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[truetype] Fix some comments in the bytecode interpreter.

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Thanks to Greg Hitchcock!
autohinter-properties
Werner Lemberg 14 years ago
parent 29a7965fd1
commit f2573a0611
1 changed files with 38 additions and 38 deletions
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  1. 76
      src/truetype/ttinterp.c

76
src/truetype/ttinterp.c
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@ -16,6 +16,10 @@
/***************************************************************************/
/* Greg Hitchcock from Microsoft has helped a lot in resolving unclear */
/* issues; many thanks! */
#include <ft2build.h>
#include FT_INTERNAL_DEBUG_H
#include FT_INTERNAL_CALC_H
@ -664,9 +668,9 @@
FT_Int i;
/* XXXX: Will probably disappear soon with all the code range */
/* management, which is now rather obsolete. */
/* */
/* XXX: Will probably disappear soon with all the code range */
/* management, which is now rather obsolete. */
/* */
size->num_function_defs = exec->numFDefs;
size->num_instruction_defs = exec->numIDefs;
@ -5095,8 +5099,8 @@
CUR_Func_move( &CUR.zp2, L, args[1] - K );
/* not part of the specs, but here for safety */
/* UNDOCUMENTED! The MS rasterizer does that with */
/* twilight points (confirmed by Greg Hitchcock) */
if ( CUR.GS.gep2 == 0 )
CUR.zp2.org[L] = CUR.zp2.cur[L];
}
@ -5920,9 +5924,9 @@
return;
}
/* XXX: UNDOCUMENTED! behaviour */
if ( CUR.GS.gep1 == 0 ) /* if the point that is to be moved */
/* is in twilight zone */
/* UNDOCUMENTED! The MS rasterizer does that with */
/* twilight points (confirmed by Greg Hitchcock) */
if ( CUR.GS.gep1 == 0 )
{
CUR.zp1.org[point] = CUR.zp0.org[CUR.GS.rp0];
CUR_Func_move_orig( &CUR.zp1, point, args[1] );
@ -5965,8 +5969,6 @@
return;
}
/* XXX: Is there some undocumented feature while in the */
/* twilight zone? ? */
if ( ( CUR.opcode & 1 ) != 0 )
{
cur_dist = CUR_fast_project( &CUR.zp0.cur[point] );
@ -6009,34 +6011,34 @@
goto Fail;
}
/* XXX: UNDOCUMENTED! */
/* */
/* The behaviour of an MIAP instruction is quite */
/* different when used in the twilight zone. */
/* */
/* First, no control value cut-in test is performed */
/* as it would fail anyway. Second, the original */
/* point, i.e. (org_x,org_y) of zp0.point, is set */
/* to the absolute, unrounded distance found in */
/* the CVT. */
/* */
/* This is used in the CVT programs of the Microsoft */
/* fonts Arial, Times, etc., in order to re-adjust */
/* some key font heights. It allows the use of the */
/* IP instruction in the twilight zone, which */
/* otherwise would be `illegal' according to the */
/* specification. */
/* */
/* We implement it with a special sequence for the */
/* twilight zone. This is a bad hack, but it seems */
/* to work. */
/* UNDOCUMENTED! */
/* */
/* The behaviour of an MIAP instruction is quite different when used */
/* in the twilight zone. */
/* */
/* First, no control value cut-in test is performed as it would fail */
/* anyway. Second, the original point, i.e. (org_x,org_y) of */
/* zp0.point, is set to the absolute, unrounded distance found in the */
/* CVT. */
/* */
/* This is used in the CVT programs of the Microsoft fonts Arial, */
/* Times, etc., in order to re-adjust some key font heights. It */
/* allows the use of the IP instruction in the twilight zone, which */
/* otherwise would be invalid according to the specification. */
/* */
/* We implement it with a special sequence for the twilight zone. */
/* This is a bad hack, but it seems to work. */
/* */
/* Confirmed by Greg Hitchcock. */
distance = CUR_Func_read_cvt( cvtEntry );
if ( CUR.GS.gep0 == 0 ) /* If in twilight zone */
{
CUR.zp0.org[point].x = TT_MulFix14( (FT_UInt32)distance, CUR.GS.freeVector.x );
CUR.zp0.org[point].y = TT_MulFix14( (FT_UInt32)distance, CUR.GS.freeVector.y ),
CUR.zp0.org[point].x = TT_MulFix14( (FT_UInt32)distance,
CUR.GS.freeVector.x );
CUR.zp0.org[point].y = TT_MulFix14( (FT_UInt32)distance,
CUR.GS.freeVector.y ),
CUR.zp0.cur[point] = CUR.zp0.org[point];
}
@ -6220,19 +6222,17 @@
cvt_dist = -CUR.GS.single_width_value;
}
/* XXX: UNDOCUMENTED! -- twilight zone */
/* UNDOCUMENTED! The MS rasterizer does that with */
/* twilight points (confirmed by Greg Hitchcock) */
if ( CUR.GS.gep1 == 0 )
{
CUR.zp1.org[point].x = CUR.zp0.org[CUR.GS.rp0].x +
TT_MulFix14( (FT_UInt32)cvt_dist,
CUR.GS.freeVector.x );
CUR.zp1.org[point].y = CUR.zp0.org[CUR.GS.rp0].y +
TT_MulFix14( (FT_UInt32)cvt_dist,
CUR.GS.freeVector.y );
CUR.zp1.cur[point] = CUR.zp0.cur[point];
CUR.zp1.cur[point] = CUR.zp0.cur[point];
}
org_dist = CUR_Func_dualproj( &CUR.zp1.org[point],

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