Q: Zoom (Accessibility feature) is extremely slow with multiple monitors [OSX 10.10]

I Have submitted a bug report to Apple pertaining to this problem.  I hope they will fix it soon as it is a very crucial feature for visually impaired people using a Mac.

The issue becomes apparent w/thunderbolt display.

Seems to behave similar to software acceleration on the video card

I too have the exact same issue.

Just filed radar 18931640

Same issue here using the following:

Model Name:    MacBook Pro

  Model Identifier:    MacBookPro11,3

  Processor Name:    Intel Core i7

  Processor Speed:    2.3 GHz

  Number of Processors:    1

  Total Number of Cores:    4

  L2 Cache (per Core):    256 KB

  L3 Cache:    6 MB

  Memory:    16 GB

  Boot ROM Version:    MBP112.0138.B11

--- V poor on Apple's behalf, my machine is hardly old and has plenty of processing power.

I'm having the issue to.

Add me to the list with this annoyingly slow zoom on my 2009 MacPro. I also have an issue where the screen looks like a mosaic when you grab a window and move it rapidly. I even tried updating the drivers for my Nvidia GeForce GT150 video card as Google search turned up a link to the Nvidia website that said it was needed for Yosemite and CUDA (I have never had to load OEM drivers for OS X before). After installing the driver and rebooting my Mac it seemed to fix the problem, but about an hour later the slowness was back.

i have it occuring here too

MBPr 650m

Zooming reduces overall fps to about 5fps

It's a little sporadic, but never gets better than maybe 10fps, and never gets noticeably worse than 5fps

Issue appeared after upgrading to Yosemite

Tested on another MBPr with 750m and can't recreate the issue (still smooth when zooming)

(note 750m and 650m are very similar, both 384 CUDA cores, just a bump in clock speed)

But we have different things installed.

Restarting tends to increase overall performance so haven't found it to specifically address this issue.

Haven't reported to Apple.

yep, after monitoring it for a while I can confirm that restart helps to at least bring performance to usable level, but then over time it gets worse and worse until I'm forced to restart again

restarting is normal right folks? I did it for ages with my PC and Windows! Actually, hold on a sec...

I guess the WindowServer Task is responsible for the performance issues. To improve responsiveness I deactivated the new transparency feature (Accessibility > Display > Less transparency). I also read about problems with third party system tools. Especially virus, cleaning, memory or tuning apps. Mac OS X does not need apps like this. Don´t install them at all.

Did what you said but it doesn't seem to help.  It still freezes sometimes when zoomed and moving around.

Same here, only I have no external display.  If I kill WindowServer (which forces me to log in again) I get much better zoom performance.

iMac (21.5-inch, Late 2013)

I have the same problem since upgrading to 10.10.

I am using the latest 15" retina macbook pro with SSD, and zoom makes its feel like an old 386 pc from the 90s.

it was working perfectly before the update, and happens on all monitor resolutions. This is one main feature i cannot live without. I hope its fixed asap.

It appears the new software update release 2014-11-17 seemed to fix this issue for me.

I turned off "Increase Contrast" + "Reduce Transparency" from System Preferences / Accessibility and still zooms smoothly.

Nope, the update mentioned above did not solve the problem for me.

10.10.1 did not fix the issue. Strange enough if i have a virtual machine in fullscreen and i have it in my primary window my external display wont lag, but if i switch from the Virtual Machine space to an OS X desktop space the lag will return.