Even at the low level, very little of the Windows GUI is hardware accelerated. The Windows cursor is probably the only part you see. Basically everything else is done by drawing into a frame buffer without any hardware support at all. There are a handful of low level graphics primitives that can be hardware accelerated, but few of these primitives are commonly used ones.

This is why the market for 2D video cards died, they had all put everything that Windows used in hardware, and had all reached the limit of resolution that anybody could actually use, and where all faster then Windows could keep up anyway. Thus price and odd ball features like TV-out became the only way to differentiate 2D video.

Part of the problem is that the Windows repaint architecture is very crude. It was designed for systems with very dumb video cards and very limited memory. Thus it doesn't try to do anything clever, nor is it setup to take advantage of any abilities that the hardware would provide.

When Windows first took off, there where actually special 2D video cards that had abilities that windows didn't use. The one I remember off the top of my head is that some video cards had build in hardware scrolling rather then the software level used by Windows even today.

Jay

There is some hardware acceleration, enough that having hardware acceleration was very important back when a high speed computer was a 486. But it does less then most people believe, it doesn't have real hardware scrolling or other advanced features and even the features it does have are often partially or stupidly implemented. There are hardware level line drawing and blitting routines, hardware cursors and font support, possibly other I can't remember.

You can see the lack of hardware scrolling by quickly scrolling a complex window up and down. If you computer is fast enough you may need to load it down a bit before you can see this effect. Right around the edge of the screen you can see Windows quickly draw in stuff. The background is solid, because that is hardware level blitting, but the higher level stuff is drawn on the screen by windows. With real hardware scrolling, Windows could draw into the section of the screen before scrolling it into view, so you would never get flicker around the edge of a scrollable windows.

You can see much the same effect by having multiple windows open and moving them around over top of each other. In a smarter system with better hardware support this wouldn't cause any flicker because each application would have their own virtual buffer space independent of each other.

Jay