30 files changed, 300 insertions, 136 deletions

diff --git a/.gitmodules b/.gitmodules
index 6332369..63a1a38 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -4,3 +4,6 @@
 [submodule "thirdparty/ctre"]
 	path = thirdparty/ctre
 	url = https://github.com/hanickadot/compile-time-regular-expressions
+[submodule "thirdparty/imgui"]
+	path = thirdparty/imgui
+	url = https://github.com/ocornut/imgui
diff --git a/Jamroot.jam b/Jamroot.jam
index 8ef10fe..b07dfdd 100644
--- a/Jamroot.jam
+++ b/Jamroot.jam
@@ -6,13 +6,13 @@ import lex ;
 import sequence ;
 import glsl ;
 
-pkg-config.import sdl2 ;
-pkg-config.import freetype2 ;
-pkg-config.import glib-2.0 ;
-pkg-config.import mxml ;
-pkg-config.import assimp ;
-lib pthread ;
-lib OpenMeshCore ;
+pkg-config.import sdl2 : : <link>shared ;
+pkg-config.import freetype2 : : <link>shared ;
+pkg-config.import glib-2.0 : : <link>shared ;
+pkg-config.import mxml : : <link>shared ;
+pkg-config.import assimp : : <link>shared ;
+lib pthread : : <link>shared ;
+lib OpenMeshCore : : <link>shared ;
 
 variant coverage : debug ;
 project i-like-trains : requirements
@@ -93,6 +93,7 @@ lib ilt :
 	<library>thirdparty/<variant>release
 	<implicit-dependency>thirdparty
 	<library>sdl2
+	<library>thirdparty//imguisdl2
 	<library>freetype2
 	<library>glib-2.0
 	<library>mxml
diff --git a/application/main.cpp b/application/main.cpp
index f0ba8bb..d58cf6d 100644
--- a/application/main.cpp
+++ b/application/main.cpp
@@ -1,6 +1,7 @@
+#include "ui/mainApplication.h"
+#include "ui/mainWindow.h"
 #include <array>
 #include <assetFactory/assetFactory.h>
-#include <chrono>
 #include <collection.h>
 #include <game/activities/go.h>
 #include <game/activities/idle.h>
@@ -31,17 +32,14 @@
 static const int DISPLAY_WIDTH = 1280;
 static const int DISPLAY_HEIGHT = 1024;
 
-class MainApplication : public GameState, public ApplicationBase {
+class DummyMainApplication : public GameState, public MainApplication {
 public:
-	using Windows = Collection<Window>;
-
 	int
 	run()
 	{
 		geoData = std::make_shared<GeoData>(GeoData::loadFromAsciiGrid("test/fixtures/height/SD19.asc"));
 
-		Windows windows;
-		windows.create<GameMainWindow>(DISPLAY_WIDTH, DISPLAY_HEIGHT);
+		windows.create<MainWindow>(DISPLAY_WIDTH, DISPLAY_HEIGHT)->setContent<GameMainWindow>();
 
 		world.create<Terrain>(geoData);
 		world.create<Water>(geoData);
@@ -89,41 +87,15 @@ public:
 			}
 		}
 
-		auto t_start = std::chrono::high_resolution_clock::now();
-		while (isRunning) {
-			processInputs(windows);
-			const auto t_end = std::chrono::high_resolution_clock::now();
-			const auto t_passed = std::chrono::duration_cast<TickDuration>(t_end - t_start);
-
-			world.apply(&WorldObject::tick, t_passed);
-			windows.apply(&Window::tick, t_passed);
-			windows.apply(&Window::refresh);
-
-			t_start = t_end;
-		}
+		mainLoop();
 
 		world.objects.clear();
 		return 0;
 	}
-
-private:
-	void
-	processInputs(const Windows & windows)
-	{
-		for (SDL_Event e; SDL_PollEvent(&e);) {
-			if (e.type == SDL_QUIT) {
-				isRunning = false;
-				return;
-			}
-			windows.applyOne(&Window::handleInput, e);
-		}
-	}
-
-	bool isRunning {true};
 };
 
 int
 main(int, char **)
 {
-	return std::make_shared<MainApplication>()->run();
+	return std::make_shared<DummyMainApplication>()->run();
 }
diff --git a/gfx/gl/uiShader.cpp b/gfx/gl/uiShader.cpp
index cf53e2c..bb9570e 100644
--- a/gfx/gl/uiShader.cpp
+++ b/gfx/gl/uiShader.cpp
@@ -7,7 +7,6 @@
 #include <gfx/gl/shaders/vs-uiShader.h>
 #include <glm/glm.hpp>
 #include <glm/gtc/type_ptr.hpp>
-#include <initializer_list>
 
 UIShader::IconProgram::IconProgram(const glm::mat4 & vp) : UIProgram {vp, uiShader_vs, uiShader_fs} { }
 
diff --git a/test/Jamfile.jam b/test/Jamfile.jam
index 1266854..0b830a8 100644
--- a/test/Jamfile.jam
+++ b/test/Jamfile.jam
@@ -55,8 +55,8 @@ run test-enumDetails.cpp ;
 run test-render.cpp : -- : test-assetFactory : <library>test ;
 run test-glContextBhvr.cpp ;
 run test-assetFactory.cpp : -- : [ sequence.insertion-sort [ glob-tree $(res) : *.* ] fixtures/rgb.txt test-instancing ] : <library>test ;
-run perf-assetFactory.cpp : <\ : test-assetFactory : <library>benchmark <library>test ;
-run perf-geoData.cpp : : : <library>test <library>benchmark ;
+run perf-assetFactory.cpp : \< : test-assetFactory : <library>benchmark <library>test ;
+run perf-geoData.cpp : \< : test-geoData : <library>test <library>benchmark ;
 run perf-persistence.cpp : \< : test-persistence : <library>benchmark <library>test ;
 run test-worker.cpp ;
 run test-instancing.cpp : -- : test-glContainer : <library>test ;
@@ -67,7 +67,7 @@ compile test-static-enumDetails.cpp ;
 compile test-static-stream_support.cpp ;
 explicit perf-assetFactory ;
 explicit perf-persistence ;
-explicit perf-terrain ;
+explicit perf-geoData ;
 explicit perf-instancing ;
-alias perf : perf-assetFactory perf-persistence perf-terrain ;
+alias perf : perf-assetFactory perf-persistence perf-geoData perf-instancing ;
 explicit perf ;
diff --git a/test/perf-assetFactory.cpp b/test/perf-assetFactory.cpp
index 147e4ba..671713c 100644
--- a/test/perf-assetFactory.cpp
+++ b/test/perf-assetFactory.cpp
@@ -1,13 +1,11 @@
 #include "assetFactory/assetFactory.h"
-#include "assetFactory/factoryMesh.h"
 #include "testMainWindow.h"
-#include "ui/applicationBase.h"
 #include <benchmark/benchmark.h>
 
 static void
 brush47xml_load(benchmark::State & state)
 {
-	TestMainWindow window;
+	TestMainWindowAppBase window;
 
 	for (auto _ : state) {
 		benchmark::DoNotOptimize(AssetFactory::loadXML(RESDIR "/brush47.xml"));
@@ -17,7 +15,7 @@ brush47xml_load(benchmark::State & state)
 static void
 foliagexml_load(benchmark::State & state)
 {
-	TestMainWindow window;
+	TestMainWindowAppBase window;
 
 	for (auto _ : state) {
 		benchmark::DoNotOptimize(AssetFactory::loadXML(RESDIR "/foliage.xml"));
diff --git a/test/perf-instancing.cpp b/test/perf-instancing.cpp
index 829ea50..3638111 100644
--- a/test/perf-instancing.cpp
+++ b/test/perf-instancing.cpp
@@ -26,7 +26,7 @@ struct data {
 static void
 partition(benchmark::State & state)
 {
-	TestMainWindow window;
+	TestMainWindowAppBase window;
 	data d(static_cast<size_t>(state.range()));
 	GlobalPosition2D pos {};
 	for (auto _ : state) {
diff --git a/test/test-assetFactory.cpp b/test/test-assetFactory.cpp
index 73370c8..1c2c417 100644
--- a/test/test-assetFactory.cpp
+++ b/test/test-assetFactory.cpp
@@ -21,10 +21,8 @@
 #include "lib/location.h"
 #include "lib/stream_support.h"
 #include "testMainWindow.h"
-#include "ui/applicationBase.h"
 
-BOOST_GLOBAL_FIXTURE(ApplicationBase);
-BOOST_GLOBAL_FIXTURE(TestMainWindow);
+BOOST_GLOBAL_FIXTURE(TestMainWindowAppBase);
 
 const std::filesystem::path TMP {"/tmp"};
 
diff --git a/test/test-glContainer.cpp b/test/test-glContainer.cpp
index ec1c0d1..332d440 100644
--- a/test/test-glContainer.cpp
+++ b/test/test-glContainer.cpp
@@ -1,7 +1,6 @@
 #define BOOST_TEST_MODULE glContainer
 
 #include "testMainWindow.h"
-#include "ui/applicationBase.h"
 #include <boost/test/data/test_case.hpp>
 #include <boost/test/unit_test.hpp>
 
@@ -15,8 +14,7 @@ BOOST_TEST_DONT_PRINT_LOG_VALUE(glContainer<int>::const_iterator);
 BOOST_TEST_DONT_PRINT_LOG_VALUE(glContainer<int>::reverse_iterator);
 BOOST_TEST_DONT_PRINT_LOG_VALUE(glContainer<int>::const_reverse_iterator);
 
-BOOST_GLOBAL_FIXTURE(ApplicationBase);
-BOOST_GLOBAL_FIXTURE(TestMainWindow);
+BOOST_GLOBAL_FIXTURE(TestMainWindowAppBase);
 
 BOOST_FIXTURE_TEST_SUITE(i, glContainer<int>)
 
diff --git a/test/test-instancing.cpp b/test/test-instancing.cpp
index 77467d8..1dd4cea 100644
--- a/test/test-instancing.cpp
+++ b/test/test-instancing.cpp
@@ -1,17 +1,15 @@
 #define BOOST_TEST_MODULE instancing
 
-#include "stream_support.h"
+#include "stream_support.h" // IWYU pragma: keep
 #include "testHelpers.h"
 #include "testMainWindow.h"
-#include "ui/applicationBase.h"
 #include <boost/test/data/test_case.hpp>
 #include <boost/test/unit_test.hpp>
 #include <set>
 
 #include <gfx/gl/instanceVertices.h>
 
-BOOST_GLOBAL_FIXTURE(ApplicationBase);
-BOOST_GLOBAL_FIXTURE(TestMainWindow);
+BOOST_GLOBAL_FIXTURE(TestMainWindowAppBase);
 
 struct TestInstanceVertices : public InstanceVertices<int> {
 	void
diff --git a/test/test-network.cpp b/test/test-network.cpp
index 174e2a5..59eebae 100644
--- a/test/test-network.cpp
+++ b/test/test-network.cpp
@@ -5,7 +5,6 @@
 #include <boost/test/unit_test.hpp>
 
 #include "testMainWindow.h"
-#include "ui/applicationBase.h"
 #include <array>
 #include <collection.h>
 #include <game/network/link.h>
@@ -20,8 +19,7 @@
 #include <utility>
 #include <vector>
 
-BOOST_GLOBAL_FIXTURE(ApplicationBase);
-BOOST_GLOBAL_FIXTURE(TestMainWindow);
+BOOST_GLOBAL_FIXTURE(TestMainWindowAppBase);
 
 struct TestLinkS;
 
diff --git a/test/test-render.cpp b/test/test-render.cpp
index 79424f5..2c4efea 100644
--- a/test/test-render.cpp
+++ b/test/test-render.cpp
@@ -69,8 +69,7 @@ public:
 	}
 };
 
-BOOST_GLOBAL_FIXTURE(ApplicationBase);
-BOOST_GLOBAL_FIXTURE(TestMainWindow);
+BOOST_GLOBAL_FIXTURE(TestMainWindowAppBase);
 
 BOOST_DATA_TEST_CASE(cam,
 		boost::unit_test::data::xrange(500, 30000, 1300) * boost::unit_test::data::xrange(500, 10000, 300)
diff --git a/test/test-text.cpp b/test/test-text.cpp
index f185cf5..b0a9503 100644
--- a/test/test-text.cpp
+++ b/test/test-text.cpp
@@ -7,7 +7,6 @@
 
 #include "testMainWindow.h"
 #include "testRenderOutput.h"
-#include "ui/applicationBase.h"
 #include "ui/text.h"
 #include <array>
 #include <gfx/models/texture.h>
@@ -16,8 +15,7 @@
 #include <unicode.h>
 #include <vector>
 
-BOOST_GLOBAL_FIXTURE(ApplicationBase);
-BOOST_GLOBAL_FIXTURE(TestMainWindow);
+BOOST_GLOBAL_FIXTURE(TestMainWindowAppBase);
 
 BOOST_AUTO_TEST_CASE(utf8_string_view_iter)
 {
diff --git a/test/testMainWindow.cpp b/test/testMainWindow.cpp
index d0b674c..4a76044 100644
--- a/test/testMainWindow.cpp
+++ b/test/testMainWindow.cpp
@@ -2,7 +2,7 @@
 #include <boost/test/test_tools.hpp>
 #include <format>
 
-TestMainWindow::TestMainWindow() : Window {1, 1, __FILE__, SDL_WINDOW_OPENGL | SDL_WINDOW_HIDDEN}
+TestMainWindow::TestMainWindow() : MainWindow {1, 1, __FILE__, SDL_WINDOW_OPENGL | SDL_WINDOW_HIDDEN}
 {
 	glEnable(GL_DEBUG_OUTPUT);
 	glDebugMessageCallback(
diff --git a/test/testMainWindow.h b/test/testMainWindow.h
index 445491d..f54eb72 100644
--- a/test/testMainWindow.h
+++ b/test/testMainWindow.h
@@ -1,15 +1,13 @@
 #pragma once
 
-#include "ui/window.h"
+#include "ui/applicationBase.h"
+#include "ui/mainWindow.h"
 
-class TestMainWindow : public Window {
+class TestMainWindow : public MainWindow {
 	// This exists only to hold an OpenGL context open for the duration of the tests,
 	// in the same way a real main window would always exist.
 public:
 	TestMainWindow();
-
-	void
-	tick(TickDuration) override
-	{
-	}
 };
+
+class TestMainWindowAppBase : public ApplicationBase, public TestMainWindow { };
diff --git a/thirdparty/Jamfile.jam b/thirdparty/Jamfile.jam
index 8b76449..7a47589 100644
--- a/thirdparty/Jamfile.jam
+++ b/thirdparty/Jamfile.jam
@@ -12,3 +12,18 @@ lib stb : stb_image.c :
 	<warnings>off
 	<warnings-as-errors>off
 	;
+
+lib imguisdl2 :
+	[ glob imgui/imgui*.cpp : imgui/imgui_demo.cpp ]
+	imgui/backends/imgui_impl_sdl2.cpp
+	imgui/backends/imgui_impl_opengl3.cpp
+	:
+	<link>static
+	<include>imgui
+	<use>..//sdl2
+	<cflags>-fPIC
+	<warnings>off
+	<warnings-as-errors>off
+	: :
+	<include>imgui
+	;
diff --git a/thirdparty/imgui b/thirdparty/imgui
new file mode 160000
+Subproject 2db79d0868f7b02d26f7557a72504a0b6f84493
diff --git a/ui/applicationBase.cpp b/ui/applicationBase.cpp
index 7764c58..961007b 100644
--- a/ui/applicationBase.cpp
+++ b/ui/applicationBase.cpp
@@ -1,9 +1,17 @@
 #include "applicationBase.h"
+#include "imgui_wrap.h"
 #include <SDL2/SDL.h>
 #include <stdexcept>
 
 ApplicationBase::ApplicationBase()
 {
+	initSDL();
+	initImGUI();
+}
+
+void
+ApplicationBase::initSDL() const
+{
 	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS) < 0) {
 		throw std::runtime_error(SDL_GetError());
 	}
@@ -27,7 +35,22 @@ ApplicationBase::ApplicationBase()
 	setGlAttribute(SDL_GL_SHARE_WITH_CURRENT_CONTEXT, 1);
 }
 
+void
+ApplicationBase::initImGUI() const
+{
+	// 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; // Enable docking
+	io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable; // Enable viewports
+	io.IniFilename = nullptr; // Disable saving settings automagically
+}
+
 ApplicationBase::~ApplicationBase()
 {
 	SDL_Quit();
+	ImGui::DestroyContext();
 }
diff --git a/ui/applicationBase.h b/ui/applicationBase.h
index 9d9b66b..082557d 100644
--- a/ui/applicationBase.h
+++ b/ui/applicationBase.h
@@ -9,4 +9,8 @@ public:
 
 	NO_COPY(ApplicationBase);
 	NO_MOVE(ApplicationBase);
+
+private:
+	void initSDL() const;
+	void initImGUI() const;
 };
diff --git a/ui/gameMainWindow.cpp b/ui/gameMainWindow.cpp
index ccbcdba..6168504 100644
--- a/ui/gameMainWindow.cpp
+++ b/ui/gameMainWindow.cpp
@@ -27,14 +27,15 @@ public:
 	}
 };
 
-GameMainWindow::GameMainWindow(size_t w, size_t h) :
-	Window {w, h, "I Like Trains", SDL_WINDOW_OPENGL}, SceneRenderer {Window::size, 0}
+GameMainWindow::GameMainWindow(size_t w, size_t h) : WindowContent {w, h}, SceneRenderer {{w, h}, 0}
 {
 	uiComponents.create<ManualCameraController>(glm::vec2 {310'727'624, 494'018'810});
 	auto gms = uiComponents.create<GameMainSelector>(&camera, ScreenAbsCoord {w, h});
 	uiComponents.create<GameMainToolbar>(gms.get());
 }
 
+GameMainWindow::~GameMainWindow() { }
+
 void
 GameMainWindow::tick(TickDuration)
 {
@@ -45,7 +46,10 @@ void
 GameMainWindow::render() const
 {
 	SceneRenderer::render(*this);
-	Window::render();
+	glEnable(GL_BLEND);
+	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+	glDisable(GL_DEPTH_TEST);
+	uiComponents.apply(&UIComponent::render, uiShader, UIComponent::Position {});
 }
 
 void
diff --git a/ui/gameMainWindow.h b/ui/gameMainWindow.h
index a4e822e..fcbd135 100644
--- a/ui/gameMainWindow.h
+++ b/ui/gameMainWindow.h
@@ -2,15 +2,18 @@
 
 #include "chronology.h"
 #include "gfx/gl/sceneRenderer.h"
-#include "window.h"
+#include "windowContent.h"
 #include <cstddef>
 
-class GameMainWindow : public Window, SceneRenderer, public SceneProvider {
+class GameMainWindow : public WindowContent, SceneRenderer, public SceneProvider {
 public:
 	GameMainWindow(size_t w, size_t h);
+	~GameMainWindow() override;
 
-	void tick(TickDuration) override;
+	NO_MOVE(GameMainWindow);
+	NO_COPY(GameMainWindow);
 
+	void tick(TickDuration) override;
 	void render() const override;
 
 private:
diff --git a/ui/imgui_wrap.h b/ui/imgui_wrap.h
new file mode 100644
index 0000000..1d619a4
--- /dev/null
+++ b/ui/imgui_wrap.h
@@ -0,0 +1,6 @@
+#pragma once
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wold-style-cast"
+#include "imgui.h" // IWYU pragma: export
+#pragma GCC diagnostic pop
diff --git a/ui/mainApplication.cpp b/ui/mainApplication.cpp
new file mode 100644
index 0000000..6cb1037
--- /dev/null
+++ b/ui/mainApplication.cpp
@@ -0,0 +1,43 @@
+#include "mainApplication.h"
+#include "game/gamestate.h"
+#include "game/worldobject.h"
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wold-style-cast"
+#include "backends/imgui_impl_sdl2.h"
+#pragma GCC diagnostic pop
+
+void
+MainApplication::mainLoop()
+{
+	auto t_start = std::chrono::high_resolution_clock::now();
+	while (isRunning) {
+		processInputs();
+		const auto t_end = std::chrono::high_resolution_clock::now();
+		const auto t_passed = std::chrono::duration_cast<TickDuration>(t_end - t_start);
+
+		if (gameState) {
+			gameState->world.apply(&WorldObject::tick, t_passed);
+		}
+		windows.apply(&Window::tick, t_passed);
+		windows.apply(&Window::refresh);
+		ImGui::UpdatePlatformWindows();
+		ImGui::RenderPlatformWindowsDefault();
+
+		t_start = t_end;
+	}
+}
+
+void
+MainApplication::processInputs()
+{
+	for (SDL_Event e; SDL_PollEvent(&e);) {
+		if (e.type == SDL_QUIT) {
+			isRunning = false;
+			return;
+		}
+		ImGui_ImplSDL2_ProcessEvent(&e);
+		if (!ImGui::GetIO().WantCaptureMouse) {
+			windows.applyOne(&Window::handleInput, e);
+		}
+	}
+}
diff --git a/ui/mainApplication.h b/ui/mainApplication.h
new file mode 100644
index 0000000..a6cb126
--- /dev/null
+++ b/ui/mainApplication.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include "applicationBase.h"
+#include "collection.h"
+#include "window.h"
+
+class MainApplication : public ApplicationBase {
+public:
+	using Windows = Collection<Window>;
+	void mainLoop();
+
+protected:
+	Windows windows;
+
+private:
+	void processInputs();
+	bool isRunning {true};
+};
diff --git a/ui/mainWindow.cpp b/ui/mainWindow.cpp
new file mode 100644
index 0000000..38d6a6e
--- /dev/null
+++ b/ui/mainWindow.cpp
@@ -0,0 +1,27 @@
+#include "mainWindow.h"
+#include <format>
+#include <stdexcept>
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wold-style-cast"
+#include "backends/imgui_impl_opengl3.h"
+#include "backends/imgui_impl_sdl2.h"
+#pragma GCC diagnostic pop
+
+MainWindow::MainWindow(size_t w, size_t h) : MainWindow {w, h, "I Like Trains", SDL_WINDOW_OPENGL} { }
+
+MainWindow::MainWindow(size_t w, size_t h, const std::string & title, Uint32 flags) : Window {w, h, title, flags}
+{
+	if (const auto version = gladLoadGL(reinterpret_cast<GLADloadfunc>(SDL_GL_GetProcAddress)); version < 30003) {
+		throw std::runtime_error {std::format("Insufficient OpenGL version: {}", version)};
+	}
+
+	ImGui_ImplSDL2_InitForOpenGL(m_window, glContext.get());
+	ImGui_ImplOpenGL3_Init();
+}
+
+MainWindow::~MainWindow()
+{
+	ImGui_ImplOpenGL3_Shutdown();
+	ImGui_ImplSDL2_Shutdown();
+}
diff --git a/ui/mainWindow.h b/ui/mainWindow.h
new file mode 100644
index 0000000..fe26c5c
--- /dev/null
+++ b/ui/mainWindow.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#include "window.h"
+#include <cstddef>
+
+class MainWindow : public Window {
+public:
+	MainWindow(size_t w, size_t h);
+	~MainWindow() override;
+
+	NO_MOVE(MainWindow);
+	NO_COPY(MainWindow);
+
+protected:
+	MainWindow(size_t width, size_t height, const std::string & title, Uint32 flags);
+};
diff --git a/ui/window.cpp b/ui/window.cpp
index dd488d7..732e9ef 100644
--- a/ui/window.cpp
+++ b/ui/window.cpp
@@ -1,28 +1,17 @@
 #include "window.h"
-#include "uiComponent.h"
-#include <format>
 #include <glad/gl.h>
 #include <glm/glm.hpp>
-#include <stdexcept>
-
-Window::GLInitHelper::GLInitHelper()
-{
-	[[maybe_unused]] static auto init = []() {
-		// NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
-		if (const auto version = gladLoadGL(reinterpret_cast<GLADloadfunc>(SDL_GL_GetProcAddress)); version < 30003) {
-			throw std::runtime_error {std::format("Insufficient OpenGL version: {}", version)};
-		}
-		else {
-			return version;
-		}
-	}();
-}
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wold-style-cast"
+#include "backends/imgui_impl_opengl3.h"
+#include "backends/imgui_impl_sdl2.h"
+#pragma GCC diagnostic pop
 
 Window::Window(size_t width, size_t height, const std::string & title, Uint32 flags) :
 	size {static_cast<int>(width), static_cast<int>(height)},
 	m_window {title.c_str(), static_cast<int>(SDL_WINDOWPOS_CENTERED), static_cast<int>(SDL_WINDOWPOS_CENTERED), size.x,
 			size.y, flags},
-	glContext {m_window}, uiShader {width, height}
+	glContext {m_window}
 {
 }
 
@@ -39,23 +28,21 @@ Window::swapBuffers() const
 	SDL_GL_SwapWindow(m_window);
 }
 
+void
+Window::tick(TickDuration elapsed)
+{
+	if (content) {
+		content->tick(elapsed);
+	}
+}
+
 bool
 Window::handleInput(const SDL_Event & e)
 {
 	if (SDL_GetWindowID(m_window) == e.window.windowID) {
-		SDL_Event eAdjusted {e};
-		switch (e.type) {
-			// SDL and OpenGL have coordinates that are vertically opposed.
-			case SDL_MOUSEBUTTONDOWN:
-			case SDL_MOUSEBUTTONUP:
-				eAdjusted.button.y = size.y - e.button.y;
-				break;
-			case SDL_MOUSEMOTION:
-				eAdjusted.motion.y = size.y - e.motion.y;
-				break;
+		if (content) {
+			return content->handleInput(e);
 		}
-		uiComponents.rapplyOne(&UIComponent::handleInput, eAdjusted, UIComponent::Position {{}, size});
-		return true;
 	}
 	return false;
 }
@@ -66,16 +53,15 @@ Window::refresh() const
 	SDL_GL_MakeCurrent(m_window, glContext);
 	clear(0.0F, 0.0F, 0.0F, 1.0F);
 
-	render();
+	ImGui_ImplOpenGL3_NewFrame();
+	ImGui_ImplSDL2_NewFrame();
+	ImGui::NewFrame();
+	if (content) {
+		content->render();
+		// Render UI stuff here
+	}
+	ImGui::Render();
+	ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
 
 	swapBuffers();
 }
-
-void
-Window::render() const
-{
-	glEnable(GL_BLEND);
-	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-	glDisable(GL_DEPTH_TEST);
-	uiComponents.apply(&UIComponent::render, uiShader, UIComponent::Position {});
-}
diff --git a/ui/window.h b/ui/window.h
index 8f2b70b..62c34de 100644
--- a/ui/window.h
+++ b/ui/window.h
@@ -1,13 +1,12 @@
 #pragma once
 
 #include "chronology.h"
-#include "collection.h"
-#include "gfx/gl/uiShader.h"
+#include "config/types.h"
 #include "ptr.h"
-#include "uiComponent.h" // IWYU pragma: keep
+#include "special_members.h"
+#include "windowContent.h"
 #include <SDL2/SDL.h>
 #include <cstddef>
-#include <special_members.h>
 #include <string>
 
 using SDL_WindowPtr = wrapped_ptrt<SDL_Window, SDL_CreateWindow, SDL_DestroyWindow>;
@@ -22,24 +21,26 @@ public:
 	NO_COPY(Window);
 	NO_MOVE(Window);
 
-	virtual void tick(TickDuration elapsed) = 0;
+	template<typename C, typename... P>
+	void
+	setContent(P &&... p)
+	{
+		glm::ivec2 size {};
+		SDL_GetWindowSizeInPixels(m_window, &size.x, &size.y);
+		content = std::make_unique<C>(size.x, size.y, std::forward<P>(p)...);
+	}
+
+	void tick(TickDuration elapsed);
 	void refresh() const;
 	bool handleInput(const SDL_Event & e);
 
-	void clear(float r, float g, float b, float a) const;
 	void swapBuffers() const;
 
 protected:
-	virtual void render() const;
-
-	struct GLInitHelper {
-		GLInitHelper();
-	};
+	void clear(float r, float g, float b, float a) const;
 
 	const ScreenAbsCoord size;
 	SDL_WindowPtr m_window;
 	SDL_GLContextPtr glContext;
-	GLInitHelper glInithelper;
-	Collection<UIComponent> uiComponents;
-	UIShader uiShader;
+	WindowContent::Ptr content;
 };
diff --git a/ui/windowContent.cpp b/ui/windowContent.cpp
new file mode 100644
index 0000000..91732a7
--- /dev/null
+++ b/ui/windowContent.cpp
@@ -0,0 +1,32 @@
+#include "windowContent.h"
+#include "SDL_events.h"
+
+WindowContent::WindowContent(size_t width, size_t height) : uiShader {width, height} { }
+
+void
+WindowContent::tick(TickDuration)
+{
+}
+
+bool
+WindowContent::handleInput(const SDL_Event & e)
+{
+	SDL_Event eAdjusted {e};
+	const auto size = [&e] {
+		glm::ivec2 size {};
+		SDL_GetWindowSizeInPixels(SDL_GetWindowFromID(e.window.windowID), &size.x, &size.y);
+		return size;
+	}();
+	switch (e.type) {
+			//  SDL and OpenGL have coordinates that are vertically opposed.
+		case SDL_MOUSEBUTTONDOWN:
+		case SDL_MOUSEBUTTONUP:
+			eAdjusted.button.y = size.y - e.button.y;
+			break;
+		case SDL_MOUSEMOTION:
+			eAdjusted.motion.y = size.y - e.motion.y;
+			break;
+	}
+	uiComponents.rapplyOne(&UIComponent::handleInput, eAdjusted, UIComponent::Position {{}, size});
+	return true;
+}
diff --git a/ui/windowContent.h b/ui/windowContent.h
new file mode 100644
index 0000000..474445a
--- /dev/null
+++ b/ui/windowContent.h
@@ -0,0 +1,26 @@
+#pragma once
+
+#include "chronology.h"
+#include "collection.h"
+#include "gfx/gl/uiShader.h"
+#include "special_members.h"
+#include "stdTypeDefs.h"
+#include "uiComponent.h" // IWYU pragma: keep
+#include <functional>
+
+class WindowContent : public StdTypeDefs<WindowContent> {
+public:
+	using Factory = std::function<Ptr(size_t width, size_t height)>;
+	WindowContent(size_t width, size_t height);
+	virtual ~WindowContent() = default;
+	NO_MOVE(WindowContent);
+	NO_COPY(WindowContent);
+
+	virtual void tick(TickDuration);
+	virtual void render() const = 0;
+	virtual bool handleInput(const SDL_Event & e);
+
+protected:
+	::Collection<UIComponent> uiComponents;
+	UIShader uiShader;
+};