/* tk_examp.q: simple example using the Tcl/Tk interface */

include tk;

/* This tiny sample Q-Tk application allows you to evaluate Q expressions in a
   Tk window. */

private init_app, main_loop;

tk_examp      = init_app || main_loop;

/* init_app: initialize (create the application's widgets) */

init_app   = // start a new interpreter
	     tk_quit ||
	     // unmap the main window (will be shown when all widgets have
	     // been created, to reduce flickering)
	     tk "wm withdraw ." ||
	     // set the window title
	     tk "wm title . \"Q-Tk Example\"" ||
	     // title label
	     tk "label .title -font 8x13bold -text \
\"A Simple Q-Tk Application\"" ||
	     tk "label .descr -text \
\"Type in a Q expression and click Eval to evaluate.\n\
Click Quit to quit.\"" ||
	     // main area: input expression and output result with labels
	     tk "frame .f" ||
	     tk "label .f.expr_l -text \"Expression:\"" ||
 	     tk "entry .f.expr_e -textvariable expr_val -width 40" ||
	     tk "label .f.result_l -text \"Result:\"" ||
	     tk "entry .f.result_e -textvariable result_val -width 40" ||
	     // buttons
	     tk "frame .buttons" ||
	     tk "button .buttons.eval -text Eval -command { q eval_cb }" ||
	     tk "button .buttons.quit -text Quit -command { q quit_cb }" ||
	     // pack widgets into the main window
	     // title and main frame
	     tk "pack .title .descr" ||
	     tk "pack .f -fill x" ||
	     // grid layout of the main frame
	     tk "grid config .f.expr_l -column 0 -row 0 -sticky w" ||
	     tk "grid config .f.expr_e -column 1 -row 0 -sticky we" ||
	     tk "grid config .f.result_l -column 0 -row 1 -sticky w" ||
	     tk "grid config .f.result_e -column 1 -row 1 -sticky we" ||
	     // make entry widgets expand horizontally to fill main window
	     tk "grid columnconfigure .f 0 -weight 0" ||
	     tk "grid columnconfigure .f 1 -weight 1" ||
	     // buttons
	     tk "pack .buttons" ||
	     tk "pack .buttons.eval .buttons.quit -side left" ||
	     // bind Return key in expression entry to evaluation command
	     tk "bind .f.expr_e <Return> { q eval_cb }" ||
	     // show the main window
	     tk "wm deiconify .";

/* main_loop: the main loop of the application */

main_loop  = tk_read || main_loop if tk_ready;
	   = () otherwise;

/* check syntax of expression and evaluate */

res 'X     = str X;
res X	   = "*** syntax error ***" otherwise;

eval S     = res (valq S);

/* callbacks */

eval_cb    = tk ("set result_val {" ++ eval (tk "return $expr_val") ++ "}");

quit_cb	   = tk_quit;