How does Photoshop (Or drawing programs) blit?

Question

I'm getting ready to make a drawing application in Windows. I'm just wondering, do drawing programs have a memory bitmap which they lock, then set each pixel, then blit?

I don't understand how Photoshop can move entire layers without lag or flicker without using hardware acceleration. Also in a program like Expression Design, I could have 200 shapes and move them around all at once with no lag. I'm really wondering how this can be done without GPU help.

Also, I don't think super efficient algorithms could justify that?

Answer 1

Look at this question:

Reduce flicker with GDI+ and C++

All you can do about DC drawing without GPU is to reduce flickering. Anything else depends on the speed of filling your memory bitmap. And here you can use efficient algorithms, multithreading and whatever you need.