Fix selection after inserting items in wxListBox in wxOSX

We need to adjust the indices of the currently selected items as we need
to keep the same items, not the same indices, selected after new items
insertion.

Closes #18902.

include/wx/osx/listbox.h

@@ -170,6 +170,8 @@ protected:
     wxArrayPtrVoid m_itemsClientData;
 
 private:
+    // Mostly the same as DoSetSelection() but doesn't call EnsureVisible().
+    void DoSetSelectionWithoutEnsureVisible(int n, bool select);
 
     wxDECLARE_DYNAMIC_CLASS(wxListBox);
     wxDECLARE_EVENT_TABLE();

src/osx/listbox_osx.cpp

@@ -191,6 +191,14 @@ void wxListBox::DoSetSelection(int n, bool select)
     wxCHECK_RET( n == wxNOT_FOUND || IsValid(n),
         wxT("invalid index in wxListBox::SetSelection") );
 
+    DoSetSelectionWithoutEnsureVisible(n, select);
+
+    if (select)
+        EnsureVisible(n);
+}
+
+void wxListBox::DoSetSelectionWithoutEnsureVisible(int n, bool select)
+{
     m_blockEvents = true;
 
     if ( n == wxNOT_FOUND )
@@ -201,9 +209,6 @@ void wxListBox::DoSetSelection(int n, bool select)
     m_blockEvents = false;
 
     UpdateOldSelections();
-
-    if (select)
-        EnsureVisible(n);
 }
 
 bool wxListBox::IsSelected(int n) const
@@ -349,6 +354,23 @@ int wxListBox::DoInsertItems(const wxArrayStringsAdapter& items,
 {
     int idx = wxNOT_FOUND;
     unsigned int startpos = pos;
+    wxArrayInt selections;
+
+    if ( !IsSorted() )
+    {
+        if ( HasMultipleSelection() )
+        {
+            GetSelections(selections);
+        }
+        else
+        {
+            int sel = GetSelection();
+            if ( sel != wxNOT_FOUND )
+            {
+                selections.Add(sel);
+            }
+        }
+    }
 
     const unsigned int numItems = items.GetCount();
     for ( unsigned int i = 0; i < numItems; ++i )
@@ -367,6 +389,30 @@ int wxListBox::DoInsertItems(const wxArrayStringsAdapter& items,
 
     GetListPeer()->UpdateLineToEnd(startpos);
 
+    const size_t numSelections = selections.size();
+    for ( size_t i = 0; i < numSelections; ++i )
+    {
+        if ( startpos <= selections[i] )
+        {
+            if ( HasMultipleSelection() )
+            {
+                size_t j;
+
+                // Do not deselect item if it is to be selected below
+                for ( j = 0; j < numSelections; ++j )
+                {
+                    if ( selections[i] == selections[j] + numItems )
+                        break;
+                }
+
+                if ( j == numSelections )
+                    Deselect(selections[i]);
+            }
+
+            DoSetSelectionWithoutEnsureVisible(selections[i] + numItems, true);
+        }
+    }
+
     InvalidateBestSize();
 
     UpdateOldSelections();