What does "Increase Contrast" option change? Many forums say, that enabling Increase Contrast option in Accessibility Preferences helps Yosemite to make the animations, like entering Mission Control to be much smoother. This is also consistent with my experience.

Increase Contrast off: https://www.youtube.com/watch?v=ctOj1U4OZio&amp;index=3&amp;list=PLsZWReFinrU5GLvs7ILwGvAVTICcjLhTD

Increase Contrast on: https://www.youtube.com/watch?v=BNac3VPZDKI&amp;index=2&amp;list=PLsZWReFinrU5GLvs7ILwGvAVTICcjLhTD

What I am interested in, debugging what causes the general slowness of Yosemite interface. It is clear, that at least one of the reasons is canceled when I turn Increase Contrast on. Common sense says, that Increase Contrast turns on Reduce Transparency option too, so it might be the reason, because calculating the transparency of the semi-transparent layers is a hard thing to do. This is not the case, because enabling Reduce Transparency only has no effect on the speed at all.

So the question is: what does Increase Contrast switch? Some GPU parameters? Less textures? Using other rendering algorithms? Something has to be.
I can't comment specifically on the Contrast setting, however there are various defaults you can enable from the terminal that will speed things up - specifically window "show" delays.

Browse some of these scripts:


https://gist.github.com/brandonb927/3195465
https://gist.github.com/maxfenton/c5a316f4254d27b18cf3


You will find various commands to reduce the delay between showing windows, 

Example:

To speed up mission control you could do:

defaults write com.apple.dock expose-animation-duration -float 0.1
killall Dock


This will reduce the animation delay to .1 second before showing mission control

Its possible some of these settings get tweaked when you go into enhanced contrast mode.