feat(ui): add lightbox viewer for screenshots

Add a lightbox to preview screenshots on click. Introduce Button::set_texture for image-backed buttons, add widget getters for window size and visibility, and block background input while the lightbox is open. Close the lightbox with Escape or a left-click.

include/Cubed/ui/button.hpp

@@ -28,6 +28,7 @@ public:
     Button& set_background_image(const std::string& path,
                                  TextureManager& texture_manager);
     Button& set_default_image(TextureManager& texture_manager);
+    Button& set_texture(const Texture* texture, bool change_button_size);
     virtual Button& set_text(const std::string& text);
 
     Button& set_auto_scale(bool auto_scale);

include/Cubed/ui/screenshot_ui.hpp

@@ -1,7 +1,9 @@
 #pragma once
 
+#include "Cubed/ui/image.hpp"
 #include "Cubed/ui/ui_manager.hpp"
 namespace Cubed {
+class Texture;
 class ScreenshotScene;
 class ScreenshotUI : public UIManager {
 public:
@@ -17,9 +19,23 @@ public:
 
     void update_layout(int width, int height);
 
+    void open_lightbox(const Texture* image);
+
 private:
-    bool handle_window_resize_event(const WindowResizeEvent& e) override;
+    struct ImageInfo {
+        const Texture* texture = nullptr;
+        int width = 0;
+        int height = 0;
+    };
 
     ScreenshotScene& m_scene;
+    std::vector<ImageInfo> m_image_infos;
+    Widget* m_lightbox = nullptr;
+    Image* m_lightbox_image = nullptr;
+    bool handle_window_resize_event(const WindowResizeEvent& e) override;
+    bool handle_key_event(const KeyEvent& e) override;
+    bool handle_mouse_button_event(const MouseButtonEvent& e) override;
+    bool handle_mouse_move_event(const MouseMoveEvent& e) override;
+    bool handle_mouse_wheel_event(const MouseWheelEvent& e) override;
 };
 } // namespace Cubed

include/Cubed/ui/widget.hpp

@@ -28,6 +28,11 @@ public:
     Widget& operator=(Widget&&) = delete;
 
     Widget(Widget* parent);
+
+    static void set_window_size(int width, int height);
+    static int get_window_height();
+    static int get_window_width();
+
     virtual ~Widget() = default;
     virtual void update(float dt);
     virtual void render(Renderer& renderer);
@@ -35,7 +40,7 @@ public:
     virtual Widget& set_offset(glm::vec2 offset);
     virtual Widget& add_offset(glm::vec2 offset);
     virtual glm::vec2 get_offset() const;
-    static void set_window_size(int width, int height);
+
     virtual Widget& set_visible(bool visible);
     // Returns the final display size
 
@@ -58,6 +63,8 @@ public:
     virtual bool handle_window_resize_event(const WindowResizeEvent& e);
     virtual bool handle_mouse_move_event(const MouseMoveEvent& e);
     virtual bool handle_text_input_event(const TextInputEvent& e);
+
+    virtual bool is_visible() const;
     void set_order(TraversalOrder order);
 
     template <typename T, typename... Args> T& add_child(Args&&... args) {