Question

happy holidays!

i have a tablelayoutpanel (10×10). within each cell i have a picturebox which are disabled (enabled = false).

i am trapping mouse move over the table to catch mouse movement. here is the code:

        private void tableLayoutPanelTest_MouseMove(object sender, MouseEventArgs e)
    {

        if (!placeShip)
        {
            c = tableLayoutPanelTest.GetControlFromPosition(homeLastPosition.Column, homeLastPosition.Row);

            if (c.GetType() == typeof(PictureBox))
            {
                PictureBox hover = new PictureBox();
                hover = (PictureBox)(c);
                hover.Image = Properties.Resources.water;
            }

            Point p = tableLayoutPanelTest.PointToClient(Control.MousePosition);
            Control picControl = tableLayoutPanelTest.GetChildAtPoint(p);


            if (picControl != null)
            {
                TableLayoutPanelCellPosition me = tableLayoutPanelTest.GetCellPosition(picControl);

                if (picControl.GetType() == typeof(PictureBox))
                {
                    PictureBox thisLocation = new PictureBox();
                    thisLocation = (PictureBox)(picControl);

                    thisLocation.Image = Properties.Resources.scan;
                    homeLastPosition = me;    
                }
            }
        }

        toolTipApp.SetToolTip(tableLayoutPanelTest, tableLayoutPanelTest.GetCellPosition(c).ToString());
    }

when i run this the tooTipApp starts consuming upto 56% of the CPU. so there is something wrong.

also the picturebox image changing code stops working for some reason.

any help is very welcome!

thank you.

Answer 1

A few thoughts:

• You’re creating another PictureBox called hover – why? This code doesn’t seem to do anything and it’s almost certainly going to slow the loop down. I think you meant to just declare hover and cast it from c, but you’re actually creating a new PictureBox instance and just throwing it away.
• You’re also never disposing of hover, as far as I can tell – so you end up allocating tons of memory and window handles. In general you should avoid creating new objects at all inside a MouseMove handler (small ones like hit tests are sometimes OK). As with the previous point – you probably didn’t mean to write the new PictureBox().
• You use PointToClient(Control.MousePosition) when the MouseMove event already gives you the control-specific mouse position (e.X and e.Y). This is costing you more time than it should.
• Probably the most important, you’re invoking SetToolTip on every MouseMove. You should only be invoking this when the tooltip has actually changed. You need to set a flag on which cell or control the tooltip was last displayed for, check for changes, then call SetToolTip.