assign QRect to client.geometry

Instead of updating fields of `client.geometry` one by one, assign a
whole new `QRect` instance. This prevents race condition caused by a
series of partial updates.

Addresses bug #13.

src/common.ts

@@ -82,6 +82,10 @@ class Rect implements IRect {
         this.x = other.x;
         this.y = other.y;
     }
+
+    public toQRect(): QRect {
+        return Qt.rect(this.x, this.y, this.width, this.height);
+    }
 }
 
 function clip(min: number, value: number, max: number): number {

src/qt.d.ts

@@ -44,4 +44,8 @@ interface QQmlTimer {
     stop(): void;
 }
 
+declare namespace Qt {
+    function rect(x: number, y: number, width: number, height: number): QRect;
+}
+
 declare var jiggleTimer: QQmlTimer;

src/tile.ts

@@ -104,7 +104,7 @@ class Tile {
         this.geometry.width  = clip(this.client.minSize.width , this.geometry.width , this.client.maxSize.width );
         this.geometry.height = clip(this.client.minSize.height, this.geometry.height, this.client.maxSize.height);
 
-        this.geometry.copyTo(this.client.geometry);
+        this.client.geometry = this.geometry.toQRect();
     }
 
     public isVisible(screenId: number): boolean {