diff --git a/common/gui_window.hh b/common/gui_window.hh
index 044b1f2..c938ffe 100644
--- a/common/gui_window.hh
+++ b/common/gui_window.hh
@@ -1,72 +1,57 @@
 #pragma once
 
-#include <utility>
+#include <functional>
 #include <string>
 #include <string_view>
+#include <utility>
 
 #include <imgui.h>
+
 #include <yas/serialize.hpp>
 #include <yas/types/utility/usertype.hpp>
 
 #include "nf7.hh"
 
+#include "common/file_base.hh"
+
 
 namespace nf7::gui {
 
-class Window {
+class Window : public nf7::FileBase::Feature {
  public:
   static std::string ConcatId(nf7::File& f, const std::string& name) noexcept {
     return f.abspath().Stringify() + " | " + std::string {name};
   }
 
   Window() = delete;
-  Window(File& owner, std::string_view title, const gui::Window* src = nullptr) noexcept :
-      owner_(&owner), title_(title),
-      shown_(src? src->shown_: false) {
+  Window(nf7::FileBase& owner, std::string_view title) noexcept :
+      nf7::FileBase::Feature(owner), owner_(&owner), title_(title), shown_(false) {
   }
   Window(const Window&) = delete;
   Window(Window&&) = delete;
   Window& operator=(const Window&) = delete;
   Window& operator=(Window&&) = delete;
 
-  bool Begin() noexcept {
-    if (std::exchange(set_focus_, false)) {
-      ImGui::SetNextWindowFocus();
-      shown_ = true;
-    }
-    if (!shown_) return false;
-
-    need_end_ = true;
-    return ImGui::Begin(id().c_str(), &shown_);
-  }
-  void End() noexcept {
-    if (need_end_) {
-      ImGui::End();
-      need_end_ = false;
-    }
+  void serialize(auto& ar) {
+    ar(shown_);
   }
 
+  void Show() noexcept {
+    shown_ = true;
+  }
   void SetFocus() noexcept {
     shown_     = true;
     set_focus_ = true;
   }
-
-  template <typename Ar>
-  Ar& serialize(Ar& ar) {
-    ar(shown_);
-    return ar;
-  }
-
-  std::string id() const noexcept {
-    return ConcatId(*owner_, title_);
-  }
-
-  bool shownInCurrentFrame() const noexcept {
-    return shown_ || set_focus_;
+  bool MenuItem() noexcept {
+    return ImGui::MenuItem(title_.c_str(), nullptr, &shown_);
   }
 
+  std::string id() const noexcept { return ConcatId(*owner_, title_); }
   bool shown() const noexcept { return shown_; }
-  bool& shown() noexcept { return shown_; }
+
+  std::function<void()> onConfig = [](){};
+  std::function<void()> onUpdate;
 
  private:
   File* const owner_;
@@ -77,6 +62,31 @@ class Window {
 
   // persistent params
   bool shown_;
+
+
+  void Handle(const nf7::File::Event& e) noexcept override {
+    switch (e.type) {
+    case nf7::File::Event::kReqFocus:
+      SetFocus();
+      return;
+    default:
+      return;
+    }
+  }
+
+  void Update() noexcept override {
+    if (std::exchange(set_focus_, false)) {
+      ImGui::SetNextWindowFocus();
+      shown_ = true;
+    }
+    if (!shown_) return;
+
+    onConfig();
+    if (ImGui::Begin(id().c_str(), &shown_)) {
+      onUpdate();
+    }
+    ImGui::End();
+  }
 };
 
 }  // namespace nf7::gui
diff --git a/file/gl_obj.cc b/file/gl_obj.cc
index e6555cb..73ca1e5 100644
--- a/file/gl_obj.cc
+++ b/file/gl_obj.cc
@@ -109,6 +109,11 @@ class ObjBase : public nf7::FileBase,
 
     if constexpr (HasWindow<T>) {
       win_.emplace(*this, T::kWindowTitle);
+      win_->onConfig = []() {
+        const auto em = ImGui::GetFontSize();
+        ImGui::SetNextWindowSize({8*em, 8*em}, ImGuiCond_FirstUseEver);
+      };
+      win_->onUpdate = [this]() { mem_->UpdateWindow(fu_); };
     }
   }
 
@@ -170,22 +175,6 @@ class ObjBase : public nf7::FileBase,
         });
   }
 
-
-  void Update() noexcept override {
-    nf7::FileBase::Update();
-
-    if constexpr (HasWindow<T>) {
-      if (win_->shownInCurrentFrame()) {
-        const auto em = ImGui::GetFontSize();
-        ImGui::SetNextWindowSize({8*em, 8*em}, ImGuiCond_FirstUseEver);
-      }
-      if (win_->Begin()) {
-        mem_->UpdateWindow(fu_);
-      }
-      win_->End();
-    }
-  }
-
   void UpdateMenu() noexcept override {
     if (ImGui::BeginMenu("object management")) {
       if (ImGui::MenuItem("create", nullptr, false, !fu_)) {
@@ -211,7 +200,7 @@ class ObjBase : public nf7::FileBase,
     }
     if constexpr (HasWindow<T>) {
       ImGui::Separator();
-      ImGui::MenuItem(T::kWindowTitle, nullptr, &win_->shown());
+      win_->MenuItem();
     }
   }
   void UpdateTooltip() noexcept override {
diff --git a/file/node_network.cc b/file/node_network.cc
index 9e1cbd4..55c4d1f 100644
--- a/file/node_network.cc
+++ b/file/node_network.cc
@@ -109,7 +109,6 @@ class Network final : public nf7::FileBase, public nf7::DirItem, public nf7::Nod
   };
 
   Network(nf7::Env& env,
-          const gui::Window*   win   = nullptr,
           ItemList&&           items = {},
           nf7::NodeLinkStore&& links = {},
           Data&&               d     = {}) :
@@ -119,9 +118,15 @@ class Network final : public nf7::FileBase, public nf7::DirItem, public nf7::Nod
                    nf7::DirItem::kWidget),
       nf7::Node(nf7::Node::kNone),
       life_(*this),
-      win_(*this, "Editor Node/Network", win),
+      win_(*this, "Editor Node/Network"),
       items_(std::move(items)), links_(std::move(links)),
       mem_(std::move(d), *this) {
+    win_.onConfig = []() {
+      const auto em = ImGui::GetFontSize();
+      ImGui::SetNextWindowSize({36*em, 36*em}, ImGuiCond_FirstUseEver);
+    };
+    win_.onUpdate = [this]() { NetworkEditor(); };
+
     Sanitize();
   }
   ~Network() noexcept {
@@ -142,7 +147,7 @@ class Network final : public nf7::FileBase, public nf7::DirItem, public nf7::Nod
       items.push_back(std::make_unique<Item>(env, *item));
     }
     return std::make_unique<Network>(
-        env, &win_, std::move(items), NodeLinkStore(links_));
+        env, std::move(items), NodeLinkStore(links_));
   }
 
   File* Find(std::string_view name) const noexcept;
@@ -243,6 +248,7 @@ class Network final : public nf7::FileBase, public nf7::DirItem, public nf7::Nod
   }
 
   // gui
+  void NetworkEditor() noexcept;
   void ItemAdder(const ImVec2&) noexcept;
   void Config() noexcept;
 
@@ -964,8 +970,6 @@ void Network::Item::Watcher::Handle(const File::Event& ev) noexcept {
 void Network::Update() noexcept {
   nf7::FileBase::Update();
 
-  const auto em = ImGui::GetFontSize();
-
   // forget expired lambdas
   lambdas_running_.erase(
       std::remove_if(lambdas_running_.begin(), lambdas_running_.end(),
@@ -977,132 +981,13 @@ void Network::Update() noexcept {
     item->Update();
   }
 
-  // ---- editor window
-  if (win_.shownInCurrentFrame()) {
-    ImGui::SetNextWindowSize({36*em, 36*em}, ImGuiCond_FirstUseEver);
-  }
-  if (win_.Begin()) {
-    // ---- editor window / toolbar
-    ImGui::BeginGroup();
-    {
-      // ---- editor window / toolbar / attached lambda combo
-      const auto current_lambda =
-          !lambda_?              "(unselected)"s:
-          lambda_->depth() == 0? "(isolated)"s:
-          nf7::gui::GetContextDisplayName(*lambda_);
-      if (ImGui::BeginCombo("##lambda", current_lambda.c_str())) {
-        if (lambda_) {
-          if (ImGui::Selectable("detach current lambda")) {
-            AttachLambda(nullptr);
-          }
-          ImGui::Separator();
-        }
-        for (const auto& wptr : lambdas_running_) {
-          auto ptr = wptr.lock();
-          if (!ptr) continue;
-
-          const auto name = nf7::gui::GetContextDisplayName(*ptr);
-          if (ImGui::Selectable(name.c_str(), ptr == lambda_)) {
-            AttachLambda(nullptr);
-            lambda_ = ptr;
-          }
-          if (ImGui::IsItemHovered()) {
-            ImGui::BeginTooltip();
-            ImGui::TextUnformatted("call stack:");
-            ImGui::Indent();
-            nf7::gui::ContextStack(*ptr);
-            ImGui::Unindent();
-            ImGui::EndTooltip();
-          }
-        }
-        if (lambdas_running_.size() == 0) {
-          ImGui::TextDisabled("no running lambda found...");
-        }
-        ImGui::EndCombo();
-      }
-    }
-    ImGui::EndGroup();
-
-    // ---- editor window / canvas
-    if (ImGui::BeginChild("canvas", {0, 0}, false, ImGuiWindowFlags_NoMove)) {
-      canvas_pos_ = ImGui::GetCursorScreenPos();
-      ImNodes::BeginCanvas(&canvas_);
-
-      // update child nodes
-      auto ed = Network::Editor {*this};
-      for (const auto& item : items_) {
-        item->UpdateNode(ed);
-      }
-
-      // handle existing links
-      for (const auto& lk : links_.items()) {
-        const auto src_id   = reinterpret_cast<void*>(lk.src_id);
-        const auto dst_id   = reinterpret_cast<void*>(lk.dst_id);
-        const auto src_name = lk.src_name.c_str();
-        const auto dst_name = lk.dst_name.c_str();
-        if (!ImNodes::Connection(dst_id, dst_name, src_id, src_name)) {
-          ExecUnlink(lk);
-        }
-      }
-
-      // handle new link
-      void*       src_ptr;
-      const char* src_name;
-      void*       dst_ptr;
-      const char* dst_name;
-      if (ImNodes::GetNewConnection(&dst_ptr, &dst_name, &src_ptr, &src_name)) {
-        ExecLink({
-          .src_id   = reinterpret_cast<ItemId>(src_ptr),
-          .src_name = src_name,
-          .dst_id   = reinterpret_cast<ItemId>(dst_ptr),
-          .dst_name = dst_name,
-        });
-      }
-      ImNodes::EndCanvas();
-
-      // popup menu for canvas
-      constexpr auto kFlags =
-          ImGuiPopupFlags_MouseButtonRight |
-          ImGuiPopupFlags_NoOpenOverExistingPopup;
-      if (ImGui::BeginPopupContextWindow(nullptr, kFlags)) {
-        const auto pos =
-            GetCanvasPosFromScreenPos(ImGui::GetMousePosOnOpeningCurrentPopup());
-        if (ImGui::BeginMenu("add")) {
-          ItemAdder(pos);
-          ImGui::EndMenu();
-        }
-        ImGui::Separator();
-        if (ImGui::MenuItem("undo", nullptr, false, !!history_.prev())) {
-          UnDo();
-        }
-        if (ImGui::MenuItem("redo", nullptr, false, !!history_.next())) {
-          ReDo();
-        }
-        ImGui::Separator();
-        if (ImGui::MenuItem("reset canvas zoom")) {
-          canvas_.Zoom = 1.f;
-        }
-        ImGui::Separator();
-        if (ImGui::BeginMenu("config")) {
-          Config();
-          ImGui::EndMenu();
-        }
-        ImGui::EndPopup();
-      }
-    }
-    ImGui::EndChild();
-  }
-  win_.End();
-
   // squash queued commands
   if (history_.Squash()) {
     Touch();
   }
 }
 void Network::UpdateMenu() noexcept {
-  if (ImGui::MenuItem("Editor", nullptr, &win_.shown()) && win_.shown()) {
-    win_.SetFocus();
-  }
+  win_.MenuItem();
   if (ImGui::BeginMenu("config")) {
     Config();
     ImGui::EndMenu();
@@ -1119,61 +1004,119 @@ void Network::UpdateWidget() noexcept {
   Config();
 }
 
-void Network::Item::UpdateNode(Node::Editor& ed) noexcept {
-  assert(owner_);
-  ImGui::PushID(node_);
 
-  const auto id = reinterpret_cast<void*>(id_);
-  if (ImNodes::BeginNode(id, &pos_, &select_)) {
-    if (node_->flags() & nf7::Node::kCustomNode) {
-      node_->UpdateNode(ed);
-    } else {
-      ImGui::TextUnformatted(file_->type().name().c_str());
-      nf7::gui::NodeInputSockets(node_->GetInputs());
-      ImGui::SameLine();
-      nf7::gui::NodeOutputSockets(node_->GetOutputs());
+void Network::NetworkEditor() noexcept {
+  // ---- editor window / toolbar
+  ImGui::BeginGroup();
+  {
+    // ---- editor window / toolbar / attached lambda combo
+    const auto current_lambda =
+        !lambda_?              "(unselected)"s:
+        lambda_->depth() == 0? "(isolated)"s:
+        nf7::gui::GetContextDisplayName(*lambda_);
+    if (ImGui::BeginCombo("##lambda", current_lambda.c_str())) {
+      if (lambda_) {
+        if (ImGui::Selectable("detach current lambda")) {
+          AttachLambda(nullptr);
+        }
+        ImGui::Separator();
+      }
+      for (const auto& wptr : lambdas_running_) {
+        auto ptr = wptr.lock();
+        if (!ptr) continue;
+
+        const auto name = nf7::gui::GetContextDisplayName(*ptr);
+        if (ImGui::Selectable(name.c_str(), ptr == lambda_)) {
+          AttachLambda(nullptr);
+          lambda_ = ptr;
+        }
+        if (ImGui::IsItemHovered()) {
+          ImGui::BeginTooltip();
+          ImGui::TextUnformatted("call stack:");
+          ImGui::Indent();
+          nf7::gui::ContextStack(*ptr);
+          ImGui::Unindent();
+          ImGui::EndTooltip();
+        }
+      }
+      if (lambdas_running_.size() == 0) {
+        ImGui::TextDisabled("no running lambda found...");
+      }
+      ImGui::EndCombo();
     }
   }
-  ImNodes::EndNode();
+  ImGui::EndGroup();
 
-  const bool moved =
-      pos_.x != prev_pos_.x || pos_.y != prev_pos_.y;
-  if (moved && !ImGui::IsMouseDragging(ImGuiMouseButton_Left)) {
-    owner_->history_.Add(std::make_unique<Item::MoveCommand>(*this, prev_pos_));
-    prev_pos_ = pos_;
-  }
+  // ---- editor window / canvas
+  if (ImGui::BeginChild("canvas", {0, 0}, false, ImGuiWindowFlags_NoMove)) {
+    canvas_pos_ = ImGui::GetCursorScreenPos();
+    ImNodes::BeginCanvas(&canvas_);
 
-  constexpr auto kFlags =
-      ImGuiPopupFlags_MouseButtonRight |
-      ImGuiPopupFlags_NoOpenOverExistingPopup;
-  if (ImGui::BeginPopupContextItem(nullptr, kFlags)) {
-    const auto pos =
-        owner_->GetCanvasPosFromScreenPos(
-            ImGui::GetMousePosOnOpeningCurrentPopup());
-    if (ImGui::MenuItem("remove")) {
-      owner_->ExecRemoveItem(id_);
+    // update child nodes
+    auto ed = Network::Editor {*this};
+    for (const auto& item : items_) {
+      item->UpdateNode(ed);
     }
-    if (ImGui::MenuItem("clone")) {
-      owner_->ExecAddItem(
-          std::make_unique<Item>(owner_->next_++, file_->Clone(env())), pos);
+
+    // handle existing links
+    for (const auto& lk : links_.items()) {
+      const auto src_id   = reinterpret_cast<void*>(lk.src_id);
+      const auto dst_id   = reinterpret_cast<void*>(lk.dst_id);
+      const auto src_name = lk.src_name.c_str();
+      const auto dst_name = lk.dst_name.c_str();
+      if (!ImNodes::Connection(dst_id, dst_name, src_id, src_name)) {
+        ExecUnlink(lk);
+      }
     }
-    if (node_->flags() & nf7::Node::kMenu_DirItem) {
+
+    // handle new link
+    void*       src_ptr;
+    const char* src_name;
+    void*       dst_ptr;
+    const char* dst_name;
+    if (ImNodes::GetNewConnection(&dst_ptr, &dst_name, &src_ptr, &src_name)) {
+      ExecLink({
+        .src_id   = reinterpret_cast<ItemId>(src_ptr),
+        .src_name = src_name,
+        .dst_id   = reinterpret_cast<ItemId>(dst_ptr),
+        .dst_name = dst_name,
+      });
+    }
+    ImNodes::EndCanvas();
+
+    // popup menu for canvas
+    constexpr auto kFlags =
+        ImGuiPopupFlags_MouseButtonRight |
+        ImGuiPopupFlags_NoOpenOverExistingPopup;
+    if (ImGui::BeginPopupContextWindow(nullptr, kFlags)) {
+      const auto pos =
+          GetCanvasPosFromScreenPos(ImGui::GetMousePosOnOpeningCurrentPopup());
+      if (ImGui::BeginMenu("add")) {
+        ItemAdder(pos);
+        ImGui::EndMenu();
+      }
       ImGui::Separator();
-      auto dir = file_->interface<nf7::DirItem>();
-      assert(dir);
-      dir->UpdateMenu();
-    }
-    if (node_->flags() & nf7::Node::kMenu) {
+      if (ImGui::MenuItem("undo", nullptr, false, !!history_.prev())) {
+        UnDo();
+      }
+      if (ImGui::MenuItem("redo", nullptr, false, !!history_.next())) {
+        ReDo();
+      }
       ImGui::Separator();
-      node_->UpdateMenu(ed);
+      if (ImGui::MenuItem("reset canvas zoom")) {
+        canvas_.Zoom = 1.f;
+      }
+      ImGui::Separator();
+      if (ImGui::BeginMenu("config")) {
+        Config();
+        ImGui::EndMenu();
+      }
+      ImGui::EndPopup();
     }
-    ImGui::EndPopup();
   }
-
-  ImGui::PopID();
+  ImGui::EndChild();
 }
 
-
 void Network::ItemAdder(const ImVec2& pos) noexcept {
   static const nf7::File::TypeInfo* type;
   if (ImGui::IsWindowAppearing()) {
@@ -1241,6 +1184,61 @@ void Network::Config() noexcept {
 }
 
 
+void Network::Item::UpdateNode(Node::Editor& ed) noexcept {
+  assert(owner_);
+  ImGui::PushID(node_);
+
+  const auto id = reinterpret_cast<void*>(id_);
+  if (ImNodes::BeginNode(id, &pos_, &select_)) {
+    if (node_->flags() & nf7::Node::kCustomNode) {
+      node_->UpdateNode(ed);
+    } else {
+      ImGui::TextUnformatted(file_->type().name().c_str());
+      nf7::gui::NodeInputSockets(node_->GetInputs());
+      ImGui::SameLine();
+      nf7::gui::NodeOutputSockets(node_->GetOutputs());
+    }
+  }
+  ImNodes::EndNode();
+
+  const bool moved =
+      pos_.x != prev_pos_.x || pos_.y != prev_pos_.y;
+  if (moved && !ImGui::IsMouseDragging(ImGuiMouseButton_Left)) {
+    owner_->history_.Add(std::make_unique<Item::MoveCommand>(*this, prev_pos_));
+    prev_pos_ = pos_;
+  }
+
+  constexpr auto kFlags =
+      ImGuiPopupFlags_MouseButtonRight |
+      ImGuiPopupFlags_NoOpenOverExistingPopup;
+  if (ImGui::BeginPopupContextItem(nullptr, kFlags)) {
+    const auto pos =
+        owner_->GetCanvasPosFromScreenPos(
+            ImGui::GetMousePosOnOpeningCurrentPopup());
+    if (ImGui::MenuItem("remove")) {
+      owner_->ExecRemoveItem(id_);
+    }
+    if (ImGui::MenuItem("clone")) {
+      owner_->ExecAddItem(
+          std::make_unique<Item>(owner_->next_++, file_->Clone(env())), pos);
+    }
+    if (node_->flags() & nf7::Node::kMenu_DirItem) {
+      ImGui::Separator();
+      auto dir = file_->interface<nf7::DirItem>();
+      assert(dir);
+      dir->UpdateMenu();
+    }
+    if (node_->flags() & nf7::Node::kMenu) {
+      ImGui::Separator();
+      node_->UpdateMenu(ed);
+    }
+    ImGui::EndPopup();
+  }
+
+  ImGui::PopID();
+}
+
+
 void Network::Initiator::UpdateNode(nf7::Node::Editor& ed) noexcept {
   ImGui::TextUnformatted("INITIATOR");
 
diff --git a/file/sequencer_timeline.cc b/file/sequencer_timeline.cc
index 698f08c..b80a001 100644
--- a/file/sequencer_timeline.cc
+++ b/file/sequencer_timeline.cc
@@ -67,14 +67,14 @@ class TL final : public nf7::FileBase, public nf7::DirItem, public nf7::Node {
 
   TL(nf7::Env& env,
      std::vector<std::unique_ptr<Layer>>&& layers = {},
-     ItemId                                next   = 1,
-     const nf7::gui::Window*               win    = nullptr) noexcept :
+     ItemId                                next   = 1) noexcept :
       nf7::FileBase(kType, env),
-      nf7::DirItem(nf7::DirItem::kMenu | nf7::DirItem::kWidget),
+      nf7::DirItem(nf7::DirItem::kMenu),
       nf7::Node(nf7::Node::kMenu_DirItem),
       life_(*this), log_(*this),
       layers_(std::move(layers)), next_(next),
-      win_(*this, "Timeline Editor", win), tl_("timeline") {
+      win_(*this, "Timeline Editor"), tl_("timeline") {
+    win_.onUpdate = [this]() { TimelineEditor(); };
   }
   ~TL() noexcept {
     history_.Clear();
@@ -103,7 +103,6 @@ class TL final : public nf7::FileBase, public nf7::DirItem, public nf7::Node {
   void Handle(const nf7::File::Event& ev) noexcept;
   void Update() noexcept override;
   void UpdateMenu() noexcept override;
-  void UpdateWidget() noexcept override;
 
   nf7::File::Interface* interface(const std::type_info& t) noexcept override {
     return nf7::InterfaceSelector<nf7::DirItem, nf7::Node>(t).Select(this);
@@ -175,8 +174,8 @@ class TL final : public nf7::FileBase, public nf7::DirItem, public nf7::Node {
   void AttachLambda(const std::shared_ptr<TL::Lambda>&) noexcept;
 
   // gui
-  void EditorWindow() noexcept;
-  void ParamPanelWindow() noexcept;
+  void TimelineEditor() noexcept;
+  void ParamPanel() noexcept;
   void LambdaSelector() noexcept;
   void ItemAdder() noexcept;
 
@@ -1089,8 +1088,10 @@ std::unique_ptr<nf7::File> TL::Clone(nf7::Env& env) const noexcept {
   std::vector<std::unique_ptr<TL::Layer>> layers;
   layers.reserve(layers_.size());
   ItemId next = 1;
-  for (const auto& layer : layers_) layers.push_back(layer->Clone(env, next));
-  return std::make_unique<TL>(env, std::move(layers), next, &win_);
+  for (const auto& layer : layers_) {
+    layers.push_back(layer->Clone(env, next));
+  }
+  return std::make_unique<TL>(env, std::move(layers), next);
 }
 void TL::Handle(const Event& ev) noexcept {
   nf7::FileBase::Handle(ev);
@@ -1127,188 +1128,174 @@ void TL::Handle(const Event& ev) noexcept {
 void TL::Update() noexcept {
   nf7::FileBase::Update();
 
+  // display param panel window
+  if (win_.shown()) {
+    const auto em = ImGui::GetFontSize();
+    const auto id = nf7::gui::Window::ConcatId(*this, "Parameter Panel");
+
+    if (std::exchange(param_panel_request_focus_, false)) {
+      ImGui::SetNextWindowFocus();
+    }
+
+    ImGui::SetNextWindowSize({16*em, 16*em}, ImGuiCond_FirstUseEver);
+    if (ImGui::Begin(id.c_str())) {
+      ParamPanel();
+    }
+    ImGui::End();
+  }
+
+  // update children
   for (const auto& layer : layers_) {
     for (const auto& item : layer->items()) {
       item->file().Update();
     }
   }
 
-  EditorWindow();
-  ParamPanelWindow();
-
+  // squash queued commands
   if (history_.Squash()) {
     env().ExecMain(std::make_shared<nf7::GenericContext>(*this),
                    [this]() { Touch(); });
   }
 }
 void TL::UpdateMenu() noexcept {
-  if (ImGui::MenuItem("editor", nullptr, &win_.shown()) && win_.shown()) {
-    win_.SetFocus();
-  }
-}
-void TL::UpdateWidget() noexcept {
-  ImGui::TextUnformatted("Sequencer/Timeline");
-  if (ImGui::Button("Editor")) {
-    win_.SetFocus();
-  }
+  win_.MenuItem();
 }
 
-void TL::EditorWindow() noexcept {
-  if (win_.shownInCurrentFrame()) {
-    const auto em = ImGui::GetFontSize();
-    ImGui::SetNextWindowSizeConstraints({32*em, 16*em}, {1e8, 1e8});
-  }
-  if (win_.Begin()) {
-    LambdaSelector();
+void TL::TimelineEditor() noexcept {
+  LambdaSelector();
 
-    // timeline
-    if (tl_.Begin()) {
-      // layer headers
-      for (size_t i = 0; i < layers_.size(); ++i) {
-        auto& layer = layers_[i];
-        tl_.NextLayerHeader(layer.get(), layer->height());
-        ImGui::PushID(layer.get());
-        layer->UpdateHeader(i);
-        ImGui::PopID();
-      }
+  // timeline
+  if (tl_.Begin()) {
+    // layer headers
+    for (size_t i = 0; i < layers_.size(); ++i) {
+      auto& layer = layers_[i];
+      tl_.NextLayerHeader(layer.get(), layer->height());
+      ImGui::PushID(layer.get());
+      layer->UpdateHeader(i);
+      ImGui::PopID();
+    }
 
-      if (tl_.BeginBody()) {
-        // context menu on timeline
-        if (ImGui::BeginPopupContextWindow()) {
-          if (ImGui::IsWindowAppearing()) {
-            action_time_  = tl_.mouseTime();
-            action_layer_ = 0;
-            if (auto layer = reinterpret_cast<TL::Layer*>(tl_.mouseLayer())) {
-              action_layer_ = layer->index();
-            }
+    if (tl_.BeginBody()) {
+      // context menu on timeline
+      if (ImGui::BeginPopupContextWindow()) {
+        if (ImGui::IsWindowAppearing()) {
+          action_time_  = tl_.mouseTime();
+          action_layer_ = 0;
+          if (auto layer = reinterpret_cast<TL::Layer*>(tl_.mouseLayer())) {
+            action_layer_ = layer->index();
           }
-          if (action_layer_ < layers_.size()) {
-            if (ImGui::BeginMenu("add new item")) {
-              ItemAdder();
-              ImGui::EndMenu();
-            }
-          }
-          if (selected_.size()) {
-            ImGui::Separator();
-            if (ImGui::MenuItem("deselect")) {
-              Deselect();
-            }
+        }
+        if (action_layer_ < layers_.size()) {
+          if (ImGui::BeginMenu("add new item")) {
+            ItemAdder();
+            ImGui::EndMenu();
           }
+        }
+        if (selected_.size()) {
           ImGui::Separator();
-          if (ImGui::MenuItem("undo", nullptr, false, !!history_.prev())) {
-            ExecUnDo();
-          }
-          if (ImGui::MenuItem("redo", nullptr, false, !!history_.next())) {
-            ExecReDo();
-          }
-          ImGui::EndPopup();
-        }
-
-        // layer body
-        for (auto& layer : layers_) {
-          tl_.NextLayer(layer.get(), layer->height());
-          for (auto& item : layer->items()) {
-            const auto& t      = item->displayTiming();
-            const bool  select = selected_.contains(item.get());
-
-            ImGui::PushStyleColor(
-                ImGuiCol_ChildBg, ImGui::GetColorU32(ImGuiCol_FrameBg, 0.3f));
-            ImGui::PushStyleColor(
-                ImGuiCol_Border,
-                ImGui::GetColorU32(select? ImGuiCol_FrameBgActive: ImGuiCol_Border));
-            ImGui::PushStyleVar(ImGuiStyleVar_ChildBorderSize, 2);
-            const bool shown = tl_.BeginItem(item.get(), t.begin(), t.end());
-            ImGui::PopStyleVar(1);
-            ImGui::PopStyleColor(2);
-            if (shown) {
-              item->Update();
-            }
-            tl_.EndItem();
-
+          if (ImGui::MenuItem("deselect")) {
+            Deselect();
           }
         }
-      }
-      tl_.EndBody();
-
-      // mouse curosr
-      constexpr auto kFlags =
-          ImGuiHoveredFlags_ChildWindows |
-          ImGuiHoveredFlags_AllowWhenBlockedByPopup;
-      if (ImGui::IsWindowHovered(kFlags)) {
-        tl_.Cursor(
-            "mouse",
-            tl_.GetTimeFromScreenX(ImGui::GetMousePos().x),
-            ImGui::GetColorU32(ImGuiCol_TextDisabled, .5f));
+        ImGui::Separator();
+        if (ImGui::MenuItem("undo", nullptr, false, !!history_.prev())) {
+          ExecUnDo();
+        }
+        if (ImGui::MenuItem("redo", nullptr, false, !!history_.next())) {
+          ExecReDo();
+        }
+        ImGui::EndPopup();
       }
 
-      // frame cursor
-      tl_.Cursor("cursor", cursor_, ImGui::GetColorU32(ImGuiCol_Text, .5f));
+      // layer body
+      for (auto& layer : layers_) {
+        tl_.NextLayer(layer.get(), layer->height());
+        for (auto& item : layer->items()) {
+          const auto& t      = item->displayTiming();
+          const bool  select = selected_.contains(item.get());
 
-      // running sessions
-      if (lambda_) {
-        const auto now = nf7::Env::Clock::now();
-        for (auto& wss : lambda_->sessions()) {
-          auto ss = wss.lock();
-          if (!ss || ss->done()) continue;
-
-          const auto elapsed =
-              static_cast<float>(
-                std::chrono::duration_cast<std::chrono::milliseconds>(
-                    now - ss->lastActive()).count()) / 1000;
-
-          const auto alpha = 1.f - std::clamp(elapsed, 0.f, 1.f)*0.6f;
-          const auto color = IM_COL32(255, 0, 0, static_cast<uint8_t>(alpha*255));
-
-          tl_.Cursor("S", ss->time(), color);
-          if (ss->layer() > 0) {
-            tl_.Arrow(ss->time(), ss->layer()-1, color);
+          ImGui::PushStyleColor(
+              ImGuiCol_ChildBg, ImGui::GetColorU32(ImGuiCol_FrameBg, 0.3f));
+          ImGui::PushStyleColor(
+              ImGuiCol_Border,
+              ImGui::GetColorU32(select? ImGuiCol_FrameBgActive: ImGuiCol_Border));
+          ImGui::PushStyleVar(ImGuiStyleVar_ChildBorderSize, 2);
+          const bool shown = tl_.BeginItem(item.get(), t.begin(), t.end());
+          ImGui::PopStyleVar(1);
+          ImGui::PopStyleColor(2);
+          if (shown) {
+            item->Update();
           }
+          tl_.EndItem();
+
         }
       }
-
-      HandleTimelineAction();
     }
-    tl_.End();
+    tl_.EndBody();
 
-    // key bindings
-    const bool focused = ImGui::IsWindowFocused(ImGuiFocusedFlags_RootAndChildWindows);
-    if (focused && !ImGui::IsAnyItemFocused()) {
-      if (!lambda_ || lambda_->depth() == 0) {
-        if (ImGui::IsKeyPressed(ImGuiKey_LeftArrow)) {
-          if (cursor_ > 0) MoveCursorTo(cursor_-1);
-        } else if (ImGui::IsKeyPressed(ImGuiKey_RightArrow)) {
-          MoveCursorTo(cursor_+1);
+    // mouse curosr
+    constexpr auto kFlags =
+        ImGuiHoveredFlags_ChildWindows |
+        ImGuiHoveredFlags_AllowWhenBlockedByPopup;
+    if (ImGui::IsWindowHovered(kFlags)) {
+      tl_.Cursor(
+          "mouse",
+          tl_.GetTimeFromScreenX(ImGui::GetMousePos().x),
+          ImGui::GetColorU32(ImGuiCol_TextDisabled, .5f));
+    }
+
+    // frame cursor
+    tl_.Cursor("cursor", cursor_, ImGui::GetColorU32(ImGuiCol_Text, .5f));
+
+    // running sessions
+    if (lambda_) {
+      const auto now = nf7::Env::Clock::now();
+      for (auto& wss : lambda_->sessions()) {
+        auto ss = wss.lock();
+        if (!ss || ss->done()) continue;
+
+        const auto elapsed =
+            static_cast<float>(
+              std::chrono::duration_cast<std::chrono::milliseconds>(
+                  now - ss->lastActive()).count()) / 1000;
+
+        const auto alpha = 1.f - std::clamp(elapsed, 0.f, 1.f)*0.6f;
+        const auto color = IM_COL32(255, 0, 0, static_cast<uint8_t>(alpha*255));
+
+        tl_.Cursor("S", ss->time(), color);
+        if (ss->layer() > 0) {
+          tl_.Arrow(ss->time(), ss->layer()-1, color);
         }
       }
     }
+
+    HandleTimelineAction();
+  }
+  tl_.End();
+
+  // key bindings
+  const bool focused = ImGui::IsWindowFocused(ImGuiFocusedFlags_RootAndChildWindows);
+  if (focused && !ImGui::IsAnyItemFocused()) {
+    if (!lambda_ || lambda_->depth() == 0) {
+      if (ImGui::IsKeyPressed(ImGuiKey_LeftArrow)) {
+        if (cursor_ > 0) MoveCursorTo(cursor_-1);
+      } else if (ImGui::IsKeyPressed(ImGuiKey_RightArrow)) {
+        MoveCursorTo(cursor_+1);
+      }
+    }
   }
-  win_.End();
 }
-void TL::ParamPanelWindow() noexcept {
-  if (!win_.shown()) return;
-
-  const auto name = abspath().Stringify() + " | Parameter Panel";
-
-  if (std::exchange(param_panel_request_focus_, false)) {
-    ImGui::SetNextWindowFocus();
-  }
-
-  const auto em = ImGui::GetFontSize();
-  ImGui::SetNextWindowSize({16*em, 16*em}, ImGuiCond_FirstUseEver);
-
-  if (ImGui::Begin(name.c_str())) {
-    if (auto item = param_panel_target_) {
-      if (item->seq().flags() & Sequencer::kParamPanel) {
-        TL::Editor ed {*item};
-        item->seq().UpdateParamPanel(ed);
-      } else {
-        ImGui::TextUnformatted("item doesn't have parameter panel");
-      }
+void TL::ParamPanel() noexcept {
+  if (auto item = param_panel_target_) {
+    if (item->seq().flags() & Sequencer::kParamPanel) {
+      TL::Editor ed {*item};
+      item->seq().UpdateParamPanel(ed);
     } else {
-      ImGui::TextUnformatted("no item selected");
+      ImGui::TextUnformatted("item doesn't have parameter panel");
     }
+  } else {
+    ImGui::TextUnformatted("no item selected");
   }
-  ImGui::End();
 }
 void TL::LambdaSelector() noexcept {
   const auto current_lambda =
diff --git a/file/system_dir.cc b/file/system_dir.cc
index 8f388d9..692efa0 100644
--- a/file/system_dir.cc
+++ b/file/system_dir.cc
@@ -36,13 +36,18 @@ class Dir final : public nf7::FileBase,
 
   using ItemMap = std::map<std::string, std::unique_ptr<File>>;
 
-  Dir(nf7::Env& env, ItemMap&& items = {}, const gui::Window* src = nullptr) noexcept :
+  Dir(nf7::Env& env, ItemMap&& items = {}) noexcept :
       nf7::FileBase(kType, env),
       nf7::DirItem(nf7::DirItem::kTree |
                    nf7::DirItem::kMenu |
                    nf7::DirItem::kTooltip |
                    nf7::DirItem::kDragDropTarget),
-      items_(std::move(items)), win_(*this, "TreeView System/Dir", src) {
+      items_(std::move(items)), win_(*this, "Tree View") {
+    win_.onConfig = []() {
+      const auto em = ImGui::GetFontSize();
+      ImGui::SetNextWindowSize({8*em, 8*em}, ImGuiCond_FirstUseEver);
+    };
+    win_.onUpdate = [this]() { TreeView(); };
   }
 
   Dir(nf7::Deserializer& ar) : Dir(ar.env()) {
@@ -113,23 +118,21 @@ class Dir final : public nf7::FileBase,
 
   void Handle(const Event& ev) noexcept override {
     nf7::FileBase::Handle(ev);
+
     switch (ev.type) {
     case Event::kAdd:
       // force to show window if this is the root
       if (name() == "$") {
-        win_.shown() = true;
+        win_.Show();
       }
       for (const auto& item : items_) item.second->MoveUnder(*this, item.first);
-      break;
+      return;
     case Event::kRemove:
       for (const auto& item : items_) item.second->Isolate();
-      break;
-    case Event::kReqFocus:
-      win_.SetFocus();
-      break;
+      return;
 
     default:
-      break;
+      return;
     }
   }
 
@@ -154,44 +157,20 @@ class Dir final : public nf7::FileBase,
   }
 
   // imgui widgets
+  void TreeView() noexcept;
   void ItemAdder() noexcept;
   void ItemRenamer(const std::string& name) noexcept;
   bool ValidateName(const std::string& name) noexcept;
 };
 
 void Dir::Update() noexcept {
-  nf7::FileBase::Update();
-
-  const auto em = ImGui::GetFontSize();
-
   // update children
   for (const auto& item : items_) {
     ImGui::PushID(item.second.get());
     item.second->Update();
     ImGui::PopID();
   }
-
-  // tree view window
-  if (win_.shownInCurrentFrame()) {
-    ImGui::SetNextWindowSize({8*em, 8*em}, ImGuiCond_FirstUseEver);
-  }
-  if (win_.Begin()) {
-    if (ImGui::BeginPopupContextWindow()) {
-      UpdateMenu();
-      ImGui::EndPopup();
-    }
-    UpdateTree();
-
-    if (nf7::gui::dnd::IsFirstAccept()) {
-      ImGui::SetCursorPos({0, 0});
-      ImGui::Dummy(ImGui::GetContentRegionAvail());
-      if (ImGui::BeginDragDropTarget()) {
-        UpdateDragDropTarget();
-        ImGui::EndDragDropTarget();
-      }
-    }
-  }
-  win_.End();
+  nf7::FileBase::Update();
 }
 void Dir::UpdateTree() noexcept {
   for (const auto& item : items_) {
@@ -315,7 +294,7 @@ void Dir::UpdateMenu() noexcept {
     ImGui::EndMenu();
   }
   ImGui::Separator();
-  ImGui::MenuItem("TreeView", nullptr, &win_.shown());
+  win_.MenuItem();
 }
 void Dir::UpdateTooltip() noexcept {
   ImGui::Text("children: %zu", items_.size());
@@ -348,6 +327,23 @@ try {
 }
 
 
+void Dir::TreeView() noexcept {
+  if (ImGui::BeginPopupContextWindow()) {
+    UpdateMenu();
+    ImGui::EndPopup();
+  }
+  UpdateTree();
+
+  if (nf7::gui::dnd::IsFirstAccept()) {
+    ImGui::SetCursorPos({0, 0});
+    ImGui::Dummy(ImGui::GetContentRegionAvail());
+    if (ImGui::BeginDragDropTarget()) {
+      UpdateDragDropTarget();
+      ImGui::EndDragDropTarget();
+    }
+  }
+}
+
 void Dir::ItemAdder() noexcept {
   static const nf7::File::TypeInfo* type;
   static std::string                name;
diff --git a/file/system_logger.cc b/file/system_logger.cc
index 34e4d7e..24f4754 100644
--- a/file/system_logger.cc
+++ b/file/system_logger.cc
@@ -17,6 +17,7 @@
 #include "nf7.hh"
 
 #include "common/dir_item.hh"
+#include "common/file_base.hh"
 #include "common/generic_context.hh"
 #include "common/generic_memento.hh"
 #include "common/generic_type_info.hh"
@@ -34,7 +35,7 @@ using namespace std::literals;
 namespace nf7 {
 namespace {
 
-class Logger final : public nf7::File,
+class Logger final : public nf7::FileBase,
     public nf7::DirItem {
  public:
   static inline const nf7::GenericTypeInfo<Logger> kType = {
@@ -110,13 +111,17 @@ class Logger final : public nf7::File,
   };
 
   Logger(nf7::Env& env, Data&& d = {}) noexcept :
-      nf7::File(kType, env), DirItem(DirItem::kMenu),
+      nf7::FileBase(kType, env), nf7::DirItem(DirItem::kMenu),
       mem_(std::move(d), *this), win_(*this, "Log View") {
-    win_.shown() = true;
-
     mem_.onCommit = mem_.onRestore = [this]() {
       store_->param(mem_.data());
     };
+
+    win_.onConfig = []() {
+      const auto em = ImGui::GetFontSize();
+      ImGui::SetNextWindowSize({48*em, 16*em}, ImGuiCond_FirstUseEver);
+    };
+    win_.onUpdate = [this]() { LogView(); };
   }
 
   Logger(nf7::Deserializer& ar) : Logger(ar.env()) {
@@ -142,7 +147,6 @@ class Logger final : public nf7::File,
     }
   }
 
-  void Update() noexcept override;
   void UpdateMenu() noexcept override;
   void UpdateRowMenu(const Row&) noexcept;
 
@@ -161,11 +165,13 @@ class Logger final : public nf7::File,
   nf7::gui::Window win_;
 
 
+  // log record management
   void DropExceededRows() noexcept {
     if (rows_.size() <= mem_->max_rows) return;
     rows_.erase(rows_.begin(), rows_.end()-mem_->max_rows);
   }
 
+  // stringify
   std::string GetPathString(File::Id id) const noexcept
   try {
     return env().GetFileOrThrow(id).abspath().Stringify();
@@ -191,6 +197,9 @@ class Logger final : public nf7::File,
     return loc.file_name()+":"s+std::to_string(loc.line());
   }
 
+  // gui
+  void LogView() noexcept;
+
 
   class ItemStore final : public nf7::Context,
       public nf7::Logger,
@@ -266,100 +275,13 @@ class Logger final : public nf7::File,
 };
 
 
-void Logger::Update() noexcept {
-  const auto em = ImGui::GetFontSize();
-
-  if (win_.shownInCurrentFrame()) {
-    ImGui::SetNextWindowSize({48*em, 16*em}, ImGuiCond_FirstUseEver);
-  }
-  if (win_.Begin()) {
-    constexpr auto kTableFlags =
-        ImGuiTableFlags_Resizable         |
-        ImGuiTableFlags_Hideable          |
-        ImGuiTableFlags_RowBg             |
-        ImGuiTableFlags_Borders           |
-        ImGuiTableFlags_ContextMenuInBody |
-        ImGuiTableFlags_SizingStretchProp |
-        ImGuiTableFlags_ScrollY;
-    if (ImGui::BeginTable("logs", 4, kTableFlags, ImGui::GetContentRegionAvail(), 0)) {
-      const bool updated    = store_->MoveItemsTo(*this);
-      const bool autoscroll = updated && ImGui::GetScrollY() == ImGui::GetScrollMaxY();
-
-      ImGui::TableSetupColumn("level");
-      ImGui::TableSetupColumn("msg");
-      ImGui::TableSetupColumn("path");
-      ImGui::TableSetupColumn("location");
-      ImGui::TableSetupScrollFreeze(0, 1);
-      ImGui::TableHeadersRow();
-
-      for (const auto& row : rows_) {
-        ImGui::TableNextRow();
-        ImGui::PushID(&row);
-
-        if (autoscroll && &row == &rows_.back()) {
-          ImGui::SetScrollHereY();
-        }
-
-        // level column
-        if (ImGui::TableSetColumnIndex(0)) {
-          constexpr auto kFlags =
-              ImGuiSelectableFlags_SpanAllColumns |
-              ImGuiSelectableFlags_AllowItemOverlap;
-          ImGui::Selectable(row.level, false, kFlags);
-          if (ImGui::BeginPopupContextItem()) {
-            UpdateRowMenu(row);
-            ImGui::EndPopup();
-          }
-        }
-        // msg column
-        if (ImGui::TableNextColumn()) {
-          ImGui::TextUnformatted(row.msg.c_str());
-          if (ImGui::IsItemHovered()) {
-            ImGui::SetTooltip(row.msg.c_str());
-          }
-        }
-        // path column
-        if (ImGui::TableNextColumn()) {
-          ImGui::TextUnformatted(row.path.c_str());
-          if (ImGui::IsItemHovered()) {
-            ImGui::SetTooltip(row.path.c_str());
-          }
-        }
-        // location column
-        if (ImGui::TableNextColumn()) {
-          ImGui::TextUnformatted(row.location.c_str());
-          if (ImGui::IsItemHovered()) {
-            ImGui::BeginTooltip();
-            ImGui::Text(row.location.c_str());
-            for (auto ptr = row.ex; ptr;)
-            try {
-              ImGui::Bullet();
-              std::rethrow_exception(ptr);
-            } catch (Exception& e) {
-              e.UpdatePanic();
-              ImGui::Spacing();
-              ptr = e.reason();
-            } catch (std::exception& e) {
-              ImGui::Text("std::exception (%s)", e.what());
-              ptr = nullptr;
-            }
-            ImGui::EndTooltip();
-          }
-        }
-        ImGui::PopID();
-      }
-      ImGui::EndTable();
-    }
-  }
-  win_.End();
-}
 void Logger::UpdateMenu() noexcept {
   if (ImGui::BeginMenu("config")) {
     nf7::gui::Config(mem_);
     ImGui::EndMenu();
   }
   ImGui::Separator();
-  ImGui::MenuItem("Log View",  nullptr, &win_.shown());
+  win_.MenuItem();
 }
 void Logger::UpdateRowMenu(const Row& row) noexcept {
   if (ImGui::MenuItem("copy as text")) {
@@ -372,5 +294,85 @@ void Logger::UpdateRowMenu(const Row& row) noexcept {
   }
 }
 
+void Logger::LogView() noexcept {
+  constexpr auto kTableFlags =
+      ImGuiTableFlags_Resizable         |
+      ImGuiTableFlags_Hideable          |
+      ImGuiTableFlags_RowBg             |
+      ImGuiTableFlags_Borders           |
+      ImGuiTableFlags_ContextMenuInBody |
+      ImGuiTableFlags_SizingStretchProp |
+      ImGuiTableFlags_ScrollY;
+  if (ImGui::BeginTable("logs", 4, kTableFlags, ImGui::GetContentRegionAvail(), 0)) {
+    const bool updated    = store_->MoveItemsTo(*this);
+    const bool autoscroll = updated && ImGui::GetScrollY() == ImGui::GetScrollMaxY();
+
+    ImGui::TableSetupColumn("level");
+    ImGui::TableSetupColumn("msg");
+    ImGui::TableSetupColumn("path");
+    ImGui::TableSetupColumn("location");
+    ImGui::TableSetupScrollFreeze(0, 1);
+    ImGui::TableHeadersRow();
+
+    for (const auto& row : rows_) {
+      ImGui::TableNextRow();
+      ImGui::PushID(&row);
+
+      if (autoscroll && &row == &rows_.back()) {
+        ImGui::SetScrollHereY();
+      }
+
+      // level column
+      if (ImGui::TableSetColumnIndex(0)) {
+        constexpr auto kFlags =
+            ImGuiSelectableFlags_SpanAllColumns |
+            ImGuiSelectableFlags_AllowItemOverlap;
+        ImGui::Selectable(row.level, false, kFlags);
+        if (ImGui::BeginPopupContextItem()) {
+          UpdateRowMenu(row);
+          ImGui::EndPopup();
+        }
+      }
+      // msg column
+      if (ImGui::TableNextColumn()) {
+        ImGui::TextUnformatted(row.msg.c_str());
+        if (ImGui::IsItemHovered()) {
+          ImGui::SetTooltip(row.msg.c_str());
+        }
+      }
+      // path column
+      if (ImGui::TableNextColumn()) {
+        ImGui::TextUnformatted(row.path.c_str());
+        if (ImGui::IsItemHovered()) {
+          ImGui::SetTooltip(row.path.c_str());
+        }
+      }
+      // location column
+      if (ImGui::TableNextColumn()) {
+        ImGui::TextUnformatted(row.location.c_str());
+        if (ImGui::IsItemHovered()) {
+          ImGui::BeginTooltip();
+          ImGui::Text(row.location.c_str());
+          for (auto ptr = row.ex; ptr;)
+          try {
+            ImGui::Bullet();
+            std::rethrow_exception(ptr);
+          } catch (Exception& e) {
+            e.UpdatePanic();
+            ImGui::Spacing();
+            ptr = e.reason();
+          } catch (std::exception& e) {
+            ImGui::Text("std::exception (%s)", e.what());
+            ptr = nullptr;
+          }
+          ImGui::EndTooltip();
+        }
+      }
+      ImGui::PopID();
+    }
+    ImGui::EndTable();
+  }
+}
+
 }
 }  // namespace nf7
diff --git a/file/value_plot.cc b/file/value_plot.cc
index 7624e39..10efa87 100644
--- a/file/value_plot.cc
+++ b/file/value_plot.cc
@@ -109,11 +109,12 @@ class Plot final : public nf7::FileBase,
     std::vector<Series> series;
   };
 
-  Plot(nf7::Env& env, const nf7::gui::Window* win = nullptr, Data&& data = {}) noexcept :
+  Plot(nf7::Env& env, Data&& data = {}) noexcept :
       nf7::FileBase(kType, env),
-      nf7::DirItem(nf7::DirItem::kMenu | nf7::DirItem::kWidget),
+      nf7::DirItem(nf7::DirItem::kMenu),
       nf7::Node(nf7::Node::kNone),
-      life_(*this), log_(*this), win_(*this, "Plot", win), mem_(std::move(data)) {
+      life_(*this), log_(*this), win_(*this, "Plot"), mem_(std::move(data)) {
+    win_.onUpdate = [this]() { PlotGraph(); };
     mem_.onRestore = mem_.onCommit = [this]() { BuildInputList(); };
     Sanitize();
   }
@@ -126,7 +127,7 @@ class Plot final : public nf7::FileBase,
     ar(win_, mem_->series);
   }
   std::unique_ptr<nf7::File> Clone(nf7::Env& env) const noexcept override {
-    return std::make_unique<Plot>(env, &win_, Data {mem_.data()});
+    return std::make_unique<Plot>(env, Data {mem_.data()});
   }
 
   std::shared_ptr<nf7::Node::Lambda> CreateLambda(
@@ -139,12 +140,8 @@ class Plot final : public nf7::FileBase,
     return {};
   }
 
-  void Update() noexcept override;
-  void UpdateWidget() noexcept override;
   void UpdateMenu() noexcept override;
 
-  void UpdatePlot() noexcept;
-
   nf7::File::Interface* interface(const std::type_info& t) noexcept override {
     return InterfaceSelector<
         nf7::DirItem, nf7::Memento, nf7::Node>(t).Select(this, &mem_);
@@ -161,6 +158,7 @@ class Plot final : public nf7::FileBase,
   std::vector<std::string> inputs_;
 
 
+  // config management
   void Sanitize() {
     nf7::util::Uniq(mem_->series);
     mem_.CommitAmend();
@@ -172,6 +170,9 @@ class Plot final : public nf7::FileBase,
       inputs_.push_back(s.name);
     }
   }
+
+  // gui
+  void PlotGraph() noexcept;
 };
 
 
@@ -237,22 +238,8 @@ std::shared_ptr<nf7::Node::Lambda> Plot::CreateLambda(
 }
 
 
-void Plot::Update() noexcept {
-  nf7::FileBase::Update();
-
-  if (win_.Begin()) {
-    UpdatePlot();
-  }
-  win_.End();
-}
-void Plot::UpdateWidget() noexcept {
-  if (ImGui::Button("plot window")) {
-    win_.SetFocus();
-  }
-  nf7::gui::Config(mem_);
-}
 void Plot::UpdateMenu() noexcept {
-  ImGui::MenuItem("plot window", nullptr, &win_.shown());
+  win_.MenuItem();
 
   if (ImGui::BeginMenu("config")) {
     nf7::gui::Config(mem_);
@@ -260,7 +247,7 @@ void Plot::UpdateMenu() noexcept {
   }
 }
 
-void Plot::UpdatePlot() noexcept {
+void Plot::PlotGraph() noexcept {
   if (ImPlot::BeginPlot("##plot", ImGui::GetContentRegionAvail())) {
     ImPlot::SetupAxis(ImAxis_X1, "X", ImPlotAxisFlags_AutoFit);
     ImPlot::SetupAxis(ImAxis_Y1, "Y", ImPlotAxisFlags_AutoFit);