Corrected shot bouncing logic

There was a problem calculating how shots with the BOUNCE_REAL attribute
would bounce off walls. The calculation was triggered when the shot
was already obstructed, which possibly got the shot stuck,
and later killed by a wrong obstruction check, which almost always killed
fast shots in narrow tunnels.

Also added some const.

Aquaria/Game.h

@@ -640,7 +640,7 @@ public:
 	int getGridRaw(unsigned int x, unsigned int y) const;
 	const signed char *getGridColumn(int tileX);
 	void setGrid(const TileVector &tile, int v);
-	bool isObstructed(const TileVector &tile, int t = -1);
+	bool isObstructed(const TileVector &tile, int t = -1) const;
 
 	void clearPointers();
 
@@ -1246,7 +1246,7 @@ void Game::setGrid(const TileVector &tile, int v)
 }
 
 inline
-bool Game::isObstructed(const TileVector &tile, int t)
+bool Game::isObstructed(const TileVector &tile, int t) const
 {
 	if (t == -1)
 		return (getGrid(tile) != 0);

Aquaria/Shot.cpp

@@ -586,7 +586,7 @@ void Shot::targetDied(Entity *target)
 	*/
 }
 
-bool Shot::isHitEnts()
+bool Shot::isHitEnts() const
 {
 	if (!shotData || shotData->hitEnts)
 	{
@@ -684,14 +684,14 @@ void Shot::noSegs()
 	}
 }
 
-int Shot::getCollideRadius()
+int Shot::getCollideRadius() const
 {
 	if (shotData)
 		return shotData->collideRadius;
 	return 0;
 }
 
-float Shot::getDamage()
+float Shot::getDamage() const
 {
 	if (shotData)
 	{
@@ -700,7 +700,7 @@ float Shot::getDamage()
 	return 0;
 }
 
-DamageType Shot::getDamageType()
+DamageType Shot::getDamageType() const
 {
 	if (shotData)
 	{
@@ -733,11 +733,11 @@ void Shot::setTargetPoint(int pt)
 	targetPt = pt;
 }
 
-bool Shot::isObstructed()
+bool Shot::isObstructed(float dt) const
 {
 	if (shotData->wallHitRadius == 0)
 	{
-		TileVector t(position);
+		TileVector t(position + velocity * dt);
 		if (dsq->game->isObstructed(t)
 			|| dsq->game->isObstructed(TileVector(t.x+1, t.y))
 			|| dsq->game->isObstructed(TileVector(t.x-1, t.y))
@@ -858,11 +858,18 @@ void Shot::onUpdate(float dt)
 		diff.z = 0;
 		if (shotData->hitWalls)
 		{
-			if (isObstructed())
+			if (isObstructed(dt))
 			{
 				switch(shotData->bounceType)
 				{
 				case BOUNCE_REAL:
+				{
+					// Should have been checked in last onUpdate()
+					// If it is stuck now, it must have been fired from a bad position,
+					// the obstruction map changed, or it was a bouncing beast form shot,
+					// fired from avatar head - which may be inside a wall.
+					// In any of these cases, there is nowhere to bounce, so we let the shot die. -- FG
+					if (!isObstructed(0))
 					{
 						if (!shotData->bounceSfx.empty())
 						{
@@ -878,13 +885,10 @@ void Shot::onUpdate(float dt)
 							velocity = 2*(-I.dot(N))*N + I;
 							velocity *= len;
 						}
-					Vector test = position+velocity;
-					if (dsq->game->isObstructed(test))
-					{
-						suicide();
-					}
-				}
 						break;
+					}
+					// fall through
+				}
 				default:
 				{
 					suicide();

Aquaria/Shot.h

@@ -109,13 +109,13 @@ public:
 	void setAimVector(const Vector &aim);
 	void setTarget(Entity *target);
 	void setTargetPoint(int pt);
-	float getDamage();
+	float getDamage() const;
-	int getCollideRadius();
+	int getCollideRadius() const;
-	DamageType getDamageType();
+	DamageType getDamageType() const;
 	ShotData *shotData;
 	void updatePosition();
-	bool isHitEnts();
+	bool isHitEnts() const;
-	bool isObstructed();
+	bool isObstructed(float dt) const;
 
 	float extraDamage;
 protected: