Fix repaint logic

Nowadays everything is buffered and composed, so we have to request that
the widget should be repainted later.

t14/cannon.cpp

@@ -39,7 +39,7 @@ void CannonField::setAngle( int degrees )
     if ( ang == degrees )
         return;
     ang = degrees;
-    repaint( cannonRect(), false );
+    update( cannonRect() );
     emit angleChanged( ang );
 }
 
@@ -72,10 +72,10 @@ void  CannonField::newTarget()
         QTime midnight( 0, 0, 0 );
         srand( midnight.secsTo(QTime::currentTime()) );
     }
-    erase( targetRect() );
+    update( targetRect() );
     target = QPoint( 200 + rand() % 190,
                      10  + rand() % 255 );
-    repaint( targetRect() );
+    update( targetRect() );
 }
 
 void CannonField::setGameOver()
@@ -85,7 +85,7 @@ void CannonField::setGameOver()
     if ( shooting )
         stopShooting();
     gameEnded = true;
-    repaint();
+    update();
 }
 
 void CannonField::restartGame()
@@ -93,12 +93,12 @@ void CannonField::restartGame()
     if ( shooting )
         stopShooting();
     gameEnded = false;
-    repaint();
+    update();
 }
 
 void CannonField::timerEvent( QTimerEvent * )
 {
-    erase( shotRect() );
+    update( shotRect() );
     timerCount++;
 
     QRect shotR = shotRect();
@@ -114,7 +114,7 @@ void CannonField::timerEvent( QTimerEvent * )
         emit missed();
         return;
     }	
-    repaint( shotR, false );
+    update( shotR );
 }
 
 void CannonField::paintEvent( QPaintEvent *e )