Make the Design tab sidebar dockable and collapsible like Prepare's

The sidebar can move to either side, float, be resized, and collapse with
the canvas button or Shift+Tab. Its layout is remembered separately from
Prepare's, starts where Prepare's sidebar is, and View > Reset Window
Layout resets both tabs.

.claude/skills/orca-wxwidgets/references/orca-architecture.md

@@ -617,8 +617,10 @@ Spacing constants come from `SidebarProps` (`Plater.hpp`): `TitlebarMargin()`, `
 
 ### Docking
 
-`Plater::priv` owns `AuiMgr m_aui_mgr` (a `wxAuiManager` subclass whose `CreateFloatingFrame` returns a
-themed `FloatFrame : wxAuiFloatingFrame`), managing the plater. Panes: `"sidebar"` (left, no close
+Docks are `AuiMgr`s (`AuiMgr.hpp`), a `wxAuiManager` subclass carrying Orca's dock art, theme and
+Wayland rule (`references/webview-gl-aui-media.md`). `Plater::priv` owns `m_aui_mgr`, managing the
+plater; the Design tab owns its own for its sidebar (`DesignPanel::m_aui`, layout in
+`design_window_layout`). Plater panes: `"sidebar"` (left, no close
 button, not top/bottom dockable), `"main"` (`CenterPane()`, the `panel_3d`), `"uv_editor"` (right,
 hidden until the texture-displacement gizmo shows it), plus dynamic dock panes. The default perspective
 is saved right after `AddPane`; the app-config `window_layout` is applied with

.claude/skills/orca-wxwidgets/references/webview-gl-aui-media.md

@@ -953,11 +953,12 @@ widgets beside the canvas (a sibling, not a child over it), or in a popup.
 - `wxAuiNotebook` (not used by Orca): page indices are logical; use `GetPagePosition()` for on-screen
   order (`docs/changes.txt:121-126`); the default tab art changed (`35-37`).
 
-**OrcaSlicer.** `Plater::priv` owns `AuiMgr m_aui_mgr`, a `wxAuiManager` whose `CreateFloatingFrame`
-returns `FloatFrame : wxAuiFloatingFrame` (applies `UpdateFrameDarkUI`).
-- Setup: `SetManagedWindow(q)` (the Plater), `SetDockSizeConstraint(1, 1)`; on Wayland clears
-  `wxAUI_MGR_ALLOW_FLOATING` (`disable_wayland_floating`); dock-art metrics set here, colours in the
-  dark-mode update (`Plater::priv::apply_color_mode`).
+**OrcaSlicer.** Orca's docks use `AuiMgr` (`AuiMgr.hpp`), a `wxAuiManager` whose `CreateFloatingFrame`
+returns a `wxAuiFloatingFrame` that applies `UpdateFrameDarkUI`. `init(window)` calls
+`SetManagedWindow(window)` and `SetDockSizeConstraint(1, 1)`, clears `wxAUI_MGR_ALLOW_FLOATING` on
+Wayland and sets the dock-art metrics and colours; `apply_color_mode()` re-colours captions, sashes and
+borders and is called from the owner's theme-switch handler. `Plater::priv::m_aui_mgr` manages the
+Plater (Prepare and Preview); `DesignPanel::m_aui` manages the Design tab's body below its toolbar.
 - Panes: `"sidebar"` (left, no close button, not top/bottom dockable, `BestSize` in em units),
   `"uv_editor"` (right, hidden; forced hidden again after a layout load), `"main"`
   (`CenterPane().PaneBorder(false)`, holding `panel_3d` with View3D, Preview and AssembleView in one
@@ -966,8 +967,8 @@ returns `FloatFrame : wxAuiFloatingFrame` (applies `UpdateFrameDarkUI`).
   `window_layout` app-config string goes through `sanitize_window_layout_for_wayland` (strips
   floating/floatable bits on Wayland) and `LoadPerspective(layout, false)`, falling back to the default
   on failure; then one `Update()`. `Plater::priv::reset` saves `SavePerspective()` back to
-  `window_layout`. An idle handler copies the docked sidebar width into `BestSize` (wxAUI does not record
-  a dragged sash there), so the width persists. `Plater::priv::reset_window_layout` is the model for
+  `window_layout`. `AuiMgr::track_docked_size` copies a docked pane's size into `BestSize` on idle
+  (wxAUI does not record a dragged sash there), so the width persists. `Plater::priv::reset_window_layout` is the model for
   re-establishing panes after a load: it loads the default perspective, then re-shows each plugin pane
   the perspective does not list.
 - Plugin panes: `Plater::add_dock_pane(window, name, caption, dock, size, on_close)` (window must be a
@@ -977,13 +978,27 @@ returns `FloatFrame : wxAuiFloatingFrame` (applies `UpdateFrameDarkUI`).
   `Destroy()`s without running `on_close`; `show_dock_pane` toggles and updates. Pane names come from
   `plugin_pane_name` (`DockPanel.cpp`), which replaces `|`, `;`, `=`, `\` — the perspective-string
   delimiters.
+- Other pages: a page outside the Plater docks through its own `AuiMgr` member, since the Plater's
+  manages only the Plater. Its managed window is a body panel below the page's toolbar; a sidebar
+  takes `AuiMgr::sidebar_pane_info()`; the layout has its own app-config key, is reset from
+  `Plater::reset_window_layout`, and is saved by a `shutdown()` called from `MainFrame::shutdown`,
+  which also detaches a floating pane (Lifetime below). Where floating is disabled it forces
+  `Dock().Floatable(false)` after loading, as plugin panes do. `DesignPanel` is the model
+  (`docs/HLSD/design-tab.md`). A `GLCanvas3D` beside such a sidebar gets that sidebar's collapse
+  button with `set_collapse_toolbar`; without it the canvas falls back to the Plater's button, which
+  collapses Prepare's sidebar.
 - Lifetime: no explicit `UnInit`. `m_aui_mgr` is a `Plater::priv` member, so it is destroyed in
   `~Plater`, before `~wxWindow` destroys the Plater's children (`wxWindowBase::DestroyChildren`,
   `src/common/wincmn.cpp:586-609`); a floating frame is such a child (`CreateFloatingFrame(m_frame, …)`,
   `src/aui/framemanager.cpp:3151`), so a pane still floating at that point outlives the manager [source].
-  Plugin panes are removed earlier (`MainFrame::shutdown` → `Plater::remove_dock_panes`). The sidebar
-  `GetPane()` reference captured by the idle lambda is safe across `AddPane`; never `DetachPane` a pane
-  whose reference is captured.
+  Plugin panes are removed earlier (`MainFrame::shutdown` → `Plater::remove_dock_panes`). A handler
+  that can outlive its pane looks the pane up when it runs, as `track_docked_size` does: an idle
+  handler bound on the pane's window outlives the `DetachPane` in `DesignPanel::shutdown`. Never detach
+  a pane whose `GetPane()` reference is captured (Pane references above). `DesignPanel::shutdown` is
+  the model for a member manager: it detaches a
+  floating sidebar, which `Destroy()`s the frame into the pending-delete list, and the main frame's
+  deletion deletes pending top-level children before its own children (`~wxTopLevelWindowBase`,
+  `src/common/toplvcmn.cpp:67-93`), while the panel and its manager are still alive [source].
 
 **Pitfalls.**
 - **Rule:** Call `Update()` once after a batch of `AddPane`/`wxAuiPaneInfo` changes.

.claude/skills/orca-wxwidgets/references/wx-33-changes.md

@@ -198,7 +198,7 @@ change, its line, and what it means for Orca.
 | `wxAuiGenericTabArt` subclasses (also via `wxAuiMSWTabArt`) override `DrawPageTab()`/`GetPageTabSize()` instead of `DrawTab()`/`GetTabSize()`; direct `wxAuiTabArt` subclasses still work | :115-120 | none: no Orca tab art |
 | `wxAuiNotebook` page index is logical (reorder-independent); `GetPagePosition()` gives the screen position | :122-126 | none; index math under `wxAUI_NB_TAB_MOVE` is what breaks |
 | `wxListbook`/`wxChoicebook` interpret mnemonics in page titles "just as the other wx*book classes already did" | :128-130 | Orca uses neither (`BedShapeDialog` uses `wxSimplebook` + a combo); every book interprets `&` (`interface/wx/bookctrl.h:141-147`) → rule 11 |
-| `wxAUI_MGR_HINT_FADE` is not in the default `wxAuiManager` style | :132-133 | Plater's `AuiMgr` keeps the default flags (minus `wxAUI_MGR_ALLOW_FLOATING` on Wayland, `Plater::priv::priv`), so the docking hint no longer fades; add the flag if wanted |
+| `wxAUI_MGR_HINT_FADE` is not in the default `wxAuiManager` style | :132-133 | Orca's `AuiMgr` keeps the default flags (minus `wxAUI_MGR_ALLOW_FLOATING` on Wayland, `AuiMgr::init`), so the docking hint no longer fades; add the flag if wanted |
 | `wxPrintDialogData::SetAllPages(false)`/`SetSelection(false)` changed meaning | :135-137 | none |
 | `wxGetTranslation()` returns `wxString` by value | :139-142 | pitfall below |
 | `wxWindow::Raise()` no longer shows a hidden window on any port | :144-146 | pitfall below; ba867cc534 |

docs/HLSD/design-tab.md

@@ -204,6 +204,14 @@ The tab is a page of Orca's main window and answers to the same settings as Prep
 - **Undo.** The tab keeps its own history (the recipe is not part of Prepare's snapshots), but
   it has no Undo/Redo of its own: the top bar, `Ctrl+Z` and Edit drive it while the tab is
   shown, greyed to what an undo would actually do.
+- **Docking.** The sidebar docks like Prepare's — either side, floating, resized, or collapsed
+  with the canvas's collapse button or `Shift+Tab` — through its own AUI manager under the
+  toolbar, because Prepare's manages the Plater and the Plater is not on this page. The button is
+  the canvas's own toolbar rather than Prepare's, which collapses Prepare's sidebar. The layout,
+  collapse included, is kept apart from Prepare's (`design_window_layout`) and starts where
+  Prepare's sidebar is, at its width, so the canvas edge holds still across the tab switch until
+  the user moves one of them. A floating sidebar is a top-level window, so it is hidden with the
+  tab rather than left over the other pages, and View > Reset Window Layout resets both tabs.
 
 ## The offer is generated, not hand-written
 

src/slic3r/CMakeLists.txt

@@ -147,6 +147,8 @@ set(SLIC3R_GUI_SOURCES
     GUI/WebPanel.hpp
     GUI/Widgets/WebHosting.cpp
     GUI/Widgets/WebHosting.hpp
+    GUI/AuiMgr.cpp
+    GUI/AuiMgr.hpp
     GUI/AuiPaneLayout.cpp
     GUI/AuiPaneLayout.hpp
     GUI/DragCanvas.cpp

src/slic3r/GUI/AuiMgr.cpp

@@ -0,0 +1,80 @@
+#include "AuiMgr.hpp"
+
+#include "GUI_App.hpp"
+#ifdef __WXGTK__
+#include "LinuxDisplayBackend.hpp"
+#endif
+
+#include <wx/aui/dockart.h>
+#include <wx/aui/floatpane.h>
+
+namespace Slic3r { namespace GUI {
+
+namespace {
+
+// TODO: listen on dark ui change
+class FloatFrame : public wxAuiFloatingFrame
+{
+public:
+    FloatFrame(wxWindow* parent, wxAuiManager* ownerMgr, const wxAuiPaneInfo& pane) : wxAuiFloatingFrame(parent, ownerMgr, pane)
+    {
+        wxGetApp().UpdateFrameDarkUI(this);
+    }
+};
+
+} // namespace
+
+void AuiMgr::init(wxWindow* window)
+{
+    SetManagedWindow(window);
+    SetDockSizeConstraint(1, 1);
+#ifdef __WXGTK__
+    // Floating and its docking hints need global pointer positions and window moves, which Wayland does not provide.
+    if (is_running_on_wayland())
+        SetFlags(GetFlags() & ~wxAUI_MGR_ALLOW_FLOATING);
+#endif
+    GetArtProvider()->SetMetric(wxAUI_DOCKART_CAPTION_SIZE, 18);
+    GetArtProvider()->SetMetric(wxAUI_DOCKART_GRADIENT_TYPE, wxAUI_GRADIENT_NONE);
+    apply_color_mode();
+}
+
+void AuiMgr::apply_color_mode()
+{
+    const bool     is_dark    = wxGetApp().dark_mode();
+    const wxColour sash_color = is_dark ? wxColour(38, 46, 48) : wxColour(206, 206, 206);
+    GetArtProvider()->SetColour(wxAUI_DOCKART_INACTIVE_CAPTION_COLOUR, sash_color);
+    GetArtProvider()->SetColour(wxAUI_DOCKART_INACTIVE_CAPTION_TEXT_COLOUR, *wxWHITE);
+    GetArtProvider()->SetColour(wxAUI_DOCKART_SASH_COLOUR, sash_color);
+    GetArtProvider()->SetColour(wxAUI_DOCKART_BORDER_COLOUR, is_dark ? *wxBLACK : wxColour(165, 165, 165));
+}
+
+void AuiMgr::track_docked_size(wxWindow* window)
+{
+    window->Bind(wxEVT_IDLE, [this, window](wxIdleEvent& evt) {
+        wxAuiPaneInfo& pane = GetPane(window);
+        if (pane.IsOk() && pane.IsShown() && pane.IsDocked() && pane.rect.GetWidth() > 0 && pane.rect.GetHeight() > 0) {
+            const bool horizontal = pane.dock_direction == wxAUI_DOCK_TOP || pane.dock_direction == wxAUI_DOCK_BOTTOM;
+            pane.BestSize(horizontal ? pane.best_size.GetWidth() : pane.rect.GetWidth(),
+                          horizontal ? pane.rect.GetHeight() : pane.best_size.GetHeight());
+        }
+        evt.Skip();
+    });
+}
+
+wxAuiPaneInfo AuiMgr::sidebar_pane_info()
+{
+    return wxAuiPaneInfo()
+        .Name("sidebar")
+        .Left()
+        .CloseButton(false)
+        .TopDockable(false)
+        .BottomDockable(false)
+        .BestSize(wxSize(39 * wxGetApp().em_unit(), 90 * wxGetApp().em_unit()));
+}
+
+wxAuiFloatingFrame* AuiMgr::CreateFloatingFrame(wxWindow* parent, const wxAuiPaneInfo& pane)
+{
+    return new FloatFrame(parent, this, pane);
+}
+
+}} // namespace Slic3r::GUI

src/slic3r/GUI/AuiMgr.hpp

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <wx/aui/framemanager.h>
+
+namespace Slic3r { namespace GUI {
+
+// The wxAuiManager behind Orca's docked sidebars: Orca's caption and sash art in both themes,
+// floating frames that follow the app theme, and no floating on Wayland.
+class AuiMgr : public wxAuiManager
+{
+public:
+    // Manages `window`, whose own wxEVT_SIZE handlers must Skip().
+    void init(wxWindow* window);
+    // Captions, sashes and borders in the current theme.
+    void apply_color_mode();
+    // Keeps the docked size of `window`'s pane in its best_size, which re-docking and a saved layout
+    // use: wxAUI does not record a dragged sash there.
+    void track_docked_size(wxWindow* window);
+
+    // A tab's sidebar pane: docked left by default, movable to the right or floating, no close button.
+    static wxAuiPaneInfo sidebar_pane_info();
+
+    wxAuiFloatingFrame* CreateFloatingFrame(wxWindow* parent, const wxAuiPaneInfo& pane) override;
+};
+
+}} // namespace Slic3r::GUI

src/slic3r/GUI/CAD/DesignCanvas.cpp

@@ -570,6 +570,21 @@ void DesignCanvas::set_show_bed(bool b)
     request_repaint();
 }
 
+void DesignCanvas::set_sidebar_collapse(std::function<CollapseSide()> side, std::function<void()> toggle)
+{
+    if (!m_canvas || !m_canvas_widget || !setup_collapse_toolbar(m_collapse_toolbar, toggle))
+        return;
+    m_canvas->set_collapse_toolbar(&m_collapse_toolbar, std::move(side));
+    m_canvas->enable_collapse_toolbar(true);
+    // Shift+Tab: the canvas posts this for its sidebar, as Prepare's canvases do.
+    m_canvas_widget->Bind(EVT_GLCANVAS_COLLAPSE_SIDEBAR, [toggle](SimpleEvent&) { toggle(); });
+}
+
+void DesignCanvas::set_sidebar_collapse_tooltip(const std::string& tooltip)
+{
+    m_collapse_toolbar.set_tooltip(m_collapse_toolbar.get_item_id("collapse_sidebar"), tooltip);
+}
+
 bool DesignCanvas::is_sketching() const { return m_sketch_tool.is_active(); }
 
 void DesignCanvas::cancel_sketch()

src/slic3r/GUI/CAD/DesignCanvas.hpp

@@ -17,6 +17,7 @@
 
 #include "slic3r/GUI/3DBed.hpp"
 #include "slic3r/GUI/Camera.hpp"
+#include "slic3r/GUI/GLToolbar.hpp"
 #include "libslic3r/Model.hpp"
 #include "libslic3r/CAD/SketchEngine.hpp"
 #include "slic3r/GUI/CAD/DesignSketchTool.hpp"
@@ -87,6 +88,10 @@ public:
     void unbind_canvas_event_handlers();   // app close / language switch, from the plater's teardown
     void reset_canvas_volumes();
     void set_show_bed(bool b);   // view option: draw the printer bed + plate grid, or not
+    // The sidebar's collapse button, as Prepare's: drawn on the edge `side` reports, it runs
+    // `toggle` on a click and on Shift+Tab. Set before the first paint.
+    void set_sidebar_collapse(std::function<CollapseSide()> side, std::function<void()> toggle);
+    void set_sidebar_collapse_tooltip(const std::string& tooltip);
     // N: look straight down the sketch plane's normal, keeping the current zoom. A sketch drawn
     // at an angle is a sketch drawn wrong, and no amount of orbiting by hand lands exactly square.
     bool view_normal_to_sketch();
@@ -368,6 +373,7 @@ private:
     wxGLCanvas* m_canvas_widget{nullptr};
     GLCanvas3D* m_canvas{nullptr};
     int         m_sw_gl{-1};   // -1 unknown, 0 hardware GL, 1 software GL
+    GLToolbar   m_collapse_toolbar{GLToolbar::Normal, "Collapse"};
 
     std::function<void(const wxPoint&)> m_on_context_menu;
     bool        m_ctx_bound{false};   // bind the RIGHT_UP handler once, however often the cb is set

src/slic3r/GUI/CAD/DesignPanel.cpp

@@ -104,6 +104,7 @@
 #include "libslic3r/BuildVolume.hpp"
 #include "slic3r/GUI/MainFrame.hpp"
 #include "slic3r/GUI/GUI_ObjectList.hpp"
+#include "slic3r/GUI/Shortcuts.hpp"
 
 // English-only pin for the Design tab (see design-ux-contract): one lever
 // de-translates this whole TU so our strings never half-translate against the host's
@@ -357,10 +358,12 @@ DesignPanel::DesignPanel(wxWindow* parent)
     // Left column: a slim feature-tree + docked tool-dialog column. All form
     // controls are parented to m_form so it can scroll independently of the
     // live GL viewport. The tool buttons live in the top toolbar (built below).
-    m_form = new wxScrolledWindow(this, wxID_ANY);
+    auto* body_panel = new wxPanel(this, wxID_ANY);   // below the toolbar, managed by m_aui
+    m_form = new wxScrolledWindow(body_panel, wxID_ANY);
     // Explicit token background in both themes, so a theme switch can move it (an inherited
     // colour stays whatever the theme was when the panel was built).
     SetBackgroundColour(dp_panel_bg());
+    body_panel->SetBackgroundColour(dp_panel_bg());
     m_form->SetBackgroundColour(dp_panel_bg());
 
     auto* root = new wxBoxSizer(wxVERTICAL);
@@ -3521,7 +3524,9 @@ DesignPanel::DesignPanel(wxWindow* parent)
     build_phase("sidebar and tool cards");
     // Right column: a small view toolbar over the live 3D viewport that mirrors
     // the CadDocument body.
-    m_viewport = new DesignCanvas(this);
+    auto* view_col = new wxPanel(body_panel, wxID_ANY);   // the centre pane: sketch banner over the viewport
+    view_col->SetBackgroundColour(dp_panel_bg());
+    m_viewport = new DesignCanvas(view_col);
     build_phase("3D canvas");
 
     m_viewport->set_on_sketch_commit([this](const SketchProfile& prof, const SketchPlane& plane) {
@@ -4339,7 +4344,7 @@ DesignPanel::DesignPanel(wxWindow* parent)
     // The sketch banner sits ABOVE the viewport rather than floating inside it: a child window
     // over a wxGLCanvas is a platform argument (it is a native window on GTK and does not
     // reliably stack over GL), and the banner's job is to be unmissable, not to be clever.
-    m_sketch_banner = new wxPanel(this, wxID_ANY);
+    m_sketch_banner = new wxPanel(view_col, wxID_ANY);
     m_sketch_banner->SetBackgroundColour(wxColour(0, 122, 116));   // Orca teal: not a plate colour
     m_sketch_banner_txt = new wxStaticText(m_sketch_banner, wxID_ANY, wxString());
     m_sketch_banner_txt->SetForegroundColour(*wxWHITE);
@@ -4356,16 +4361,33 @@ DesignPanel::DesignPanel(wxWindow* parent)
     // The bottom 3D-navigator orb handles all view orientation, so no separate view buttons.
     // Fit view is a double-click on the viewport (the tool intercepts it -> zoom_to_volumes).
     vcol->Add(m_viewport, 1, wxEXPAND);
+    view_col->SetSizer(vcol);
 
-    // Onshape layout: top toolbar over [ slim left column | center viewport ].
-    auto* body = new wxBoxSizer(wxHORIZONTAL);
-    body->Add(m_form, 0, wxEXPAND);
-    body->Add(vcol,   1, wxEXPAND);
+    // Onshape layout: top toolbar over [ slim left column | center viewport ], with the column
+    // docked like Prepare's sidebar: left by default, movable to the right or floating, resizable
+    // and collapsible.
+    m_aui.init(body_panel);
+    m_aui.AddPane(m_form, AuiMgr::sidebar_pane_info().MinSize(m_form->GetMinSize()));
+    m_aui.AddPane(view_col, wxAuiPaneInfo().Name("main").CenterPane().PaneBorder(false));
+    m_default_layout = m_aui.SavePerspective();
+    load_window_layout();
+    m_aui.track_docked_size(m_form);
+    // The collapse button sits on the canvas edge the sidebar is docked on, and is gone while it
+    // floats. A click arrives inside the canvas's mouse handler, so the relayout waits for it.
+    m_viewport->set_sidebar_collapse(
+        [this] {
+            const wxAuiPaneInfo& sidebar = m_aui.GetPane(m_form);
+            if (!sidebar.IsOk() || sidebar.IsFloating())
+                return CollapseSide::None;
+            return sidebar.dock_direction == wxAUI_DOCK_RIGHT ? CollapseSide::Right : CollapseSide::Left;
+        },
+        [this] { CallAfter([this] { collapse_sidebar(!m_sidebar_collapsed); }); });
+    collapse_sidebar(m_sidebar_collapsed);   // the button's tooltip
 
     auto* outer = new wxBoxSizer(wxVERTICAL);
     outer->Add(m_toolbar, 0, wxEXPAND);
     outer->Add(new wxStaticLine(this, wxID_ANY), 0, wxEXPAND);
-    outer->Add(body, 1, wxEXPAND);
+    outer->Add(body_panel, 1, wxEXPAND);
     SetSizer(outer);
 
     // The atlas says a verb is wired; the registrations above say what it runs. Nothing checks
@@ -7215,6 +7237,7 @@ void DesignPanel::on_tab_hidden()
 {
     if (m_viewport)
         m_viewport->leave_viewport();   // hand the shared camera back to the editor tabs
+    update_sidebar_pane();
 }
 
 void DesignPanel::on_tab_shown()
@@ -7232,7 +7255,7 @@ void DesignPanel::on_tab_shown()
     update_reference_planes();   // entering the Design tab: show the XY/XZ/YZ planes if no object yet
     if (show_clock.Time() > 100)   // a slow first show is what users report; the usual one is not news
         BOOST_LOG_TRIVIAL(info) << "Design tab shown: bed, project recipe and planes in " << show_clock.Time() << " ms";
-    sync_sidebar_width();        // keep the panel as wide as Prepare's so the canvas edge doesn't jump
+    update_sidebar_pane();
     if (m_viewport) m_viewport->force_repaint();   // the page was just re-shown: paint it for real
 }
 
@@ -7267,6 +7290,7 @@ void DesignPanel::msw_rescale()
 
 void DesignPanel::on_sys_color_changed()
 {
+    m_aui.apply_color_mode();
     // Every chrome colour here was set from a DpToken in the theme that was current at the time.
     // Move each one, background and text, onto the same token in the new theme; any other colour
     // (the teal accents, the status colours) is the same in both and stays.
@@ -7325,19 +7349,83 @@ void DesignPanel::reset_canvas_volumes()
     if (m_viewport) m_viewport->reset_canvas_volumes();
 }
 
-// Match Prepare's sidebar width instead of hardcoding one. Design used a fixed 264 px against
-// Prepare's ~467, so the canvas edge jumped sideways on every tab switch; reading the live width
-// also means the two stay aligned if Orca ever changes its sidebar.
-void DesignPanel::sync_sidebar_width()
+void DesignPanel::shutdown()
 {
-    if (m_form == nullptr) return;
-    Plater* pl = wxGetApp().plater();
-    if (pl == nullptr) return;
-    const int w = pl->sidebar().GetSize().GetWidth();
-    if (w < 200) return;                       // sidebar not laid out yet — keep what we have
-    if (m_form->GetMinSize().GetWidth() == w) return;
-    m_form->SetMinSize(wxSize(w, -1));
-    Layout();
+    wxAuiPaneInfo& sidebar = m_aui.GetPane(m_form);
+    if (!sidebar.IsOk())   // shut down already, floating: a layout saved now would lack the sidebar
+        return;
+    // Saved hidden only when collapsed, whichever tab is shown.
+    sidebar.Show(!m_sidebar_collapsed);
+    wxGetApp().app_config->set("design_window_layout", m_aui.SavePerspective().utf8_string());
+    // A floating frame is a child of the managed panel and dereferences its manager when it is
+    // deleted, so it must not outlive m_aui, a member. Detaching queues the frame for deletion, which
+    // runs before the main frame destroys its children (~wxTopLevelWindowBase deletes pending child
+    // frames).
+    if (sidebar.IsFloating())
+        m_aui.DetachPane(m_form);
+}
+
+void DesignPanel::reset_window_layout()
+{
+    load_default_layout();
+    collapse_sidebar(false);
+    update_sidebar_pane(true);
+}
+
+// The sidebar where the user left it, collapsed if it was.
+void DesignPanel::load_window_layout()
+{
+    const wxString saved = wxString::FromUTF8(wxGetApp().app_config->get("design_window_layout"));
+    if (saved.empty() || !m_aui.LoadPerspective(saved, false)) {
+        if (!saved.empty())
+            BOOST_LOG_TRIVIAL(warning) << "Design tab: failed to restore the saved window layout";
+        load_default_layout();
+    }
+    wxAuiPaneInfo& sidebar = m_aui.GetPane(m_form);
+    m_sidebar_collapsed = !sidebar.IsShown();
+    if ((m_aui.GetFlags() & wxAUI_MGR_ALLOW_FLOATING) == 0)   // saved where windows can float
+        sidebar.Dock().Floatable(false);
+    update_sidebar_pane(true);
+}
+
+// Docked where Prepare's sidebar is, and as wide, so the canvas edge does not move between the tabs.
+void DesignPanel::load_default_layout()
+{
+    m_aui.LoadPerspective(m_default_layout, false);
+    Plater* plater = wxGetApp().plater();
+    const Sidebar::DockingState prepare = plater != nullptr ? plater->get_sidebar_docking_state() : Sidebar::None;
+    if (prepare == Sidebar::None)
+        return;
+    wxAuiPaneInfo& sidebar = m_aui.GetPane(m_form);
+    if (prepare == Sidebar::Right)
+        sidebar.Right();
+    const int width = plater->sidebar().GetSize().GetWidth();
+    if (width >= sidebar.min_size.GetWidth())   // Prepare's sidebar has been laid out
+        sidebar.BestSize(width, sidebar.best_size.GetHeight());
+}
+
+// The collapse button on the canvas and Shift+Tab, as in Prepare.
+void DesignPanel::collapse_sidebar(bool collapse)
+{
+    m_sidebar_collapsed = collapse;
+    if (m_viewport)
+        m_viewport->set_sidebar_collapse_tooltip(wxGetApp().shortcuts().with_key(
+            (collapse ? _L("Expand sidebar") : _L("Collapse sidebar")).utf8_string(), Shortcut::CollapseSidebar));
+    update_sidebar_pane();
+}
+
+// The sidebar shows unless collapsed; a floating one also only while the tab is shown, since it is
+// a top-level window and does not hide with the page.
+void DesignPanel::update_sidebar_pane(bool force_update)
+{
+    wxAuiPaneInfo& sidebar = m_aui.GetPane(m_form);
+    const bool     show    = !m_sidebar_collapsed && (sidebar.IsDocked() || IsShownOnScreen());
+    if (sidebar.IsOk() && sidebar.IsShown() != show) {
+        sidebar.Show(show);
+        force_update = true;
+    }
+    if (force_update)
+        m_aui.Update();
 }
 
 void DesignPanel::load_recipe(const std::string& blob)

src/slic3r/GUI/CAD/DesignPanel.hpp

@@ -21,6 +21,7 @@
 
 #include "libslic3r/CAD/CadDocument.hpp"
 #include "slic3r/GUI/CAD/DesignInteraction.hpp"   // CadLevel: what one Esc press means
+#include "slic3r/GUI/AuiMgr.hpp"
 #include "slic3r/GUI/Lazy.hpp"
 
 class ComboBox;    // Orca dropdown (Widgets/ComboBox.hpp) — replaces wxChoice everywhere here
@@ -70,6 +71,8 @@ public:
     void on_sys_color_changed();
     void unbind_canvas_event_handlers();   // app close / language switch, from the plater's teardown
     void reset_canvas_volumes();
+    void shutdown();            // app close / language switch, from MainFrame: save the window layout
+    void reset_window_layout(); // View > Reset Window Layout, with Prepare's
     void clear_document();      // New Project / Open Project: drop the document with the project
     // Rebuild off the UI thread (progress dialog only if it turns out to be slow), so a feature
     // op on a heavy imported solid does not freeze the window. Returns m_doc.recompute()'s result.
@@ -497,6 +500,17 @@ private:
     wxScrolledWindow* m_form{nullptr};
     DesignCanvas*     m_viewport{nullptr};
 
+    // Below the toolbar, m_form docks beside the viewport column like Prepare's sidebar: it can
+    // move to the other side, float, be resized and be collapsed, and the layout is kept between
+    // sessions.
+    AuiMgr   m_aui;
+    wxString m_default_layout;
+    bool     m_sidebar_collapsed{false};
+    void load_window_layout();
+    void load_default_layout();
+    void collapse_sidebar(bool collapse);
+    void update_sidebar_pane(bool force_update = false);
+
     // Top contextual toolbar (parented to the panel, above the form/viewport row).
     UiMode    m_ui_mode{UiMode::Feature};
     // Sketch environment banner: a strip across the top of the viewport saying, in words, that
@@ -938,7 +952,6 @@ private:
     int  tree_selection() const;          // selected feature row, or wxNOT_FOUND
     int  tree_body_selection() const;     // selected Parts-list body index, or -1
     void refresh_parts();                 // rebuild the Bodies list under the feature tree
-    void sync_sidebar_width();            // keep the panel as wide as Prepare's sidebar
     void set_tree_selection(int row);
     static int tree_icon_for(CadFeatureType t);
 

src/slic3r/GUI/GLCanvas3D.cpp

@@ -1440,7 +1440,7 @@ void GLCanvas3D::on_change_color_mode(bool is_dark, bool reinit) {
             // set dirty to re-generate icon texture
             m_separator_toolbar.set_icon_dirty();
             m_main_toolbar.set_icon_dirty();
-            wxGetApp().plater()->get_collapse_toolbar().set_icon_dirty();
+            collapse_toolbar().set_icon_dirty();
             m_assemble_view_toolbar.set_icon_dirty();
             m_gizmos.set_icon_dirty();
         }
@@ -1972,6 +1972,12 @@ void GLCanvas3D::enable_collapse_toolbar(bool enable)
     m_collapse_toolbar_enabled = enable;
 }
 
+void GLCanvas3D::set_collapse_toolbar(GLToolbar* toolbar, std::function<CollapseSide()> side)
+{
+    m_collapse_toolbar = toolbar;
+    m_collapse_side    = std::move(side);
+}
+
 void GLCanvas3D::enable_plate_chrome(bool enable)
 {
     m_plate_chrome_enabled = enable;
@@ -2052,24 +2058,33 @@ void GLCanvas3D::update_volumes_colors_by_extruder()
 
 bool GLCanvas3D::is_collapse_toolbar_on_left() const
 {
-    auto state = wxGetApp().plater()->get_sidebar_docking_state();
-    return state == Sidebar::Left;
+    return collapse_side() == CollapseSide::Left;
 }
 
 float GLCanvas3D::get_collapse_toolbar_width() const
 {
-    GLToolbar& collapse_toolbar = wxGetApp().plater()->get_collapse_toolbar();
-    const auto state            = wxGetApp().plater()->get_sidebar_docking_state();
-
-    return state != Sidebar::None ? collapse_toolbar.get_width() : 0;
+    return collapse_side() != CollapseSide::None ? collapse_toolbar().get_width() : 0;
 }
 
 float GLCanvas3D::get_collapse_toolbar_height() const
 {
-    GLToolbar& collapse_toolbar = wxGetApp().plater()->get_collapse_toolbar();
-    const auto state            = wxGetApp().plater()->get_sidebar_docking_state();
+    return collapse_side() != CollapseSide::None ? collapse_toolbar().get_height() : 0;
+}
 
-    return state != Sidebar::None ? collapse_toolbar.get_height() : 0;
+GLToolbar& GLCanvas3D::collapse_toolbar() const
+{
+    return m_collapse_toolbar != nullptr ? *m_collapse_toolbar : wxGetApp().plater()->get_collapse_toolbar();
+}
+
+CollapseSide GLCanvas3D::collapse_side() const
+{
+    if (m_collapse_side)
+        return m_collapse_side();
+    switch (wxGetApp().plater()->get_sidebar_docking_state()) {
+    case Sidebar::Left: return CollapseSide::Left;
+    case Sidebar::Right: return CollapseSide::Right;
+    default: return CollapseSide::None;
+    }
 }
 
 bool GLCanvas3D::make_current_for_postinit() {
@@ -2274,7 +2289,7 @@ void GLCanvas3D::_render_frame(bool scene_dirty, bool only_init)
             tooltip = m_assemble_view_toolbar.get_tooltip();
 
 	    if (tooltip.empty())
-            tooltip = wxGetApp().plater()->get_collapse_toolbar().get_tooltip();
+            tooltip = collapse_toolbar().get_tooltip();
 
         // BBS
 #if 0
@@ -3475,7 +3490,7 @@ void GLCanvas3D::on_idle(wxIdleEvent& evt)
     m_overlay_dirty |= m_assemble_view_toolbar.update_items_state();
     // BBS
     //m_dirty |= wxGetApp().plater()->get_view_toolbar().update_items_state();
-    m_overlay_dirty |= wxGetApp().plater()->get_collapse_toolbar().update_items_state();
+    m_overlay_dirty |= collapse_toolbar().update_items_state();
     // apply() DRAINS the 3D-mouse queue, so only the canvas actually on screen may call it: a
     // hidden canvas renders nothing, so the motion it swallowed moves the shared camera without
     // ever being drawn and the next visible frame jumps several states at once.
@@ -4267,6 +4282,13 @@ void GLCanvas3D::on_mouse(wxMouseEvent& evt)
     // (drag/orbit/wheel) so the camera keeps working over the display-only plate.
 #ifdef SLIC3R_CAD
     if (m_design_sketch_tool != nullptr && m_design_sketch_tool->has_display()) {
+        // Except over the sidebar collapse button, which is drawn over the sketch.
+        if (collapse_toolbar().on_mouse(evt, *this)) {
+            if (evt.LeftUp() || evt.MiddleUp() || evt.RightUp())
+                mouse_up_cleanup();
+            m_mouse.set_start_position_3D_as_invalid();
+            return;
+        }
         if (evt.LeftDown() && m_canvas != nullptr)
             m_canvas->SetFocus();   // grab keyboard focus so Delete/keys reach this canvas
         if (m_design_sketch_tool->on_mouse(evt, *this)) {
@@ -4315,7 +4337,7 @@ void GLCanvas3D::on_mouse(wxMouseEvent& evt)
         return;
     }
 
-    if (!mouse_in_layer_editing && wxGetApp().plater()->get_collapse_toolbar().on_mouse(evt, *this)) {
+    if (!mouse_in_layer_editing && collapse_toolbar().on_mouse(evt, *this)) {
         if (evt.LeftUp() || evt.MiddleUp() || evt.RightUp())
             mouse_up_cleanup();
         m_mouse.set_start_position_3D_as_invalid();
@@ -6892,7 +6914,7 @@ void GLCanvas3D::_switch_toolbars_icon_filename()
     m_main_toolbar.init(background_data);
     m_assemble_view_toolbar.init(background_data);
     m_separator_toolbar.init(background_data);
-    wxGetApp().plater()->get_collapse_toolbar().init(background_data);
+    collapse_toolbar().init(background_data);
 
     // main toolbar
     {
@@ -7320,7 +7342,17 @@ bool GLCanvas3D::_init_view_toolbar()
 
 bool GLCanvas3D::_init_collapse_toolbar()
 {
-    return wxGetApp().plater()->init_collapse_toolbar();
+    if (m_collapse_toolbar == nullptr)
+        return wxGetApp().plater()->init_collapse_toolbar();
+
+    // Its owner laid it out; the background needs the GL context.
+    BackgroundTexture::Metadata background_data;
+    background_data.filename = m_is_dark ? "toolbar_background_dark.png" : "toolbar_background.png";
+    background_data.left = 16;
+    background_data.top = 16;
+    background_data.right = 16;
+    background_data.bottom = 16;
+    return m_collapse_toolbar->init(background_data);
 }
 
 bool GLCanvas3D::_set_current()
@@ -9085,11 +9117,12 @@ void GLCanvas3D::_render_sequential_clearance()
 void GLCanvas3D::_check_and_update_toolbar_icon_scale()
 {
     // Update collapse toolbar
-    GLToolbar& collapse_toolbar = wxGetApp().plater()->get_collapse_toolbar();
-    collapse_toolbar.set_enabled(wxGetApp().plater()->get_sidebar_docking_state() != Sidebar::None);
+    GLToolbar& collapse_toolbar = this->collapse_toolbar();
+    collapse_toolbar.set_enabled(collapse_side() != CollapseSide::None);
 
-    // Don't update a toolbar scale, when we are on a Preview
-    if (wxGetApp().plater()->is_preview_shown()) {
+    // Don't update a toolbar scale, when we are on a Preview. Asked of this canvas, not of the
+    // plater: the Design tab's canvas is on screen while the plater's current view may be Preview.
+    if (m_canvas_type == CanvasPreview) {
         IMSlider   *m_layers_slider = get_gcode_viewer().get_layers_slider();
         IMSlider   *m_moves_slider  = get_gcode_viewer().get_moves_slider();
         float sc              = get_scale();
@@ -9161,7 +9194,9 @@ void GLCanvas3D::_check_and_update_toolbar_icon_scale()
     // set minimum scale as a auto scale for the toolbars
     float new_scale = std::min(new_h_scale, new_v_scale);
     new_scale /= get_scale();
-    if (fabs(new_scale - scale) > 0.05) // scale is changed by 5% and more
+    // Only a canvas with toolbars to fit sets the shared size: a collapse button alone (the Design
+    // tab's canvas) always fits at the largest.
+    if (items_cnt > collapse_toolbar.get_visible_items_cnt() && fabs(new_scale - scale) > 0.05) // scale is changed by 5% and more
         wxGetApp().set_auto_toolbar_icon_scale(new_scale);
 }
 
@@ -9243,7 +9278,7 @@ size_t GLCanvas3D::_overlay_signature(const ImDrawData* draw_data) const
     size_t hash = ImGuiWrapper::draw_data_signature(draw_data);
     for (size_t state_hash : { m_main_toolbar.get_state_hash(), m_separator_toolbar.get_state_hash(),
                                m_assemble_view_toolbar.get_state_hash(),
-                               wxGetApp().plater()->get_collapse_toolbar().get_state_hash(),
+                               collapse_toolbar().get_state_hash(),
                                m_gizmos.get_overlay_state_hash() })
         boost::hash_combine(hash, state_hash);
     return hash;
@@ -10298,18 +10333,17 @@ void GLCanvas3D::_render_collapse_toolbar() const
     if (!m_collapse_toolbar_enabled)
         return;
 
-    auto&      plater              = *wxGetApp().plater();
-    const auto sidebar_docking_dir = plater.get_sidebar_docking_state();
-    if (sidebar_docking_dir == Sidebar::None) {
+    const CollapseSide side = collapse_side();
+    if (side == CollapseSide::None) {
         return;
     }
 
-    GLToolbar& collapse_toolbar = plater.get_collapse_toolbar();
+    GLToolbar& collapse_toolbar = this->collapse_toolbar();
 
     const Size cnv_size = get_canvas_size();
     const float top  = 0.5f * (float)cnv_size.get_height();
-    const float left = sidebar_docking_dir == Sidebar::Right ? 0.5f * (float) cnv_size.get_width() - (float) collapse_toolbar.get_width() :
-                                                               -0.5f * (float) cnv_size.get_width();
+    const float left = side == CollapseSide::Right ? 0.5f * (float) cnv_size.get_width() - (float) collapse_toolbar.get_width() :
+                                                     -0.5f * (float) cnv_size.get_width();
 
     collapse_toolbar.set_position(top, left);
     collapse_toolbar.render(*this);
@@ -11705,7 +11739,7 @@ bool GLCanvas3D::_deactivate_layersediting_menu()
 
 bool GLCanvas3D::_deactivate_collapse_toolbar_items()
 {
-    GLToolbar& collapse_toolbar = wxGetApp().plater()->get_collapse_toolbar();
+    GLToolbar& collapse_toolbar = this->collapse_toolbar();
     if (collapse_toolbar.is_item_pressed("print")) {
         collapse_toolbar.force_left_action(collapse_toolbar.get_item_id("print"), *this);
         return true;

src/slic3r/GUI/GLCanvas3D.hpp

@@ -20,6 +20,7 @@
 #include "libslic3r/Line.hpp"
 #include "slic3r/GUI/Gizmos/GLGizmoBase.hpp"
 #include <stddef.h>
+#include <functional>
 #include <memory>
 #include <chrono>
 #include <cstdint>
@@ -594,6 +595,9 @@ private:
     mutable float m_sc{1};
     mutable float m_paint_toolbar_width;
     bool m_collapse_toolbar_enabled{true};
+    // The collapse button of a sidebar other than Prepare's, from set_collapse_toolbar().
+    GLToolbar*                    m_collapse_toolbar{nullptr};
+    std::function<CollapseSide()> m_collapse_side;
     bool m_plate_chrome_enabled{true};
     // Design tab: render the world-axis triad at the bed centre (= modeling origin) instead of
     // the bed corner. Default false preserves the main editor's corner triad.
@@ -1008,6 +1012,10 @@ public:
     void enable_return_toolbar(bool enable);
     void enable_separator_toolbar(bool enable);
     void enable_collapse_toolbar(bool enable);
+    // A canvas beside a sidebar other than Prepare's shows that sidebar's collapse button: `toolbar`,
+    // set up with setup_collapse_toolbar(), on the edge `side` reports. Call before the canvas is
+    // initialized, which loads the toolbar's background.
+    void set_collapse_toolbar(GLToolbar* toolbar, std::function<CollapseSide()> side);
     void enable_plate_chrome(bool enable);
     void set_axes_at_bed_center(bool b) { m_axes_at_bed_center = b; }
     void set_show_bed(bool b) { m_show_bed = b; }
@@ -1374,6 +1382,8 @@ private:
     // BBS
     //bool _init_view_toolbar();
     bool _init_collapse_toolbar();
+    GLToolbar&   collapse_toolbar() const;
+    CollapseSide collapse_side() const;
 
     bool _set_current();
     bool _set_shown_canvas_current();

src/slic3r/GUI/GLToolbar.cpp

@@ -1672,5 +1672,27 @@ float GLToolbar::get_scaled_icon_size()
     return m_layout.icons_size * m_layout.scale;
 }
 
+bool setup_collapse_toolbar(GLToolbar& toolbar, std::function<void()> toggle)
+{
+    toolbar.set_layout_type(GLToolbar::Layout::Vertical);
+    toolbar.set_horizontal_orientation(GLToolbar::Layout::HO_Right);
+    toolbar.set_vertical_orientation(GLToolbar::Layout::VO_Top);
+    toolbar.set_border(4.0f);
+    toolbar.set_separator_size(4);
+    toolbar.set_gap_size(2);
+
+    toolbar.del_all_item();
+
+    GLToolbarItem::Data item;
+
+    item.name = "collapse_sidebar";
+    // set collapse svg name
+    item.icon_filename = "collapse.svg";
+    item.sprite_id = 0;
+    item.left.action_callback = std::move(toggle);
+
+    return toolbar.add_item(item);
+}
+
 } // namespace GUI
 } // namespace Slic3r

src/slic3r/GUI/GLToolbar.hpp

@@ -457,6 +457,14 @@ private:
     bool update_items_enabled_state();
 };
 
+// The canvas edge a sidebar collapse button sits on: the side its sidebar is docked on, or none
+// while that sidebar floats.
+enum class CollapseSide { None, Left, Right };
+
+// Lays `toolbar` out as a sidebar collapse button that runs `toggle`: Prepare's, and those of
+// other sidebars (GLCanvas3D::set_collapse_toolbar()).
+bool setup_collapse_toolbar(GLToolbar& toolbar, std::function<void()> toggle);
+
 } // namespace GUI
 } // namespace Slic3r
 

src/slic3r/GUI/MainFrame.cpp

@@ -1249,6 +1249,10 @@ void MainFrame::shutdown()
     m_plugin_pages.shutdown();
     if (m_plater != nullptr)
         m_plater->remove_dock_panes();
+#ifdef SLIC3R_CAD
+    if (DesignPanel* design = DesignPanel::if_built())
+        design->shutdown();
+#endif
 #ifdef __WXGTK__
     // Edge panels are child windows — wxWidgets destroys them automatically.
     m_edge_bottom = nullptr;
@@ -3377,6 +3381,10 @@ void MainFrame::init_menubar_as_editor()
             viewMenu, wxID_ANY, _L("Reset Window Layout"), _L("Reset to default window layout"),
             [this](wxCommandEvent&) { m_plater->reset_window_layout(); }, "", this,
             [this]() {
+#ifdef SLIC3R_CAD
+                if (shown_design_panel() != nullptr)
+                    return true;
+#endif
                 return is_prepare_or_preview_tab() && m_plater->is_sidebar_enabled();
             },
             this);

src/slic3r/GUI/Plater.cpp

@@ -191,6 +191,7 @@
 #ifdef __WXGTK__
 #include "LinuxDisplayBackend.hpp"
 #endif
+#include "AuiMgr.hpp"
 #include "AuiPaneLayout.hpp"
 #include "GUI_Utils.hpp"
 #include "GUI_Factories.hpp"
@@ -7111,28 +7112,6 @@ enum ExportingStatus{
     EXPORTING_TO_LOCAL
 };
 
-
-// TODO: listen on dark ui change
-class FloatFrame : public wxAuiFloatingFrame
-{
-public:
-    FloatFrame(wxWindow* parent, wxAuiManager* ownerMgr, const wxAuiPaneInfo& pane) : wxAuiFloatingFrame(parent, ownerMgr, pane)
-    {
-        wxGetApp().UpdateFrameDarkUI(this);
-    }
-};
-
-class AuiMgr : public wxAuiManager
-{
-public:
-    AuiMgr() : wxAuiManager(){}
-
-    virtual wxAuiFloatingFrame* CreateFloatingFrame(wxWindow* parent, const wxAuiPaneInfo& p) override
-    {
-        return new FloatFrame(parent, this, p);
-    }
-};
-
 // Plater / private
 struct Plater::priv
 {
@@ -7616,7 +7595,6 @@ struct Plater::priv
     //BBS: change dark/light mode
     void on_change_color_mode(SimpleEvent& evt);
     void on_apple_change_color_mode(wxSysColourChangedEvent& evt);
-    void apply_color_mode();
     void on_update_geometry(Vec3dsEvent<2>&);
     void on_3dcanvas_mouse_dragging_started(SimpleEvent&);
     void on_3dcanvas_mouse_dragging_finished(SimpleEvent&);
@@ -7829,20 +7807,7 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame)
 {
     m_is_dark = wxGetApp().app_config->get("dark_color_mode") == "1";
 
-#ifdef __WXGTK__
-    const bool disable_wayland_floating = Slic3r::GUI::is_running_on_wayland();
-#endif
-
-    m_aui_mgr.SetManagedWindow(q);
-    m_aui_mgr.SetDockSizeConstraint(1, 1);
-#ifdef __WXGTK__
-    if (disable_wayland_floating)
-        m_aui_mgr.SetFlags(m_aui_mgr.GetFlags() & ~wxAUI_MGR_ALLOW_FLOATING);
-#endif
-    //m_aui_mgr.GetArtProvider()->SetMetric(wxAUI_DOCKART_PANE_BORDER_SIZE, 0);
-    //m_aui_mgr.GetArtProvider()->SetMetric(wxAUI_DOCKART_SASH_SIZE, 2);
-    m_aui_mgr.GetArtProvider()->SetMetric(wxAUI_DOCKART_CAPTION_SIZE, 18);
-    m_aui_mgr.GetArtProvider()->SetMetric(wxAUI_DOCKART_GRADIENT_TYPE, wxAUI_GRADIENT_NONE);
+    m_aui_mgr.init(q);
 
     this->q->SetFont(Slic3r::GUI::wxGetApp().normal_font());
 
@@ -7925,13 +7890,7 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame)
     update();
 
     // Orca: Make sidebar dockable
-    m_aui_mgr.AddPane(sidebar, wxAuiPaneInfo()
-                                   .Name("sidebar")
-                                   .Left()
-                                   .CloseButton(false)
-                                   .TopDockable(false)
-                                   .BottomDockable(false)
-                                   .BestSize(wxSize(39 * wxGetApp().em_unit(), 90 * wxGetApp().em_unit())));
+    m_aui_mgr.AddPane(sidebar, AuiMgr::sidebar_pane_info());
 
     // UV editor pane for GLGizmoTextureDisplacement's LSCM unwrap preview - a resizable/dockable
     // sibling of "sidebar"/"main" like everything else registered on this same AUI manager, not a
@@ -7983,8 +7942,7 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame)
         if (!layout.empty()) {
             bool removed_floating_state = false;
 #ifdef __WXGTK__
-            if (disable_wayland_floating)
-                layout = sanitize_window_layout_for_wayland(layout, &removed_floating_state);
+            layout = sanitize_window_layout_for_wayland(layout, &removed_floating_state);
 #endif
 
             if (!m_aui_mgr.LoadPerspective(layout, false)) {
@@ -8006,12 +7964,7 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame)
 
         // Keep tracking the current sidebar size, by storing it using `best_size`, which will be stored
         // in the config and re-applied when the app is opened again.
-        this->sidebar->Bind(wxEVT_IDLE, [&sidebar](wxIdleEvent& e) {
-            if (sidebar.IsShown() && sidebar.IsDocked() && sidebar.rect.GetWidth() > 0) {
-                sidebar.BestSize(sidebar.rect.GetWidth(), sidebar.best_size.GetHeight());
-            }
-            e.Skip();
-        });
+        m_aui_mgr.track_docked_size(this->sidebar);
 
         // Hide sidebar initially, will re-show it after initialization when we got proper window size
         sidebar.Hide();
@@ -8236,8 +8189,6 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame)
     q->SetDropTarget(new PlaterDropTarget(*main_frame, *q));   // if my understanding is right, wxWindow takes the owenership
     q->Layout();
 
-    apply_color_mode();
-
     set_current_panel(wxGetApp().is_editor() ? static_cast<wxPanel*>(view3D) : static_cast<wxPanel*>(preview));
 
     // updates camera type from .ini file
@@ -8716,18 +8667,7 @@ void Plater::priv::add_dock_pane(wxWindow* window, const std::string& name, cons
     info.Show(dock_pane_visible(dock_pane, info));
     m_aui_mgr.AddPane(window, info);
 
-    // wxAUI does not record a dragged sash in best_size, so track the docked size like the sidebar
-    // does, for the saved layout.
-    window->Bind(wxEVT_IDLE, [this, window](wxIdleEvent& evt) {
-        wxAuiPaneInfo& pane = m_aui_mgr.GetPane(window);
-        if (pane.IsOk() && pane.IsShown() && pane.IsDocked() && pane.rect.GetWidth() > 0 && pane.rect.GetHeight() > 0) {
-            const bool horizontal = pane.dock_direction == wxAUI_DOCK_TOP || pane.dock_direction == wxAUI_DOCK_BOTTOM;
-            pane.BestSize(horizontal ? pane.best_size.GetWidth() : pane.rect.GetWidth(),
-                          horizontal ? pane.rect.GetHeight() : pane.best_size.GetHeight());
-        }
-        evt.Skip();
-    });
-
+    m_aui_mgr.track_docked_size(window);
     m_aui_mgr.Update();
 }
 
@@ -13908,7 +13848,7 @@ void Plater::priv::on_apple_change_color_mode(wxSysColourChangedEvent& evt) {
         assemble_view->get_canvas3d()->on_change_color_mode(m_is_dark);
     }
 
-    apply_color_mode();
+    m_aui_mgr.apply_color_mode();
 }
 
 void Plater::priv::on_change_color_mode(SimpleEvent& evt) {
@@ -13919,19 +13859,7 @@ void Plater::priv::on_change_color_mode(SimpleEvent& evt) {
     assemble_view->get_canvas3d()->on_change_color_mode(m_is_dark);
     if (m_send_to_sdcard_dlg) m_send_to_sdcard_dlg->on_change_color_mode();
 
-    apply_color_mode();
-}
-
-void Plater::priv::apply_color_mode()
-{
-    const bool is_dark         = wxGetApp().dark_mode();
-    wxColour   orca_color      = wxColour(59, 68, 70);//wxColour(ColorRGBA::ORCA().r_uchar(), ColorRGBA::ORCA().g_uchar(), ColorRGBA::ORCA().b_uchar());
-    orca_color                 = is_dark ? StateColor::darkModeColorFor(orca_color) : StateColor::lightModeColorFor(orca_color);
-    wxColour sash_color = is_dark ? wxColour(38, 46, 48) : wxColour(206, 206, 206);
-    m_aui_mgr.GetArtProvider()->SetColour(wxAUI_DOCKART_INACTIVE_CAPTION_COLOUR, sash_color);
-    m_aui_mgr.GetArtProvider()->SetColour(wxAUI_DOCKART_INACTIVE_CAPTION_TEXT_COLOUR, *wxWHITE);
-    m_aui_mgr.GetArtProvider()->SetColour(wxAUI_DOCKART_SASH_COLOUR, sash_color);
-    m_aui_mgr.GetArtProvider()->SetColour(wxAUI_DOCKART_BORDER_COLOUR, is_dark ? *wxBLACK : wxColour(165, 165, 165));
+    m_aui_mgr.apply_color_mode();
 }
 
 static void get_position(wxWindowBase* child, wxWindowBase* until_parent, int& x, int& y) {
@@ -14592,26 +14520,9 @@ bool Plater::priv::init_collapse_toolbar()
     if (!collapse_toolbar.init(background_data))
         return false;
 
-    collapse_toolbar.set_layout_type(GLToolbar::Layout::Vertical);
-    collapse_toolbar.set_horizontal_orientation(GLToolbar::Layout::HO_Right);
-    collapse_toolbar.set_vertical_orientation(GLToolbar::Layout::VO_Top);
-    collapse_toolbar.set_border(4.0f);
-    collapse_toolbar.set_separator_size(4);
-    collapse_toolbar.set_gap_size(2);
-
-    collapse_toolbar.del_all_item();
-
-    GLToolbarItem::Data item;
-
-    item.name = "collapse_sidebar";
-    // set collapse svg name
-    item.icon_filename = "collapse.svg";
-    item.sprite_id = 0;
-    item.left.action_callback = []() {
-        wxGetApp().plater()->collapse_sidebar(!wxGetApp().plater()->is_sidebar_collapsed());
-    };
-
-    if (!collapse_toolbar.add_item(item))
+    if (!setup_collapse_toolbar(collapse_toolbar, []() {
+            wxGetApp().plater()->collapse_sidebar(!wxGetApp().plater()->is_sidebar_collapsed());
+        }))
         return false;
 
     // Now "collapse" sidebar to current state. This is done so the tooltip
@@ -18481,7 +18392,15 @@ bool Plater::is_sidebar_collapsed() const { return p->sidebar_layout.is_collapse
 void Plater::collapse_sidebar(bool collapse) { p->collapse_sidebar(collapse); }
 Sidebar::DockingState Plater::get_sidebar_docking_state() const { return p->get_sidebar_docking_state(); }
 
-void Plater::reset_window_layout() { p->reset_window_layout(); }
+void Plater::reset_window_layout()
+{
+    p->reset_window_layout();
+#ifdef SLIC3R_CAD
+    // The Design tab docks its own sidebar.
+    if (DesignPanel* design = DesignPanel::if_built())
+        design->reset_window_layout();
+#endif
+}
 
 void Plater::add_dock_pane(wxWindow* window, const std::string& name, const wxString& caption, const std::string& dock,
                            const wxSize& size, std::function<void()> on_close)