Moving a picturebox with a timer

Question

Hi,

I'm trying to move a picturebox in a containing control by changing its Top and Left properties every 20ms. On a black background it's a bit smoother but when assigning a BackgroundImage to the control, the picturebox leaves a trail behind it until the control is redrawn a few seconds later, slows down abruptly then launches forward, or moves in a jagged trajectory.

I think when the PictureBox control is redrawn, the thread that changes its left and top properties is halted until redrawn is complete and that causes it to queue up any iterations of the timer loop that were held up, when the redraw is complete.

Is there anyway to smoothen up the picturebox's movement?

Thanks F

Answer 1

I don't know exactly how to resolve the problem (other than switching to WPF) but I can say the lag you're getting is coming from the invalidation of the areas that are being updated as you move the PictureBox. What you want to do is somehow back-buffer the new position and switch to the buffer, rather than relying on GDI to do the redraw in realtime. HTH.

Answer 2

I'd suggest drawing an image in one control as opposed to moving around controls.

Create a custom control, override OnPaint and draw your "picture box" inside there. If you do this you can also back buffer. Do this by calling Graphics.FromImage() to create a graphics object from an image. Paint onto that and finally call g.DrawImage on the REAL graphics object (in the eventArgs) once you're done drawing.