Trigger Media events in Applescript?

Question

Hello,
I've been searching a lot on this and i cant for the life of me find how to trigger media events in Applescript.
I have found that i can tell specific applications to playpause like itunes for example, this is not what i want.
What im trying to do is make an applescript that behaves like the play/pause button that you can find on any Apple Keyboard when executed.
I imagined that this would be as simple as to tell System Events to trigger a media event, regretfully this does not work.
If anyone could shed some light on this i would greatly appreciate it!
Regards,
Jonathan

Answer 1

Hello
Some time ago I've written a rubycocoa code to post media key events. Here's an AppleScript wrapper for it.
Code is tested under 10.6.8. This won't work under 10.5.8. Don't know about later versions.
Regards,
H
PS. If you're just trying to keep iTunes from launching when PLAY_PAUSE key is pressed, this script is not what you need. The rcd daemon is the culprit to launch iTunes by that specific key and so you'd need to "fix" it by modifying its executable. There's a tried and true method to do it, which I myself has employed.
--post_media_key_events("MUTE", 1, 0, {})
--post_media_key_events("VOLUME_UP", 12, 0.01, {option down, shift down})
--post_media_key_events("VOLUME_DOWN", 12, 0.01, {option down, shift down})
post_media_key_events("PLAY_PAUSE", 1, 0, {})
on post_media_key_events(subtype, k, d, mods)
        string subytpe : event subtype name, one of the following -
                VOLUME_UP
                VOLUME_DOWN
                BRIGHTNESS_UP
                BRIGHTNESS_DOWN
                MUTE
                PLAY_PAUSE
                FORWARD
                REWIND
                ILLUMINATION_UP
                ILLUMINATION_DOWN
        integer k : number of key repeat
        number d : delay inserted after each key release [sec]
        list mods : any combination of the following enumerations
                shift down
                option down
                command down
                control down
                caps lock down
                * constants other than listed above are ignored
    set args to ""
    repeat with m in mods
        set m to m's contents
        if m = shift down then set args to args & space & "shift"
        if m = option down then set args to args & space & "option"
        if m = command down then set args to args & space & "command"
        if m = caps lock down then set args to args & space & "capslock"
    end repeat
    set args to subtype & space & k & space & d & space & args
    considering numeric strings
        if (system info)'s system version < "10.9" then
            set ruby to "/usr/bin/ruby"
        else
            set ruby to "/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby"
        end if
    end considering
    do shell script ruby & " <<'EOF' - " & args & "
require 'osx/cocoa'
include OSX
class AppDelegate < NSObject
    # event subtypes
    # cf. /System/Library/Frameworks/IOKit.framework/Versions/A/Headers/hidsystem/ev_keymap.h
    VOLUME_UP             = 0
    VOLUME_DOWN             = 1
    BRIGHTNESS_UP         = 2
    BRIGHTNESS_DOWN         = 3
    MUTE                 = 7
    PLAY_PAUSE             = 16
    FORWARD                = 19
    REWIND                 = 20
    ILLUMINATION_UP         = 21
    ILLUMINATION_DOWN    = 22
    # keyboard event
    # cf. /System/Library/Frameworks/IOKit.framework/Versions/A/Headers/hidsystem/IOLLEvent.h
    KEYDOWN                = 10
    KEYUP                = 11
    def initWithArguments(args)
        @subtype, @count, @delay, *@mods = args
        @count = @count.to_i
        @delay = @delay.to_f
        @mods = @mods.join(' ')
        self
    end
    def applicationDidFinishLaunching(notif)
        begin
            @win = NSWindow.alloc.objc_send(
                :initWithContentRect, NSMakeRect(0, 0, 600, 600),
                :styleMask, NSTitledWindowMask | NSClosableWindowMask | NSMiniaturizableWindowMask | NSResizableWindowMask,
                :backing, NSBackingStoreBuffered,
                :defer, false)
            @win.setLevel(NSStatusWindowLevel)
            @win.center
            if NSApp.respondsToSelector?('setActivationPolicy')                    # 10.6 or later only
                NSApp.setActivationPolicy(NSApplicationActivationPolicyRegular)
            end
            NSApp.activateIgnoringOtherApps(true)
            ev1 = createMediaKeyEvent(@win, @subtype, 'keydown', @mods)
            ev2 = createMediaKeyEvent(@win, @subtype, 'keyup', @mods)
            @count.times do
                postMediaKeyEvent(ev1)
                postMediaKeyEvent(ev2, @delay)
            end
        ensure
            NSApp.terminate(self)
        end
    end
    def applicationShouldTerminateAfterLastWindowClosed(app)
        true
    end
    def applicationShouldTerminate(sender)
        NSTerminateNow
    end
    def createMediaKeyEvent(win, subtype, keystate, modifiers = '')
        #    NSWindow win : target window device which receives the event
        #    uint16 subtype : event subtype for event type = NSSystemDefined
        #    string keystate : one of ['keydown', 'repeat', 'keyup']
        #    string modifiers : modifier key names (shift control option command capslock) separated by white space
        mtable = {
            'capslock'    => KCGEventFlagMaskAlphaShift,
            'shift'        => KCGEventFlagMaskShift,
            'control'    => KCGEventFlagMaskControl,
            'option'    => KCGEventFlagMaskAlternate,
            'command'    => KCGEventFlagMaskCommand,
        mflag = modifiers.split.inject(0) { |mflag, x| (m = mtable[x]) ? mflag | m : mflag }
        mflag |= KCGEventFlagMaskNonCoalesced
        kstate =
            case keystate
                when 'keydown'    then KEYDOWN << 8
                when 'keyup'    then KEYUP << 8
                when 'repeat'    then KEYDOWN << 8 | 1
                else 0
            end
        raise ArgumentError, %[invalid keystate : #{keystate}] if kstate == 0
        raise ArgumentError, %[unsupported media key event subtype : #{subtype}] unless
                VOLUME_UP,
                VOLUME_DOWN,
                BRIGHTNESS_UP,
                BRIGHTNESS_DOWN,
                MUTE,
                PLAY_PAUSE,
                FORWARD,
                REWIND,
                ILLUMINATION_UP,
                ILLUMINATION_DOWN,
            ].include?(subtype)
        data1 = subtype << 16 | kstate
        data2 = 0xffffffff
        event = NSEvent.objc_send(
            :otherEventWithType, NSSystemDefined,
            :location, NSMakePoint(0.0, 0.0),
            :modifierFlags, mflag,
            :timestamp, 0,
            :windowNumber, win.windowNumber,
            :context, win.graphicsContext,
            :subtype, 8,
            :data1, data1,
            :data2, data2)
        raise RuntimeError, %[failed to create event] unless event
        return event
    end
    def postMediaKeyEvent(event, delay = 0.0)
        CGEventPost(KCGHIDEventTap, event.CGEvent)
        sleep delay
    end
end
def main
    raise ArgumentError, %[Usage: #{File.basename($0)} subtype [count [delay [modifiers]]]] unless ARGV.length > 0
    begin
        s, k, d, *mods = ARGV
        subtype = AppDelegate.const_get(s.to_sym)
        k = k ? k.to_i : 1
        d = d ? d.to_f : 0.0
    rescue => ex
        $stderr.puts %[#{ex.class} : #{ex.message}]
        exit 1
    end
    args = [subtype, k, d] + mods
    app = NSApplication.sharedApplication
    delegate = AppDelegate.alloc.initWithArguments(args)
    app.setDelegate(delegate)
    app.run
end
if __FILE__ == $0
    main
end
EOF"
end post_media_key_events