MacOS: wxDataViewModel ItemsChanged() calls reloadItem: repeatedly (Issue #25972)

Will Cosgrove

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Nov 13, 2025, 1:58:07 PM (7 days ago) Nov 13

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willco007 created an issue (wxWidgets/wxWidgets#25972)

Description

When doing batch updating of a wxDataViewCtrl with a wxDataViewModel, using ItemsChanged to signal updates to existing items it is causing the macOS NSOutlineView to reload and resort on every item (calling reloadItem:). This is extremely slow and quickly overwhelms the main thread with a minimal amount of objects ~1500 causing hangs.

Bug description:

Using the batch update API ItemsChanged on wxDataViewModel triggers the NSOutlineView to reload the item (and possibly subitems) and redraw for each item in the array. This quickly overwhelms the OS control and effectively hangs the app.

bool wxOSXDataViewModelNotifier::ItemsChanged(wxDataViewItemArray const& items)
{
  size_t const noOfItems = items.GetCount();

  for (size_t indexItem=0; indexItem<noOfItems; ++indexItem)
    if (m_DataViewCtrlPtr->GetDataViewPeer()->Update(GetOwner()->GetParent(items[indexItem]),items[indexItem])) //This needs to change
    {
     // send for all changed items a wxWidgets event:
      wxDataViewEvent dataViewEvent(wxEVT_DATAVIEW_ITEM_VALUE_CHANGED,m_DataViewCtrlPtr,items[indexItem]);
      m_DataViewCtrlPtr->HandleWindowEvent(dataViewEvent);
    }
    else
      return false;
 // if this location is reached all items have been updated:
  AdjustRowHeights(items);
  AdjustAutosizedColumns();
 // done:
  return true;
}

Expected vs observed behaviour:

All items should be inserted into the model, then the control is resorted and redrawn one time after insertions are complete.

Stack trace:

Stacktrace.png (view on web)

Patch or snippet allowing to reproduce the problem:

Something like this:

wxDataViewItemArray itemsChanged;
....
for (_node in updatedNotes)
    itemsChanged.Add(_node);

ItemsChanged(itemsChanged);

Platform and version information

wxWidgets version you use: 3.3.1
wxWidgets port you use: wxOSX
OS and its version: macOS 26.1

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VZ

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Nov 13, 2025, 5:30:37 PM (7 days ago) Nov 13

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vadz left a comment (wxWidgets/wxWidgets#25972)

cc @hwiesmann who I believe originally wrote this code

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Will Cosgrove

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Nov 14, 2025, 2:55:55 PM (6 days ago) Nov 14

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willco007 left a comment (wxWidgets/wxWidgets#25972)

Looking at the code more, this is a tough one. I know my intention is to update multiple items with the same parent, thus only requiring the parent to be refreshed one time. However, the kit is trying to do something in a more generic manor which isn't wrong per se, but results in a major performance problem. Also, in some cases, refreshing the parent items would be the wrong choice, so changing this behavior to refresh just parent nodes isn't ideal either.

This leads me back to this comment. In some of these edge cases it would be useful to have the ability to turn off notifiers and then be able to turn them back on causing a full control refresh (or maybe just refreshing passed in items?) instead of trying to guess the users intention and getting it wrong like in this case.