Delphi support for Aero Glass and the DoubleBuffered property - what is going on and how do we use them?

Question

I am confused by Delphi 2009/2010 support for the Aero Theme Glass features in Windows, and by what, exactly DoubleBuffered means, and what it has to do with Aero glass. I

Answer 1

DoubleBuffered is a standard graphics technique used to reduce flicker. Basically, you draw a new version of your form on a second canvas then swap it for the current one. That swap is fast, even if the drawing process is slow. There's no direct relationship between that and Aero - you can use either or both independently. Double buffering has been around very a very long time in Delphi, but now we have a lot more processor cycles per screen refresh it's less necessary. Which may be why you haven't heard of it.

Double buffering is something you should only use reactively - if you see flicker when your app is repainting the screen turn it on and see what happens. In that case though your first recourse would be DisableUpdates/EnableUpdates (see the Delphi help for those) and the Windows API LockWindowUpdate (ditto).

ParentDoubleBuffered, like most Parent... properties, tells you whether this form will use the DoubleBuffered property from its parent. This lets you set the property once on your app main form and have it affect every form you create. Or not, if you set that property to false.

This is a typical situation when you have backward compatible code - there's things in there that are rarely used today but still work (and are sometimes still necessary), even though most people never need to worry about them. For most people they're just there and you can ignore them, but for some of us they're desperately necessary (we have a couple of really, really complex forms that we redraw in occasionally complex patterns to stop the flickering)