SCI32: Implement kCelLink

kCelLink exists in SSCI since 2.1mid, but it is only known to be
used in Lighthouse, during the weapon creation puzzle near the end
of the game.

5 files changed, 65 insertions, 1 deletions

diff --git a/engines/sci/engine/kernel.h b/engines/sci/engine/kernel.h
index d1dce37e48..baa891650e 100644
--- a/engines/sci/engine/kernel.h
+++ b/engines/sci/engine/kernel.h
@@ -636,6 +636,9 @@ reg_t kCelInfo(EngineState *s, int argc, reg_t *argv);
 reg_t kCelInfoGetOriginX(EngineState *s, int argc, reg_t *argv);
 reg_t kCelInfoGetOriginY(EngineState *s, int argc, reg_t *argv);
 reg_t kCelInfoGetPixel(EngineState *s, int argc, reg_t *argv);
+reg_t kCelLink(EngineState *s, int argc, reg_t *argv);
+reg_t kCelLinkGetX(EngineState *s, int argc, reg_t *argv);
+reg_t kCelLinkGetY(EngineState *s, int argc, reg_t *argv);
 
 reg_t kSetLanguage(EngineState *s, int argc, reg_t *argv);
 reg_t kScrollWindow(EngineState *s, int argc, reg_t *argv);
diff --git a/engines/sci/engine/kernel_tables.h b/engines/sci/engine/kernel_tables.h
index c65356470a..ac932199d3 100644
--- a/engines/sci/engine/kernel_tables.h
+++ b/engines/sci/engine/kernel_tables.h
@@ -575,6 +575,16 @@ static const SciKernelMapSubEntry kCelInfo_subops[] = {
 };
 
 //    version,         subId, function-mapping,                    signature,              workarounds
+static const SciKernelMapSubEntry kCelLink_subops[] = {
+	{ SIG_SINCE_SCI21MID,  0, MAP_DUMMY(CelLink0),                 "",                     NULL },
+	{ SIG_SINCE_SCI21MID,  1, MAP_DUMMY(CelLink1),                 "",                     NULL },
+	{ SIG_SINCE_SCI21MID,  2, MAP_CALL(CelLinkGetX),               "iiii",                 NULL },
+	{ SIG_SINCE_SCI21MID,  3, MAP_CALL(CelLinkGetY),               "iiii",                 NULL },
+	{ SIG_SINCE_SCI21MID,  4, MAP_DUMMY(CelLink4),                 "",                     NULL },
+	SCI_SUBOPENTRY_TERMINATOR
+};
+
+//    version,         subId, function-mapping,                    signature,              workarounds
 static const SciKernelMapSubEntry kScrollWindow_subops[] = {
 	{ SIG_SCI32,           0, MAP_CALL(ScrollWindowCreate),        "oi",                   NULL },
 	{ SIG_SCI32,           1, MAP_CALL(ScrollWindowAdd),           "iriii(i)",             kScrollWindowAdd_workarounds },
@@ -988,7 +998,7 @@ static SciKernelMapEntry s_kernelMap[] = {
 	{ MAP_DUMMY(FindClass),         SIG_EVERYWHERE,           "(.*)",                 NULL,            NULL },
 	{ MAP_DUMMY(CelRect),           SIG_EVERYWHERE,           "(.*)",                 NULL,            NULL },
 	{ MAP_DUMMY(BaseLineSpan),      SIG_EVERYWHERE,           "(.*)",                 NULL,            NULL },
-	{ MAP_DUMMY(CelLink),           SIG_EVERYWHERE,           "(.*)",                 NULL,            NULL },
+	{ MAP_CALL(CelLink),            SIG_SINCE_SCI21MID, SIGFOR_ALL, "(.*)",           kCelLink_subops, NULL },
 	{ MAP_DUMMY(AddPolygon),        SIG_EVERYWHERE,           "(.*)",                 NULL,            NULL },
 	{ MAP_DUMMY(DeletePolygon),     SIG_EVERYWHERE,           "(.*)",                 NULL,            NULL },
 	{ MAP_DUMMY(UpdatePolygon),     SIG_EVERYWHERE,           "(.*)",                 NULL,            NULL },
diff --git a/engines/sci/engine/kgraphics32.cpp b/engines/sci/engine/kgraphics32.cpp
index 44a3517458..c07282f53e 100644
--- a/engines/sci/engine/kgraphics32.cpp
+++ b/engines/sci/engine/kgraphics32.cpp
@@ -449,6 +449,23 @@ reg_t kCelInfoGetPixel(EngineState *s, int argc, reg_t *argv) {
 	return make_reg(0, view.readPixel(argv[3].toSint16(), argv[4].toSint16(), view._mirrorX));
 }
 
+// Used by Lighthouse, room 800, script 16, when in the weapon-building puzzle
+reg_t kCelLink(EngineState *s, int argc, reg_t *argv) {
+	if (!s)
+		return make_reg(0, getSciVersion());
+	error("not supposed to call this");
+}
+
+reg_t kCelLinkGetX(EngineState *s, int argc, reg_t *argv) {
+	CelObjView view(argv[0].toUint16(), argv[1].toSint16(), argv[2].toSint16());
+	return make_reg(0, view.getLinkPosition(argv[3].toSint16()).x);
+}
+
+reg_t kCelLinkGetY(EngineState *s, int argc, reg_t *argv) {
+	CelObjView view(argv[0].toUint16(), argv[1].toSint16(), argv[2].toSint16());
+	return make_reg(0, view.getLinkPosition(argv[3].toSint16()).y);
+}
+
 reg_t kScrollWindow(EngineState *s, int argc, reg_t *argv) {
 	if (!s)
 		return make_reg(0, getSciVersion());
diff --git a/engines/sci/graphics/celobj32.cpp b/engines/sci/graphics/celobj32.cpp
index 49b3b0053b..687ecd64f3 100644
--- a/engines/sci/graphics/celobj32.cpp
+++ b/engines/sci/graphics/celobj32.cpp
@@ -1081,6 +1081,38 @@ const SciSpan<const byte> CelObjView::getResPointer() const {
 	return *resource;
 }
 
+Common::Point CelObjView::getLinkPosition(const int16 linkId) const {
+	const SciSpan<const byte> resource = getResPointer();
+
+	if (resource[18] < 0x84) {
+		error("%s unsupported version %u for Links", _info.toString().c_str(), resource[18]);
+	}
+
+	const SciSpan<const byte> celHeader = resource.subspan(_celHeaderOffset);
+	const int16 numLinks = celHeader.getInt16SEAt(40);
+
+	if (numLinks) {
+		const int recordSize = 6;
+		SciSpan<const byte> linkTable = resource.subspan(celHeader.getInt32SEAt(36), recordSize * numLinks);
+		for (int16 i = 0; i < numLinks; ++i) {
+			if (linkTable[4] == linkId) {
+				Common::Point point;
+				point.x = linkTable.getInt16SEAt(0);
+				if (_mirrorX) {
+					// NOTE: SSCI had an off-by-one error here (missing -1)
+					point.x = _width - point.x - 1;
+				}
+				point.y = linkTable.getInt16SEAt(2);
+				return point;
+			}
+
+			linkTable += recordSize;
+		}
+	}
+
+	return Common::Point(-1, -1);
+}
+
 #pragma mark -
 #pragma mark CelObjPic
 
diff --git a/engines/sci/graphics/celobj32.h b/engines/sci/graphics/celobj32.h
index d51913473c..6e50f7232e 100644
--- a/engines/sci/graphics/celobj32.h
+++ b/engines/sci/graphics/celobj32.h
@@ -540,6 +540,8 @@ public:
 
 	virtual CelObjView *duplicate() const override;
 	virtual const SciSpan<const byte> getResPointer() const override;
+
+	Common::Point getLinkPosition(const int16 linkId) const;
 };
 
 #pragma mark -