Descriptive Problem Summary:

Some undo steps in the map editor don't repaint the view until something forces a full update.

Numbered Steps to Reproduce Problem:

1. Select an opaque turf in the palette. (The pencil tool will automatically be selected.)
2. Click and drag the mouse over the map to overdraw turfs with the choice from the palette.
3. Use the Undo command from the menu or Ctrl+Z.

Expected Results:

The original turfs should reappear.

Actual Results:

Nothing changes visually. However new drawing map cause the map to update.