GradientFill, but it comes up black

Trying to use GradientFill to paint a picturebox with a gradient from left to right, but it all comes up black.

Code:

VB Code:

Public Sub PaintMe( _
    ByVal x As Long, _
    ByVal y As Long, _
    Optional ByVal pfForceRepaint As Boolean = False _
)
'...
Dim lStartColour        As Long
Dim lEndColour          As Long
Dim tvxVertices(1)      As TRIVERTEX
Dim udtGradRect         As GRADIENT_RECT
 
    ' ...
 
        ' paint the background gradient
        lStartColour = GradientColorStart
        lEndColour = GradientColorEnd
 
        RGBToTriplex lStartColour, VarPtr(tvxVertices(0).Red), 2
 
        With tvxVertices(1)
            RGBToTriplex lEndColour, VarPtr(.Red), 2
 
            .x = picBkgd.ScaleWidth
            .y = picBkgd.ScaleHeight
        End With
 
        udtGradRect.LowerRight = 1
 
        GradientFill picBkgd.hDC, _
                     tvxVertices(0), _
                     2, _
                     udtGradRect, _
                     1, _
                     menmGradientDirection
 
    ' ...
 
End Sub

In case you're wondering (and this bit works):

VB Code:

Sub RGBToTriplex( _
    ByVal lRGB As Long, _
    ByVal lOutAddress As Long, _
    ByVal cbComponentSize As Long _
)
    RtlMoveMemory ByVal lOutAddress, ByVal VarPtr(lRGB), 1
    RtlMoveMemory ByVal lOutAddress + cbComponentSize, ByVal VarPtr(lRGB) + 1, 1
    RtlMoveMemory ByVal lOutAddress + 2 * cbComponentSize, ByVal VarPtr(lRGB) + 2, 1
End Sub

The snipped sections are unrelated to the drawing itself.

Anyone spot anything from the API call that I've missed?

Penegate:

I assume GradientColorStart and GradientColorEnd are properties and are globally or modually declared and the values are assigned outside of this proc.??

David

They return correct RGB values which are then correctly converted into 3 separate Integers by my RGBToTriplex sub. The coordinates are also correct. However all that is painted is blackness.