====== Keypad Widget / Keypad Driver ======

The keypad widget and keypad driver allows use of common buttons like up, down, left, right, ok/confirm and cancel.  Added to CVS/SVN in Feb. 2006, the keypad code is still undergoing some development, and is only available on a couple of displays: [[:Crystalfontz|Crystalfontz]] 635, [[:LCD2USB|LCD2USB]] and [[:LW_ABP|LW_ABP]]. LCD4Linux-0.10.1-RC1 also supports [[:CwLinux]].

It's currently the only widget which doesn't make use of the //update// parameter.  Instead of using preset time intervals, updates are performed when the button is actually pressed or released.  At that time the expression is re-evaluated.  This allows you to [[:plugin_exec|execute some program]] (perhaps reboot?) or simply change the value of a variable which is used by another widget.

The mapping between keypad widgets and output lines is done in the //Layout// section: Just as you would place other widgets with //Row*.Col*// lines, you can map a keypad widget using a 'Keypad#' line.  Note that the '#' used is of little consequence, just make it unique from the other keys used in that same layout.

Here's the definition of a keypad widget:
<code>
Widget <name> {
    class      'Keypad'
    position   <confirm|cancel|up|down|left|right>
    state      <pressed|released>
    expression <string>
}
</code>


----

===== Parameters: =====

|**position**|what button is toggled, defaults to confirm|
|**state**|whether holding the button down or letting it go, defaults to pressed|
|**expression**|expression to evaluate on button toggle|

----

===== Example: =====

simple keypad example to increment a displayed variable:

<code>
Widget mytext {
    class 'Text'
    expression foo
    update 100
}

Widget keyok {
    class 'Keypad'
    position 'confirm'
    expression foo = foo + 1
}

Variable {
    foo 1
}

Layout demokeypad {
    Row1.Col1 'mytext'
    Keypad1 'keyok'
}
</code>


more sophisticated example to scroll thru dmesg output:

<code>
Widget dmesg1 {
    class 'Text'
    expression file::readline('/var/log/dmesg',currline)
    width 20
    update tick
}

Widget dmesg2 {
    class 'Text'
    expression file::readline('/var/log/dmesg',currline+1)
    width 20
    update tick
}

Widget dmesg3 {
    class 'Text'
    expression file::readline('/var/log/dmesg',currline+2)
    width 20
    update tick
}

Widget dmesg4 {
    class 'Text'
    expression file::readline('/var/log/dmesg',currline+3)
    width 20
    update tick
}

Widget keyup {
    class 'Keypad'
    position 'up'
    state 'pressed'
    expression currline = currline-1
}

Widget keydown {
    class 'Keypad'
    position 'down'
    state 'pressed'
    expression currline = currline+1
}

Layout showdmesg {
    Row1 {
        Col1 'dmesg1'
    }
    Row2 {
        Col1 'dmesg2'
    }
    Row3 {
        Col1 'dmesg3'
    }
    Row4 {
        Col1 'dmesg4'
    }
    Keypad1 'keyup'
    Keypad2 'keydown'
}

Variables {
    tick 100
    currline 1
}
</code>


an example to use with reboot confirm: (right arrow selects reboot, left arrow cancels, confirm reboots using exec)

<code>
widget keyRight{
        class 'Keypad'
        position 'right'
        state 'pressed'
        expression msg = 'Reboot? OK to confirm' ; rebootmenu = 1
}

widget keyConfirm{
        class 'Keypad'
        position 'confirm'
        state 'pressed'
        expression  msg = rebootmenu == 1 ? exec('/sbin/shutdown -r now',1000000) : 'Right arrow to reboot'
        exec('/sbin/shutdown -r now', 1000000);
}

widget keyLeft{
        class 'Keypad'
        position 'left'
        state 'pressed'
        expression msg = 'Right arrow to reboot' ; rebootmenu = 0
}

widget msgtxt {
        class 'Text'
        expression msg
        width 20
        update 100
}


Layout Default {
        Row1.Col1 'msgtxt'
	Row2.Col1 rebootmenu
        Keypad1 'keyRight'
        Keypad2 'keyConfirm'
        Keypad3 'keyLeft'
}


Variables {
   tick 500
   msg 'Right arrow to reboot'
   rebootmenu 0
}

</code>


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