Some visibility cleanup. Add comment on broken code.

visGetBlockingWall() was broken with introduction
of ECM support a while back, but nobody noticed until
now. From code point of view, mostly because this
function used magic globals to get its data. Was broken
in 55a6259. Removing
the useless globals for now, since they just make it
look like things are working when they are not.

src/visibility.cpp

@@ -81,9 +81,6 @@ static std::vector<SPOTTER *> apsInvisibleViewers;
 
 #define MIN_VIS_HEIGHT 80
 
-static int *gNumWalls = nullptr;
-static Vector2i *gWall = nullptr;
-
 // forward declarations
 static void setSeenBy(BASE_OBJECT *psObj, unsigned viewer, int val);
 
@@ -487,14 +484,14 @@ int visibleObject(const BASE_OBJECT *psViewer, const BASE_OBJECT *psTarget, bool
 	}
 
 	/* First see if the target is in sensor range */
-	int dist = iHypot((psTarget->pos - psViewer->pos).xy);
+	const int dist = iHypot((psTarget->pos - psViewer->pos).xy);
 	if (dist == 0)
 	{
 		return UBYTE_MAX;	// Should never be on top of each other, but ...
 	}
 
-	MAPTILE *psTile = mapTile(map_coord(psTarget->pos.x), map_coord(psTarget->pos.y));
-	bool jammed = psTile->jammerBits & ~alliancebits[psViewer->player];
+	const MAPTILE *psTile = mapTile(map_coord(psTarget->pos.x), map_coord(psTarget->pos.y));
+	const bool jammed = psTile->jammerBits & ~alliancebits[psViewer->player];
 
 	// Special rule for VTOLs, as they are not affected by ECM
 	if (((psTarget->type == OBJ_DROID && isVtolDroid((DROID *)psTarget))
@@ -525,38 +522,10 @@ int visibleObject(const BASE_OBJECT *psViewer, const BASE_OBJECT *psTarget, bool
 // Find the wall that is blocking LOS to a target (if any)
 STRUCTURE *visGetBlockingWall(const BASE_OBJECT *psViewer, const BASE_OBJECT *psTarget)
 {
-	int numWalls = 0;
-	Vector2i wall;
-
-	// HACK Using globals to not clutter visibleObject() interface too much
-	gNumWalls = &numWalls;
-	gWall = &wall;
-
-	visibleObject(psViewer, psTarget, true);
-
-	gNumWalls = nullptr;
-	gWall = nullptr;
-
-	// see if there was a wall in the way
-	if (numWalls > 0)
-	{
-		Vector2i tile = map_coord(wall);
-		unsigned int player;
-
-		for (player = 0; player < MAX_PLAYERS; player++)
-		{
-			STRUCTURE *psWall;
-
-			for (psWall = apsStructLists[player]; psWall; psWall = psWall->psNext)
-			{
-				if (map_coord(psWall->pos.xy) == tile)
-				{
-					return psWall;
-				}
-			}
-		}
-	}
-
+	// TBD - reimplement this function; the previous implementation ended up
+	// doing nothing due to changes in other code. The perils of doing magic
+	// by globals - all dependencies are sometimes quite hard to see. Broken
+	// in commit 55a6259b121515b2d0ca9b2c580361dca970171d
 	return nullptr;
 }
 
@@ -575,8 +544,7 @@ bool hasSharedVision(unsigned viewer, unsigned ally)
 static void setSeenBy(BASE_OBJECT *psObj, unsigned viewer, int val /*= UBYTE_MAX*/)
 {
 	//forward out vision to our allies
-	int ally;
-	for (ally = 0; ally < MAX_PLAYERS; ++ally)
+	for (int ally = 0; ally < MAX_PLAYERS; ++ally)
 	{
 		if (hasSharedVision(viewer, ally))
 		{
@@ -588,8 +556,7 @@ static void setSeenBy(BASE_OBJECT *psObj, unsigned viewer, int val /*= UBYTE_MAX
 static void setSeenByInstantly(BASE_OBJECT *psObj, unsigned viewer, int val /*= UBYTE_MAX*/)
 {
 	//forward out vision to our allies
-	int ally;
-	for (ally = 0; ally < MAX_PLAYERS; ++ally)
+	for (int ally = 0; ally < MAX_PLAYERS; ++ally)
 	{
 		if (hasSharedVision(viewer, ally))
 		{