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diff --git a/libs/imgui-1.92.1/docs/BACKENDS.md b/libs/imgui-1.92.1/docs/BACKENDS.md new file mode 100644 index 0000000..fa05d55 --- /dev/null +++ b/libs/imgui-1.92.1/docs/BACKENDS.md @@ -0,0 +1,378 @@ +_(You may browse this at https://github.com/ocornut/imgui/blob/master/docs/BACKENDS.md or view this file with any Markdown viewer)_ + +# Dear ImGui: Backends + +## Index + +- [Introduction](#introduction) + - [Getting Started](#getting-started) + - [What are Backends?](#what-are-backends) +- [Using standard Backends](#using-standard-backends) +- [Using third-party Backends](#using-third-party-backends) +- [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) + +## Introduction + +### Getting Started + +💡 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. + +### What are Backends? + +Dear ImGui is highly portable and only requires a few things to run and render, typically: + + - Required: providing mouse/keyboard inputs (fed into the `ImGuiIO` structure). + - Required: creating, updating and destroying textures. + - Required: rendering indexed textured triangles with a clipping rectangle. + + Extra features are opt-in, our backends try to support as many as possible: + + - Optional: custom texture binding support. + - Optional: clipboard support. + - Optional: gamepad support. + - Optional: mouse cursor shape support. + - Optional: IME support. + - Optional: multi-viewports support. + etc. + +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). + +It is important to understand the difference between the core Dear ImGui library (files in the root folder) +and the backends which we are describing here (backends/ folder). + +- Some issues may only be backend or platform specific. +- You should be able to write backends for pretty much any platform and any 3D graphics API. + e.g. you can get creative and use software rendering or render remotely on a different machine. + +## Using standard Backends + +**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.** + +### List of standard Backends + +In the [backends/](https://github.com/ocornut/imgui/blob/master/backends) folder: + +List of Platforms Backends: + + imgui_impl_android.cpp ; Android native app API + imgui_impl_glfw.cpp ; GLFW (Windows, macOS, Linux, etc.) http://www.glfw.org/ + imgui_impl_osx.mm ; macOS native API (not as feature complete as glfw/sdl backends) + imgui_impl_sdl2.cpp ; SDL2 (Windows, macOS, Linux, iOS, Android) https://www.libsdl.org + imgui_impl_sdl3.cpp ; SDL3 (Windows, macOS, Linux, iOS, Android) https://www.libsdl.org + imgui_impl_win32.cpp ; Win32 native API (Windows) + imgui_impl_glut.cpp ; GLUT/FreeGLUT (this is prehistoric software and absolutely not recommended today!) + +List of Renderer Backends: + + imgui_impl_dx9.cpp ; DirectX9 + imgui_impl_dx10.cpp ; DirectX10 + imgui_impl_dx11.cpp ; DirectX11 + imgui_impl_dx12.cpp ; DirectX12 + imgui_impl_metal.mm ; Metal (ObjC or C++) + imgui_impl_opengl2.cpp ; OpenGL 2 (legacy fixed pipeline. Don't use with modern OpenGL code!) + imgui_impl_opengl3.cpp ; OpenGL 3/4, OpenGL ES 2/3, WebGL + imgui_impl_sdlgpu3.cpp ; SDL_GPU (portable 3D graphics API of SDL3) + imgui_impl_sdlrenderer2.cpp ; SDL_Renderer (optional component of SDL2 available from SDL 2.0.18+) + imgui_impl_sdlrenderer3.cpp ; SDL_Renderer (optional component of SDL3. Prefer using SDL_GPU!). + imgui_impl_vulkan.cpp ; Vulkan + imgui_impl_wgpu.cpp ; WebGPU (web + desktop) + +List of high-level Frameworks Backends (combining Platform + Renderer): + + imgui_impl_allegro5.cpp + +Emscripten is also supported! +The SDL2+GL, SDL3+GL, GLFW+GL and GLFW+WebGPU examples are all ready to build and run with Emscripten. + +### Recommended Backends + +If you are not sure which backend to use, the recommended platform/frameworks for portable applications: + +|Library |Website |Backend |Note | +|--------|--------|--------|-----| +| SDL3 | https://www.libsdl.org | imgui_impl_sdl3.cpp | Recommended | +| SDL2 | https://www.libsdl.org | imgui_impl_sdl2.cpp | | +| GLFW | https://github.com/glfw/glfw | imgui_impl_glfw.cpp | | +| Sokol | https://github.com/floooh/sokol | [util/sokol_imgui.h](https://github.com/floooh/sokol/blob/master/util/sokol_imgui.h) | Lower-level than GLFW/SDL | + +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). + +## Writing your own Backend + +### Using a custom engine? + +You will likely be tempted to start by rewrite your own backend using your own custom/high-level facilities...<BR> +Think twice! + +TL;DR; +- Writing your own Renderer Backend is easy. +- Writing your own Platform Backend is harder and you are more likely to introduce bugs. +- **It is unlikely you will add value to your project by creating your own backend.** + +**Consider using the existing backends as-is**. +You will save lots of time integrating the library. +Standard backends are battle-tested and handle subtleties that you are likely to implement incorrectly. +You can LATER decide to rewrite yourself a custom backend if you really need to. +In most situations, custom backends have fewer features and more bugs than the standard backends we provide. +If you want portability, you can use multiple backends and choose between them either at compile time +or at runtime. + +**Example A**: your engine is built over Windows + DirectX11 but you have your own high-level rendering +system layered over DirectX11.<BR> +Suggestion: try using imgui_impl_win32.cpp + imgui_impl_dx11.cpp first. +Once it works, if you really need it, you can replace the imgui_impl_dx11.cpp code with a +custom renderer using your own rendering functions, and keep using the standard Win32 code etc. + +**Example B**: your engine runs on Windows, Mac, Linux and uses DirectX11, Metal, and Vulkan respectively.<BR> +Suggestion: use multiple generic backends! +Once it works, if you really need it, you can replace parts of backends with your own abstractions. + +**Example C**: your engine runs on platforms we can't provide public backends for (e.g. PS4/PS5, Switch), +and you have high-level systems everywhere.<BR> +Suggestion: try using a non-portable backend first (e.g. win32 + underlying graphics API) to get +your desktop builds working first. This will get you running faster and get your acquainted with +how Dear ImGui works and is setup. You can then rewrite a custom backend using your own engine API... + +Also: +The [multi-viewports feature](https://github.com/ocornut/imgui/wiki/Multi-Viewports) of the 'docking' branch allows +Dear ImGui windows to be seamlessly detached from the main application window. This is achieved using an +extra layer to the Platform and Renderer backends, which allows Dear ImGui to communicate platform-specific +requests such as: "create an additional OS window", "create a render context", "get the OS position of this +window", but some things are more difficult "find OS window under mouse position BUT with some windows marked as passthrough". See 'ImGuiPlatformIO' for details. +Supporting the multi-viewports feature correctly using 100% of your own abstractions is more difficult +than supporting single-viewport. +If you decide to use unmodified imgui_impl_XXXX.cpp files, you can automatically benefit from +improvements and fixes related to viewports and platform windows without extra work on your side. + +### Platform: Implementing your Platform Backend + +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_PlatformHasViewports` supports multiple viewports. (multi-viewports only) + - `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. + +```cpp +void MyImGuiBackend_RenderDrawData(ImDrawData* draw_data) +{ + // TODO: Update textures. + // - Most of the times, the list will have 1 element with an OK status, aka nothing to do. + // - This almost always points to ImGui::GetPlatformIO().Textures[] but is part of ImDrawData to allow overriding or disabling texture updates. + if (draw_data->Textures != nullptr) + for (ImTextureData* tex : *draw_data->Textures) + if (tex->Status != ImTextureStatus_OK) + MyImGuiBackend_UpdateTexture(tex); + + // TODO: Setup render state: + // - Alpha-blending enabled + // - No backface culling + // - No depth testing, no depth writing + // - Scissor enabled + MyEngineSetupenderState(); + + // TODO: Setup texture sampling state + // - Sample with bilinear filtering (NOT point/nearest filtering). + // - Use 'io.Fonts->Flags |= ImFontAtlasFlags_NoBakedLines;' to allow point/nearest filtering. + + // TODO: Setup viewport covering draw_data->DisplayPos to draw_data->DisplayPos + draw_data->DisplaySize + + // TODO: Setup orthographic projection matrix cover draw_data->DisplayPos to draw_data->DisplayPos + draw_data->DisplaySize + + // TODO: Setup shader: vertex { float2 pos, float2 uv, u32 color }, fragment shader sample color from 1 texture, multiply by vertex color. + + // Render command lists + ImVec2 clip_off = draw_data->DisplayPos; + ImVec2 clip_scale = draw_data->FramebufferScale; + for (int n = 0; n < draw_data->CmdListsCount; n++) + { + const ImDrawList* cmd_list = draw_data->CmdLists[n]; + const ImDrawVert* vtx_buffer = cmd_list->VtxBuffer.Data; // vertex buffer generated by Dear ImGui + const ImDrawIdx* idx_buffer = cmd_list->IdxBuffer.Data; // index buffer generated by Dear ImGui + for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++) + { + const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i]; + if (pcmd->UserCallback) + { + 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) + ImVec2 clip_min((pcmd->ClipRect.x - clip_off.x) * clip_scale.x, (pcmd->ClipRect.y - clip_off.y) * clip_scale.y); + ImVec2 clip_max((pcmd->ClipRect.z - clip_off.x) * clip_scale.x, (pcmd->ClipRect.w - clip_off.y) * clip_scale.y); + if (clip_max.x <= clip_min.x || clip_max.y <= clip_min.y) + continue; + + // We are using scissoring to clip some objects. All low-level graphics API should support it. + // - If your engine doesn't support scissoring yet, you may ignore this at first. You will get some small glitches + // (some elements visible outside their bounds) but you can fix that once everything else works! + MyEngineSetScissor(clip_min.x, clip_min.y, clip_max.x, clip_max.y); + + // The texture for the draw call is specified by pcmd->GetTexID(). + // The vast majority of draw calls will use the Dear ImGui texture atlas, which value you have set yourself during initialization. + MyEngineBindTexture((MyTexture*)pcmd->GetTexID()); + + // Render 'pcmd->ElemCount/3' indexed triangles. + // By default the indices ImDrawIdx are 16-bit, you can change them to 32-bit in imconfig.h if your engine doesn't support 16-bit indices. + MyEngineDrawIndexedTriangles(pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer + pcmd->IdxOffset, vtx_buffer, pcmd->VtxOffset); + } + } + } +} +``` + +### 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:** + +- Allegro5: [ee8941e](https://github.com/ocornut/imgui/commit/ee8941e) (+35 lines) +- DirectX9: [75efba7](https://github.com/ocornut/imgui/commit/75efba7) (+48 lines) +- DirectX10: [2d2b1bc](https://github.com/ocornut/imgui/commit/2d2b1bc) (+40 lines) +- DirectX11: [372fd27](https://github.com/ocornut/imgui/commit/372fd27) (+40 lines) +- DirectX12: [eefe5d5](https://github.com/ocornut/imgui/commit/eefe5d5) (+87 lines) +- Metal: [26c017d](https://github.com/ocornut/imgui/commit/26c017d) (+55 lines) +- OpenGL Legacy: [0430c55](https://github.com/ocornut/imgui/commit/0430c55) (+25 lines) +- OpenGL3/WebGL/ES: [dbb91a5](https://github.com/ocornut/imgui/commit/dbb91a5) (+47 lines) +- SDL_Renderer2: [9fa65cd](https://github.com/ocornut/imgui/commit/9fa65cd) (+20 lines) +- SDL_Renderer3: [e538883](https://github.com/ocornut/imgui/commit/e538883) (+19 lines) +- SDL_GPU: [16fe666](https://github.com/ocornut/imgui/commit/16fe666) (+41 lines) +- Vulkan: [abe294b](https://github.com/ocornut/imgui/commit/abe294b) (+33 lines) +- WGPU: [571dae9](https://github.com/ocornut/imgui/commit/571dae9) (+30 lines) + +**Instructions:** + +- 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.) + +Pseudo-code for processing a texture: +```cpp +if (draw_data->Textures != nullptr) + for (ImTextureData* tex : *draw_data->Textures) + if (tex->Status != ImTextureStatus_OK) + MyImGuiBackend_UpdateTexture(tex); +``` +```cpp +void MyImGuiBackend_UpdateTexture(ImTextureData* tex) +{ + if (tex->Status == ImTextureStatus_WantCreate) + { + // Create texture based on tex->Width, tex->Height. + // - Most backends only support tex->Format == ImTextureFormat_RGBA32. + // - Backends for particularly memory constrainted platforms may support tex->Format == ImTextureFormat_Alpha8. + + // Upload all texture pixels + // - Read from our CPU-side copy of the texture and copy to your graphics API. + // - Use tex->Width, tex->Height, tex->GetPixels(), tex->GetPixelsAt(), tex->GetPitch() as needed. + + // Store your data, and acknowledge creation. + tex->SetTexID(xxxx); // Specify backend-specific ImTextureID identifier which will be stored in ImDrawCmd. + tex->SetStatus(ImTextureStatus_OK); + tex->BackendUserData = xxxx; // Store more backend data if needed (most backend allocate a small texture to store data in there) + } + if (tex->Status == ImTextureStatus_WantUpdates) + { + // Upload a rectangle of pixels to the existing texture + // - We only ever write to textures regions which have never been used before! + // - Use tex->TexID or tex->BackendUserData to retrieve your stored data. + // - Use tex->UpdateRect.x/y, tex->UpdateRect.w/h to obtain the block position and size. + // - Use tex->Updates[] to obtain individual sub-regions within tex->UpdateRect. Not recommended. + // - Read from our CPU-side copy of the texture and copy to your graphics API. + // - Use tex->Width, tex->Height, tex->GetPixels(), tex->GetPixelsAt(), tex->GetPitch() as needed. + + // Acknowledge update + tex->SetStatus(ImTextureStatus_OK); + } + if (tex->Status == ImTextureStatus_WantDestroy && tex->UnusedFrames > 0) + { + // If you use staged rendering and have in-flight renders, changed tex->UnusedFrames > 0 check to higher count as needed e.g. > 2 + + // Destroy texture + // - Use tex->TexID or tex->BackendUserData to retrieve your stored data. + // - Destroy texture in your graphics API. + + // Acknowledge destruction + tex->SetTexID(ImTextureID_Invalid); + tex->SetStatus(ImTextureStatus_Destroyed); + } +} +``` +Refer to "List of commits which added support for `ImGuiBackendFlags_RendererHasTextures` in standard backends" above for concrete examples of this. |