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object Geom {
trait Shape;
case class Point(x: int, y: int) extends Shape;
case class Rectangle(ll: Point, ur: Point) extends Shape {
def inset(delta: int) =
Rectangle(Point(ll.x - delta, ll.y - delta), Point(ur.x + delta, ur.y + delta));
}
}
object Color {
type Color = int;
val black = 0x000000;
val grey = 0x808080;
}
trait Screen {
type Color = int;
def drawRect(r: Geom.Rectangle, c: Color): unit;
def fillRect(r: Geom.Rectangle, c: Color): unit;
}
object DummyScreen extends Screen {
def drawRect(r: Geom.Rectangle, c: Color): unit =
System.out.println("draw " + r + " with " + c);
def fillRect(r: Geom.Rectangle, c: Color): unit =
System.out.println("fill " + r + " with " + c);
}
object GUI {
object Controller {
def addMouseCtl(c: MouseCtl) = ()
}
trait Glyph {
def getRect: Geom.Rectangle;
def setLoc(p: Geom.Point): unit;
def draw() = System.out.println("draw " + this);
}
class Label(scr: Screen, p: Geom.Point, name: String) extends Glyph {
private var origin = p;
def getRect = Geom.Rectangle(origin, origin).inset(10);
def setLoc(p: Geom.Point) = { origin = p }
}
trait Ctl {
def getGlyph: Glyph;
def enable(b: Boolean): this.type;
}
trait MouseCtl extends Ctl {
def mouseDown(p: Geom.Point): unit;
}
abstract class Button(scr: Screen, p: Geom.Point, name: String)
extends Glyph with MouseCtl {
var enabled: boolean = false;
val label = new Label(scr, p, name);
/* Glyph methods */
override def draw(): unit = {
if (enabled) scr.drawRect(getRect, Color.black)
else scr.fillRect(getRect, Color.grey);
label.draw();
}
def setLoc(p: Geom.Point) = label.setLoc(p);
def getRect = label.getRect.inset(-2);
/* Ctl methods */
def enable(b: boolean): this.type = { enabled = b; draw(); this }
def getGlyph = label;
final def mouseDown(p: Geom.Point): unit =
if (enabled) doit() else System.out.println("button is disabled");
/* deferred method to be specified by client */
def doit(): unit;
}
}
object GUIClient {
class Application {
def quit() = System.out.println("application exited");
}
class QuitButton (scr: Screen, p: Geom.Point, name: String, a: Application)
extends GUI.Button(scr, p, name) {
def doit(): unit = a.quit();
}
def main(args: Array[String]) = {
val b = new QuitButton(
DummyScreen, Geom.Point(1, 1), "quit", new Application);
b.draw();
b.enable(true).mouseDown(Geom.Point(1, 2));
}
}
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