Mission Control Hot Corners and Gestures don’t work

OS X Finder can easily clutter up with open application windows. Mission Control is a function of Mac OS X dedicated just to quickly find the right window again by temporarily resizing all windows to fit the screen.

App Exposé does the same, but with just the windows of the active application. Show Desktop speaks for itself. Launchpad shows all apps without the need to go to the applications folder. Dashboard can be used for all kinds of ‘widgets’ which I find convenient for the conversion of units, valuta and comparing time zones.

Mission Control Hot CornersActive Corners alias Hot Corners

All these functions can be triggered via the keyboard, mouse buttons, gestures or… hot corners. Hot corners are triggered by driving the cursor into the corners of the screen. This is also a nice option if you don’t use a single-button mouse or can’t remember other ways to trigger Mission Control and the like.  You can find Active Screen Corners or Hot Corners via the System Preferences / Mission Control / Hot Corners button.

When Hot Corners and Gestures don’t work

Except when Hot Corners and Gestures don’t work. This happend to me on one Mac, while the other with a very similar setup didn’t have this problem. First I tried to fix it by more or less common ways to reset preferences:

  • Logging out and in the user account
  • Restarting the Finder, then the whole Mac
  • Repairing rights while starting up from another partition
  • Changing Hot Corners settings
  • Changing Mission Control settings
  • Deleting the ./Library/Preferences/com.apple.dock.plist so it would be re-created
  • Resetting the RMC and PRAM

None of these actions helped me to get Hot Corners or Gestures to trigger Mission Control, Exposé or Show Desktop again. Symptoms were:

  • Mission Control didn’t work at all.
  • Hot Corners didn’t work, except for the Screensaver option.
  • I especially missed the Show Desktop and
  • Spaces had quirks: I could get back to the main screen / first Desktop (Space) with CMD-1, but going back to the full screen application only worked with a 4-finger horizontal swipe.
  • Function keys for App Exposé and Launchpad would only work when set on certain Function keys.

I noticed Hot Corners worked fine with a different user account that I created just for testing purposes. Now I knew it had to be a problem with this specific user account. However, I didn’t feel much for migrating my complete user account just for this.

A year past and meanwhile I had updated to OS X 10.11 Yosemite, but this also didn’t fix it.

Get Mission Control to work again

Then I found the solution to get Mission Control to work again and Hot Corners in the proces. I found that the file responsible is com.apple.dock.plist which sits in ~/Library/Preferences. In this file exists an entry to enable/disable mission control.

  • Go to the Terminal app
  • Type or copy: defaults write com.apple.dock mcx-expose-disabled -bool FALSE to activate the mission control function.
  • Then type: killall Dock to stop the Dock that will then automatically be restarted. Only then the Exposé activation will take effect.

I have no clue how or why Exposé was disabled, but this got Exposé working again. Hot Corners and more specifically the active corners for Dashboard and Show Desktop work again.