Implemented positionRect and supporting functions.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4186 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/util/DisplayUtil.as

@@ -5,6 +5,26 @@ import flash.geom.Rectangle;
 
 public class DisplayUtil
 {
+    /**
+     * Returns the most reasonable position for the specified rectangle to
+     * be placed at so as to maximize its containment by the specified
+     * bounding rectangle while still placing it as near its original
+     * coordinates as possible.
+     *
+     * @param rect the rectangle to be positioned.
+     * @param bounds the containing rectangle.
+     */
+    public static function fitRectInRect (
+            rect :Rectangle , bounds :Rectangle) :Point
+    {
+        // Guarantee that the right and bottom edges will be contained
+        // and do our best for the top and left edges.
+        var br :Point = bounds.bottomRight;
+        return new Point(
+            Math.min(br.x - rect.width, Math.max(rect.x, bounds.x)),
+            Math.min(br.y - rect.height, Math.max(rect.y, bounds.y)));
+    }
+
     /**
      * Position the specified rectangle within the bounds, avoiding
      * any of the Rectangles in the avoid array, which may be destructively
@@ -18,8 +38,86 @@ public class DisplayUtil
             r :Rectangle, bounds :Rectangle, avoid :Array) :Boolean
     {
         var origPos :Point = r.topLeft;
+        var pointSorter :Function = createPointSorter(origPos);
+        var possibles :Array = new Array();
+        // start things off with the passed-in point (adjusted to
+        // be inside the bounds, if needed)
+        possibles.push(fitRectInRect(r, bounds));
 
-        return true;
+        // keep track of area that doesn't generate new possibles
+        var dead :Array = new Array();
+
+        while (possibles.length > 0) {
+            try {
+                var p :Point = (possibles.shift() as Point);
+                r.x = p.x;
+                r.y = p.y;
+
+                // make sure the rectangle is in the view
+                if (!bounds.containsRect(r)) {
+                    continue;
+                }
+
+                // and not over a dead area
+                for each (var deadRect :Rectangle in dead) {
+                    if (deadRect.intersects(r)) {
+                        throw true; // continue outer loop
+                    }
+                }
+
+                // see if it hits any rects we're trying to avoid
+                for (var ii :int = 0; ii < avoid.length; ii++) {
+                    var avoidRect :Rectangle = (avoid[ii] as Rectangle);
+                    if (avoidRect.intersects(r)) {
+                        // remove it from the avoid list
+                        avoid.splice(ii, 1);
+                        // but add it to the dead list
+                        dead.push(avoidRect);
+
+                        // add 4 new possible points, each pushed in
+                        // one direction
+                        possibles.push(
+                            new Point(avoidRect.x - r.width, r.y),
+                            new Point(r.x, avoidRect.y - r.height),
+                            new Point(avoidRect.x + avoidRect.width, r.y),
+                            new Point(r.x, avoidRect.y + avoidRect.height));
+
+                        // re-sort the list
+                        possibles.sort(pointSorter);
+                        throw true; // continue outer loop
+                    }
+                }
+
+                // hey! if we got here, then it worked!
+                return true;
+
+            } catch (continueWhile :Boolean) {
+                // simply catch the boolean and use it to continue inner loops
+            }
+        }
+
+        // we never found a match, move the rectangle back
+        r.x = origPos.x;
+        r.y = origPos.y;
+        return false;
+    }
+
+    /**
+     * Create a sort Function that can be used to compare Points in an
+     * Array according to their distance from the specified Point.
+     *
+     * Note: The function will always sort according to distance from the
+     * passed-in point, even if that point's coordinates change after
+     * the function is created.
+     */
+    public static function createPointSorter (origin :Point) :Function
+    {
+        return function (p1 :Point, p2 :Point) :Number {
+            var dist1 :Number = Point.distance(origin, p1);
+            var dist2 :Number = Point.distance(origin, p2);
+
+            return (dist1 > dist2) ? 1 : ((dist1 < dist2) ? -1 : 0); // signum
+        };
     }
 }
 }