Fix ribbon page layout wrong when scroll button is shown or hidden due to a scroll operation

See #17454

include/wx/ribbon/page.h

@@ -75,7 +75,7 @@ protected:
 
     bool ExpandPanels(wxOrientation direction, int maximum_amount);
     bool CollapsePanels(wxOrientation direction, int minimum_amount);
-    void ShowScrollButtons();
+    bool ShowScrollButtons();
     void HideScrollButtons();
 
     void CommonInit(const wxString& label, const wxBitmap& icon);

src/ribbon/page.cpp

@@ -338,7 +338,8 @@ bool wxRibbonPage::ScrollPixels(int pixels)
         child->SetPosition(wxPoint(x, y));
     }
 
-    ShowScrollButtons();
+    if (ShowScrollButtons())
+        DoActualLayout();
     Refresh();
     return true;
 }
@@ -788,7 +789,7 @@ void wxRibbonPage::HideScrollButtons()
     ShowScrollButtons();
 }
 
-void wxRibbonPage::ShowScrollButtons()
+bool wxRibbonPage::ShowScrollButtons()
 {
     bool show_left = true;
     bool show_right = true;
@@ -891,6 +892,8 @@ void wxRibbonPage::ShowScrollButtons()
     {
         wxDynamicCast(GetParent(), wxRibbonBar)->RepositionPage(this);
     }
+
+    return reposition;
 }
 
 static int GetSizeInOrientation(wxSize size, wxOrientation orientation)