From 587c1ad3106752e703197f8063bf03a0fb877561 Mon Sep 17 00:00:00 2001
From: Martin Kiewitz
Date: Tue, 9 Feb 2016 17:37:01 +0100
Subject: AGI: Check xPos/yPos when building sprite lists

And ignore sprites, that are placed outside of visual screen
Fixes memory corruption during intro of fan made Get Outta SQ game.
Original AGI did not do checks at all.
---
 engines/agi/sprite.cpp | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/engines/agi/sprite.cpp b/engines/agi/sprite.cpp
index c68641fb33..09935c93f9 100644
--- a/engines/agi/sprite.cpp
+++ b/engines/agi/sprite.cpp
@@ -106,6 +106,28 @@ void SpritesMgr::buildSpriteListAdd(uint16 givenOrderNr, ScreenObjEntry *screenO
 	spriteEntry.yPos = (screenObj->yPos) - (screenObj->ySize) + 1;
 	spriteEntry.xSize = screenObj->xSize;
 	spriteEntry.ySize = screenObj->ySize;
+
+	// Checking, if xPos/yPos/right/bottom are valid and do not go outside of playscreen (visual screen)
+	// Original AGI did not do this (but it then resulted in memory corruption)
+	if (spriteEntry.xPos < 0) {
+		warning("buildSpriteListAdd(): ignoring screen obj %d, b/c xPos < 0", screenObj->objectNr, spriteEntry.xPos);
+		return;
+	}
+	if (spriteEntry.yPos < 0) {
+		warning("buildSpriteListAdd(): ignoring screen obj %d, b/c yPos (%d) < 0", screenObj->objectNr, spriteEntry.yPos);
+		return;
+	}
+	int16 xRight = spriteEntry.xPos + spriteEntry.xSize;
+	if (xRight > SCRIPT_HEIGHT) {
+		warning("buildSpriteListAdd(): ignoring screen obj %d, b/c rightPos > %d", screenObj->objectNr, xRight, SCRIPT_WIDTH);
+		return;
+	}
+	int16 yBottom = spriteEntry.yPos + spriteEntry.ySize;
+	if (yBottom > SCRIPT_HEIGHT) {
+		warning("buildSpriteListAdd(): ignoring screen obj %d, b/c bottomPos > %d", screenObj->objectNr, yBottom, SCRIPT_HEIGHT);
+		return;
+	}
+
 //	warning("list-add: %d, %d, original yPos: %d, ySize: %d", spriteEntry.xPos, spriteEntry.yPos, screenObj->yPos, screenObj->ySize);
 	spriteEntry.backgroundBuffer = (uint8 *)malloc(spriteEntry.xSize * spriteEntry.ySize * 2); // for visual + priority data
 	assert(spriteEntry.backgroundBuffer);
-- 
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