How to get the PID of every window of every process

This code works great. Please pay attention to "radio group 1" part. Took me several hours to figure that out. :-/

tell application "System Preferences"
    activate
    set current pane to pane id "com.noodlesoft.Hazel"
end tell
tell application "System Events"
    tell process "System Preferences"
        set frontmost to true
        click radio button "Info" of radio group 1 of window "Hazel"
        delay 1
        click button "Stop Hazel" of group 0 of group 0 of window "Hazel"
    end tell 
end tell

I'm looking to write a script which outputs a list of all the window titles of all the currently running programs.

The easy, one-liner method of achieving this in AppleScript is:

    tell application "System Events" to get the name of every window of ¬
        (every process whose background only is false)

Annoyingly, this returns a nested lists, which you'll either have to loop through in a repeat with block, or flatten the nest into a simple list (which isn't too hard).

Running AppleScript from the command line has the advantage that the returned data are in text format, which can be manipulated quite easily. You can even make use of the command line from within AppleScript to get the benefits of each:

    do shell script "osascript -e \" ¬
        set text item delimiters to tab
        tell app \\\"system events\\\" to get name of every window of ¬
            (every process whose background only is false)
        return the result as text \" | egrep -oi -e '[^\t]+'"

    return paragraphs of result

which returns a nice, straight forward, text list of window titles.

Finally, here's a formal AppleScript to get the job done properly, in a way that allows you to retain the ability to reference the window object if you need to get other properties or manipuoate it:

    use application "System Events"

    property R : {WindowTitle:missing value, AttachedToProcess:missing value}

    set WindowList to {}

    set P to a reference to (every process whose background only is false)

    repeat with proc in P
        set [proc] to proc
        set W to (a reference to every window of proc)

        repeat with _w in W
            set [_w] to _w

            copy R to end of WindowList
            tell last item of WindowList
                set its WindowTitle to title of _w
                set its AttachedToProcess to name of proc
            end tell
        end repeat
    end repeat

    return WindowList

The resulting list is a list of records that have the structure of property R. Each record represents a single window, which contains the window's title and the name of the process it belongs to, e.g. {WindowTitle:"Downloads", AttachedToProcess:"Finder"}. This way, it's easy to do things with the window, such as:

    set TheWindow to item 2 of WindowList --> {WindowTitle:"...", AttachedToProcess:"..."}

    tell process named (TheWindow's ProcName) to ¬
        tell window named (TheWindow's WindowTitle) to ¬
            set [focused, position, size] to [true, {0, 0}, {400, 777}]