Enumify terrain blockage and generalize the line of sight function

This should probably be two separate commits, but they're tangled together and I don't want to spend the effort to disentangle them.

osx/tools/graphtool.cpp

@@ -1203,3 +1203,48 @@ void tileImage(RgnHandle area, GWorldPtr img, RECT srcRect, short mode){
 	}
 }
 #endif
+
+short can_see(location p1,location p2,std::function<short(short,short)> get_obscurity) {
+	short storage = 0;
+	
+	if(p1.y == p2.y) {
+		if(p1.x > p2.x) {
+			for(short count = p2.x + 1; count < p1.x; count++)
+				storage += get_obscurity(count, p1.y);
+		} else {
+			for(short count = p1.x + 1; count < p2.x; count++)
+				storage += get_obscurity(count, p1.y);
+		}
+	} else if(p1.x == p2.x) {
+		if(p1.y > p2.y) {
+			for(short count = p1.y - 1; count > p2.y; count--)
+				storage += get_obscurity(p1.x, count);
+		} else {
+			for(short count = p1.y + 1; count < p2.y; count++) 
+				storage += get_obscurity(p1.x, count);
+		}
+	} else {
+		short dx = p2.x - p1.x;
+		short dy = p2.y - p1.y;
+		
+		if(abs(dy) > abs(dx)) {
+			if(p2.y > p1.y) {
+				for(short count = 1; count < dy; count++)
+					storage += get_obscurity(p1.x + (count * dx) / dy, p1.y + count);
+			} else {
+				for(short count = -1; count > dy; count--)
+					storage += get_obscurity(p1.x + (count * dx) / dy, p1.y + count);
+			}
+		}
+		if(abs(dy) <= abs(dx)) {
+			if(p2.x > p1.x) {
+				for(short count = 1; count < dx; count++)
+					storage += get_obscurity(p1.x + count, p1.y + (count * dy) / dx);
+			} else {
+				for(short count = -1; count > dx; count--)
+					storage += get_obscurity(p1.x + count, p1.y + (count * dy) / dx);
+			}
+		}
+	}
+	return storage;
+}