Tk - graphics toolkit module

include "tk.m";
tk:= load Tk Tk->PATH;

Tki: type ref Draw->Image;
Toplevel: adt
{
	id:	int;
	image:	Tki;
};
toplevel: fn(screen: ref Draw->Screen, arg: string)

: ref Toplevel;
intop: fn(screen: ref Draw->Screen, x, y: int)

: ref Toplevel;
namechan: fn(t: ref Toplevel, c: chan of string, n: string)

: string;
cmd: fn(t: ref Toplevel, arg: string): string;
mouse: fn(screen: ref Draw->Screen, x, y, button: int);
keyboard: fn(screen: ref Draw->Screen, key: int);
imageput: fn(t: ref Toplevel, name: string, i, m: Tki)

: string;
imageget: fn(t: ref Toplevel, name: string) 

: (Tki, Tki, string);

Description

The Tk module provides primitives for building user interfaces, based on Ousterhout's Tcl/Tk. The interface to the toolkit itself is primarily the passing of strings to and from the elements of the toolkit using the cmd function.

toplevel

toplevel: fn(screen: ref Draw->Screen, arg: string)

: ref Toplevel;

## returns nil on error.

The toplevel function, given an existing Screen (usually one inherited from the graphics Context; see Context - graphics environment in Chapter 11), creates a new window, called a Toplevel, under the control of the Limbo/Tk toolkit. The Toplevel is passed to the cmd and namechan functions to drive the widgets in the window. The arg parameter is a string containing creation options (such as -borderwidth 2) that are applied when creating the toplevel window.

cmd

cmd: fn(t: ref Toplevel, arg: string): string;

## returns string result from Limbo/Tk command.

The cmd function passes command strings to the widgets in the Toplevel t and returns the string resulting from their execution. For example, given a canvas .c in the Toplevel t,

	x:= int tk->cmd (t, ".c cget -actx");

returns the integer x coordinate of the canvas.

namechan

namechan: fn(t: ref Toplevel, c: chan of string, n: string)

: string;

## returns empty string on success; error message on 
failure.

Bindings can be created in a Toplevel that trigger strings to be sent on Limbo channels. Such channels must be declared to the Tk module using namechan. The following example creates a button that sends the word Ouch when it is pressed:

hitchannel:= chan of string;
tk->namechan(t, hitchannel, "channel");
tk->cmd(t, "button.b.Hit -text Hit -command {send channel
        Ouch}");
expl:= <-hitchannel; # will see "Ouch" when button pressed

mouse and keyboard

mouse: fn(screen: ref Draw->Screen, x, y, button: int);
keyboard: fn(screen: ref Draw->Screen, key: int);

The mouse and keyboard functions deliver mouse and keyboard events to Limbo/Tk for delivery to widgets. They are usually called only by the Window Manager.

Caveat

Because Limbo/Tk input is handled globally, there can be only one instance of a Limbo/Tk implementation on a given machine or a given emulator.