Question

When dynamically changing the size of the elements within a wxNotebook (e.g. hiding a button), the size of the whole notebook element is not updated. This can leave white space or prevent some elements from being shown.

Normally, a call to the parent window’s Fit() or FitInside() should do the trick, but doesn’t for the notebook. How can we resize it?

Minimal example demonstrating the problem:

#include <wx/wx.h>
#include <wx/gbsizer.h>
#include <wx/notebook.h>

const int HIDEME_ID = 512, SHOWME_ID = 513;

class MyApp: public wxApp
{
    wxButton* hideme;
    wxSizer* panel_sizer, *frame_sizer, *sw_sizer;
    wxScrolledWindow* sw;
    wxNotebook* nb;

    void hide_button( wxCommandEvent& ) {
        hideme->Hide();
        relayout();
    }
    void relayout() {
        /* Insert layout code here */
    }
    void show_button( wxCommandEvent& ) {
        hideme->Show();
        relayout();
    }
    virtual bool OnInit() {
        wxFrame *frame = new wxFrame( NULL, wxID_ANY, _("Hello World"), wxPoint(50, 50), wxSize(450, 340) );
        frame_sizer = new wxBoxSizer( wxVERTICAL );
        frame->SetSizer( frame_sizer );

        sw = new wxScrolledWindow( frame, wxID_ANY );
        sw->SetScrollRate( 5, 5 );
        frame_sizer->Add( sw, 1, wxEXPAND );

        sw_sizer = new wxBoxSizer( wxVERTICAL );
        sw->SetSizer( sw_sizer );

        nb = new wxNotebook( sw, wxID_ANY );
        wxPanel* panel = new wxPanel( nb, wxID_ANY );
        nb->AddPage( panel, wxT("Tab1") );

        sw_sizer->Add( new wxButton( sw, wxID_ANY, _("Button1"), wxDefaultPosition, wxSize(200,200) ), 0, wxEXPAND );
        sw_sizer->Add( nb, 0, wxEXPAND );
        sw_sizer->Add( new wxButton( sw, wxID_ANY, _("Button3") ), 1, wxEXPAND );
        sw_sizer->Add( new wxButton( sw, wxID_ANY, _("Button4") ), 0, wxEXPAND );

        panel_sizer = new wxBoxSizer( wxVERTICAL );
        panel_sizer->Add( hideme = new wxButton(panel, HIDEME_ID, wxT("HideMe")), 0, wxEXPAND );
        hideme->Hide();
        panel_sizer->Add( new wxButton(panel, SHOWME_ID, wxT("ShowMe")), 0, wxEXPAND );
        panel->SetSizer( panel_sizer );

        frame->Show(true);
        SetTopWindow(frame);
        return true;
    }

    DECLARE_EVENT_TABLE();
};

BEGIN_EVENT_TABLE(MyApp, wxApp)
    EVT_BUTTON(HIDEME_ID, MyApp::hide_button)
    EVT_BUTTON(SHOWME_ID, MyApp::show_button)
END_EVENT_TABLE()


IMPLEMENT_APP( MyApp );

Answer 1

The somewhat surprising pitfall here is that, unlike many other windows, a wxNotebook caches its best size. We have to invalidate the cache before doing any layouting:

nb->InvalidateBestSize();
sw->FitInside();