[Scummvm-cvs-logs] scummvm master -> 587c1ad3106752e703197f8063bf03a0fb877561

[m-kiewitz]

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Summary:
587c1ad310 AGI: Check xPos/yPos when building sprite lists


Commit: 587c1ad3106752e703197f8063bf03a0fb877561
    https://github.com/scummvm/scummvm/commit/587c1ad3106752e703197f8063bf03a0fb877561
Author: Martin Kiewitz (m_kiewitz at users.sourceforge.net)
Date: 2016-02-09T17:37:28+01:00

Commit Message:
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.

Changed paths:
    engines/agi/sprite.cpp



diff --git a/engines/agi/sprite.cpp b/engines/agi/sprite.cpp
index c68641f..09935c9 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);