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.

2 files changed, 34 insertions, 0 deletions

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 -