Overlay

[Luugi Marsan]

Hello,

I've been going through how Xserver implements Overlay. I still find information on this very limited. So I'm hoping that this thread will enlighten me more about this.

First of all the Chips and Technologies driver implements overlay using 2 different framebuffers. Unfortunatly I can't get my hands on one to see how it works. But here's my questions:

Let's say you have 2 different visuals. One PseudoColor and one TrueColor. You have an application that runs only in PseudoColor. As I understand the 8 bit app will be drawn on the overlay surface. I need to confirm on how does it know where to draw itself. For example, when I move the window with a border that is TrueColor. How does it get updated? How does it know where to display the overlay surface?

The color key concept is confusing for me. For example: the driver has index 255 to be the color key. What does that mean for an 8 bit app? Anything with color index 255 will be transparent? Or does that mean that anything with that color index will be visible?

There's overlay for diplaying an 8 bit app on a 24 bit surface. But there's also overlay when you want draw something over something you don't want to destroy. By reserving color cells for overlay.It doesn't seem the same kind of overlay.


Luugi

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