SCI: Implementation of kCelInfo subop 4

kCelInfo subop 4 returns the pixel color at the
passed in x,y coordinates for the passed in view,
loop, cel.  Shivers uses this function for the
red door puzzle, room 23601 to determine what
blocks on the puzzle board are already occupied
by pieces.

1 files changed, 17 insertions, 5 deletions

diff --git a/engines/sci/engine/kgraphics.cpp b/engines/sci/engine/kgraphics.cpp
index c60c0a44b9..ce670b21fe 100644
--- a/engines/sci/engine/kgraphics.cpp
+++ b/engines/sci/engine/kgraphics.cpp
@@ -1471,10 +1471,8 @@ reg_t kSetShowStyle(EngineState *s, int argc, reg_t *argv) {
 }
 
 reg_t kCelInfo(EngineState *s, int argc, reg_t *argv) {
-	// TODO: This is all a stub/skeleton, thus we're invoking kStub() for now
-	kStub(s, argc, argv);
-
-	// Used by Shivers 1, room 23601
+	// Used by Shivers 1, room 23601 to determine what blocks on the red door puzzle board
+	// are occupied by pieces already
 
 	// 6 arguments, all integers:
 	// argv[0] - subop (0 - 4). It's constantly called with 4 in Shivers 1
@@ -1490,7 +1488,21 @@ reg_t kCelInfo(EngineState *s, int argc, reg_t *argv) {
 	// 2, 3 - nop
 	// 4 - return value of pixel at x, y
 
-	return s->r_acc;
+	switch (argv[0].toUint16()) {
+		case 4: {
+			GuiResourceId viewId = argv[1].toSint16();
+			int16 loopNo = argv[2].toSint16();
+			int16 celNo = argv[3].toSint16();
+			int16 x = argv[4].toUint16();
+			int16 y = argv[5].toUint16();
+			byte color = g_sci->_gfxCache->kernelViewGetColorAtCoordinate(viewId, loopNo, celNo, x, y);
+			return make_reg(0, color);
+		}
+		default: {
+			kStub(s, argc, argv);
+			return s->r_acc;
+		}
+	}
 }
 
 reg_t kScrollWindow(EngineState *s, int argc, reg_t *argv) {