SpriteCollection - more notes on PCK+TAB files

XCom/Resources/Images/SpriteCollection.cs

@@ -238,10 +238,9 @@ public SpriteCollection(
 					}
 				}
 
-				// NOTE: I'd just like to point out here that a Tabfile is
-				// utterly redundant if the Pckfile is wellformed. But if the
-				// Pckfile is *not* wellformed you might as well be screwing the
-				// dog anyway.
+				// NOTE: I'd just like to point out that a Tabfile is redundant
+				// if the Pckfile is wellformed. But if the Pckfile is *not*
+				// wellformed you might as well be screwing the dog anyway.
 				//
 				// At least under my conception of PCK-RLE-compression.
 				// Obviously there are others. Which is what makes PCKs so
@@ -253,9 +252,22 @@ public SpriteCollection(
 				// b) the first byte in a sprite shall not be FE or FF
 				// c) the first byte shall always be a quantity of transparent fullrows
 				// c) the final byte of a sprite shall be FF
-				// d) FE shall be followed by a byte that is a quantity of transparent pixels (FF is allowed as a quantity)
+				// d) FE shall be followed by a byte that is a quantity of
+				//    transparent pixels (FF is allowed as a quantity)
 				// f) do not allow FE or FF to be used as a palette-color
-				// e) a decoding program shall initialize the entire buffer of a sprite with transparent pixels first.
+				// e) a decoding program shall initialize the entire buffer of a
+				//    sprite with transparent pixels first. Hence a contiguous
+				//    sequence of transparent pixels that hit the final FF do
+				//    not need to be written.
+				//
+				// I've seen a fair few whacky PCK files, including ones with
+				// "FE 01" <- "make the next pixel transparent". Hint, that's
+				// the equivalent of simply "00". Another common occurance is to
+				// write a blank sprite as FF only; while this could be valid
+				// if it were policy (and ofc not preceeded by FE), decoding
+				// problems can occur depending on the decoding application.
+				//
+				// protip: a Minimal (blank) sprite would/could/should be "00 FF".
 
 				if (CountSprites == CountOffsets) // avoid throwing 1 or 15000 exceptions ...
 				{