Jonathan Laliberte :
AFAIK, there is no way to get the size of the main display with Applescript (not easily anyway). The current Finder block gets the size of the desktop, which is going to be the size of all connected displays. The following change would accomplish what you are asking for though:
At the top of the script, remove the Finder tell block:
tell application “Finder”
set _b to bounds of window of desktop
set screen_width to item 3 of _b
set screen_height to item 4 of _b
end tell
replace it with:
set screen_width to
set screen_height to
So, if your screen resolution is 1440×900, you would have
set screen_width to 1440
set screen_height to 900

After doing that, it works for me perfectly. Any windows placed anywhere on my three displays will all magically transport themselves to the screen that contains my dock.

FYI, I found this exact same script (verbatim) on another blog. http://www.leonamarant.com/2008/04/02/how-to-get-off-screen-windows-back-on-your-mac-os-x-v105/#comments

I’m not sure who the real author is, but that blog didn’t have the solution to modify the script for 3 displays, and the blog here did.

So thank you to the original author, whomever that may be. I’m very happy now.

tell application “System Events”

tell process “Safari”

repeat with x from 1 to (count windows)
set winPos to position of window x
set _x to item 1 of winPos
set _y to item 2 of winPos

if _x > 1920 then
name of window x
set position of window x to {_x – 1920, _y}
end if
end repeat

end tell
end tell

tell application “System Preferences”
set current pane to pane id “com.apple.preference.displays”
reveal (first anchor of current pane whose name is “displaysArrangementTab”)
tell application “System Events” to tell process “System Preferences”
set frontmost to true
click checkbox “Recopie vidéo” of group 1 of tab group 1 of front window
end tell
set current pane to pane id “com.apple.preference.displays”
reveal (first anchor of current pane whose name is “displaysArrangementTab”)
tell application “System Events” to tell process “System Preferences”
set frontmost to true
click checkbox “Recopie vidéo” of group 1 of tab group 1 of front window
end tell
end tell
property brightness_level : 0.0
tell application “System Preferences”
activate
set current pane to pane “com.apple.preference.displays”
tell application “System Events”
set value of slider 1 of group 2 of tab group 1 of window “LCD couleur” of process “System Preferences” to brightness_level
end tell
quit
end tell

Be sure to replace “LCD couleur” with “color LCD” and “Recopie vidéo” with “Mirror displays” for English language installations of MacOS.

The last 8 lines of code turn the laptop display brightness all the way down, as I like to do when I work with an external monitor. If you would rather keep the laptop monitor active, just delete those lines of code.

Enjoy!

This is a pretty slick idea. Could this idea be extended to iterate through all open applications, generically, and their child windows? In my case I am running Spaces (6 of them) and have work and projects setup up in each – not necessarily all the same all the time…

I will try it but I am not sure I am Applescript-savvy enough…

“can’t get bounds of window of desktop”

and it highlights the ‘bounds’ in the line:
set _b to bounds of window of desktop

can you help?

This would be for the situation where your MBP is connected with an external monitor with apps everywhere on both. Then you sleep your MBP, disconnect the external, and you decide you need to open it without the external connected. All your apps get shoved to the laptop screen – annoying but understandable. Then you sleep it again, come back to your external monitor and wake up your MBP. How to get all those apps (times how many ever Spaces you use…) back to the external monitor without moving them all manually?

Could there be a Restore Window Position script?