OK Kidz, I've finally gotten it down pat.
The problem for me is that Marco is useless. It's very bare-bones and doesn't do desktop zoom. Compiz does. However, when you enable Compiz it's the dog's breakfast - nothing is set up by default and it's a complete disaster. You can't export the settings from Mint 10 and inhale them into Mint 13 because it's two different versions of Compiz and they're NOT compatible.
I *refuse* to do the hunt and peck rubbish to figure out what to enable and what not to.
So what to do?
Zorin OS.
Yup, another distro came to the rescue - they did the work that should have been done here.
I installed Zorin OS 6 in a VM and exported the Compiz settings using CCSM. Then I went to Mint 13 MATE and changed the default window manager from Marco to Compiz using mateconf-editor. Finally, I installed CCSM, ran it and imported the Zorin config file. Because they're both 12.04 and have the same version of Compiz installed, they match!
Voila! Compiz as the default window manager with intelligent settings AND Enhanced Desktop Zoom. CPU utilization on an AMD 4600 Dual Core (hoary with age!) oscillates between 2% and 6%. I'm guessing that on my Quad Core it won't even register.
Who knows, this solution might even make it into a point release of the LTS (it bloody well SHOULD!). I tried to upload the config file and attach it to this message but this board software isn't intelligent enough to like either .config or .txt files. so sadly, I cannot.
Now all I gotta do is get DocBarX working with MATE and decide which I prefer better: Mint 13 / MATE / Compiz or Zorin OS 6.
Cheery-Bye!


