Speed up inserting many items in sorted wxChoice in wxQt

Only sort the combobox once instead of doing it for every item.

See https://github.com/wxWidgets/wxWidgets/pull/1054

src/qt/choice.cpp

@@ -141,7 +141,28 @@ int wxChoice::DoInsertItems(const wxArrayStringsAdapter & items,
                   wxClientDataType type)
 {
     InvalidateBestSize();
+
+    // Hack: to avoid resorting the model many times in DoInsertOneItem(),
+    // which will be called for each item from DoInsertItemsInLoop(), reset the
+    // wxCB_SORT style if we have it temporarily and only sort once at the end.
+    bool wasSorted = false;
+    if ( IsSorted() )
+    {
+        wasSorted = true;
+        ToggleWindowStyle(wxCB_SORT);
+    }
+
     int n = DoInsertItemsInLoop(items, pos, clientData, type);
+
+    if ( wasSorted )
+    {
+        // Restore the flag turned off above.
+        ToggleWindowStyle(wxCB_SORT);
+
+        // And actually sort items now.
+        m_qtComboBox->model()->sort(0);
+    }
+
     return n;
 }