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MarsleyBar1 edited this page Jul 3, 2024 · 36 revisions

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Preamble

This is a Tutorial for getting Dear ImGui integrated in your application.
Also refer to our FAQ and others Wiki pages.

Before anything, Build and run one of the examples application, play around with it.
With Visual Studio, open examples/imgui_examples.sln. XCode projects and Makefiles are also often provided.
You may not have all of the corresponding SDKs installed as we support many systems, but you should get some working out of the box.

The examples/ folder is populated with applications demonstrating Dear ImGui with a variety of common windowing and graphics API. They are designed to be as straightforward possible. However in most cases, a majority of the example-specific code is related to setting up the windowing and graphics API (aka setting up a basic application) rather than setting up Dear ImGui itself.

If you have issues integrating Dear ImGui in your app, most of the time to easiest thing to do it refer to those examples.

For various reasons, our examples are very raw: we don't load fancy fonts and generally the Demo window cannot read anything from the filesystem, so our examples cannot showcase the use of e.g. texture.

Game Loop?

Dear ImGui comes from a game development background, where applications are expected to updating continuously at interactive framerates (e.g. 60 FPS) and where it is expected that an underlying graphics-heavy application is running and showing behind Dear ImGui. This is how our examples are generally structured. While it is technically possible to lift some of those assumptions when using Dear ImGui (e.g. going idle, using variable frame rates, having no "main viewport"), those uses cases are currently not well supported by default, requires a more intimate understanding of both the system and dear imgui, and are outside the scope of this article.

A typical game-like application taking advantage of GPU rendering would run in a loop:

while (application_not_closed)
{
   // Poll events
   // Update application/game state
   // Render contents into a framebuffer
   // Swap/Present framebuffer to the screen
   // Wait some time (e.g. 1/60 of a second)
}

In the case of your example application, we explicitly attempt to synchronize to screen refresh when swap/present, making the application refresh at the natural screen refresh rate. A full-fledged application may use different timing mechanism to throttle framerate, but this is outside of our scope.

Compiling/Linking

  • (1) Decide which branch to pull:
    • master or docking, the later adds support for Docking and Multi-viewports.
    • Both branches are maintained, you can easily switch anytime.
  • (2) Pull the repository into a submodule of your project, or simply download/copy the repository in yours and commit it.
  • (3) Add files to your project or build system of your choice, so they get compiled and linked into your app.
    • Add all source files in the root folder: imgui/{*.cpp,*.h}.
    • Add selected imgui/backends/imgui_impl_xxxx{.cpp,.h} files corresponding to the technology you use from the imgui/backends/ folder (e.g. if your app uses SDL2 + DirectX11, add imgui_impl_sdl2.cpp, imgui_impl_dx11.cpp etc.). If your engine uses multiple APIs you may include multiple backends.
    • Visual Studio users: Add misc/debuggers/imgui.natvis and misc/debuggers/imgui.natstepfilter to improve the debugging experience.
    • std::string users: Add misc/cpp/imgui_stdlib.* to easily use InputText with std::string.

If your application already uses the API you pulled the backends for, things should compile and link already.

Most users with linking problems are in fact having problems because of the underlying windowing or graphics tech they use. e.g. If you use DirectX11 you need to link with d3d11.lib, if you use SDL2 you need to obtain the library (from their website or vcpkg) and link with SDL2.lib+SDL2main.lib etc. If you already have an app running then by definition you shouldn't have a problem including corresponding header files and linking libraries.

If you are creating a new application from scratch: while it is generally outside of scope of Dear ImGui to document how to use every windowing/graphics stacks, you can refer to our examples/ folder to see which libs/settings we are using. Some people just copy our example to start a new testbed app. For the convenience of providing easy-to-compile examples, for years our repository has included an (old) precompiled version of GLFW 3.2 for Windows.

Setting up Dear ImGui & Backends

After this list we will show the corresponding code.

  • (1) Add imgui/ to include paths. Include header files for main lib (#include "imgui.h") + backends (e.g. #include "imgui_impl_win32.h", #include "imgui_impl_dx11.h").
  • (2) Create Dear ImGui context with ImGui::CreateContext().
  • (3) Optionally set configuration flags, load fonts, setup style.
  • (4) Initialize Platform and Rendering backends (e.g. ImGui_ImplWin32_Init() + ImGui_ImplDX11_Init()).
  • (5) Start of main loop: call backends' ImGui_ImplXXX_NewFrame() functions + call ImGui::NewFrame().
  • (6) End of main loop: call ImGui::Render() + call Render function of Rendering backend (e.g. ImGui_ImplDX11_Render()).
  • (7) Most backends require some extra steps to hook or forward events. (e.g. calling ImGui_ImplWin32_WndProcHandler)
  • (8) Call backend shutdown functions and destroy Dear ImGui context with ImGui::DestroyContext().
  • (9) In your application's input logic: you can poll ImGui::GetIO().WantCaptureMouse/WantCaptureKeyboard to check if Dear ImGui wants to obstruct mouse/keyboard inputs from underlying apps. e.g. when hovering a window WantCaptureMouse will be set to true, one possible strategy would be to stop passing mouse events to your main application.

Example: If you are using Raw Win32 API + DirectX11

Full standalone example: example_win32_directx11/main.cpp

Add to Includes:

#include "imgui.h"
#include "imgui_impl_win32.h"
#include "imgui_impl_dx11.h"

Add to Initialization:

// Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // IF using Docking Branch

// Setup Platform/Renderer backends
ImGui_ImplWin32_Init(YOUR_HWND);
ImGui_ImplDX11_Init(YOUR_D3D_DEVICE, YOUR_D3D_DEVICE_CONTEXT);

Add to start of main loop:

// (Your code process and dispatch Win32 messages)
// Start the Dear ImGui frame
ImGui_ImplDX11_NewFrame();
ImGui_ImplWin32_NewFrame();
ImGui::NewFrame();
ImGui::ShowDemoWindow(); // Show demo window! :)

Add to end of main loop:

// Rendering
// (Your code clears your framebuffer, renders your other stuff etc.)
ImGui::Render();
ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());
// (Your code calls swapchain's Present() function)

Add to your WndProc handler:

extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
    return true;
// (Your code process Win32 messages)

Add to Shutdown:

ImGui_ImplDX11_Shutdown();
ImGui_ImplWin32_Shutdown();
ImGui::DestroyContext();

That should be all!

Example: If you are using Raw Win32 API + DirectX12

Full standalone example: example_win32_directx12/main.cpp

Add to Includes:

#include "imgui.h"
#include "imgui_impl_win32.h"
#include "imgui_impl_dx12.h"

Add to Initialization:

// Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // IF using Docking Branch

// Setup Platform/Renderer backends
ImGui_ImplWin32_Init(YOUR_HWND);
ImGui_ImplDX12_Init(YOUR_D3D_DEVICE, NUM_FRAME_IN_FLIGHT, YOUR_RENDER_TARGET_DXGI_FORMAT, 
 YOUR_SRV_DESC_HEAP,
 // You'll need to designate a descriptor from your descriptor heap for Dear ImGui to use internally for its font texture's SRV
 YOUR_CPU_DESCRIPTOR_HANDLE_FOR_FONT_SRV,
 YOUR_GPU_DESCRIPTOR_HANDLE_FOR_FONT_SRV);

Add to start of main loop:

// (Your code process and dispatch Win32 messages)
// Start the Dear ImGui frame
ImGui_ImplDX12_NewFrame();
ImGui_ImplWin32_NewFrame();
ImGui::NewFrame();
ImGui::ShowDemoWindow(); // Show demo window! :)

Add to end of main loop:

// Rendering
// (Your code clears your framebuffer, renders your other stuff etc.)
ImGui::Render();
ImGui_ImplDX12_RenderDrawData(ImGui::GetDrawData(), YOUR_DX12_COMMAND_LIST);
// (Your code calls ExecuteCommandLists, swapchain's Present(), etc.)

Add to your WndProc handler:

extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
    return true;
(Your code process Windows messages.)

Add to Shutdown:

ImGui_ImplDX12_Shutdown();
ImGui_ImplWin32_Shutdown();
ImGui::DestroyContext();

That should be all!

Example: If you are using GLFW + OpenGL/WebGL

Full standalone example: example_glfw_opengl3/main.cpp

Add to Includes:

#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_opengl3.h"

Add to Initialization:

// Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // IF using Docking Branch

// Setup Platform/Renderer backends
ImGui_ImplGlfw_InitForOpenGL(YOUR_WINDOW, true);          // Second param install_callback=true will install GLFW callbacks and chain to existing ones.
ImGui_ImplOpenGL3_Init();

Add to start of main loop:

// (Your code calls glfwPollEvents())
// ...
// Start the Dear ImGui frame
ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplGlfw_NewFrame();
ImGui::NewFrame();
ImGui::ShowDemoWindow(); // Show demo window! :)

Add to end of main loop:

// Rendering
// (Your code clears your framebuffer, renders your other stuff etc.)
ImGui::Render();
ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
// (Your code calls glfwSwapBuffers() etc.)

Add to Shutdown:

ImGui_ImplOpenGL3_Shutdown();
ImGui_ImplGlfw_Shutdown();
ImGui::DestroyContext();

That should be all!

Example: If you are using GLFW + Metal (on Apple devices)

Full standalone example: example_glfw_apple/main.mm

Add to Includes:

#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_metal.h"

Add to Initialization:

// Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // IF using Docking Branch

// Setup Platform/Renderer backends
ImGui_ImplGlfw_InitForOpenGL(YOUR_WINDOW, true);          // Second param install_callback=true will install GLFW callbacks and chain to existing ones.
ImGui_ImplMetal_Init(YOUR_METAL_DEVICE);

Add to start of main loop:

// (Your code calls glfwPollEvents())
// ...
// Start the Dear ImGui frame
ImGui_ImplMetal_NewFrame(YOUR_RENDER_PASS_DESCRIPTOR);
ImGui_ImplGlfw_NewFrame();
ImGui::NewFrame();
ImGui::ShowDemoWindow(); // Show demo window! :)

Add to end of main loop:

// Rendering
// (Your code clears your framebuffer, renders your other stuff etc.)
ImGui::Render();
ImGui_ImplMetal_RenderDrawData(ImGui::GetDrawData(), YOUR_METAL_COMMAND_BUFFER, YOUR_METAL_RENDER_ENCODER);
// (Your code calls endEncoding, presentDrawable, commit etc.)

Add to Shutdown:

ImGui_ImplMetal_Shutdown();
ImGui_ImplGlfw_Shutdown();
ImGui::DestroyContext();

That should be all!

Example: If you are using SDL2 + OpenGL/WebGL

Full standalone example: example_sdl2_opengl3/main.cpp

Add to Includes:

#include "imgui.h"
#include "imgui_impl_sdl2.h"
#include "imgui_impl_opengl3.h"

Add to Initialization:

// Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // IF using Docking Branch

// Setup Platform/Renderer backends
ImGui_ImplSDL2_InitForOpenGL(window, YOUR_SDL_GL_CONTEXT);
ImGui_ImplOpenGL3_Init();

Add to start of main loop:

// (Where your code calls SDL_PollEvent())
ImGui_ImplSDL2_ProcessEvent(&event); // Forward your event to backend

// (After event loop)
// Start the Dear ImGui frame
ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplSDL2_NewFrame();
ImGui::NewFrame();
ImGui::ShowDemoWindow(); // Show demo window! :)

Add to end of main loop:

// Rendering
// (Your code clears your framebuffer, renders your other stuff etc.)
ImGui::Render();
ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
// (Your code calls SDL_GL_SwapWindow() etc.)

Add to Shutdown:

ImGui_ImplOpenGL3_Shutdown();
ImGui_ImplSDL2_Shutdown();
ImGui::DestroyContext();

That should be all!

Example: If you are using SDL2 + Vulkan

Full standalone example: example_sdl2_vulkan/main.cpp

Unfortunately this is the most complex one and may not work with all app setups. We are always working on making imgui_impl_vulkan.cpp more compatible with existing engines, so please don't hesitate to post feedback.

Add to Includes:

#include "imgui.h"
#include "imgui_impl_sdl2.h"
#include "imgui_impl_vulkan.h"

static void check_vk_result(VkResult err)
{
    if (err == 0)
        return;
    fprintf(stderr, "[vulkan] Error: VkResult = %d\n", err);
    if (err < 0)
        abort();
}

Add to Initialization:

// Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // IF using Docking Branch

// Setup Platform/Renderer backends
ImGui_ImplSDL2_InitForVulkan(YOUR_SDL_WINDOW);
ImGui_ImplVulkan_InitInfo init_info = {};
init_info.Instance = YOUR_INSTANCE;
init_info.PhysicalDevice = YOUR_PHYSICAL_DEVICE;
init_info.Device = YOUR_DEVICE;
init_info.QueueFamily = YOUR_QUEUE_FAMILY;
init_info.Queue = YOUR_QUEUE;
init_info.PipelineCache = YOUR_PIPELINE_CACHE;
init_info.DescriptorPool = YOUR_DESCRIPTOR_POOL;
init_info.Subpass = 0;
init_info.MinImageCount = 2;
init_info.ImageCount = 2;
init_info.MSAASamples = VK_SAMPLE_COUNT_1_BIT;
init_info.Allocator = YOUR_ALLOCATOR;
init_info.CheckVkResultFn = check_vk_result;
ImGui_ImplVulkan_Init(&init_info, wd->RenderPass);
// (this gets a bit more complicated, see example app for full reference)
ImGui_ImplVulkan_CreateFontsTexture(YOUR_COMMAND_BUFFER);
// (your code submit a queue)
ImGui_ImplVulkan_DestroyFontUploadObjects();

Add to start of main loop:

// (Where your code calls SDL_PollEvent())
ImGui_ImplSDL2_ProcessEvent(&event); // Forward your event to backend

// (After event loop)
// Start the Dear ImGui frame
ImGui_ImplVulkan_NewFrame();
ImGui_ImplSDL2_NewFrame();
ImGui::NewFrame();
ImGui::ShowDemoWindow(); // Show demo window! :)

Add to end of main loop:

// Rendering
// (Your code clears your framebuffer, renders your other stuff etc.)
ImGui::Render();
ImGui_ImplVulkan_RenderDrawData(ImGui::GetDrawData(), YOUR_COMMAND_BUFFER);
// (Your code calls vkCmdEndRenderPass, vkQueueSubmit, vkQueuePresentKHR etc.)

Add to Shutdown:

ImGui_ImplVulkan_Shutdown();
ImGui_ImplSDL2_Shutdown();
ImGui::DestroyContext();

That should be all!

Using another combination of backends?

The various examples above should reflect integration with a majority of backends, so you can follow the same logic. Some backends require more information from you (e.g. in particular Vulkan and DirectX12 rendering backends). When in doubt, refer to the corresponding examples application.

Additional code to enable Docking

To use the Docking feature, pull the docking branch and enable the configuration flag:

io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;

Additional code to enable Multi-viewports

To use the Multi-viewports feature, pull the docking branch and enable the configuration flag:

io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;

At the end of your render loop, generally after rendering your main viewport but before presenting/swapping it:

if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
{
    // Update and Render additional Platform Windows
    ImGui::UpdatePlatformWindows();
    ImGui::RenderPlatformWindowsDefault();

    // TODO for OpenGL: restore current GL context.
}

Note that there may be additional calls required surrounding this depending on the backend you are using (OpenGL in particular needs backup/restore of current GL context). Check the example project appropriate to your setup for details.

Once you are setup...

  • Run ImGui::ShowDemoWindow(). Browse imgui_demo.cpp to find how things are done.
  • You may also refer to @pthom's interactive imgui_manual which matches the output of the demo window with corresponding source code.
  • Use Item Picker to easily debug break into the code of a given item.
  • Read Wiki for more.
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