examples/image_viewer/CMakeLists.txt

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+add_executable(image_viewer main.cpp)
+
+target_link_libraries(image_viewer PRIVATE ${PROJECT_NAME})
+
+target_compile_definitions(image_viewer PRIVATE
+  IMAGE_VIEWER_ASSET_DIR="${CMAKE_CURRENT_SOURCE_DIR}"
+)

examples/image_viewer/main.cpp

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+#include <imgui.h>
+
+#include <algorithm>
+#include <sophia/application.hpp>
+#include <sophia/components.hpp>
+#include <sophia/entity.hpp>
+#include <sophia/scene_view.hpp>
+#include <sophia/ui/panel.hpp>
+#include <string>
+
+// Shows a render target filling the whole panel.
+class ViewportPanel : public sophia::Panel {
+ public:
+  ViewportPanel(sophia::UI& ui, sophia::RenderTargetHandle target)
+      : Panel{{.name = "Image",
+               .windowFlags = ImGuiWindowFlags_NoScrollbar |
+                              ImGuiWindowFlags_NoScrollWithMouse}},
+        ui{ui},
+        target{target} {}
+
+  void onUpdate(const sophia::FrameInfo&) override { ui.image(target); }
+
+ private:
+  sophia::UI& ui;
+  sophia::RenderTargetHandle target;
+};
+
+// Displays an image file (anything stb_image reads: JPEG, PNG, BMP, ...) as a
+// sprite in a 2D scene, scaled to fit the viewport.
+//   image_viewer [path]
+class ImageViewer : public sophia::Application {
+ public:
+  ImageViewer()
+      : Application{{.width = 1000, .height = 750, .name = "ImageViewer"}} {}
+
+  void onCreate() override {
+    std::string path =
+        args.size() > 1 ? args[1] : IMAGE_VIEWER_ASSET_DIR "/dog.jpeg";
+
+    sophia::SceneHandle sceneHandle = scenes().create();
+    sophia::Scene& scene = scenes().get(sceneHandle);
+
+    camera = scene.createEntity("Camera");
+    camera.addComponent<sophia::CameraComponent>();
+
+    sophia::TextureHandle texture = resources().load<sophia::Texture>(path);
+    imageSize = resources().getExtent(texture);
+
+    // One world unit per image pixel; the camera zooms to fit.
+    sophia::Entity image = scene.createEntity("Image");
+    image.addComponent<sophia::SpriteComponent>(
+        sophia::SpriteComponent{.texture = texture, .size = imageSize});
+
+    target = resources().create<sophia::RenderTarget>();
+    views().create({.scene = sceneHandle,
+                    .target = target,
+                    .camera = camera,
+                    .clearColor = {0.1f, 0.1f, 0.15f, 1.f}});
+
+    panels().emplace<ViewportPanel>(ui(), target);
+    // panels().setDefaultLayout({.center = {"Image"}});
+  }
+
+  void onUpdate(const sophia::FrameInfo&) override {
+    // Fit the whole image: show enough height that neither dimension of the
+    // image overflows the viewport.
+    glm::vec2 viewport = resources().getExtent(target);
+    float viewportAspect = viewport.x / viewport.y;
+    camera.getComponent<sophia::CameraComponent>().ortho.height =
+        std::max(imageSize.y, imageSize.x / viewportAspect);
+  }
+
+ private:
+  sophia::Entity camera;
+  sophia::RenderTargetHandle target{};
+  glm::vec2 imageSize{1.f};
+};
+
+SOPHIA_MAIN(ImageViewer)