Question

I have a Windows Forms application which is using a FlowLayoutPanel control to display a Picture boxes that are built dynamically. I have enabled the drag drop effect as they may want to reorder them, this works fine with only a few picture boxes (right now the screen shows about 6) but if there are more you try to drag an item below the control it will not scroll, so you cannot put an image that is currently on the screen (say image 4) to an image that is below what is visible (say image 13).

I have seen several posts where the ScrollControllIntoViewMethod should be used, I have tried in a few spots unsuccessfully.

Thanks!

Answer 1

Here is what I ended up doing.

Create the event on the DragLeave event
Getting the position of the control
Calculating the height of the control to get the lower boundary.
check the mouse position and if above the bounds, change the vertical scroll (or horizontal scroll) by a value in a Constant..

private void thumbFlow_DragLeave(object sender, EventArgs e)
{
    int BegY_ThumbFlow = this.thumbFlow.FindForm().PointToClient(this.thumbFlow.Parent.PointToScreen(this.thumbFlow.Location)).Y;
    int thumbFlowBound_Y = this.thumbFlow.Height + BegY_ThumbFlow;
    int mouseY = this.thumbFlow.FindForm().PointToClient(MousePosition).Y;

    while (mouseY >= thumbFlowBound_Y)
    {
        thumbFlow.VerticalScroll.Value = thumbFlow.VerticalScroll.Value + DRAG_DROP_SCROLL_AMT;
        mouseY = thumbFlow.FindForm().PointToClient(MousePosition).Y;
        thumbFlow.Refresh();
    }

    while (mouseY <= BegY_ThumbFlow)
    {
        thumbFlow.VerticalScroll.Value = thumbFlow.VerticalScroll.Value - DRAG_DROP_SCROLL_AMT;
        mouseY = thumbFlow.FindForm().PointToClient(MousePosition).Y;
        thumbFlow.Refresh();
    }
}

Hope this helps others.