Add processing.gallery.trails

extra/processing/gallery/trails/trails.factor

@@ -0,0 +1,62 @@
+
+USING: kernel arrays sequences math qualified circular processing ui ;
+
+IN: processing.gallery.trails
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+! Example 33-15 from the Processing book
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+QUALIFIED: circular
+
+: push-circular ( seq elt -- seq ) over circular:push-circular ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: each-percent ( seq quot -- )
+  >r
+  dup length
+  dup [ / ] curry
+  [ 1+ ] swap compose
+  r> compose
+  2each ;                       inline
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: point-list ( n -- seq ) [ drop 0 0 2array ] map <circular> ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: dot ( pos percent -- ) 1 swap - 25 * 5 max circle ;
+
+: step ( seq -- )
+
+  no-stroke
+  { 1 0.4 } fill
+
+  0 background
+
+  mouse push-circular
+    [ dot ]
+  each-percent ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: go* ( -- )
+
+  500 500 size*
+
+  [
+    100 point-list
+      [ step ]
+    curry
+      draw
+  ] setup
+
+  run ;
+
+: go ( -- ) [ go* ] with-ui ;
+
+MAIN: go