SVN commit 1191716 by majewsky:

Propery set physical velocities with b2Body::ApplyLinearImpulse, and remove dependency of BlackHole::eject on Ball::doAdvance.

 M  +13 -13    canvasitem.cpp  
 M  +0 -3      canvasitem.h  
 M  +4 -10     game.cpp  


--- trunk/KDE/kdegames/kolf/canvasitem.cpp #1191715:1191716
@@ -30,7 +30,6 @@
 	, m_body(0)
 	, m_overlay(0)
 	, m_simulationType(CanvasItem::CollisionSimulation)
-	, m_velocityChanged(true)
 {
 	b2BodyDef bodyDef;
 	bodyDef.userData = this;
@@ -133,25 +132,30 @@
 
 QPointF CanvasItem::physicalVelocity() const
 {
-	return m_physicalVelocity;
+	b2Vec2 v = m_body->GetLinearVelocity();
+	return QPointF(v.x, v.y);
 }
 
-void CanvasItem::setPhysicalVelocity(const QPointF& physicalVelocity)
+void CanvasItem::setPhysicalVelocity(const QPointF& newVelocity)
 {
-	if (m_physicalVelocity != physicalVelocity)
+	const QPointF currentVelocity = this->physicalVelocity();
+	if (newVelocity != currentVelocity)
 	{
-		m_physicalVelocity = physicalVelocity;
-		m_velocityChanged = true;
+		const qreal mass = m_body->GetMass();
+		if (mass == 0)
+			m_body->SetLinearVelocity(b2Vec2(newVelocity.x(), newVelocity.y()));
+		else
+		{
+			const QPointF impulse = (newVelocity - currentVelocity) * mass;
+			m_body->ApplyLinearImpulse(b2Vec2(impulse.x(), impulse.y()), m_body->GetPosition());
 	}
 }
+}
 
 void CanvasItem::startSimulation()
 {
 	const QPointF position = getPosition();
 	m_body->SetTransform(b2Vec2(position.x(), position.y()), 0);
-	if (m_velocityChanged)
-		m_body->SetLinearVelocity(b2Vec2(m_physicalVelocity.x(), m_physicalVelocity.y()));
-	m_velocityChanged = false;
 }
 
 void CanvasItem::endSimulation()
@@ -165,10 +169,6 @@
 		//have a non-standard behavior with some classes (e.g. Ball), i.e. these
 		//arguments trigger some black magic
 		setPosition(position);
-	//read velocity
-	v = m_body->GetLinearVelocity();
-	setPhysicalVelocity(QPointF(v.x, v.y));
-	m_velocityChanged = false; //this was no manual change
 }
 
 Kolf::Overlay* CanvasItem::overlay(bool createIfNecessary)
--- trunk/KDE/kdegames/kolf/canvasitem.h #1191715:1191716
@@ -183,9 +183,6 @@
 		Kolf::Overlay* m_overlay;
 		QList<Kolf::Shape*> m_shapes;
 		CanvasItem::SimulationType m_simulationType;
-		QPointF m_physicalVelocity;
-		bool m_velocityChanged; //tells whether velocity has been changed programmatically after last simulation step
-		//The rationale behind this variable is that Box2D sometimes has very low velocities (~1e-10) during contacts. The QPointF conversion could create rounding errors on some platforms.
 };
 
 //WARNING: pos() is at center (not at top-left edge of bounding rect!)
--- trunk/KDE/kdegames/kolf/game.cpp #1191715:1191716
@@ -1277,17 +1277,11 @@
 
 void BlackHole::eject(Ball *ball, double speed)
 {
-	ball->setPos(exitItem->pos());
+	//place ball 10 units after exit, and set exit velocity
+	const Vector direction = Vector::fromMagnitudeDirection(1, -deg2rad(exitDeg));
+	ball->setPos(exitItem->pos() + 10 * direction);
+	ball->setVelocity(speed * direction);
 
-	Vector v = Vector::fromMagnitudeDirection(10, -deg2rad(exitDeg));
-	ball->setVelocity(v);
-
-	// advance ball by 10 units
-	ball->doAdvance();
-
-	v.setMagnitude(speed);
-	ball->setVelocity(v);
-
 	ball->setForceStillGoing(false);
 	ball->setVisible(true);
 	ball->setState(Rolling);