--- /dev/null
+load ('def.lefty');
+definit ();
+#
+# initialize window data
+#
+canvas = defcanvas;
+wrect = [0 = ['x' = 0; 'y' = 0;]; 1 = ['x' = 400; 'y' = 500;];];
+setwidgetattr (canvas, ['window' = wrect;]);
+
+sq = function (x) {
+ return x * x;
+};
+
+# data structures
+#
+length = 300;
+center = ['x' = 200; 'y' = 250;];
+radius = 2 * length / sqrt (12);
+fractalangle = 0;
+maxlevel = 2;
+
+# drawing functions
+#
+# draw a Koch curve (a ``snowflake'' fractal)
+#
+# start with a triangle and keep replacing edges
+# with the construct: _/\_
+# until the recursion level reaches 'maxlevel'
+#
+fractal = function (level, length, angle) {
+ local nlength, newpenpos;
+
+ if (level >= maxlevel) {
+ newpenpos.x = penpos.x + length * cos (angle);
+ newpenpos.y = penpos.y + length * sin (angle);
+ line (canvas, null, penpos, newpenpos, ['color' = 1;]);
+ penpos = newpenpos;
+ return;
+ }
+ nlength = length / 3;
+ fractal (level + 1, nlength, angle);
+ fractal (level + 1, nlength, angle + 60);
+ fractal (level + 1, nlength, angle - 60);
+ fractal (level + 1, nlength, angle);
+};
+drawfractal = function () {
+ clear (canvas);
+ setpick (canvas, center, wrect);
+ penpos = [
+ 'x' = center.x + cos (fractalangle + 210) * radius;
+ 'y' = center.y + sin (fractalangle + 210) * radius;
+ ];
+ fractal (0, length, fractalangle + 60);
+ fractal (0, length, fractalangle - 60);
+ fractal (0, length, fractalangle - 180);
+ remove ('penpos');
+};
+
+# editing functions
+#
+# transform the fractal.
+#
+# map point 'prevpoint' to point 'currpoint'
+# with respect to the center of the fractal.
+#
+transformfractal = function (prevpoint, currpoint) {
+ local prevtan, currtan, prevradius, currradius;
+
+ prevtan = atan (prevpoint.y - center.y, prevpoint.x - center.x);
+ currtan = atan (currpoint.y - center.y, currpoint.x - center.x);
+ fractalangle = fractalangle + (currtan - prevtan);
+ prevradius = sqrt (sq (prevpoint.y - center.y) +
+ sq (prevpoint.x - center.x));
+ currradius = sqrt (sq (currpoint.y - center.y) +
+ sq (currpoint.x - center.x));
+ radius = radius / prevradius * currradius;
+ length = radius / 2 * sqrt (12);
+};
+
+# user interface functions
+#
+# bind changes to the fractal to user actions
+#
+leftup = function (data) {
+ transformfractal (data.ppos, data.pos);
+ drawfractal ();
+};
+dops = function () {
+ local s;
+
+ s = ['x' = 8 * 300; 'y' = 10.5 * 300;];
+ canvas = createwidget (-1, ['type' = 'ps'; 'size' = s;]);
+ setwidgetattr (canvas, ['window' = wrect;]);
+ drawfractal ();
+ destroywidget (canvas);
+ canvas=defcanvas;
+};
+transformfractal (['x' = 0; 'y' = 0;], ['x' = 0; 'y' = 0;]);
+drawfractal ();
--- /dev/null
+#
+# data structures
+#
+length = 300;
+center = ['x' = 200; 'y' = 250;];
+radius = 2 * length / sqrt (12);
+fractalangle = 0;
+maxlevel = 2;
+sizes = [
+ 'button' = [ 'x' = 100; 'y' = 40; ];
+ 'canvas' = [ 'x' = 400; 'y' = 500; ];
+ 'view' = [ 'x' = 400; 'y' = 600; ];
+];
+sq = function (x) {
+ return x * x;
+};
+#
+# create view and other widgets
+#
+init = function () {
+ view = createwidget (-1, [
+ 'type' = 'view'; 'name' = 'fractal'; 'size' = sizes.view;
+ ]);
+
+ array1 = createwidget (view, [
+ 'type' = 'array'; 'borderwidth' = 1; 'mode' = 'vertical';
+ ]);
+ widgets[array1].resize = resize;
+
+ array2 = createwidget (array1, [
+ 'type' = 'array'; 'borderwidth' = 1; 'mode' = 'horizontal';
+ ]);
+ widgets[array2].resize = resize;
+
+ array3 = createwidget (array2, [
+ 'type' = 'array'; 'borderwidth' = 1; 'mode' = 'vertical';
+ ]);
+ widgets[array3].resize = resize;
+
+ morebutton = createwidget (array3, [
+ 'type' = 'button'; 'text' = 'more';
+ ]);
+ widgets[morebutton].pressed = pressed;
+ lessbutton = createwidget (array3, [
+ 'type' = 'button'; 'text' = 'less';
+ ]);
+ widgets[lessbutton].pressed = pressed;
+ setwidgetattr (morebutton, ['size' = sizes.button;]);
+ setwidgetattr (lessbutton, ['size' = sizes.button;]);
+
+ atext = createwidget (array2, [
+ 'type' = 'text'; 'mode' = 'oneline';
+ ]);
+ widgets[atext].oneline = oneline;
+ setwidgetattr (atext, [
+ 'size' = ['x' = sizes.button.x; 'y' = sizes.button.y * 2;];
+ ]);
+
+ scroll = createwidget (array1, ['type' = 'scroll';]);
+ canvas = createwidget (scroll, ['type' = 'canvas';]);
+ wrect = [0 = ['x' = 0; 'y' = 0;]; 1 = sizes.canvas;];
+ setwidgetattr (canvas, ['window' = wrect; 'viewport' = wrect[1];]);
+};
+#
+# drawing functions
+#
+# draw a Koch curve (a ``snowflake'' fractal)
+#
+# start with a triangle and keep replacing edges
+# with the construct: _/\_
+# until the recursion level reaches 'maxlevel'
+#
+fractal = function (level, length, angle) {
+ local nlength, newpenpos;
+
+ if (level >= maxlevel) {
+ newpenpos.x = penpos.x + length * cos (angle);
+ newpenpos.y = penpos.y + length * sin (angle);
+ line (canvas, null, penpos, newpenpos, ['color' = 1;]);
+ penpos = newpenpos;
+ return;
+ }
+ nlength = length / 3;
+ fractal (level + 1, nlength, angle);
+ fractal (level + 1, nlength, angle + 60);
+ fractal (level + 1, nlength, angle - 60);
+ fractal (level + 1, nlength, angle);
+};
+redrawfractal = function () {
+ clear (canvas);
+ setpick (canvas, center, wrect);
+ penpos = [
+ 'x' = center.x + cos (fractalangle + 210) * radius;
+ 'y' = center.y + sin (fractalangle + 210) * radius;
+ ];
+ fractal (0, length, fractalangle + 60);
+ fractal (0, length, fractalangle - 60);
+ fractal (0, length, fractalangle - 180);
+ remove ('penpos');
+};
+#
+# editing functions
+#
+# transform the fractal.
+#
+# map point 'prevpoint' to point 'currpoint'
+# with respect to the center of the fractal.
+#
+transformfractal = function (prevpoint, currpoint) {
+ local prevtan, currtan, prevradius, currradius;
+
+ prevtan = atan (prevpoint.y - center.y, prevpoint.x - center.x);
+ currtan = atan (currpoint.y - center.y, currpoint.x - center.x);
+ fractalangle = fractalangle + (currtan - prevtan);
+ prevradius = sqrt (sq (prevpoint.y - center.y) +
+ sq (prevpoint.x - center.x));
+ currradius = sqrt (sq (currpoint.y - center.y) +
+ sq (currpoint.x - center.x));
+ radius = radius / prevradius * currradius;
+ length = radius / 2 * sqrt (12);
+};
+#
+# main actions
+#
+redraw = function (data) {
+ redrawfractal ();
+};
+changemaxlevel = function (dn) {
+ maxlevel = maxlevel + dn;
+ if (maxlevel < 0)
+ maxlevel = 0;
+ redrawfractal ();
+};
+resize = function (data) {
+ local ret;
+ if (data.widget == array1) {
+ ret = [
+ array2 = [
+ 'x' = data.size.x;
+ 'y' = sizes.button.y * 2;
+ ];
+ scroll = [
+ 'x' = data.size.x;
+ 'y' = data.size.y - sizes.button.y * 2;
+ ];
+ ];
+ } else if (data.widget == array2) {
+ ret = [
+ array3 = [
+ 'x' = sizes.button.x;
+ 'y' = 2 * sizes.button.y;
+ ];
+ atext = [
+ 'x' = data.size.x - sizes.button.x;
+ 'y' = 2 * sizes.button.y;
+ ];
+ ];
+ } else if (data.widget == array3) {
+ ret = [
+ morebutton = sizes.button;
+ lessbutton = sizes.button;
+ ];
+ }
+ return ret;
+};
+#
+# user interface functions
+#
+# bind changes to the fractal to user actions
+#
+leftup = function (data) {
+ transformfractal (data.ppos, data.pos);
+ redrawfractal ();
+};
+menu = [
+ 0 = 'more';
+ 1 = 'less';
+];
+domenu = function (i) {
+ local s;
+ s = menu[i];
+ if (s == 'more')
+ changemaxlevel (1);
+ else if (s == 'less')
+ changemaxlevel (-1);
+};
+rightdown = function (data) {
+ domenu (displaymenu (canvas, menu));
+};
+pressed = function (data) {
+ if (data.widget == morebutton)
+ changemaxlevel (1);
+ else if (data.widget == lessbutton)
+ changemaxlevel (-1);
+};
+oneline = function (data) {
+ local dn;
+ dn = ston (data.text);
+ if (dn > 0 | dn < 0)
+ changemaxlevel (dn - maxlevel);
+};
+#
+# postscript generation
+#
+dops = function () {
+ local r;
+
+ r = [0 = ['x' = 0; 'y' = 0;]; 1 = ['x' = 8 * 300; 'y' = 10.5 * 300;];];
+ canvas = opencanvas ('pscanvas', '', r);
+ setwidgetattr (canvas, ['window' = wrect;]);
+ redraw ();
+ closecanvas (canvas);
+ canvas=defcanvas;
+};
+init ();
+#txtview ('off');