Repainting a GDBG while dragging

[Doug Lind]

I am trying to implement an OLE D&D on a GridDataBoundGrid. Everything is working great except for erasing the old drop target line. Per examples provided by you, I''ve come up with the following DragOver handler.

Private Sub gdbdOrders_DragOver(ByVal sender As Object, ByVal e As DragEventArgs) Handles gdbgOrders.DragOver
If draggingRows Then
Dim row As Integer, col As Integer
Dim pt As Point = New Point(e.X, e.Y)
pt = gdbgOrders.PointToClient(pt)
gdbgOrders.PointToRowCol(pt, row, col)

''Evaluate position and draw drop target
Dim cellBounds As Rectangle = New Rectangle(gdbgOrders.ViewLayout.ClientRowColToPoint(row, 0, GridCellSizeKind.ActualSize), New Size(gdbgOrders.GetColWidth(0), gdbgOrders.GetRowHeight(row)))

If Not (cellBounds.Equals(oldDropRect)) Then
Dim pt1 As Point
Dim pt2 As Point
Dim g As Graphics = gdbgOrders.CreateGridGraphics()
Dim p As Pen = New Pen(Color.FromArgb(100, Color.Blue), 6)
Dim py As Pen = New Pen(Color.FromArgb(100, Color.Yellow), 6)
If (Not oldDropRect.IsEmpty) Then

''''''This is what I am trying to use to clear the drop target line
''''''
''gdbgOrders.Invalidate(oldDropRect, True)
''gdbgOrders.Update()
''''''
''''''

''''''This is verifying that I have the correct coordinates in oldDropRect. It successfully overpaints the blue drop target
pt1 = New Point(oldDropRect.Left, oldDropRect.Top + 3)
pt2 = New Point(oldDropRect.Right, oldDropRect.Top + 3)
g.DrawLine(py, pt1, pt2)
py.Dispose()
End If
oldDropRect = cellBounds

pt1 = New Point(cellBounds.Left, cellBounds.Top + 3)
pt2 = New Point(cellBounds.Right, cellBounds.Top + 3)
''p.EndCap = LineCap.Flat
''p.EndCap = LineCap.DiamondAnchor
''p.StartCap = LineCap.DiamondAnchor
g.DrawLine(p, pt1, pt2)
g.Dispose()
p.Dispose()
dropTargetRow = row
End If

End If
End Sub

The example I followed was for a GridControl and worked as expected. The troublesome lines are:

It works for the GridControl but not a GDBG. The code that draws the yellow line was to validate that the oldDropRect had sane coordinates. I correctly overdraws the previous target.

I use ...
gdbgOrders.Invalidate()
gdbgOrders.Update()
... im DragDrop to successfully remove all target line from the grid.

Any ideas why it doesn''t work from DragOver? It''s interesting that I can draw graphics but not trigger a paint event to clear the old target.

Thanks,

Doug

[Administrator]

Just something to try. After this line,

gdbgOrders.Invalidate(oldDropRect, True)

try calling Application.DoEvents() to see if that will trigger the update.

[Doug Lind]

That didn''t work Clay. It paints one line and locks up. I believe it is due to this warning from Microsoft:

CAUTION Calling this method can cause code to be re-entered if a message raises an event.

Since I''m doing an invalidate, my guess is the handler is getting rentered. I tried just grid.refresh and grid.update with DoEvents and got the same result. DoEvents by itself does not cause the reentry so it must be the event being raise in conjunction with DoEvents.

I''m looking into getting the row header background color and drawing over the old target.

Any thing else you can think of to try?

Thanks, Doug

[Administrator]

Maybe the there is an open call to grid.BeginUpdate that is preventing the painting. So, maybe this will work.

if gdbgOrders.Updating Then gdbgOrders.CancelUpdate()
gdbgOrders.Invalidate(oldDropRect, True)
gdbgOrders.Update()