after idle<->0

package require Tk
label .l
frame .f
button .f.b
pack .l
pack .f
pack .f.b
puts 00:[winfo reqwidth .]
after 0 [list after idle "puts 0i:\[winfo reqwidth .\]"]
after idle [list after 0 "puts i0:\[winfo reqwidth .\]"]
# 00:200
# 0i:4      -- only label .l's reqwidth
# i0:28