## 21 JAPI GUI Library Binding ¶

### Introduction:: ¶

The JAPI GUI library is hosted on the internet at:

      http://www.japi.de

It has bindings to many common languages.

### Including JAPI in your GCL build:: ¶

The GCL binding presented here is based on the C language version of the library, statically linked into GCL and uses the standard GCL FFI macros to import the functions and constants provided by JAPI.

To include the library in your build of GCL, simply download the version of JAPI needed for your computer system, install the headers and libraries, and add the GCL configure switch “–enable-japi=yes” to your usual configuration parameters. Build GCL as usual.

To run the GUI from GCL programs, you do need to have either of the executables "java" or "jre" in your PATH.

### How it works:: ¶

As downloaded from the above web site, JAPI uses a socket connection to a Java GUI which is, fortunately for us, invisible to GCL. This gives the GCL JAPI binding the advantages and disadvantages of any non-native GUI system which trades off portability, speed and OS specific look and feel.

The GCL JAPI binding works on Windows which is it’s main advantage over GCL-Tk other than ease of maintenance at the Lisp level.

The main disadvantage of GCL JAPI relative to GCL-Tk is that the JAPI library is no longer actively developed. It has also been criticised for depending on Java, a proprietary system.

This binding does nothing more than provide Lisp wrappers around the JAPI primitives; there are no higher order functional wrappers. Never-the-less the interface is easy to understand, maintain and use at the Lisp level.

The documentation for JAPI available from the web site is pretty much all you need to get started with the library under GCL. All of the exposed library functions and constants are provided in GCL and a comprehensive example is provided here to give you some idea of how to start using the system.

Here is a simple example of how to use JAPI. It displays an empty frame for five seconds and then kills the GUI.

    ;; Run a five second frame in a Japi server
    (with-server ("GCL Japi library test GUI 1" 0)
    	     (with-frame (frame "Five Second Blank Test Frame")
    			 (j_show frame)
    			 (j_sleep 5000)))

The macros “with-server” and “with-frame” are defined in the larger example below.

The first, “with-server”, takes two arguments, an application name string and a debug level. With debug level zero there is no debug output on the console.

The second, “with-frame” takes two arguments, a variable name and a frame title string. You use the variable name, here “frame”, to refer to the frame in later function calls.

The longer example below which includes the small example just explained, also displays various kinds of dialog, does some graphics and mouse handling including the ability to save graphics to disk, and shows one way of implementing a very simple text editor.

### Example:: ¶

    ;;;
    ;;; Japi is a cross-platform, easy to use (rough and ready) Java based GUI library
    ;;; Download a library and headers for your platform, and get the C examples
    ;;; and documentation from:
    ;;;
    ;;;     http://www.japi.de/
    ;;;
    ;;; This file shows how to use some of the available functions.  You may assume
    ;;; that the only functions tested so far in the binding are those which appear
    ;;; below, as this file doubles as the test program.  The binding is so simple
    ;;; however that so far no binding (APART FROM J_PRINT) has gone wrong of those
    ;;; tested so far!
    ;;;
    ;;;
    ;;; HOW TO USE THIS FILE
    ;;;
    ;;; (compile-file "c:/cvs/gcl/japitest.lsp") (load "c:/cvs/gcl/japitest.o")
    ;;;
    ;;; Requires either "java" or "jre" in the path to work.
    ;;;

    (in-package :japi-primitives)

    ;; Start up the Japi server (needs to find either "java" or "jre" in your path
    (defmacro with-server ((app-name debug-level) . body)
      (multiple-value-bind (ds b)
    		       (si::find-declarations body)
    		       `(if (= 0 (j_start))
    			    (format t (format nil "~S can't connect to the Japi GUI server." ,app-name))
    			  (progn
    			    (j_setdebug ,debug-level)
    			    ,@ds
    			    (unwind-protect
    				(progn ,@b)
    			      (j_quit))))))

    ;; Use a frame and clean up afterwards even if trouble ensues
    (defmacro with-frame ((frame-var-name title) . body)
      (multiple-value-bind (ds b)
    		       (si::find-declarations body)
    		       `(let ((,frame-var-name (j_frame ,title)))
    			  ,@ds
    			  (unwind-protect
    			      (progn ,@b)
    			    (j_dispose ,frame-var-name)))))

    ;; Use a canvas and clean up afterwards even if trouble ensues
    (defmacro with-canvas ((canvas-var-name frame-obj x-size y-size) . body)
      (multiple-value-bind (ds b)
    		       (si::find-declarations body)
    		       `(let ((,canvas-var-name (j_canvas ,frame-obj ,x-size ,y-size)))
    			  ,@ds
    			  (unwind-protect
    			      (progn ,@b)
    			    (j_dispose ,canvas-var-name)))))

    ;; Use a text area and clean up afterwards even if trouble ensues
    (defmacro with-text-area ((text-area-var-name panel-obj x-size y-size) . body)
      (multiple-value-bind (ds b)
    		       (si::find-declarations body)
    		       `(let ((,text-area-var-name (j_textarea ,panel-obj ,x-size ,y-size)))
    			  ,@ds
    			  (unwind-protect
    			      (progn ,@b)
    			    (j_dispose ,text-area-var-name)))))

    ;; Use a pulldown menu bar and clean up afterwards even if trouble ensues
    (defmacro with-menu-bar ((bar-var-name frame-obj) . body)
      (multiple-value-bind (ds b)
    		       (si::find-declarations body)
    		       `(let ((,bar-var-name (j_menubar ,frame-obj)))
    			  ,@ds
    			  (unwind-protect
    			      (progn ,@b)
    			    (j_dispose ,bar-var-name)))))

    ;; Add a pulldown menu and clean up afterwards even if trouble ensues
    (defmacro with-menu ((menu-var-name bar-obj title) . body)
      (multiple-value-bind (ds b)
    		       (si::find-declarations body)
    		       `(let ((,menu-var-name (j_menu ,bar-obj ,title)))
    			  ,@ds
    			  (unwind-protect
    			      (progn ,@b)
    			    (j_dispose ,menu-var-name)))))

    ;; Add a pulldown menu item and clean up afterwards even if trouble ensues
    (defmacro with-menu-item ((item-var-name menu-obj title) . body)
      (multiple-value-bind (ds b)
    		       (si::find-declarations body)
    		       `(let ((,item-var-name (j_menuitem ,menu-obj ,title)))
    			  ,@ds
    			  (unwind-protect
    			      (progn ,@b)
    			    (j_dispose ,item-var-name)))))

    ;; Add a mouse listener and clean up afterwards even if trouble ensues
    (defmacro with-mouse-listener ((var-name obj type) . body)
      (multiple-value-bind (ds b)
    		       (si::find-declarations body)
    		       `(let ((,var-name (j_mouselistener ,obj ,type)))
    			  ,@ds
    			  (unwind-protect
    			      (progn ,@b)
    			    (j_dispose ,var-name)))))

    ;; Use a panel and clean up afterwards even if trouble ensues
    (defmacro with-panel ((panel-var-name frame-obj) . body)
      (multiple-value-bind (ds b)
    		       (si::find-declarations body)
    		       `(let ((,panel-var-name (j_panel ,frame-obj)))
    			  ,@ds
    			  (unwind-protect
    			      (progn ,@b)
    			    (j_dispose ,panel-var-name)))))

    ;; Get a pointer to an array of ints
    (defCfun "static void* inta_ptr(object s)" 0
      " return(s->fixa.fixa_self);")
    (defentry inta-ptr (object) (int "inta_ptr"))

    ;; Draw function
    (defun drawgraphics (drawable xmin ymin xmax ymax)
      (let* ((fntsize 10)
    	 (tmpstrx (format nil "XMax = ~D" xmax))
    	 (tmpstry (format nil "YMax = ~D" ymax))
    	 (tmpstrwidx (j_getstringwidth drawable tmpstrx)))
        (j_setfontsize drawable fntsize)
        (j_setnamedcolor drawable J_RED)

        (j_drawline drawable xmin ymin        (- xmax 1)      (- ymax 1))
        (j_drawline drawable xmin (- ymax 1)  (- xmax 1)      ymin)
        (j_drawrect drawable xmin ymin        (- xmax xmin 1) (- ymax xmin 1))

        (j_setnamedcolor drawable J_BLACK)
        (j_drawline drawable xmin (- ymax 30) (- xmax 1)      (- ymax 30))
        (j_drawstring drawable (- (/ xmax 2) (/ tmpstrwidx 2)) (- ymax 40) tmpstrx)

        (j_drawline drawable (+ xmin 30) ymin (+ xmin 30) (- ymax 1))
        (j_drawstring drawable (+ xmin 50) 40 tmpstry)

        (j_setnamedcolor drawable J_MAGENTA)
        (loop for i from 1 to 10
    	  do (j_drawoval drawable
    			 (+ xmin (/ (- xmax xmin) 2))
    			 (+ ymin (/ (- ymax ymin) 2))
    			 (* (/ (- xmax xmin) 20) i)
    			 (* (/ (- ymax ymin) 20) i)))

        (j_setnamedcolor drawable J_BLUE)
        (let ((y ymin)
    	  (teststr "JAPI Test Text"))
          (loop for i from 5 to 21 do
    	    (j_setfontsize drawable i)
    	    (let ((x (- xmax (j_getstringwidth drawable teststr))))
    	      (setf y (+ y (j_getfontheight drawable)))
    	      (j_drawstring drawable x y teststr))))))

    ;; Run a five second frame in a Japi server
    (with-server ("GCL Japi library test GUI 1" 0)
    	     (with-frame (frame "Five Second Blank Test Frame")
    			 (j_show frame)
    			 (j_sleep 5000)))

    ;; Run some more extensive tests
    (with-server
     ("GCL Japi library test GUI 2" 0)
     (with-frame
      (frame "Draw")
      (j_show frame)
      (let ((alert (j_messagebox frame "Two second alert box" "label")))
        (j_sleep 2000)
        (j_dispose alert))
      (let ((result1 (j_alertbox frame "label1" "label2" "OK"))
    	(result2 (j_choicebox2 frame "label1" "label2" "Yes" "No"))
    	(result3 (j_choicebox3 frame "label1" "label2" "Yes" "No" "Cancel")))
        (format t "Requestor results were: ~D, ~D, ~D~%" result1 result2 result3))
      (j_setborderlayout frame)
      (with-menu-bar
       (menubar frame)
       (with-menu
        (file menubar "File")
        (with-menu-item
         (print file "Print")
         (with-menu-item
          (save file "Save BMP")
          (with-menu-item
           (quit file "Quit")
           (with-canvas
    	(canvas frame 400 600)
    	(j_pack frame)
    	(drawgraphics canvas 0 0 (j_getwidth canvas) (j_getheight canvas))
    	(j_show frame)
    	(do ((obj (j_nextaction) (j_nextaction)))
    	    ((or (= obj frame) (= obj quit)) t)
    	    (when (= obj canvas)
    	      (j_setnamedcolorbg canvas J_WHITE)
    	      (drawgraphics canvas 10 10
    			    (- (j_getwidth canvas) 10)
    			    (- (j_getheight canvas) 10)))
    	    (when (= obj print)
    	      (let ((printer (j_printer frame)))
    		(when (> 0 printer)
    		  (drawgraphics printer 40 40
    				(- (j_getwidth printer) 80)
    				(- (j_getheight printer) 80))
    		  (j_print printer))))
    	    (when (= obj save)
    	      (let ((image (j_image 600 800)))
    		(drawgraphics image 0 0 600 800)
    		(when (= 0 (j_saveimage image "test.bmp" J_BMP))
    		  (j_alertbox frame "Problems" "Can't save the image" "OK")))))))))))))

    ;; Try some mouse handling
    (with-server
     ("GCL Japi library test GUI 3" 0)
     (with-frame
      (frame "Move and drag the mouse")
      (j_setsize frame 430 240)
      (j_setnamedcolorbg frame J_LIGHT_GRAY)
      (with-canvas
       (canvas1 frame 200 200)
       (with-canvas
        (canvas2 frame 200 200)
        (j_setpos canvas1 10 30)
        (j_setpos canvas2 220 30)
        (with-mouse-listener
         (pressed canvas1 J_PRESSED)
         (with-mouse-listener
          (dragged canvas1 J_DRAGGED)
          (with-mouse-listener
           (released canvas1 J_RELEASED)
           (with-mouse-listener
    	(entered canvas2 J_ENTERERD)
    	(with-mouse-listener
    	 (moved canvas2 J_MOVED)
    	 (with-mouse-listener
    	  (exited canvas2 J_EXITED)
    	  (j_show frame)
              ;; Allocate immovable storage for passing data back from C land.
    	  ;; Uses the GCL only make-array keyword :static
    	  (let* ((xa (make-array 1 :initial-element 0 :element-type 'fixnum :static t))
    		 (ya (make-array 1 :initial-element 0 :element-type 'fixnum :static t))
    		 (pxa (inta-ptr xa))
    		 (pya (inta-ptr ya))
    		 (x 0)
    		 (y 0)
    		 (get-mouse-xy (lambda (obj)
    				 (progn (j_getmousepos obj pxa pya)
    					(setf x (aref xa 0))
    					(setf y (aref ya 0)))))
    		 (startx 0)
    		 (starty 0))
    	    (do ((obj (j_nextaction) (j_nextaction)))
    		((= obj frame) t)
    		(when (= obj pressed)
    		  (funcall get-mouse-xy pressed)
    		  (setf startx x)
    		  (setf starty y))
    		(when (= obj dragged)
    		  (funcall get-mouse-xy dragged)
    		  (j_drawrect canvas1 startx starty (- x startx) (- y starty)))
    		(when (= obj released)
    		  (funcall get-mouse-xy released)
    		  (j_drawrect canvas1 startx starty (- x startx) (- y starty)))
    		(when (= obj entered)
    		  (funcall get-mouse-xy entered)
    		  (setf startx x)
    		  (setf starty y))
    		(when (= obj moved)
    		  (funcall get-mouse-xy moved)
    		  (j_drawline canvas2 startx starty x y)
    		  (setf startx x)
    		  (setf starty y))
    		(when (= obj exited)
    		  (funcall get-mouse-xy exited)
    		  (j_drawline canvas2 startx starty x y))))))))))))))

    ;; Text editor demo
    (with-server
     ("GCL Japi library test text editor" 0)
     (with-frame
      (frame "A simple editor")
      (j_setgridlayout frame 1 1)
      (with-panel
       (panel frame)
       (j_setgridlayout panel 1 1)
       (with-menu-bar
        (menubar frame)
        (with-menu
         (file-mi menubar "File")
         (with-menu-item
          (new-mi file-mi "New")
          (with-menu-item
           (save-mi file-mi "Save")
           (j_seperator file-mi)
           (with-menu-item
    	(quit-mi file-mi "Quit")

    	(with-menu
    	 (edit-mi menubar "Edit")
    	 (with-menu-item
    	  (select-all-mi edit-mi "Select All")
    	  (j_seperator edit-mi)
    	  (with-menu-item
    	   (cut-mi edit-mi "Cut")
    	   (with-menu-item
    	    (copy-mi edit-mi "Copy")
    	    (with-menu-item
    	     (paste-mi edit-mi "Paste")

    	     (with-text-area
    	      (text panel 15 4)
    	      (j_setfont text J_DIALOGIN J_BOLD 18)
    	      (let ((new-text (format nil "JAPI (Java Application~%Programming Interface)~%a platform and language~%independent API")))
    		(j_settext text new-text)
    		(j_show frame)
    		(j_pack frame)
    		(j_setrows text 4)
    		(j_setcolumns text 15)
    		(j_pack frame)
    		;; Allocate immovable storage for passing data back from C land.
    		;; Uses the GCL only make-array keyword :static
    		(let* ((xa (make-array 1 :initial-element 0 :element-type 'fixnum :static t))
    		       (ya (make-array 1 :initial-element 0 :element-type 'fixnum :static t))
    		       (pxa (inta-ptr xa))
    		       (pya (inta-ptr ya))
    		       (x 0)
    		       (y 0)
    		       (get-mouse-xy (lambda (obj)
    				       (progn (j_getmousepos obj pxa pya)
    					      (setf x (aref xa 0))
    					      (setf y (aref ya 0)))))
    		       (startx 0)
    		       (starty 0)
    		       (selstart 0)
    		       (selend 0)
    		       (text-buffer (make-array 64000 :initial-element 0 :element-type 'character :static t))
    					;	      (text-buffer (make-string 64000 :initial-element #\0))
    		       (p-text-buffer (inta-ptr text-buffer)))
    		  (do ((obj (j_nextaction) (j_nextaction)))
    		      ((or (= obj frame) (= obj quit-mi))t)
    		      (when (= obj panel)
    			(format t "Size changed to ~D rows ~D columns~%" (j_getrows text) (j_getcolumns text))
    			(format t "Size changed to ~D x ~D pixels~%" (j_getwidth text) (j_getheight text)))
    		      (when (= obj text) (format t "Text changed (len=~D)~%" (j_getlength text) ))
    		      (when (= obj new-mi) (j_settext new-text))
    		      (when (= obj save-mi) (j_gettext text text-buffer))
    		      (when (= obj select-all-mi) (j_selectall text))
    		      (when (or (= obj cut-mi)
    				(= obj copy-mi)
    				(= obj paste-mi))
    			(setf selstart (1- (j_getselstart text)))
    			(setf selend (1- (j_getselend text))))
    		      (when (= obj cut-mi)
    			(j_getseltext text p-text-buffer)
    			(j_delete text (1- (j_getselstart text)) (1- (j_getselend text)))
    			(setf selend selstart))
    		      (when (= obj copy-mi)
    			(j_getseltext text p-text-buffer))
    		      (when (= obj paste-mi)
    			(if (= selstart selend)
    			    (j_inserttext text p-text-buffer (1- (j_getcurpos text)))
    			  (j_replacetext text p-text-buffer (1- (j_getselstart text)) (1- (j_getselend text))))
    			))))))))))))))))))

    (defun mandel (drawable min_x max_x min_y max_y step_x step_y)
      (let* ((scale_x (/ 1 step_x))
    	 (scale_y (/ 1 step_y)))
        (loop for y from min_y to max_y by step_y do
    	  (loop for x from min_x to max_x by step_x do
    		(let* ((c 255)
    		       (z (complex x y))
    		       (a z))
    		  (loop while (and (< (abs
    				       (setq z (+ (* z z) a)))
    				      2)
    				   (>= (decf c) 0)))
    		  (j_setcolor drawable c c c)
    		  (j_drawpixel drawable (* scale_x (+ (abs min_x) x)) (* scale_y (+ (abs min_y) y)) ))))))

    ;;; Monochrome Mandelbrot
    (with-server
     ("GCL Japi library test GUI 4" 0)
     (let* ((min_x -2)
    	(max_x  1)
    	(min_y -1)
    	(max_y  1.1)
    	(step_x 0.01)
    	(step_y 0.01)
    	(size_x (+ 1 (/ (- max_x min_x) step_x)))
    	(size_y (+ 1 (/ (- max_y min_y) step_y))))
       (with-frame
        (frame "Mandelbrot")
        (j_setsize frame size_x size_y)
        (j_setborderlayout frame)
        (with-menu-bar
         (menubar frame)
         (with-menu
          (file menubar "File")
          (with-menu-item
           (save file "Save BMP")
           (with-menu-item
    	(quit file "Quit")
    	(with-canvas
    	 (canvas1 frame size_x size_y)
    	 (j_pack frame)
    	 (j_show frame)
    	 (j_show canvas1)
    	 (mandel canvas1  min_x max_x min_y max_y step_x step_y)
    	 (do ((obj (j_nextaction) (j_nextaction)))
    	     ((or (= obj frame) (= obj quit)) t)
    	     (when (= obj save)
    	       (let ((image (j_getimage canvas1)))
    		 (when (= 0 (j_saveimage image "mandel.bmp" J_BMP))
    		   (j_alertbox frame "Problems" "Can't save the image" "OK"))
    		 (j_dispose image) )))))))))))