feat: UI for dropdown to select which plugin to show past max visible pages

src/slic3r/GUI/Notebook.cpp

@@ -272,6 +272,24 @@ wxString ButtonsListCtrl::GetPageText(size_t n) const
     return btn->GetLabel();
 }
 
+// ORCA
+void ButtonsListCtrl::SetOverflowButton(wxWindow* button)
+{
+    if (m_overflow_button == button)
+        return;
+
+    if (m_overflow_button != nullptr)
+        m_sizer->Detach(m_overflow_button);
+
+    m_overflow_button = button;
+
+    if (m_overflow_button != nullptr)
+        // Right after the tab buttons (index 0), ahead of any stretch spacer / side_tools.
+        m_sizer->Insert(1, m_overflow_button, 0, wxALIGN_CENTER_VERTICAL | wxLEFT | wxBOTTOM, m_btn_margin);
+
+    m_sizer->Layout();
+}
+
 //#endif // _WIN32
 
 void Notebook::Init()

src/slic3r/GUI/Notebook.hpp

@@ -36,6 +36,9 @@ public:
     void SetCompact(size_t n, bool compact); // ORCA
     wxString GetPageText(size_t n) const;
     wxFlexGridSizer* GetBtnsSizer(){return m_buttons_sizer;}; // ORCA
+    // ORCA: a companion widget shown right after the tab buttons (before any side_tools), e.g.
+    // an overflow indicator. Pass nullptr to remove it; ownership stays with the caller.
+    void SetOverflowButton(wxWindow* button);
 
 private:
     wxFlexGridSizer*                m_buttons_sizer;
@@ -47,6 +50,7 @@ private:
     int                             m_line_margin;
     std::vector<wxString>           m_pageLabels; // ORCA
     wxImageList*                    m_imageList{nullptr};
+    wxWindow*                       m_overflow_button{nullptr}; // ORCA
 };
 
 class Notebook : public wxBookCtrlBase
@@ -324,6 +328,7 @@ public:
     }
 
     ButtonsListCtrl* GetBtnsListCtrl() const { return static_cast<ButtonsListCtrl*>(m_bookctrl); }
+    void SetOverflowButton(wxWindow* button) { GetBtnsListCtrl()->SetOverflowButton(button); }
 
     int FindPageByName(const wxString& id) const
     {