Visualization of calendar events. Algorithm to layout events with maximum width

Question

I need your help with an algorithm (it will be developed on client side with javascript, but doesn\'t really matter, I\'m mostly interested in the algorithm itself) laying o

Answer 1

1. Think of an unlimited grid with just a left edge.
2. Each event is one cell wide, and the height and vertical position is fixed based on starting and ending times.
3. Try to place each event in a column as far left as possible, without it intersecting any earlier event in that column.
4. Then, when each connected group of events is placed, their actual widths will be 1/n of the maximum number of columns used by the group.
5. You could also expand the events at the far left and right to use up any remaining space.

/// Pick the left and right positions of each event, such that there are no overlap.
/// Step 3 in the algorithm.
void LayoutEvents(IEnumerable events)
{
    var columns = new List>();
    DateTime? lastEventEnding = null;
    foreach (var ev in events.OrderBy(ev => ev.Start).ThenBy(ev => ev.End))
    {
        if (ev.Start >= lastEventEnding)
        {
            PackEvents(columns);
            columns.Clear();
            lastEventEnding = null;
        }
        bool placed = false;
        foreach (var col in columns)
        {
            if (!col.Last().CollidesWith(ev))
            {
                col.Add(ev);
                placed = true;
                break;
            }
        }
        if (!placed)
        {
            columns.Add(new List { ev });
        }
        if (lastEventEnding == null || ev.End > lastEventEnding.Value)
        {
            lastEventEnding = ev.End;
        }
    }
    if (columns.Count > 0)
    {
        PackEvents(columns);
    }
}

/// Set the left and right positions for each event in the connected group.
/// Step 4 in the algorithm.
void PackEvents(List> columns)
{
    float numColumns = columns.Count;
    int iColumn = 0;
    foreach (var col in columns)
    {
        foreach (var ev in col)
        {
            int colSpan = ExpandEvent(ev, iColumn, columns);
            ev.Left = iColumn / numColumns;
            ev.Right = (iColumn + colSpan) / numColumns;
        }
        iColumn++;
    }
}

/// Checks how many columns the event can expand into, without colliding with
/// other events.
/// Step 5 in the algorithm.
int ExpandEvent(Event ev, int iColumn, List> columns)
{
    int colSpan = 1;
    foreach (var col in columns.Skip(iColumn + 1))
    {
        foreach (var ev1 in col)
        {
            if (ev1.CollidesWith(ev))
            {
                return colSpan;
            }
        }
        colSpan++;
    }
    return colSpan;
}

Edit: Now sorts the events, instead of assuming they is sorted.

Edit2: Now expands the events to the right, if there are enough space.