Spec problem creating dynamci UIs

I'm probably doing this all wrong, but I have a problem creating a dynamic UI with Spec.

I want a small window which shows more information when a Show more details button is clicked.

Here's an example.



when I click Show More I want something like this (a bigger window with more fields):



But when I change the Spec layout the window size remains the same as it was set in initialExtent - so it does not display properly with the extra fields.



I can't find any way of rebuilding the window so that it shows the bigger layout properly.

Here's the spec for the basic window:

basicSpec
<spec: #default>
|row1|

row1 := SpecLayout composed
        newRow: [ :row |
                row
                        add: #label1;
                        add: #field1
        ] height: self inputTextHeight;
        yourself.

       

^SpecLayout composed
        newColumn:[:column|
                column add:row1; addSplitter; add:#btnMode height: self toolbarHeight ; addSplitter].

Here's the spec for the detailed window:

detailedSpec
<spec>
|row2 row3|

row2 := SpecLayout composed
        newRow: [ :row |
                row
                        add: #label2;
                        add: #field2
        ] height: self inputTextHeight  ;
        yourself.
       
row3 := SpecLayout composed
        newRow: [ :row |
                row
                        add: #label3;
                        add: #field3
        ] height: self inputTextHeight  ;
        yourself.

^SpecLayout composed
         newColumn: [ :column |
        column
                add: self basicSpec;
            add: row2;
        add:row3
    ];
    yourself.




Here's the code that switches Spec layouts:
initializePresenter
        super initializePresenter.
        btnMode action:  
                [ self needRebuild: false.
                 self label1 needRebuild: false.
                self field1 needRebuild: false.
                self btnMode needRebuild: false.
                                               
                self buildWithSpecLayout: self class detailedSpec. ]



Is this a problem in Spec or just me being stupid?

There is no way to tell to spec that this layout should automatically 

self extent: and self  window extent: do not work. First thing i tried.