Route app shutdown staging through app core

src/app.cpp

@@ -6,6 +6,7 @@
 #include "node_progress_bar.h"
 #include "mp4enc.h"
 #include "app_core/app_frame.h"
+#include "app_core/app_shutdown.h"
 #include "app_core/app_status.h"
 #include "app_core/app_startup.h"
 #include "app_core/canvas_tool_ui.h"
@@ -642,27 +643,41 @@ void App::update(float dt)
 void App::terminate()
 {
     LOG("App::terminate");
-    ui_save();
+    const auto shutdown_plan = pp::app::plan_app_shutdown();
 
-    NodeStrokePreview::terminate_renderer();
-    rec_stop();
+    if (shutdown_plan.save_ui_state)
+        ui_save();
+
+    if (shutdown_plan.terminate_stroke_preview_renderer)
+        NodeStrokePreview::terminate_renderer();
+    if (shutdown_plan.stop_recording)
+        rec_stop();
     
-    TextureManager::invalidate();
-    ShaderManager::invalidate();
-    layout.unload();
-    layout_designer.unload();
-    uirtt.destroy();
-    m_face_plane.destroy();
-    layers.reset();
-    color.reset();
-    stroke.reset();
-    grid.reset();
-    presets.reset();
-    floating_presets.reset();
-    floating_color.reset();
-    floating_layers.reset();
-    floating_picker.reset();
-    quick_mode_state.clear();
+    if (shutdown_plan.invalidate_textures)
+        TextureManager::invalidate();
+    if (shutdown_plan.invalidate_shaders)
+        ShaderManager::invalidate();
+    if (shutdown_plan.unload_layouts) {
+        layout.unload();
+        layout_designer.unload();
+    }
+    if (shutdown_plan.destroy_ui_render_target)
+        uirtt.destroy();
+    if (shutdown_plan.destroy_face_plane)
+        m_face_plane.destroy();
+    if (shutdown_plan.release_panel_nodes) {
+        layers.reset();
+        color.reset();
+        stroke.reset();
+        grid.reset();
+        presets.reset();
+        floating_presets.reset();
+        floating_color.reset();
+        floating_layers.reset();
+        floating_picker.reset();
+    }
+    if (shutdown_plan.clear_quick_mode_state)
+        quick_mode_state.clear();
 }
 
 void App::update_memory_usage(size_t bytes)