Programming Markers
For More information, see Adding Markers.
Markers provide a way to identify a particular data element on the screen or a particular value in a plot.
On plots, area graphs and bar charts, two markers are defined: an X-marker and a Y-marker. The X-marker is a line perpendicular to the X-axis, and the Y-marker is a line perpendicular to the Y-axis.
On stacking bar charts, the X-marker is a short line drawn through one of the bar blocks, and the Y-marker is a line perpendicular to the Y-axis.
On pie charts, only the X-marker is defined, and is a line drawn from the center of the pie outward through the center of the selected slice.
In the 2D Chart control, the X- and Y-markers are represented by the Markerscollection, and are named “X” and “Y” respectively. To display a marker, set its IsShowing property:
Chart2D1.ChartArea.Markers("Y").IsShowing = True
Once the marker is displayed, it can be positioned. For example, the following code positions the Y-marker at the point where the mouse is currently located. As the mouse moves, the Y-marker moves with it.
Private Sub Chart2D1_MouseMove(Button As Integer, Shift As Integer, _
x As Single, y As Single)
Dim px As Long
Dim py As Long
Dim vx As Double
Dim vy As Double
px = x / Screen.TwipsPerPixelX ' Get the current mouse X position
py = y / Screen.TwipsPerPixelY ' Get the current mouse Y position
' Convert to chart coordinates
Chart2D1.ChartGroups(1).CoordToDataCoord px, py, vx, vy
' Set position of Y-marker
Chart2D1.ChartArea.Markers("Y").Value.y = vy
End Sub
This procedure positions the marker using chart coordinates. You can also position a marker by specifying a dataset and point through which the marker should be drawn. To do this, use the Index property instead of the Value property.
Performance Issues