Question

I am implementing a custom control which derives from ListView.

I would like for the final column to fill the remaining space (Quite a common task), I have gone about this via overriding the OnResize method:

     protected override void OnResize(EventArgs e)
    {
        base.OnResize(e);

        if (Columns.Count == 0)
            return;
        Columns[Columns.Count - 1].Width = -2; // -2 = Fill remaining space
    }

or via another method:

        protected override void OnResize(EventArgs e)
    {

        base.OnResize(e);

        if (!_autoFillLastColumn)
            return;

        if (Columns.Count == 0)
            return;

        int TotalWidth = 0;
        int i = 0;
        for (; i < Columns.Count - 1; i++)
        {
            TotalWidth += Columns[i].Width;
        }

        Columns[i].Width = this.DisplayRectangle.Width - TotalWidth;
    }

Edit:

This works fine until I dock the ListView into a parent container and resize via that control. Every second time the control size shrinks (IE, drag the the border one pixel), I get a scroll bar on the bottom which can’t move at all (not even one pixel).

The result of which is when I drag the size of the parent I am left with a flickering scroll bar in the ListView, and a 50% chance it will be there when the dragging stops.

Answer 1

ObjectListView (an open source wrapper around .NET WinForms ListView) allows this “expand-last-column-to-fill-available-space”. It’s actually more difficult to get right than it first appears — do not believe anyone who tells you otherwise 🙂

If you use ObjectListView, you get the solution to that problem — and several others — for free. But if you want to do all the work yourself, you’ll need to:

• use ClientSize instead of DisplayRectangle (as @zxpro has already said)
• use Layout event rather than Resize event.
• listen for ColumnResized event and do the same work
• not do the auto resizing in design mode — it gets very confusing.

The trickiest problem only appears when the window shrinks — the horizontal scroll bar flickers annoyingly and sometimes remains after the shrinking is finished. Which appears to be exactly what is happening in your case.

The solution is to intercept the WM_WINDOWPOSCHANGING message and resize the ListView to what the new size is going to be.

protected override void WndProc(ref Message m) {
    switch (m.Msg) {
        case 0x46: // WM_WINDOWPOSCHANGING
            this.HandleWindowPosChanging(ref m);
            base.WndProc(ref m);
            break;
        default:
            base.WndProc(ref m);
            break;
    }
}

protected virtual void HandleWindowPosChanging(ref Message m) {
    const int SWP_NOSIZE = 1;

    NativeMethods.WINDOWPOS pos = (NativeMethods.WINDOWPOS)m.GetLParam(typeof(NativeMethods.WINDOWPOS));
    if ((pos.flags & SWP_NOSIZE) == 0) {
        if (pos.cx < this.Bounds.Width) // only when shrinking
            // pos.cx is the window width, not the client area width, so we have to subtract the border widths
            this.ResizeFreeSpaceFillingColumns(pos.cx - (this.Bounds.Width - this.ClientSize.Width));
    }
}