ref: b7ef2b096867d7351c873c44dd4053d90d7997ef
parent: 48641d60ae853a34a5c683d69cf35f879d2567d1
author: David Turner <[email protected]>
date: Tue May 2 07:01:12 EDT 2000
in order to ensure that the bytecode interpretation is exactly equivalent to the one in FT 1.4, moved some code from the old version of FreeType in order to compute vector normalization a bit differently
--- a/src/truetype/ttinterp.c
+++ b/src/truetype/ttinterp.c
@@ -825,6 +825,22 @@
}
+#ifdef FT_CONFIG_OPTION_OLD_CALCS
+
+ static TT_F26Dot6 Norm( TT_F26Dot6 X, TT_F26Dot6 Y )
+ {+ FT_Int64 T1, T2;
+
+ MUL_64( X, X, T1 );
+ MUL_64( Y, Y, T2 );
+
+ ADD_64( T1, T2, T1 );
+
+ return (TT_F26Dot6)SQRT_64( T1 );
+ }
+#endif
+
+
/*************************************************************************/
/* */
/* Before an opcode is executed, the interpreter verifies that there are */
@@ -1194,7 +1210,7 @@
else
{TT_Long x, y;
-#if 0
+#ifdef FT_CONFIG_OPTION_OLD_CALCS
x = TT_MULDIV( CUR.GS.projVector.x, CUR.tt_metrics.x_ratio, 0x4000 );
y = TT_MULDIV( CUR.GS.projVector.y, CUR.tt_metrics.y_ratio, 0x4000 );
CUR.tt_metrics.ratio = Norm( x, y );
@@ -2126,6 +2142,98 @@
/* In case Vx and Vy are both zero, Normalize() returns SUCCESS, and */
/* R is undefined. */
/* */
+
+#ifdef FT_CONFIG_OPTION_OLD_CALCS
+ static TT_Bool Normalize( EXEC_OP_ TT_F26Dot6 Vx,
+ TT_F26Dot6 Vy,
+ TT_UnitVector* R )
+ {+ TT_F26Dot6 W;
+ TT_Bool S1, S2;
+
+ if ( ABS( Vx ) < 0x10000L && ABS( Vy ) < 0x10000L )
+ {+ Vx *= 0x100;
+ Vy *= 0x100;
+
+ W = Norm( Vx, Vy );
+
+ if ( W == 0 )
+ {+ /* XXX : UNDOCUMENTED! It seems that it's possible to try */
+ /* to normalize the vector (0,0). Return immediately */
+ return SUCCESS;
+ }
+
+ R->x = (TT_F2Dot14)FT_MulDiv( Vx, 0x4000L, W );
+ R->y = (TT_F2Dot14)FT_MulDiv( Vy, 0x4000L, W );
+
+ return SUCCESS;
+ }
+
+ W = Norm( Vx, Vy );
+
+ Vx = FT_MulDiv( Vx, 0x4000L, W );
+ Vy = FT_MulDiv( Vy, 0x4000L, W );
+
+ W = Vx * Vx + Vy * Vy;
+
+ /* Now, we want that Sqrt( W ) = 0x4000 */
+ /* Or 0x1000000 <= W < 0x1004000 */
+
+ if ( Vx < 0 )
+ {+ Vx = -Vx;
+ S1 = TRUE;
+ }
+ else
+ S1 = FALSE;
+
+ if ( Vy < 0 )
+ {+ Vy = -Vy;
+ S2 = TRUE;
+ }
+ else
+ S2 = FALSE;
+
+ while ( W < 0x1000000L )
+ {+ /* We need to increase W, by a minimal amount */
+ if ( Vx < Vy )
+ Vx++;
+ else
+ Vy++;
+
+ W = Vx * Vx + Vy * Vy;
+ }
+
+ while ( W >= 0x1004000L )
+ {+ /* We need to decrease W, by a minimal amount */
+ if ( Vx < Vy )
+ Vx--;
+ else
+ Vy--;
+
+ W = Vx * Vx + Vy * Vy;
+ }
+
+ /* Note that in various cases, we can only */
+ /* compute a Sqrt(W) of 0x3FFF, eg. Vx = Vy */
+
+ if ( S1 )
+ Vx = -Vx;
+
+ if ( S2 )
+ Vy = -Vy;
+
+ R->x = (TT_F2Dot14)Vx; /* Type conversion */
+ R->y = (TT_F2Dot14)Vy; /* Type conversion */
+
+ return SUCCESS;
+ }
+#else
static
TT_Bool Normalize( EXEC_OP_ TT_F26Dot6 Vx,
TT_F26Dot6 Vy,
@@ -2203,9 +2311,42 @@
R->y = (TT_F2Dot14)TT_MULDIV( Vy >> shift, 0x4000, d );
}
+ {+ TT_ULong x, y, w;
+ TT_Int sx, sy;
+
+ sx = ( R->x >= 0 ? 1 : -1 );
+ sy = ( R->y >= 0 ? 1 : -1 );
+ x = (TT_ULong)sx*R->x;
+ y = (TT_ULong)sy*R->y;
+
+ w = x*x+y*y;
+
+ /* we now want to adjust (x,y) in order to have sqrt(w) == 0x4000 */
+ /* which means 0x1000000 <= w < 0x1004000 */
+ while ( w <= 0x10000000L )
+ {+ /* increment the smallest coordinate */
+ if ( x < y ) x++;
+ else y++;
+
+ w = x*x+y*y;
+ }
+
+ while ( w >= 0x10040000L )
+ {+ /* decrement the smallest coordinate */
+ if ( x < y ) x--;
+ else y--;
+ w = x*x+y*y;
+ }
+
+ R->x = sx*x;
+ R->y = sy*y;
+ }
return SUCCESS;
}
-
+#endif
/*************************************************************************/
/* */