From 13888147068c06121cb9c69b21b6ca239a354819 Mon Sep 17 00:00:00 2001
From: James Brown
Date: Sun, 29 Sep 2002 15:20:02 +0000
Subject: Patch 616144: Sam and Max layering fix (drawMaskOnBoth rewrite)

svn-id: r5036
---
 scumm/gfx.cpp    | 82 ++++++++++++++++++++++++++++++++++----------------------
 scumm/gfx.h      |  2 +-
 scumm/object.cpp |  2 +-
 3 files changed, 52 insertions(+), 34 deletions(-)

diff --git a/scumm/gfx.cpp b/scumm/gfx.cpp
index 1eaa1a9d48..11c7139f56 100644
--- a/scumm/gfx.cpp
+++ b/scumm/gfx.cpp
@@ -924,44 +924,62 @@ void Gdi::drawBitmap(byte *ptr, VirtScreen *vs, int x, int y, int h,
 			}
 		}
 		CHECK_HEAP;
-		if (flag & dbDrawMaskOnBoth) {
-			_z_plane_ptr = zplane_list[1] + READ_LE_UINT16(zplane_list[1] + stripnr * 2 + 8);
-			_mask_ptr_dest = _vm->getResourceAddress(rtBuffer, 9) + y * NUM_STRIPS + x;
-			if (_useOrDecompress && flag & dbAllowMaskOr)
-				decompressMaskImgOr();
-			else
-				decompressMaskImg();
-		}
 
-		for (i = 1; i < numzbuf; i++) {
-			uint16 offs;
+		// Sam & Max uses dbDrawMaskOnAll for things like the inventory
+		// box and the speech icons. While these objects only have one
+		// mask, it should be applied to all the Z-planes in the room,
+		// i.e. they should mask every actor.
+		//
+		// This flag used to be called dbDrawMaskOnBoth, and all it
+		// would do was to mask Z-plane 0. (Z-plane 1 would also be
+		// masked, because what is now the else-clause used to be run
+		// always.) While this seems to be the only way there is to
+		// mask Z-plane 0, this wasn't good enough since actors in
+		// Z-planes >= 2 would not be masked.
+		//
+		// The flag is also used by The Dig and Full Throttle, but I
+		// don't know what for. At the time of writing, these games
+		// are still too unstable for me to investigate.
+
+		if (flag & dbDrawMaskOnAll) {
+			_z_plane_ptr = zplane_list[1] + READ_LE_UINT16(zplane_list[1] + stripnr * 2 + 8);
+			for (i = 0; i < numzbuf; i++) {
+				_mask_ptr_dest = _vm->getResourceAddress(rtBuffer, 9) + y * NUM_STRIPS + x + _imgBufOffs[i];
+				if (_useOrDecompress && flag & dbAllowMaskOr)
+					decompressMaskImgOr();
+				else
+					decompressMaskImg();
+			}
+		} else {
+			for (i = 1; i < numzbuf; i++) {
+				uint16 offs;
 
-			if (!zplane_list[i])
-				continue;
+				if (!zplane_list[i])
+					continue;
 
-			if (_vm->_features & GF_SMALL_HEADER)
-				if (_vm->_features & GF_OLD256)
-					offs = READ_LE_UINT16(zplane_list[i] + stripnr * 2 + 4);
-				else
-					offs = READ_LE_UINT16(zplane_list[i] + stripnr * 2 + 2);
-			else
-				offs = READ_LE_UINT16(zplane_list[i] + stripnr * 2 + 8);
+				if (_vm->_features & GF_SMALL_HEADER) {
+					if (_vm->_features & GF_OLD256)
+						offs = READ_LE_UINT16(zplane_list[i] + stripnr * 2 + 4);
+					else
+						offs = READ_LE_UINT16(zplane_list[i] + stripnr * 2 + 2);
+				} else
+					offs = READ_LE_UINT16(zplane_list[i] + stripnr * 2 + 8);
 
-			_mask_ptr_dest = _vm->getResourceAddress(rtBuffer, 9) + y * NUM_STRIPS + x + _imgBufOffs[i];
+				_mask_ptr_dest = _vm->getResourceAddress(rtBuffer, 9) + y * NUM_STRIPS + x + _imgBufOffs[i];
 
-			if (offs) {
-				_z_plane_ptr = zplane_list[i] + offs;
+				if (offs) {
+					_z_plane_ptr = zplane_list[i] + offs;
 
-				if (_useOrDecompress && flag & dbAllowMaskOr)
-					decompressMaskImgOr();
-				else
-					decompressMaskImg();
-			} else {
-				if (_useOrDecompress && flag & dbAllowMaskOr);	/* nothing */
-				else
-					for (int h = 0; h < _numLinesToProcess; h++)
-						_mask_ptr_dest[h * NUM_STRIPS] = 0;
-				/* needs better abstraction, FIXME */
+					if (_useOrDecompress && flag & dbAllowMaskOr)
+						decompressMaskImgOr();
+					else
+						decompressMaskImg();
+				} else {
+					if (!(_useOrDecompress && flag & dbAllowMaskOr));
+						for (int h = 0; h < _numLinesToProcess; h++)
+							_mask_ptr_dest[h * NUM_STRIPS] = 0;
+					/* needs better abstraction, FIXME */
+				}
 			}
 		}
 		CHECK_HEAP;
diff --git a/scumm/gfx.h b/scumm/gfx.h
index 93eec1e64c..b1f605d193 100644
--- a/scumm/gfx.h
+++ b/scumm/gfx.h
@@ -184,7 +184,7 @@ struct Gdi {
 
 	enum DrawBitmapFlags {
 		dbAllowMaskOr = 1,
-		dbDrawMaskOnBoth = 2,
+		dbDrawMaskOnAll = 2,
 		dbClear = 4
 	};
 };
diff --git a/scumm/object.cpp b/scumm/object.cpp
index e05a1e16ba..40896990a7 100644
--- a/scumm/object.cpp
+++ b/scumm/object.cpp
@@ -378,7 +378,7 @@ void Scumm::drawObject(int obj, int arg)
 		// Sam & Max needs this to fix object-layering problems with
 		// the inventory and conversation icons.
 		if ((_features & GF_AFTER_V7 || _gameId == GID_SAMNMAX) && getClass(od->obj_nr, 22))
-			flags |= Gdi::dbDrawMaskOnBoth;
+			flags |= Gdi::dbDrawMaskOnAll;
 		gdi.drawBitmap(ptr, _curVirtScreen, x, ypos, height, x - xpos, numstrip, flags);
 	}
 }
-- 
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