/****************************************************************

                      Uebungen zur Vorlesung
		  "Graphische Datenverarbeitung"
                       Sommersemester  1996

       Programm: drawtest2.c
       Autor:    Christian Boehm

       Programm zeichnet fraktale Schneeflocke.
       Hier wird eine Pixmap als Puffer verwendet.
       Bei einem Expose-Event wird nur Pixmap-Inhalt in die
       Drawing Area kopiert. Bei Resize Neuaufbau der Pixmap.

****************************************************************/

# include <stdio.h>
# include <stdlib.h>
# include <Xm/Xm.h>
# include <Xm/XmAll.h>

Widget       DrawAr;               /* Drawing Area */
GC           fensterGC, pixmapGC;  /* Graphik-Kontext fuer XDrawLine...*/
Display*     display;
Pixmap       GraphikPixmap = 0;

double SQ36 = 0.288675134;   /* sqrt (3.0)/6.0 */
double absw (double a) {return a < 0 ? -a : a ; }

void RecursiveDraw (double x1, double y1, double x2, double y2, Drawable w, GC g)
{
        if (absw(x1-x2)<1.0 && absw (y1-y2)<1.0) 
	        XDrawLine (display, w, g, (Dimension) x1, (Dimension) y1, 
			                  (Dimension) x2, (Dimension) y2) ;
	else {
	        RecursiveDraw (x1, y1, (2*x1+x2)/3, (2*y1+y2)/3, w, g);
	        RecursiveDraw ((2*x1+x2)/3, (2*y1+y2)/3, (x1+x2)/2-SQ36*(y2-y1), (y1+y2)/2+SQ36*(x2-x1), w, g);
		RecursiveDraw ((x1+x2)/2-SQ36*(y2-y1), (y1+y2)/2+SQ36*(x2-x1), (x1+2*x2)/3, (y1+2*y2)/3, w, g);
		RecursiveDraw ((x1+2*x2)/3, (y1+2*y2)/3, x2, y2, w, g);
	}
}

void resizeCB (Widget widget, XtPointer dum2, XtPointer dum3)
{
        Dimension w, h ;
	double w1, h1 ;
	XGCValues     werte;       /* Struktur zum Setzen von GC-Attributen */

	XtVaGetValues (widget, XmNheight, &h, XmNwidth, &w, NULL) ;
	
	if (GraphikPixmap) {
	        XFreeGC (display, pixmapGC) ;
		XFreePixmap (display, GraphikPixmap) ;
	} 
	GraphikPixmap = XCreatePixmap (display, XtWindow (widget), w, h, 1) ;

	werte.foreground = 0 ;
	werte.background = 1 ;
	pixmapGC = XCreateGC (display, GraphikPixmap, 
			      GCForeground | GCBackground, &werte) ;
	XFillRectangle (display, GraphikPixmap, pixmapGC, 0, 0, w, h) ;
	
	werte.foreground = 1 ;
	werte.background = 0 ;
	XChangeGC (display, pixmapGC, GCForeground | GCBackground, &werte) ;
	w1 = (double) w ; h1 = (double) h ;
	if (w1*1.154700538>h1)
	        w1=h1/4/SQ36 ;
	else
	        h1=w1*4*SQ36 ;
	RecursiveDraw (0.0, 0.75*h1, w1, 0.75*h1, GraphikPixmap, pixmapGC) ;
	RecursiveDraw (w1, 0.75*h1, 0.5*w1, 0.0, GraphikPixmap, pixmapGC) ;
	RecursiveDraw (0.5*w1, 0.0, 0.0, 0.75*h1, GraphikPixmap, pixmapGC) ;
	XClearArea (display, XtWindow (DrawAr), 0, 0, w, h, True) ;
}

void exposeCB (Widget widget, XtPointer clientDaten, XtPointer aufrufDaten)
{
        XmDrawingAreaCallbackStruct* DAinfos;

	/* Callback-Informationen mit Event-Struktur */
	DAinfos = (XmDrawingAreaCallbackStruct*)aufrufDaten;

	if (! GraphikPixmap)
	        resizeCB (widget, (XtPointer) 0, (XtPointer) 0) ;

	/* Im Expose-Event angegebenen Fenster-Ausschnitt 
	 * von Graphik-Bitmap ins Graphik-Fenster kopieren
	 */
	XCopyPlane (display, GraphikPixmap, XtWindow(widget), fensterGC,
		    DAinfos->event->xexpose.x, DAinfos->event->xexpose.y,
		    DAinfos->event->xexpose.width,
		    DAinfos->event->xexpose.height,
		    DAinfos->event->xexpose.x, DAinfos->event->xexpose.y,
		    1);
}

void exitCB (Widget dum1, XtPointer dum2, XtPointer dum3)
{
	exit (0) ;
}

static char * fallbackRessourcen [] = {
        "Drawtest.geometry: 200x200+0+0", 
	NULL
} ;

main (int argc, char ** argv)
{
	XtAppContext  kontext;     /* Applikations-Umgebung */
	Widget        applShell;   /* Applikations-Shell */
	Widget        ExBt;
	XGCValues     werte;       /* Struktur zum Setzen von GC-Attributen */

	applShell = XtAppInitialize (&kontext, "Drawtest",
				     (XrmOptionDescRec*)NULL, 0,
				     &argc, argv, fallbackRessourcen,
				     (Arg*)NULL, 0);

	DrawAr = XtCreateManagedWidget	("drawingarea", xmDrawingAreaWidgetClass,
					 applShell, (Arg*)NULL, 0) ;
	ExBt = XtCreateManagedWidget ("exit", xmPushButtonWidgetClass, 
				      DrawAr, (Arg*)NULL, 0) ;
	XtRealizeWidget (applShell);
	display = XtDisplay (applShell);

	/* Fuer die Graphik-Ausgabe wird ein Graphik-Kontext (GC) erzeugt
	   und mit den Vorder- und Hintergrundfarben der Drawing-Area-Widget
	   besetzt. */
	XtVaGetValues (DrawAr, XmNforeground, &(werte.foreground), 
		       XmNbackground, &(werte.background), NULL) ;
	fensterGC = XCreateGC (display, XtWindow (DrawAr), 
			       GCForeground | GCBackground, &werte) ;

	/* Callbacks registrieren. Der Resize-Callback darf erst
	   nach XtRealizeWidget registriert werden */
	XtAddCallback (DrawAr, XmNexposeCallback, exposeCB, (XtPointer)NULL);
	XtAddCallback (DrawAr, XmNresizeCallback, resizeCB, (XtPointer)NULL);
	XtAddCallback (ExBt, XmNactivateCallback, exitCB, (XtPointer) NULL);

	XtAppMainLoop (kontext);
}