Fix unwanted focus events when deleting a wxTreeCtrl item in wxMSW.

Disable setting focus in response to TVN_SELCHANGING when deleting an item in
a single selection control too -- this was already done in multi selection
case but not in this one, for some reason.

Also refactor the code to avoid duplicating TreeView_DeleteItem() calls.

Closes #15721.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75308 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/treectrl.h

@@ -304,6 +304,9 @@ private:
     // item visually spans the entire breadth of the window then
     bool MSWIsOnItem(unsigned flags) const;
 
+    // Delete the given item from the native control.
+    bool MSWDeleteItem(const wxTreeItemId& item);
+
 
     // the hash storing the items attributes (indexed by item ids)
     wxMapTreeAttr m_attrs;

src/msw/treectrl.cpp

@@ -1598,6 +1598,18 @@ wxTreeItemId wxTreeCtrl::DoInsertItem(const wxTreeItemId& parent,
     return DoInsertAfter(parent, idPrev, text, image, selectedImage, data);
 }
 
+bool wxTreeCtrl::MSWDeleteItem(const wxTreeItemId& item)
+{
+    TempSetter set(m_changingSelection);
+    if ( !TreeView_DeleteItem(GetHwnd(), HITEM(item)) )
+    {
+        wxLogLastError(wxT("TreeView_DeleteItem"));
+        return false;
+    }
+
+    return true;
+}
+
 void wxTreeCtrl::Delete(const wxTreeItemId& item)
 {
     // unlock tree selections on vista, without this the
@@ -1619,14 +1631,8 @@ void wxTreeCtrl::Delete(const wxTreeItemId& item)
             }
         }
 
-        {
-            TempSetter set(m_changingSelection);
-            if ( !TreeView_DeleteItem(GetHwnd(), HITEM(item)) )
-            {
-                wxLogLastError(wxT("TreeView_DeleteItem"));
-                return;
-            }
-        }
+        if ( !MSWDeleteItem(item) )
+            return;
 
         if ( !selected )
         {
@@ -1657,10 +1663,7 @@ void wxTreeCtrl::Delete(const wxTreeItemId& item)
     }
     else
     {
-        if ( !TreeView_DeleteItem(GetHwnd(), HITEM(item)) )
-        {
-            wxLogLastError(wxT("TreeView_DeleteItem"));
-        }
+        MSWDeleteItem(item);
     }
 }