app: Move render_pass into scene

src/core/scene/manager.rs

@@ -0,0 +1,46 @@
+use super::{Scene, SceneContext};
+
+pub struct SceneManager {
+    current_scene: Option<Box<dyn Scene>>,
+}
+
+impl SceneManager {
+    pub fn new() -> Self {
+        Self {
+            current_scene: None,
+        }
+    }
+
+    pub fn load_scene_if_not_loaded(&mut self, scene_context: &SceneContext) {
+        if let Some(current_scene) = self.current_scene.as_mut() {
+            if !current_scene.loaded() {
+                current_scene.load(scene_context);
+            }
+        }
+    }
+
+    pub fn load_scene(&mut self, scene: Box<dyn Scene>) {
+        if let Some(current_scene) = self.current_scene.as_mut() {
+            current_scene.unload();
+        }
+        self.current_scene = Some(scene);
+    }
+
+    pub fn current_scene(&self) -> Option<&Box<dyn Scene>> {
+        if let Some(current_scene) = self.current_scene.as_ref() {
+            if current_scene.loaded() {
+                return Some(current_scene);
+            }
+        }
+        None
+    }
+
+    pub fn current_scene_mut(&mut self) -> Option<&mut Box<dyn Scene>> {
+        if let Some(current_scene) = self.current_scene.as_mut() {
+            if current_scene.loaded() {
+                return Some(current_scene);
+            }
+        }
+        None
+    }
+}