Allow modifying wxComboBox from its CLOSEUP handler with wxGTK2

Doing this resulted in GTK errors about invalid iterators, so postpone the
generation of the CLOSEUP event for slightly later to allow changing the
combobox contents from it with GTK+ 2 (this is not necessary with GTK+ 3).

Also add a demon of a dynamic combobox, creating and destroying its items on
the fly, to the widgets sample.

Closes #17223.

interface/wx/combobox.h

@@ -67,8 +67,7 @@
            Process a @c wxEVT_COMBOBOX_CLOSEUP event, which is generated
            when the list box of the combo box disappears (closes up). This
            event is only generated for the same platforms as
-           @c wxEVT_COMBOBOX_DROPDOWN above. Also note that only wxMSW and
+           @c wxEVT_COMBOBOX_DROPDOWN above.
-           wxOSX/Cocoa support adding or deleting items in this event.
     @endEventTable
 
     @library{wxcore}

samples/widgets/combobox.cpp

@@ -74,7 +74,8 @@ enum
     ComboPage_SetValue,
     ComboPage_SetValueText,
     ComboPage_Combo,
-    ComboPage_ContainerTests
+    ComboPage_ContainerTests,
+    ComboPage_Dynamic
 };
 
 // kinds of comboboxes
@@ -121,6 +122,8 @@ protected:
 
     void OnDropdown(wxCommandEvent& event);
     void OnCloseup(wxCommandEvent& event);
+    void OnPopup(wxCommandEvent &event);
+    void OnDismiss(wxCommandEvent &event);
     void OnComboBox(wxCommandEvent& event);
     void OnComboText(wxCommandEvent& event);
     void OnComboTextPasted(wxClipboardTextEvent& event);
@@ -155,7 +158,7 @@ protected:
                *m_chkProcessEnter;
 
     // the combobox itself and the sizer it is in
-    wxComboBox *m_combobox;
+    wxComboBox *m_combobox, *m_combobox1;
     wxSizer *m_sizerCombo;
 
     // the text entries for "Add/change string" and "Delete" buttons
@@ -380,6 +383,13 @@ void ComboboxWidgetsPage::CreateContent()
                                 0, NULL,
                                 0);
     sizerRight->Add(m_combobox, 0, wxGROW | wxALL, 5);
+    m_combobox1 = new wxComboBox( this, ComboPage_Dynamic );
+    m_combobox1->Append( "Dynamic ComboBox Test - Click me!" );
+    m_combobox1->SetSelection( 0 );
+    sizerRight->Add( 20, 20, 0, wxEXPAND, 0 );
+    sizerRight->Add( m_combobox1, 0, wxGROW | wxALL, 5 );
+    m_combobox1->Bind( wxEVT_COMBOBOX_DROPDOWN, &ComboboxWidgetsPage::OnPopup, this );
+    m_combobox1->Bind( wxEVT_COMBOBOX_CLOSEUP, &ComboboxWidgetsPage::OnDismiss, this );
     sizerRight->SetMinSize(150, 0);
     m_sizerCombo = sizerRight; // save it to modify it later
 
@@ -699,4 +709,24 @@ void ComboboxWidgetsPage::OnCloseup(wxCommandEvent& WXUNUSED(event))
     wxLogMessage(wxT("Combobox closed up"));
 }
 
+void ComboboxWidgetsPage::OnPopup(wxCommandEvent &WXUNUSED(event))
+{
+    m_combobox1->Clear();
+    m_combobox1->Append( "Selection 1" );
+    m_combobox1->Append( "Selection 2" );
+    m_combobox1->Append( "Selection 3" );
+    wxLogMessage("The number of items is %d", m_combobox1->GetCount());
+}
+
+void ComboboxWidgetsPage::OnDismiss(wxCommandEvent &WXUNUSED(event))
+{
+    if ( m_combobox1->GetSelection() == wxNOT_FOUND )
+    {
+        m_combobox1->Clear();
+        m_combobox1->Append( "Dynamic ComboBox Test - Click me!" );
+        m_combobox1->SetSelection( 0 );
+    }
+    wxLogMessage("The number of items is %d", m_combobox1->GetCount());
+}
+
 #endif // wxUSE_COMBOBOX

src/gtk/combobox.cpp

@@ -55,7 +55,19 @@ gtkcombobox_popupshown_callback(GObject *WXUNUSED(gobject),
                                   : wxEVT_COMBOBOX_CLOSEUP,
                           combo->GetId() );
     event.SetEventObject( combo );
-    combo->HandleWindowEvent( event );
+
+#ifndef __WXGTK3__
+    // Process the close up event once the combobox is already closed with GTK+
+    // 2, otherwise changing the combobox from its handler result in errors.
+    if ( !isShown )
+    {
+        combo->GetEventHandler()->AddPendingEvent( event );
+    }
+    else
+#endif // GTK+ < 3
+    {
+        combo->HandleWindowEvent( event );
+    }
 }
 
 }