bring About and Pref window to front
tansparency -> opacity
add "_window" to gentle delegate
implements autohide window
define hotkey code
bug fix
del unused file
implements history(alpha)
history limit 5
del message shadow
delete message shadow in transpalent img
change timing hasshadow validator
delete tabs
press arrow key to move window.
bug fixed about mem leaks
change thumb height
add close button
update tracking area when resized
bug fix: remove close icon shadow
refactoring