Update to Original Picom

This adds support for desktop switching animations by keeping track of _NET_CURRENT_DESKTOP atom on the root window. 

As far as I understand this atom is set by window managers and so if it changes we can know that it's a desktop switch happening. Unfortunately window manager may need to set this BEFORE hiding/showing windows so we can animate correctly, me personally using FluxBox and this quick change pijulius/fluxbox@83ee4db  makes it work just fine.

It adds the following animation triggers:
* workspace-out
* workspace-out-inverse
* workspace-in
* workspace-in-inverse

Unfortunately had to add inverse variables too as you may navigate to the next workspace from for e.g. 1st to 2nd but you may also go to 2nd from 1st and in that case the animations have to be totally different.

Here is a config example for switching workspace:

animations = ({
    triggers = ["workspace-out"];
    offset-y = {
        timing = "0.2s cubic-bezier(0.21, 0.02, 0.76, 0.36)";
        start = "0";
        end = "-window-height";
    };
    shadow-offset-y = "offset-y";
    opacity = {
        timing = "0.2s linear";
        start = "window-raw-opacity-before";
        end = "window-raw-opacity";
    };
    blur-opacity = "opacity";
    shadow-opacity = "opacity";
},
{
    triggers = ["workspace-out-inverse"];
    offset-y = {
        timing = "0.2s cubic-bezier(0.21, 0.02, 0.76, 0.36)";
        start = "0";
        end = "window-height + window-y";
    };
    shadow-offset-y = "offset-y";
    opacity = {
        timing = "0.2s linear";
        start = "window-raw-opacity-before";
        end = "window-raw-opacity";
    };
    blur-opacity = "opacity";
    shadow-opacity = "opacity";
},
{
    triggers = ["workspace-in"];
    offset-y = {
        timing = "0.2s cubic-bezier(0.24, 0.64, 0.79, 0.98)";
        start = "window-height + window-y";
        end = "0";
    };
    shadow-offset-y = "offset-y";
    opacity = {
        timing = "0.2s linear";
        start = "0";
        end = "window-raw-opacity";
    };
    blur-opacity = "opacity";
    shadow-opacity = "opacity";
},
{
    triggers = ["workspace-in-inverse"];
    offset-y = {
        timing = "0.2s cubic-bezier(0.24, 0.64, 0.79, 0.98)";
        start = "-window-height";
        end = "0";
    };
    shadow-offset-y = "offset-y";
    opacity = {
        timing = "0.2s linear";
        start = "0";
        end = "window-raw-opacity";
    };
    blur-opacity = "opacity";
    shadow-opacity = "opacity";
})

….conf

This adds the possibility to define the frame opacity but also include all colors in the window that match the frame color and make those also transparent. It even supports the possibility to define the tolerance for color difference between the frame and other parts of the window and make those or gradually more opaque or also transparent just like the frame.

NOTE: tested with flat window frame so not sure how it will work with gradient frames and also only added for GLX atm, lets see if it's interesting enough to be included in the core or otherwise will just keep it for myself.

It adds the following config options:

# Enable frame opacity for colors that match the frame
frame-opacity-for-same-colors = true;

# Tolerance for similar colors (0 exact match, 1 all colors, default 0.5)
frame-opacity-for-same-colors-constraint = 0.5;

# Make different colors opaque by a factor of x (default 5)
frame-opacity-for-same-colors-multiplier = 5;

and for them to work you will have to active frame opacity for e.g.
frame-opacity = 0.7;

With these options you can now have blurred transparent frame + menubar + toolbar or on popup like File Open have transparent window background but list of files be opaque and so on.

Tried to come up with better way to get the color of the frame and if I understood texelFetch correctly it should gather the correct pixel now and even exclude the border in case your windows have some.