Give the Design tab its own camera view

The Camera is Plater-owned and shared by every canvas, and Design sits
outside the panel switch that saves and restores it for Prepare,
Preview and Assemble — so orbiting in Design moved what the editor
tabs showed, and Design lost its own view on every switch. Trade the
live camera for a parked one on the way in and back on the way out, so
Design keeps its view the way Assemble already does.

src/slic3r/GUI/CAD/DesignCanvas.cpp

@@ -189,6 +189,15 @@ DesignCanvas::DesignCanvas(wxWindow* parent)
 
     refresh_bed();
 
+    // The view this canvas opens on. Built lazily, on the way into the Design tab, so this
+    // is the view the user is looking at right now.
+    m_parked_camera = wxGetApp().plater()->get_camera();
+
+    // Before any of this class's own Binds below: wx calls dynamically bound handlers in
+    // reverse order of binding, and GLCanvas3D::on_mouse takes wxEVT_RIGHT_UP / ENTER_WINDOW
+    // without skipping them — so whatever is bound last is the only handler that sees them.
+    // The context menu, the focus-follows-mouse and the status-chip re-anchor all depend on
+    // running first, which is only true while this call stays ahead of them.
     m_canvas->bind_event_handlers();
 
     // The Design GL canvas only receives key events (Esc to exit/enter Select, Ctrl+Z undo)
@@ -268,6 +277,24 @@ void DesignCanvas::request_repaint()
     }
 }
 
+void DesignCanvas::enter_viewport()
+{
+    if (!m_camera_swapped) swap_camera();
+}
+
+void DesignCanvas::leave_viewport()
+{
+    if (m_camera_swapped) swap_camera();
+}
+
+void DesignCanvas::swap_camera()
+{
+    Plater* plater = wxGetApp().plater();
+    if (plater == nullptr) return;
+    std::swap(plater->get_camera(), m_parked_camera);
+    m_camera_swapped = !m_camera_swapped;
+}
+
 void DesignCanvas::force_repaint()
 {
     if (m_canvas == nullptr || m_canvas_widget == nullptr)

src/slic3r/GUI/CAD/DesignCanvas.hpp

@@ -9,6 +9,7 @@
 #include <string>
 
 #include "slic3r/GUI/3DBed.hpp"
+#include "slic3r/GUI/Camera.hpp"
 #include "libslic3r/Model.hpp"
 #include "libslic3r/CAD/SketchEngine.hpp"
 #include "slic3r/GUI/CAD/DesignSketchTool.hpp"
@@ -69,6 +70,13 @@ public:
     void finish_sketch();
     bool is_sketching() const;
     void refresh_bed();   // re-sync the bed to the current printer (call on tab activation)
+    // The Camera is Plater-owned and shared with Prepare/Preview/Assemble; GLCanvas3D has no
+    // per-canvas camera, so every orbit here would otherwise overwrite what the editor tabs
+    // show. Exactly one of the two views is live at a time, so entering and leaving are the
+    // same operation: trade the live camera for the parked one. That also keeps this canvas's
+    // own view across a tab switch.
+    void enter_viewport();
+    void leave_viewport();
     void set_show_bed(bool b);   // view option: draw the printer bed + plate grid, or not
     void cancel_sketch();
     void set_on_sketch_commit(std::function<void(const SketchProfile&, const SketchPlane&)> cb);
@@ -324,6 +332,7 @@ public:
 
 private:
     void reload(bool keep_view);
+    void swap_camera();   // enter_viewport / leave_viewport, in the one direction they share
 
     wxGLCanvas* m_canvas_widget{nullptr};
     GLCanvas3D* m_canvas{nullptr};
@@ -334,6 +343,11 @@ private:
     wxPoint     m_ctx_press{0, 0};    // right-press origin: a right-DRAG pans, it must not offer
 
     Bed3D       m_bed;
+    // The half of the camera swap above that is NOT on screen: the editor tabs' view while
+    // Design is up, this canvas's view while it is not. Seeded in the constructor so the first
+    // entry inherits the view the user was already looking at.
+    Camera      m_parked_camera;
+    bool        m_camera_swapped{false};   // guards a leave without an enter, and the reverse
     Model       m_model;
     bool        m_first_frame{true};
     bool        m_body_selected{false};   // tree selected a body feature → tint the solid

src/slic3r/GUI/CAD/DesignPanel.cpp

@@ -6937,12 +6937,18 @@ wxString DesignPanel::idle_hint() const
 // Nothing else in the panel needs to know: the popup keeps its text and comes straight back.
 void DesignPanel::on_tab_hidden()
 {
-    if (m_viewport) m_viewport->show_status_hud(false);
+    if (m_viewport) {
+        m_viewport->show_status_hud(false);
+        m_viewport->leave_viewport();   // hand the shared camera back to the editor tabs
+    }
 }
 
 void DesignPanel::on_tab_shown()
 {
-    if (m_viewport) m_viewport->show_status_hud(true);   // ...and back on the way in
+    if (m_viewport) {
+        m_viewport->show_status_hud(true);   // ...and back on the way in
+        m_viewport->enter_viewport();        // borrow the shared camera; on_tab_hidden gives it back
+    }
 
     if (m_active == Tool::None && m_doc.display_mesh.its.indices.empty())
         set_status(idle_hint());   // first paint: the tab has never been edited