diff --git a/include/wx/generic/collpaneg.h b/include/wx/generic/collpaneg.h
index 27f1e87a75..7ea14bb26c 100644
--- a/include/wx/generic/collpaneg.h
+++ b/include/wx/generic/collpaneg.h
@@ -73,7 +73,7 @@ public:
 
 protected:
     // overridden methods
-    virtual wxSize DoGetBestSize() const wxOVERRIDE;
+    virtual wxSize DoGetBestClientSize() const wxOVERRIDE;
 
     int GetBorder() const;
 
diff --git a/src/generic/collheaderctrlg.cpp b/src/generic/collheaderctrlg.cpp
index ac5527a312..7d0d2cd034 100644
--- a/src/generic/collheaderctrlg.cpp
+++ b/src/generic/collheaderctrlg.cpp
@@ -77,17 +77,28 @@ bool wxGenericCollapsibleHeaderCtrl::Create(wxWindow *parent,
 
 wxSize wxGenericCollapsibleHeaderCtrl::DoGetBestClientSize() const
 {
-    wxClientDC dc(const_cast<wxGenericCollapsibleHeaderCtrl*>(this));
-    wxSize btnSize = wxRendererNative::Get().GetCollapseButtonSize(const_cast<wxGenericCollapsibleHeaderCtrl*>(this), dc);
+    wxGenericCollapsibleHeaderCtrl* const
+        self = const_cast<wxGenericCollapsibleHeaderCtrl*>(this);
+
+    // The code here parallels that of OnPaint() -- except without drawing.
+    wxClientDC dc(self);
+
+    wxSize size = wxRendererNative::Get().GetCollapseButtonSize(self, dc);
+
     wxString text;
     wxControl::FindAccelIndex(GetLabel(), &text);
-    wxSize textSize = dc.GetTextExtent(text);
-    // Add some padding if the label is not empty
-    if ( textSize.x > 0 )
-        textSize.x += FromDIP(4);
 
-    return wxSize(btnSize.x + textSize.x,
-        wxMax(textSize.y, btnSize.y));
+    const wxSize textSize = dc.GetTextExtent(text);
+
+    size.x += FromDIP(2) + textSize.x;
+    if ( textSize.y > size.y )
+        size.y = textSize.y;
+
+#ifdef __WXMSW__
+    size.IncBy(1);
+#endif // __WXMSW__
+
+    return size;
 }
 
 void wxGenericCollapsibleHeaderCtrl::SetCollapsed(bool collapsed)
diff --git a/src/generic/collpaneg.cpp b/src/generic/collpaneg.cpp
index 6a7a17af4d..5c570df37a 100644
--- a/src/generic/collpaneg.cpp
+++ b/src/generic/collpaneg.cpp
@@ -84,8 +84,7 @@ bool wxGenericCollapsiblePane::Create(wxWindow *parent,
     m_pButton = new wxCollapsibleHeaderCtrl(this, wxID_ANY, label, wxPoint(0, 0),
                              wxDefaultSize);
 
-    // on other platforms we put the static line and the button horizontally
-    m_sz->Add(m_pButton, 0, wxLEFT|wxTOP|wxBOTTOM, GetBorder());
+    m_sz->Add(m_pButton, wxSizerFlags().Border(wxALL, GetBorder()));
 
     // FIXME: at least under wxGTK1 the background is black if we don't do
     //        this, no idea why...
@@ -112,7 +111,7 @@ wxGenericCollapsiblePane::~wxGenericCollapsiblePane()
     wxDELETE(m_sz);
 }
 
-wxSize wxGenericCollapsiblePane::DoGetBestSize() const
+wxSize wxGenericCollapsiblePane::DoGetBestClientSize() const
 {
     // NB: do not use GetSize() but rather GetMinSize()
     wxSize sz = m_sz->GetMinSize();
diff --git a/src/osx/dataview_osx.cpp b/src/osx/dataview_osx.cpp
index 60e57b70f2..ee20e3bfaf 100644
--- a/src/osx/dataview_osx.cpp
+++ b/src/osx/dataview_osx.cpp
@@ -220,7 +220,15 @@ bool wxOSXDataViewModelNotifier::ValueChanged(wxDataViewItem const& item, unsign
 
 bool wxOSXDataViewModelNotifier::Cleared()
 {
-  return m_DataViewCtrlPtr->GetDataViewPeer()->Reload();
+  // As when individual items are deleted, we must ensure that we don't touch
+  // the model item possibly being edited, as it's not valid any more.
+  m_DataViewCtrlPtr->SetDeleting(true);
+
+  const bool rc = m_DataViewCtrlPtr->GetDataViewPeer()->Reload();
+
+  m_DataViewCtrlPtr->SetDeleting(false);
+
+  return rc;
 }
 
 void wxOSXDataViewModelNotifier::Resort()