Add vicious.change_timer: a helper to change the timeout

This is useful in case you want to change the timeout value for a
registered widget, e.g. from the format callback function.

I am using this to have a shorter timeout interval for the temperature
widget when its value is above some threshold.

Signed-off-by: Daniel Hahler <git@thequod.de>

init.lua

@@ -352,5 +352,16 @@ function vicious.call_async(wtype, format, warg, callback)
 end
 -- }}}
 
+-- {{{ Change the timer of a registered widget.
+function vicious.change_timer(reg, timer_)
+  if not reg then return end
+  if timer_ ~= reg.timer then
+    vicious.unregister(nil, true, reg)
+    reg.timer = timer_
+    regregister(reg)
+  end
+end
+-- }}}
+
 return vicious
 -- }}}