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SCI: Clarify fix for KQ5 witch freeze bug #3034714

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The cause for this bug turns out to be a corrupt object that as
a side effect accidentally bypasses its own corruption. See the
added comments for details.

Also add a warning that points out similarly corrupted objects.
This commit is contained in:
Willem Jan Palenstijn 2011-03-11 23:09:13 +01:00
parent 3d576c184a
commit bd6602ea6f
2 changed files with 23 additions and 13 deletions
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11
engines/sci/engine/object.cpp
View File

@ -172,6 +172,17 @@ bool Object::initBaseObject(SegManager *segMan, reg_t addr, bool doInitSuperClas
const Object *baseObj = segMan->getObject(getSpeciesSelector());
if (baseObj) {
if (_variables.size() != baseObj->getVarCount()) {
warning("Object %04x:%04x varnum doesn't match baseObj's: obj %d, base %d ", PRINT_REG(_pos), _variables.size(), baseObj->getVarCount());
// These objects are probably broken.
// An example is 'witchCage' in script 200 in KQ5, but also
// 'girl' in script 216 and 'door' in script 22.
// In LSL3 a number of sound objects trigger this right away.
// The effect is that a number of its method selectors may be
// treated as variable selectors, causing unpredictable effects.
// In the case of KQ5/witchCage, this caused bug #3034714.
}
_variables.resize(baseObj->getVarCount());
// Copy base from species class, as we need its selector IDs
_baseObj = baseObj->_baseObj;

25
engines/sci/engine/script_patches.cpp
View File

@ -500,19 +500,18 @@ const uint16 kq5PatchCdHarpyVolume[] = {
// This is a heap patch, and it modifies the properties of an object, instead
// of patching script code.
// The witchCage object in script 200 is different than other objects, as it
// has 4 properties for its bounding box (top, left, bottom, right), but it
// initializes 4 extra ones before them to 0. The fact that this object's
// bounding box is invalid confuses the game scripts and makes the game enter
// an endless loop, as the scripts are trying to see if the witch can be inside
// an empty rectangle (which will never be true). The dimensions of the actual
// bounding box can be observed from the values of these invalid parameters.
// This object is also invalid in SV, so there must be special code to treat
// such situations. The following heap patch sets the first four valid object
// properties (which are what the game scripts refer to) to their valid values,
// equal to the values of the subsequent four invalid values. We don't know why
// or how this worked in SSCI, but this simple patch fixes this situation.
// Fixes bug #3034714.
//
// The witchCage object in script 200 is broken and claims to have 12
// variables instead of the 8 it should have because it is a Cage.
// Additionally its top,left,bottom,right properties are set to 0 rather
// than the right values. We fix the object by setting the right values.
// If they are all zero, this causes an impossible position check in
// witch::cantBeHere and an infinite loop when entering room 22 (bug #3034714).
//
// This bug is accidentally not triggered in SSCI because the invalid number
// of variables effectively hides witchCage::doit, causing this position check
// to be bypassed entirely.
// See also the warning+comment in Object::initBaseObject
const byte kq5SignatureWitchCageInit[] = {
16,
0x00, 0x00, // top