAtlas` functions such as `Build()`, `GetTexDataAsRGBA32()`, `GetTexDataAsAlpha8()`, `SetTexID()`, `IsBuilt()` were obsoleted in favor if iterating a `Textures[]` array and updating their state when requested by Dear ImGui.
**TD;DR: List of commits which added support for `ImGuiBackendFlags_RendererHasTextures` in standard backends:**
- Set `ImGuiBackendFlags_RendererHasTextures` to signify your backend can handle the feature.
- During rendering, e.g. in your RenderDrawData function, iterate `ImDrawData->Textures` array and process all textures.
- During shutdown, iterate the `ImGui::GetPlatformIO().Textures` and destroy all textures.
- (Both arrays are `ImVector<ImTextureData*>`. They are only in different location because: to allow advanced users to perform multi-threaded rendering, we store a pointer to the texture list in ImDrawData, with the aim that multi-threaded rendering users replace it with their own pointer.)
