Keep the balloon from getting stuck in an infinite loop when floating near the borders of the screen.

See the detailed explanation in walk.cpp.

svn-id: r49619

1 files changed, 13 insertions, 0 deletions

diff --git a/engines/parallaction/walk.cpp b/engines/parallaction/walk.cpp
index 4468a7a678..d6df23d415 100644
--- a/engines/parallaction/walk.cpp
+++ b/engines/parallaction/walk.cpp
@@ -626,6 +626,19 @@ void PathWalker_BR::doWalk(State &s) {
 	int xStep = (scale * 16) / 100 + 1;
 	int yStep = (scale * 10) / 100 + 1;
 
+
+	/* WORKAROUND: in the balloon scene, the position of the balloon (which is implemented as a 
+	Character) is controlled by the user (for movement, via this walking code) and by the scripts
+	(to simulate the balloon floating in the air, in a neverending loop that alters the position
+	coordinates).
+	When the two step sizes are equal in magnitude and opposite in direction, then the walk code
+	enters an infinite loop without giving control back to the user (this happens quite frequently
+	when navigating the balloon near the borders of the screen, where the calculated step is 
+	forcibly small because of clipping). Since the "floating" script (part1/scripts/mongolo.scr) 
+	uses increments of 3 for both x and y, we tweak the calculated steps accordingly here. */
+	if (xStep == 3) xStep--;
+	if (yStep == 3) yStep--;
+
 	debugC(9, kDebugWalk, "calculated step: (%i, %i)", xStep, yStep);
 
 	s._fieldC = 0;