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[truetype] Perform variation store delta computation with 64-bit precision. 

* include/freetype/internal/ftmmtypes.h (FT_ItemVarDelta): Make type
explicitly 32-bit.
* include/freetype/internal/services/svmm.h
(FT_Var_Get_Item_Delta_Func): Change return type to `FT_ItemVarDelta`
* truetype/ttgxvar.h (tt_var_get_item_delta): Change return type to
`FT_ItemVarDelta`.
* truetype/ttgxvar.c (tt_var_get_item_delta): Store scalars and deltas
to intermediate array, perform computation using new method
`FT_MulAddFix`.
This commit is contained in:
Dominik Röttsches 2022-06-29 11:48:53 +03:00 committed by Werner Lemberg
parent 15fef219d6
commit dece953516
4 changed files with 37 additions and 15 deletions
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2
include/freetype/internal/ftmmtypes.h
View File

@ -24,7 +24,7 @@
FT_BEGIN_HEADER
typedef FT_Long FT_ItemVarDelta;
typedef FT_Int32 FT_ItemVarDelta;
typedef struct GX_ItemVarDataRec_
{

2
include/freetype/internal/services/svmm.h
View File

@ -109,7 +109,7 @@ FT_BEGIN_HEADER
FT_ULong offset,
GX_ItemVarStore itemStore );
typedef FT_Int
typedef FT_ItemVarDelta
(*FT_Var_Get_Item_Delta_Func)( FT_Face face,
GX_ItemVarStore itemStore,
FT_UInt outerIndex,

46
src/truetype/ttgxvar.c
View File

@ -939,19 +939,23 @@
}
FT_LOCAL_DEF( FT_Int )
FT_LOCAL_DEF( FT_ItemVarDelta )
tt_var_get_item_delta( TT_Face face,
GX_ItemVarStore itemStore,
FT_UInt outerIndex,
FT_UInt innerIndex )
{
FT_Stream stream = FT_FACE_STREAM( face );
FT_Memory memory = stream->memory;
FT_Error error = FT_Err_Ok;
GX_ItemVarData varData;
FT_ItemVarDelta* deltaSet;
FT_UInt master, j;
FT_Fixed netAdjustment = 0; /* accumulated adjustment */
FT_Fixed scaledDelta;
FT_Fixed delta;
FT_UInt master, j;
FT_Fixed* scalars;
FT_ItemVarDelta returnValue;
/* OpenType 1.8.4+: No variation data for this item
* as indices have special value 0xFFFF. */
@ -964,6 +968,9 @@
varData = &itemStore->varData[outerIndex];
deltaSet = &varData->deltaSet[varData->regionIdxCount * innerIndex];
if ( FT_QNEW_ARRAY( scalars, varData->regionIdxCount ) )
return 0;
/* outer loop steps through master designs to be blended */
for ( master = 0; master < varData->regionIdxCount; master++ )
{
@ -1013,18 +1020,33 @@
FT_MulDiv( scalar,
axis->endCoord - face->blend->normalizedcoords[j],
axis->endCoord - axis->peakCoord );
} /* per-axis loop */
/* get the scaled delta for this region */
delta = FT_intToFixed( deltaSet[master] );
scaledDelta = FT_MulFix( scalar, delta );
/* accumulate the adjustments from each region */
netAdjustment = netAdjustment + scaledDelta;
scalars[master] = scalar;
} /* per-region loop */
return FT_fixedToInt( netAdjustment );
/* Compute the scaled delta for this region.
*
* From: https://docs.microsoft.com/en-us/typography/opentype/spec/otvarcommonformats#item-variation-store-header-and-item-variation-data-subtables:
*
* `Fixed` is a 32-bit (16.16) type and, in the general case, requires
* 32-bit deltas. As described above, the `DeltaSet` record can
* accommodate deltas that are, logically, either 16-bit or 32-bit.
* When scaled deltas are applied to `Fixed` values, the `Fixed` value
* is treated like a 32-bit integer.
*
* `FT_MulAddFix` internally uses 64-bit precision; it thus can handle
* deltas ranging from small 8-bit to large 32-bit values that are
* applied to 16.16 `FT_Fixed` / OpenType `Fixed` values.
*/
returnValue = FT_MulAddFix( scalars, deltaSet, varData->regionIdxCount );
FT_FREE( scalars );
return returnValue;
}

2
src/truetype/ttgxvar.h
View File

@ -391,7 +391,7 @@ FT_BEGIN_HEADER
GX_ItemVarStore itemStore,
FT_ULong table_len );
FT_LOCAL( FT_Int )
FT_LOCAL( FT_ItemVarDelta )
tt_var_get_item_delta( TT_Face face,
GX_ItemVarStore itemStore,
FT_UInt outerIndex,