public void RecordUndo(CanvasState state)
{
if (undostack.Count > 0 && undostack.Last.Equals(state))
{
return;
}
undostack.AddLast(state);
if (undostack.Count > 20)
{
undostack.RemoveFirst();
}
}
CanvasState MakeState(Rectangle area)
{
var sel = Selection;
_selection = area;
var r = new CanvasState()
{
data = Copy(),
area = area,
selection = sel,
};
_selection = sel;
return(r);
}
void ApplyState(CanvasState state)
{
_selection = state.area;
Paste(state.data, false);
Selection = state.selection;
}