Adding Interactivity To A User Control

When developing a Graph User Control in Visual Basic 5 for a client, I was asked to provide a event on the control which would return the data index as the mouse moved across the control. As a graphical user control has only dumb line and print objects, there was no special event that I could use to provide this feature. So I created one using the following techniques.

In the user control, make a public event as follows

Public Event ucMouseMove()

Now add a MouseMove subroutine to the control

Private Sub UserControl_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)

Dim i As Integer

' Define which graph column the user is pointing at

GrafDataId = 0

For i = dataRowsMaxRows To 1 Step -1

Check the current position of the mouse against an array that holds the X axis positions of the different objects in the graph

If X > grafX(i) Then

' Set the plot indexes and raise the event that can be trapped by the control holding the user control

GrafDataId = i

RaiseEvent ucMouseMove

Exit Sub

End If

Next i

GrafDataId = 0

End Sub

Public Property Get GrafDataPos () As Variant

GrafDataPos = GrafDataId

End Property 

Private Sub myGraph1_ucMouseMove

' Find the current index of a bar in a graph by using the following code

MsgBox " Index " & myGraph1.GrafDataPos

End Sub

Where GrafDataPos is a property of the graph that holds the current position of the graph

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