[Scummvm-git-logs] scummvm master -> 4fe69dbf2e1325fecccc2ee69b2f70af579f805c

[athrxx]

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pushed to the 'scummvm' repo located at https://github.com/scummvm/scummvm .

Summary:
4fe69dbf2e SCUMM:  fix bug no. 12499 ("Curse of Monkey Island Sprite Vertical Colour Artifacts")


Commit: 4fe69dbf2e1325fecccc2ee69b2f70af579f805c
    https://github.com/scummvm/scummvm/commit/4fe69dbf2e1325fecccc2ee69b2f70af579f805c
Author: athrxx (athrxx at scummvm.org)
Date: 2021-08-03T20:26:59+02:00

Commit Message:
SCUMM:  fix bug no. 12499 ("Curse of Monkey Island Sprite Vertical Colour Artifacts")

(regression from b542fad7)

The introduction of the skip_column variable caused skipping of columns that are actually meant to be drawn. The original interpreter has a similiar mechanism, but it only applies to colors that are translated via the shadow palette. This avoids recursive shading (pixels that already got translated via the shadow palette could get passed through the table again in case of horizontal scaling). I guess that is what b542fad7 actually meant to fix.

Changed paths:
    engines/scumm/akos.cpp


diff --git a/engines/scumm/akos.cpp b/engines/scumm/akos.cpp
index 65bbfe7e76..d5d2609e6c 100644
--- a/engines/scumm/akos.cpp
+++ b/engines/scumm/akos.cpp
@@ -543,12 +543,12 @@ void AkosRenderer::codec1_genericDecode(Codec1 &v1) {
 	const byte *mask, *src;
 	byte *dst;
 	byte len, maskbit;
-	int y;
+	int lastColumnX, y;
 	uint16 color, height, pcolor;
 	const byte *scaleytab;
 	bool masked;
-	bool skip_column = false;
 
+	lastColumnX = -1;
 	y = v1.y;
 	src = _srcptr;
 	dst = v1.destptr;
@@ -579,31 +579,50 @@ void AkosRenderer::codec1_genericDecode(Codec1 &v1) {
 					}
 				} else {
 					masked = (y < v1.boundsRect.top || y >= v1.boundsRect.bottom) || (v1.x < 0 || v1.x >= v1.boundsRect.right) || (*mask & maskbit);
+					bool skipColumn = false;
 
-					if (color && !masked && !skip_column) {
+					if (color && !masked) {
 						pcolor = _palette[color];
 						if (_shadow_mode == 1) {
-							if (pcolor == 13)
+							if (pcolor == 13) {
+								// In shadow mode 1 skipColumn works more or less the same way as in shadow
+								// mode 3. It is only ever checked and applied if pcolor is 13.
+								skipColumn = (lastColumnX == v1.x);
 								pcolor = _shadow_table[*dst];
+							}
 						} else if (_shadow_mode == 2) {
 							error("codec1_spec2"); // TODO
 						} else if (_shadow_mode == 3) {
 							if (_vm->_game.features & GF_16BIT_COLOR) {
+								// I add the column skip here, too, although I don't know whether it always
+								// applies. But this is the only way to prevent recursive shading of pixels.
+								// This might need more fine tuning...
+								skipColumn = (lastColumnX == v1.x);
 								uint16 srcColor = (pcolor >> 1) & 0x7DEF;
 								uint16 dstColor = (READ_UINT16(dst) >> 1) & 0x7DEF;
 								pcolor = srcColor + dstColor;
 							} else if (_vm->_game.heversion >= 90) {
+								// I add the column skip here, too, although I don't know whether it always
+								// applies. But this is the only way to prevent recursive shading of pixels.
+								// This might need more fine tuning...
+								skipColumn = (lastColumnX == v1.x);
 								pcolor = (pcolor << 8) + *dst;
 								pcolor = xmap[pcolor];
-							} else if (pcolor < 8) {
+							} else if (pcolor < 8 ) {
+								// This mode is used in COMI. The column skip only takes place when the shading
+								// is actually applied (for pcolor < 8). The skip avoids shading of pixels that
+								// already have been shaded.
+								skipColumn = (lastColumnX == v1.x);
 								pcolor = (pcolor << 8) + *dst;
 								pcolor = _shadow_table[pcolor];
 							}
 						}
-						if (_vm->_bytesPerPixel == 2) {
-							WRITE_UINT16(dst, pcolor);
-						} else {
-							*dst = pcolor;
+						if (!skipColumn) {
+							if (_vm->_bytesPerPixel == 2) {
+								WRITE_UINT16(dst, pcolor);
+							} else {
+								*dst = pcolor;
+							}
 						}
 					}
 				}
@@ -618,16 +637,16 @@ void AkosRenderer::codec1_genericDecode(Codec1 &v1) {
 				y = v1.y;
 
 				scaleytab = &v1.scaletable[v1.scaleYindex];
+				lastColumnX = v1.x;
 
-				if (_scaleX == 255 || v1.scaletable[v1.scaleXindex] < _scaleX) {
+				if (_scaleX == 255 || v1.scaletable[v1.scaleXindex] < _scaleX) {	
 					v1.x += v1.scaleXstep;
 					if (v1.x < 0 || v1.x >= v1.boundsRect.right)
 						return;
 					maskbit = revBitMask(v1.x & 7);
 					v1.destptr += v1.scaleXstep * _vm->_bytesPerPixel;
-					skip_column = false;
-				} else
-					skip_column = true;
+				}
+
 				v1.scaleXindex += v1.scaleXstep;
 				dst = v1.destptr;
 				mask = _vm->getMaskBuffer(v1.x - (_vm->_virtscr[kMainVirtScreen].xstart & 7), v1.y, _zbuf);