View menu — panel visibility toggles for all 5 panels

Each panel (Stage Editor, Scene Hierarchy, Viewport, Property Panel,
Timeline) now has a checkable menu item under View. Closing a panel via
its X button also unchecks the entry. Stage Info and Demo Window follow
below a separator.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ui/Application.cpp

@@ -7,6 +7,7 @@
 #include <pxr/usd/sdf/path.h>
 #include <pxr/base/tf/token.h>
 #include <imgui.h>
+#include <imgui_internal.h>
 #include <vector>
 #include <string>
 #include <filesystem>
@@ -35,6 +36,11 @@ static std::string SanitizeUsdNameApp(const std::string& raw) {
 Application::Application()
     : m_showDemoWindow(false)
     , m_showStageInfo(true)
+    , m_showStageEditor(true)
+    , m_showSceneHierarchy(true)
+    , m_showViewport(true)
+    , m_showPropertyPanel(true)
+    , m_showTimeline(true)
     , m_running(false) {
 }
 
@@ -195,6 +201,10 @@ void Application::Update() {
 void Application::RenderUI() {
     m_imguiContext->NewFrame();
 
+    // Status bar must be rendered before DockSpaceOverViewport so it
+    // reserves space at the bottom before the dockspace claims the rest.
+    RenderStatusBar();
+
     ImGui::DockSpaceOverViewport(0, ImGui::GetMainViewport());
 
     if (m_showDemoWindow) {
@@ -207,30 +217,73 @@ void Application::RenderUI() {
         RenderStageInfo();
     }
 
-    ImGui::Begin("Stage Editor", nullptr, ImGuiWindowFlags_NoCollapse);
-    m_stageEditorPanel->Render();
-    ImGui::End();
+    if (m_showStageEditor) {
+        ImGui::Begin("Stage Editor", &m_showStageEditor, ImGuiWindowFlags_NoCollapse);
+        m_stageEditorPanel->Render();
+        ImGui::End();
+    }
 
-    m_viewportPanel->Render();
+    if (m_showViewport) {
+        m_viewportPanel->Render(&m_showViewport);
+    }
 
     // Scene Hierarchy is rendered AFTER the viewport so that viewport picks
     // (OnPrimPicked / OnPrimsPickedRect) are visible to the hierarchy in the
     // same frame — eliminating the one-frame-late scroll/highlight lag.
-    ImGui::Begin("Scene Hierarchy", nullptr, ImGuiWindowFlags_NoCollapse);
-    m_sceneHierarchyPanel->Render();
-    ImGui::End();
+    if (m_showSceneHierarchy) {
+        ImGui::Begin("Scene Hierarchy", &m_showSceneHierarchy, ImGuiWindowFlags_NoCollapse);
+        m_sceneHierarchyPanel->Render();
+        ImGui::End();
+    }
 
-    ImGui::Begin("Property Panel", nullptr, ImGuiWindowFlags_NoCollapse);
-    m_propertyPanel->Render();
-    ImGui::End();
+    if (m_showPropertyPanel) {
+        ImGui::Begin("Property Panel", &m_showPropertyPanel, ImGuiWindowFlags_NoCollapse);
+        m_propertyPanel->Render();
+        ImGui::End();
+    }
 
-    ImGui::Begin("Timeline", nullptr, ImGuiWindowFlags_NoCollapse);
-    m_timelinePanel->Render();
-    ImGui::End();
+    if (m_showTimeline) {
+        ImGui::Begin("Timeline", &m_showTimeline, ImGuiWindowFlags_NoCollapse);
+        m_timelinePanel->Render();
+        ImGui::End();
+    }
 
     m_imguiContext->Render();
 }
 
+void Application::RenderStatusBar() {
+    ImGuiViewport* vp     = ImGui::GetMainViewport();
+    float          height = ImGui::GetFrameHeight();
+
+    ImGuiWindowFlags flags =
+        ImGuiWindowFlags_NoScrollbar     |
+        ImGuiWindowFlags_NoSavedSettings |
+        ImGuiWindowFlags_MenuBar;
+
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(8.f, 2.f));
+    bool open = ImGui::BeginViewportSideBar("##statusbar", vp,
+                                            ImGuiDir_Down, height, flags);
+    ImGui::PopStyleVar();
+
+    if (open) {
+        ImGui::BeginMenuBar();
+
+        // FPS
+        ImGuiIO& io = ImGui::GetIO();
+        char buf[32];
+        snprintf(buf, sizeof(buf), "FPS: %.1f", io.Framerate);
+        // Right-align: measure text, then position cursor.
+        float textW = ImGui::CalcTextSize(buf).x;
+        float avail = ImGui::GetContentRegionAvail().x;
+        if (avail > textW)
+            ImGui::SetCursorPosX(ImGui::GetCursorPosX() + avail - textW);
+        ImGui::TextDisabled("%s", buf);
+
+        ImGui::EndMenuBar();
+    }
+    ImGui::End();
+}
+
 void Application::RenderMenuBar() {
     if (ImGui::BeginMainMenuBar()) {
         if (ImGui::BeginMenu("File")) {
@@ -320,8 +373,14 @@ void Application::RenderMenuBar() {
         }
         
         if (ImGui::BeginMenu("View")) {
-            ImGui::MenuItem("Stage Info", nullptr, &m_showStageInfo);
-            ImGui::MenuItem("Show Demo Window", nullptr, &m_showDemoWindow);
+            ImGui::MenuItem("Stage Editor",     nullptr, &m_showStageEditor);
+            ImGui::MenuItem("Scene Hierarchy",  nullptr, &m_showSceneHierarchy);
+            ImGui::MenuItem("Viewport",         nullptr, &m_showViewport);
+            ImGui::MenuItem("Property Panel",   nullptr, &m_showPropertyPanel);
+            ImGui::MenuItem("Timeline",         nullptr, &m_showTimeline);
+            ImGui::Separator();
+            ImGui::MenuItem("Stage Info",       nullptr, &m_showStageInfo);
+            ImGui::MenuItem("Demo Window",      nullptr, &m_showDemoWindow);
             ImGui::EndMenu();
         }