1st right click - set channel, can't be changed after that.
Following right clicks displays touchscreen form.

Sent message as a table. Each command can be sent individually or as
indexes of a table to run as batch.


Clears the current form.
{
	command = "clear"
}


Adds elements to the form. The form is size[10,8]. The parameters are as
for formspec (see api docs). No version is specified.

{
	command = "realcoordinates",
	enabled = true or false
}

{
	command = "addimage",
	X = n,
	Y = n,
	W = n,
	H = n,
	texture_name = string
}

{
	command = "addfield",
	X = n,
	Y = n,
	W = n,
	H = n,
	name = string,
	label = string,
	default = string
}

{
	command = "addpwdfield",
	X = n,
	Y = n,
	W = n,
	H = n,
	name = string,
	label = string
}

{
	command = "addtextarea",
	X = n,
	Y = n,
	W = n,
	H = n,
	name = string,
	label = string,
	default = string
}

{
	command = "addlabel",
	X = n,
	Y = n,
	label = string
}

{
	command = "addvertlabel",
	X = n,
	Y = n,
	label = string
}

{
	command = "addbutton",
	X = n,
	Y = n,
	W = n,
	H = n,
	name = string,
	label = string
}

{
	command = "addbutton_exit",
	X = n,
	Y = n,
	W = n,
	H = n,
	name = string,
	label = string
}

{
	command = "addimage_button",
	X = n,
	Y = n,
	W = n,
	H = n,
	image = string,
	name = string,
	label = string
}

{
	command = "addimage_button_exit",
	X = n,
	Y = n,
	W = n,
	H = n,
	image = string,
	name = string,
	label = string
}

{
	command = "adddropdown",
	X = n,
	Y = n,
	W = n,
	H = n,
	name = string,
	selected_id = n,
	choices = { string [, string ... ] }
}

{
	command = "addtextlist",
	X = n,
	Y = n,
	W = n,
	H = n,
	transparent = true/false,
	name = string,
	selected_id = n,
	listelements = { string [, string ... ] }
}


If unlocked ignores protection.

{
	command = "lock"
}


{
	command = "locked"
}



When the touchscreen form is accessed a message is sent with the
touchscreen's channel with the 'fields' parameter from the on_receive_fields
handler, with an additional field 'clicker' with the name of the player
that accessed the form.