Session Range Box

Annotations placed on the bars, in groups, updated in realtime.

Source: src/Annotations/SessionRangeBox.cs · Calculated on: desktop or server

A box around the high and the low of every session, with its size in ticks written on it.

What it shows

• Creating annotations and adding them to a group.
• Absolute coordinates: bars on X, prices on Y.
• Two groups, one per kind of annotation.
• Updating the annotation of the session in progress, removing the old ones.

Groups

A group holds annotations or other groups, not both. The boxes and the labels get a group each, inside the group of the indicator:

public override void OnLoad()
{
    sessions.Clear();
    boxes = VAn.CreateAnnGroup();
    labels = VAn.CreateAnnGroup();
    IndVars.Ann_List.AddGroup(boxes);
    IndVars.Ann_List.AddGroup(labels);
}

Placing a box on the bars

// The bar of index i is at i + 1, and it is one unit wide
session.Box.X = session.FirstIndex + 0.5;
session.Box.X2 = lastIndex + 1.5;
session.Box.Y = session.High;
session.Box.Y2 = session.Low;

The same method is called when the session starts and every time it grows: setting an annotation again is how it is updated.

Limiting what is drawn

if (sessions.Count > MaxSessions)
{
    var oldest = sessions[0];
    boxes.RemoveAnnotation(oldest.Box);
    // ...
}

Without a limit, a chart with years of history would hold thousands of annotations nobody looks at.

Things to notice

• A new session is detected with bar.IsNewDay, which follows the session times of the chart.
• The indicator keeps its own list of sessions and clears it in OnLoad: the chart empties the groups before every calculation, but not your fields.

Try

• Draw the middle of the range as a Line limited to the session.
• Color the box by whether the session closed above or below its open.