examples added for draw/idraw Canvases in htdch

svn: r3866

collects/htdch/Examples/draw-multiple-canvas.ss

@@ -0,0 +1,44 @@
+import draw.*;
+import colors.*;
+import geometry.*;
+
+class Example {
+ Canvas create(int w, int h, Color bg) { 
+   Canvas c = new Canvas(w,h);
+   boolean tstC = c.show();
+   boolean tstCDraw = c.drawRect(new Posn(0,0),w,h,bg);
+   return c; 
+ }
+}
+
+class Example1 extends Example {
+ Canvas c = create(100,200,new Black());
+ Canvas d = create(200,100,new White());
+ 
+ boolean tst = c.close();
+
+ String result = "the white 200 x 100 canvas is visible; the black one has disappeared";
+}
+
+class Example2 extends Example {
+ Canvas c = create(100,200,new Blue());
+ Canvas d = create(200,100,new Red());
+ 
+ boolean tst = d.close();
+
+ String result = "the blue canvas is visible; the green one has disappeared";
+}
+
+class Example3 extends Example {
+ Canvas c = create(100,100,new Green());
+ String sc = "a green 100 x 100 canvas pops up";
+
+ Canvas d = create(200,200,new Black());
+ String sd = "a black 200 x 200 canvas pops up";
+ 
+ boolean tst = c.close();
+ String st = "the green screen has disappeared";
+ boolean tst2 = c.show();
+ String result = "the black canvas is visible; a second white one (of 100 x 100) is visible";
+}
+

collects/htdch/Examples/draw-multiple-worlds.ss

@@ -0,0 +1,36 @@
+import draw.*;
+import colors.*;
+import geometry.*;
+
+class SW extends World {
+ int x = 50; 
+ int y;
+ int low; 
+ Color c;
+ Color white = new White();
+ 
+ SW(int y, int low, Color c) { this.y = y; this.low = low; this.c = c; }
+
+ boolean go() { return this.bigBang(100,100,.1); }
+ 
+ World onTick() { 
+  if (y >= low)
+    return endOfWorld();
+  else
+   return new SW(this.y+1,this.low,this.c); 
+ }
+
+ World onKeyEvent(String ke) { return this; }
+
+ boolean draw() { return this.theCanvas.drawDisk(new Posn(this.x,this.y),3,c); }
+ 
+ boolean erase() { return this.theCanvas.drawRect(new Posn(0,0),100,100,white); }
+}
+
+class Example {
+  SW sw1 = new SW(10,40,new Red());
+  SW sw2 = new SW(10,90,new Green());
+  boolean tst1 = sw1.go();
+  boolean tst2 = sw2.go();
+  String result = "two worlds, green goes to bottom, red goes to center";
+}

collects/htdch/Examples/draw-world-close-canvas.ss

@@ -0,0 +1,39 @@
+/*  Let's have a second canvas into which the world can draw. 
+    See whether it interferes. 
+*/
+
+import draw.*;
+import colors.*;
+import geometry.*;
+
+// can I close the canvas of a world? 
+class SW extends World {
+ int x = 50; 
+ int y;
+ Color red = new Red();
+ Color white = new White();
+ 
+ SW(int v) { y = v; }
+
+ boolean go() { return this.bigBang(100,100,.1); }
+ 
+ World onTick() { return new SW(this.y+1); }
+
+ World onKeyEvent(String ke) { 
+  if (ke.equals("s"))
+   return this.endOfWorld();
+  else if (ke.equals("*"))
+   return new SW(99);
+  else 
+   return this; 
+ }
+
+ boolean draw() { return this.theCanvas.drawDisk(new Posn(this.x,this.y),3,red); }
+ 
+ boolean erase() { return this.theCanvas.drawRect(new Posn(0,0),100,100,white); }
+}
+
+class Example {
+  SW sw = new SW(10);
+  boolean tst1 = sw.go();
+}