First commit.

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.20)
+
+project(hdk-imgui-sdl-renderer 
+  VERSION 0.0.1
+  LANGUAGES CXX
+)
+
+option(HDK_IMGUI_SDL_RENDERER_TESTS "Build hdk-imgui-sdl-renderer tests" ${HDK_TESTS})
+option(HDK_IMGUI_SDL_RENDERER_EXAMPLES "Build hdk-imgui-sdl-renderer examples" ${HDK_EXAMPLES})
+
+if(HDK_IMGUI_SDL_RENDERER_EXAMPLES)
+  add_subdirectory(examples)
+endif()
+
+if(HDK_IMGUI_SDL_RENDERER_TESTS)
+  add_subdirectory(tests)
+endif()
+
+find_package(SDL3 REQUIRED)
+
+include(FetchContent)
+FetchContent_Declare(imgui
+  GIT_REPOSITORY https://github.com/ocornut/imgui
+  GIT_TAG docking
+)
+FetchContent_MakeAvailable(imgui)
+
+set(HDK_IMGUI_SDL_RENDERER_SOURCES
+  ${imgui_SOURCE_DIR}/imgui.cpp
+  ${imgui_SOURCE_DIR}/imgui_demo.cpp
+  ${imgui_SOURCE_DIR}/imgui_draw.cpp
+  ${imgui_SOURCE_DIR}/imgui_tables.cpp
+  ${imgui_SOURCE_DIR}/imgui_widgets.cpp
+  ${imgui_SOURCE_DIR}/backends/imgui_impl_sdl3.cpp
+  ${imgui_SOURCE_DIR}/backends/imgui_impl_sdlrenderer3.cpp
+)
+
+add_library(hdk-is3r STATIC ${HDK_IMGUI_SDL_RENDERER_SOURCES})
+target_link_libraries(hdk-is3r PUBLIC hdk-sdl SDL3::SDL3)
+target_include_directories(hdk-is3r PUBLIC
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+  $<BUILD_INTERFACE:${imgui_SOURCE_DIR}>
+  $<BUILD_INTERFACE:${imgui_SOURCE_DIR}/backends>
+  $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+)
+
+target_compile_features(hdk-is3r PUBLIC cxx_std_17)

README.md

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+# imgui-sdl-renderer
+
+This is the glue library required to have an ImGui renderer implementation for SDL's rendering API.
+
+As simple as it sounds but it may get split into three libraries in the future:
+- `imgui-sdl-renderer`: Just the SDL Renderer glue for ImGui
+- `imgui-sdl`: General SDL glue for ImGui (input handling, clipboard, etc.)
+- 'imgui': Core ImGUI code that has no dependencies on any backend.
+
+This will be so that we can very easily add `imgui-sdl-opengl` and `imgui-sdl-vulkan`, etc. in the future without having to duplicate the SDL glue or ImGUI core code.

examples/CMakeLists.txt

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+
+add_executable(is3r-basics is3r-basics.cpp)
+target_link_libraries(is3r-basics PRIVATE hdk-is3r)

examples/is3r-basics.cpp

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+#include <hdk/sdl.hpp>
+#include <imgui.h>
+#include <hdk/sdl/main.hpp>
+
+#include "hdk/is3r.hpp"
+
+namespace simui_example {
+  using namespace hdk;
+
+  class SimGuiApp : public is3r::Is3rApp {
+    public:
+      grid::eps::TapScope taps;
+      const sdl::evt::EventConduit::Callback_t LOG_EVENT = [&](SDL_Event* event) {
+        auto description = sdl::Event::GetDescription<1024>(event);
+        AppLog.Debug("Event received: %s", description.c_str());
+      };
+
+      sdl::Window window { nullptr };
+      sdl::Renderer renderer { nullptr };
+      sdl::Surface surface { nullptr };
+      sdl::Texture texture { nullptr };
+
+      float main_scale = 1.0f;
+      ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
+
+      void InitIMUI() {
+        // Setup Dear ImGui context
+        IMGUI_CHECKVERSION();
+        ImGui::CreateContext();
+        ImGuiIO& io = ImGui::GetIO();
+        (void)io;
+        io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard; // Enable Keyboard Controls
+        io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad; // Enable Gamepad Controls
+
+        // Setup Dear ImGui style
+        ImGui::StyleColorsDark();
+        // ImGui::StyleColorsLight();
+
+        // Setup scaling
+        ImGuiStyle& style = ImGui::GetStyle();
+        style.ScaleAllSizes(main_scale); // Bake a fixed style scale. (until we have a solution for dynamic style
+                                         // scaling, changing this requires resetting Style + calling this again)
+        style.FontScaleDpi
+          = main_scale; // Set initial font scale. (in docking branch: using io.ConfigDpiScaleFonts=true automatically
+                        // overrides this for every window depending on the current monitor)
+
+        // Setup Platform/Renderer backends
+        ImGui_ImplSDL3_InitForSDLRenderer(window, renderer);
+        ImGui_ImplSDLRenderer3_Init(renderer);
+      }
+
+      virtual SDL_AppResult Init(int argc, char* argv[]) override {
+        SDL_SetAppMetadata("SimGui Example", "0.0.1", "institute.ufp.hdk.simui.examples.simgui");
+        sdl::Log::SetPriorities(SDL_LOG_PRIORITY_DEBUG);
+        auto [w, r] = sdl::CreateWindowAndRenderer("SimGui Example", 800, 600, 0);
+        window = w;
+        renderer = r;
+        if (!window || !renderer) {
+          SDL_Log("Failed to create window or renderer: %s", SDL_GetError());
+          return AppStatus = SDL_APP_FAILURE;
+        }
+        InitIMUI();
+
+        taps << events.Quit.Attach([&](SDL_Event* event) {
+          AppStatus = SDL_APP_SUCCESS;
+          printf("Quit event received, exiting...\n");
+        });
+
+        return AppStatus;
+      }
+
+      virtual SDL_AppResult Iterate() override {
+
+        // Start the Dear ImGui frame
+        ImGui_ImplSDLRenderer3_NewFrame();
+        ImGui_ImplSDL3_NewFrame();
+        ImGui::NewFrame();
+        {
+          ImGui::Begin("ImGUI SDL Renderer Basics Example");
+          ImGui::Text("Hello, world!");
+          ImGui::Button("Quit") && (AppStatus = SDL_APP_SUCCESS);
+          ImGui::ColorEdit3("clear color", (float*)&clear_color);
+          ImGui::End();
+        }
+        ImGui::Render();
+        ImGuiIO& io = ImGui::GetIO();
+        renderer.SetScale(io.DisplayFramebufferScale.x, io.DisplayFramebufferScale.y);
+        renderer.SetDrawColorFloat(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
+        renderer.Clear();
+        ImGui_ImplSDLRenderer3_RenderDrawData(ImGui::GetDrawData(), renderer);
+        renderer.Present();
+        return AppStatus;
+      }
+
+      virtual void Quit(SDL_AppResult code) override {
+        ImGui_ImplSDLRenderer3_Shutdown();
+        ImGui_ImplSDL3_Shutdown();
+        ImGui::DestroyContext();
+        renderer = nullptr;
+        window = nullptr;
+      }
+  };
+}
+
+HDK_SDL_MAIN_CLASS(simui_example::SimGuiApp)

include/hdk/is3r.hpp

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+#pragma once
+
+#include <hdk/sdl.hpp>
+#include <imgui.h>
+#include <imgui_impl_sdl3.h>
+#include <imgui_impl_sdlrenderer3.h>
+
+#include <hdk/sdl/Application.hpp>
+
+namespace hdk::is3r {
+  class Is3rWindowContext;
+  class Is3rApp : public sdl::ProtectedApp {
+    public:
+      virtual SDL_AppResult Event(SDL_Event* event) override {
+        ImGui_ImplSDL3_ProcessEvent(event);
+        return ProtectedApp::Event(event);
+      }
+
+      Is3rWindowContext CreateWindow(const char* title, int width, int height, SDL_WindowFlags flags);
+  };
+
+  struct Is3rWindowData {
+      sdl::Window window { nullptr };
+      sdl::Renderer renderer { nullptr };
+      sdl::evt::WindowEvents window_events;
+      grid::eps::Conduit<> on_iterate;
+      grid::eps::Conduit<> on_frame;
+      grid::eps::TapScope taps;
+  };
+
+  class Is3rWindowContext : public grid::SharedPtrWrapper<Is3rWindowData> {
+    public:
+      using SharedPtrWrapper<Is3rWindowData>::SharedPtrWrapper;
+
+      static Is3rWindowContext Create(const char* title, int width, int height, SDL_WindowFlags flags) {
+        auto [window, renderer] = sdl::CreateWindowAndRenderer(title, width, height, flags);
+        if (!window || !renderer) {
+          SDL_Log("Failed to create window or renderer: %s", SDL_GetError());
+          return Is3rWindowContext(nullptr);
+        }
+        auto* data = new Is3rWindowData{.window = window, .renderer = renderer};
+        auto context = Is3rWindowContext(get_or_cache(data, [](Is3rWindowData* data) { delete data; }));
+        return context;
+      }
+  };
+
+  inline Is3rWindowContext Is3rApp::CreateWindow(const char* title, int width, int height, SDL_WindowFlags flags) {
+    auto ctx = Is3rWindowContext::Create(title, width, height, flags);
+    auto wid = ctx->window.GetID();
+    ctx->taps << events.Window[wid] %  ctx->window_events;
+    ctx->taps << OnIterate %  ctx->on_iterate;
+    return ctx;
+  }
+
+}