Ensure that wxAuiNotebook center pane uses expected dock values

Avoid the wxAuiNotebook center pane having non-zero dock_layer,
dock_row, or dock_pos values as it doesn't make sense for it.

Closes #26679.

docs/changes.txt

@@ -145,6 +145,10 @@ Changes in behaviour not resulting in compilation errors
   wxTextDataObject, but for the code working with the raw bytes in this format
   you may need to change it to use wxConvUTF8 instead of wxConvLocal.
 
+- Creating central wxAUI pane window with non-zero layer, row or position
+  values was previously silently allowed but couldn't work correctly, so now
+  attempting to do it will assert. Don't set these values for the central pane.
+
 
 Changes in behaviour which may result in build errors
 -----------------------------------------------------

include/wx/aui/framemanager.h

@@ -243,9 +243,16 @@ public:
     wxAuiPaneInfo& Right() { dock_direction = wxAUI_DOCK_RIGHT; return *this; }
     wxAuiPaneInfo& Top() { dock_direction = wxAUI_DOCK_TOP; return *this; }
     wxAuiPaneInfo& Bottom() { dock_direction = wxAUI_DOCK_BOTTOM; return *this; }
-    wxAuiPaneInfo& Center() { dock_direction = wxAUI_DOCK_CENTER; return *this; }
-    wxAuiPaneInfo& Centre() { dock_direction = wxAUI_DOCK_CENTRE; return *this; }
-    wxAuiPaneInfo& Direction(int direction) { dock_direction = direction; return *this; }
+    wxAuiPaneInfo& Center() { dock_direction = wxAUI_DOCK_CENTER; return Layer(0).Row(0).Position(0); }
+    wxAuiPaneInfo& Centre() { dock_direction = wxAUI_DOCK_CENTRE; return Layer(0).Row(0).Position(0); }
+    wxAuiPaneInfo& Direction(int direction)
+    {
+        if (dock_direction == wxAUI_DOCK_CENTRE)
+            return Centre();
+
+        dock_direction = direction;
+        return *this;
+    }
     wxAuiPaneInfo& Layer(int layer) { dock_layer = layer; return *this; }
     wxAuiPaneInfo& Row(int row) { dock_row = row; return *this; }
     wxAuiPaneInfo& Position(int pos) { dock_pos = pos; return *this; }

src/aui/floatpane.cpp

@@ -85,8 +85,7 @@ void wxAuiFloatingFrame::SetPaneWindow(const wxAuiPaneInfo& pane)
     wxAuiPaneInfo contained_pane = pane;
     contained_pane.Dock().Center().Show().
                     CaptionVisible(false).
-                    PaneBorder(false).
-                    Layer(0).Row(0).Position(0);
+                    PaneBorder(false);
 
     // Carry over the minimum size
     wxSize pane_min_size = pane.window->GetMinSize();

src/aui/framemanager.cpp

@@ -532,6 +532,12 @@ static int PaneSortFunc(wxAuiPaneInfo** p1, wxAuiPaneInfo** p2)
 
 bool wxAuiPaneInfo::IsValid() const
 {
+    if ( dock_direction == wxAUI_DOCK_CENTRE &&
+        !(dock_layer == 0 && dock_row == 0 && dock_pos == 0) )
+    {
+        return false;
+    }
+
     // Should this RTTI and function call be rewritten as
     // sending a new event type to allow other window types
     // to check the pane settings?