direct access to frame buffer


I’m a newbie.
Happy new year to everybody.
Wireless Keyboards, such as Logitech’s LX710, doesn’t have “Num Lock”, “Caps Lock”, and “Scroll Lock” lights on the keyboard itself. Instead, when the user presses one of those buttons, a corresponding message such as “Num Lock On” or “Caps Lock On”, appears on the lower part of the display. I asked someone how do they (logitech) do this? he replied that it looks like the logitech application directly writes to the frame buffer but he doesn’t know how to access frame buffer.

My final goal is

  1. read the frame buffer right before it is sent to the display,
  2. perform pixel relocation, such as mirroring (of course, what i’m trying to do is more complex than mirroring)
  3. write back to the frame buffer

Does any one know how this technique(??) called?
Does any can answer where I can find some related information about this, such as example code, books, and etc.

Thank you very much.


On Linux it’s easy. Here’s a thread on doing it in Windows:

But I seriously doubt Logitech is writing straight to the framebuffer instead of using an OS API. That’s a crazy approach.

Dear Kim,

I also studying how to access the framebuffer at MS-windows recently, but I still don’t know how to write date to framebuffer now.
But for your requirement, this article may be helpful to you.