ref: f8efbcfb8ef77797f5f2c7095a6030080e4c0855
parent: d2935e2969c443a7a6485ac3474a87cd639ab49d
author: Alexei Podtelezhnikov <[email protected]>
date: Tue Aug 12 19:22:17 EDT 2014
[base] Avoid undefined FT_MSB in `BBox_Cubic_Check'. * src/base/ftbbox.c (BBox_Cubic_Check): Update. (update_cubic_max): Repalce with... (cubic_peak): ... this, which now handles upscaling.
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2014-08-12 Alexei Podtelezhnikov <[email protected]>
+
+ [base] Avoid undefined FT_MSB in `BBox_Cubic_Check'.
+
+ * src/base/ftbbox.c (BBox_Cubic_Check): Update.
+ (update_cubic_max): Repalce with...
+ (cubic_peak): ... this, which now handles upscaling.
+
2014-08-11 Alexei Podtelezhnikov <[email protected]>
[base] Handle collapsed outlines to avoid undefined FT_MSB.
--- a/src/base/ftbbox.c
+++ b/src/base/ftbbox.c
@@ -203,15 +203,48 @@
/* max :: The address of the current maximum. */
/* */
static FT_Pos
- update_cubic_max( FT_Pos q1,
- FT_Pos q2,
- FT_Pos q3,
- FT_Pos q4,
- FT_Pos max )
+ cubic_peak( FT_Pos q1,
+ FT_Pos q2,
+ FT_Pos q3,
+ FT_Pos q4 )
{+ FT_Pos peak = 0;
+ FT_Int shift;
+
+ /* This function finds a peak of a cubic segment if it is above 0 */
+ /* using iterative bisection of the segment, or returns 0. */
+ /* The fixed-point arithmetic of bisection is inherently stable */
+ /* but may loose accuracy in the two lowest bits. To compensate, */
+ /* we upscale the segment if there is room. Large values may need */
+ /* to be downscaled to avoid overflows during bisection. */
+ /* It is called with either q2 or q3 positive, which is necessary */
+ /* for the peak to exist and avoids undefined FT_MSB. */
+
+ shift = 27 -
+ FT_MSB( FT_ABS( q1 ) | FT_ABS( q2 ) | FT_ABS( q3 ) | FT_ABS( q4 ) );
+
+ if ( shift > 0 )
+ {+ /* upscaling too much just wastes time */
+ if ( shift > 2 )
+ shift = 2;
+
+ q1 <<= shift;
+ q2 <<= shift;
+ q3 <<= shift;
+ q4 <<= shift;
+ }
+ else
+ {+ q1 >>= -shift;
+ q2 >>= -shift;
+ q3 >>= -shift;
+ q4 >>= -shift;
+ }
+
/* for a cubic segment to possibly reach new maximum, at least */
/* one of its off-points must stay above the current value */
- while ( q2 > max || q3 > max )
+ while ( q2 > 0 || q3 > 0 )
{/* determine which half contains the maximum and split */
if ( q1 + q2 > q3 + q4 ) /* first half */
@@ -240,17 +273,22 @@
/* check whether either end reached the maximum */
if ( q1 == q2 && q1 >= q3 )
{- max = q1;
+ peak = q1;
break;
}
if ( q3 == q4 && q2 <= q4 )
{- max = q4;
+ peak = q4;
break;
}
}
- return max;
+ if ( shift > 0 )
+ peak >>= shift;
+ else
+ peak <<= -shift;
+
+ return peak;
}
@@ -262,65 +300,18 @@
FT_Pos* min,
FT_Pos* max )
{- FT_Pos nmin, nmax;
- FT_Int shift;
-
-
/* This function is only called when a control off-point is outside */
- /* the bbox that contains all on-points. It finds a local extremum */
- /* within the segment using iterative bisection of the segment. */
- /* The fixed-point arithmetic of bisection is inherently stable */
- /* but may loose accuracy in the two lowest bits. To compensate, */
- /* we upscale the segment if there is room. Large values may need */
- /* to be downscaled to avoid overflows during bisection. */
- /* The control off-point outside the bbox is likely to have the top */
- /* absolute value among arguments. */
+ /* the bbox that contains all on-points. So at least one of the */
+ /* conditions below holds and cubic_peak is called with at least one */
+ /* non-zero argument. */
- shift = 27 - FT_MSB( FT_ABS( p2 ) | FT_ABS( p3 ) );
+ if ( p2 > *max || p3 > *max )
+ *max += cubic_peak( p1 - *max, p2 - *max, p3 - *max, p4 - *max );
- if ( shift > 0 )
- {- /* upscaling too much just wastes time */
- if ( shift > 2 )
- shift = 2;
-
- p1 <<= shift;
- p2 <<= shift;
- p3 <<= shift;
- p4 <<= shift;
- nmin = *min << shift;
- nmax = *max << shift;
- }
- else
- {- p1 >>= -shift;
- p2 >>= -shift;
- p3 >>= -shift;
- p4 >>= -shift;
- nmin = *min >> -shift;
- nmax = *max >> -shift;
- }
-
- nmax = update_cubic_max( p1, p2, p3, p4, nmax );
-
/* now flip the signs to update the minimum */
- nmin = -update_cubic_max( -p1, -p2, -p3, -p4, -nmin );
+ if ( p2 < *min || p3 < *min )
+ *min -= cubic_peak( *min - p1, *min - p2, *min - p3, *min - p4 );
- if ( shift > 0 )
- {- nmin >>= shift;
- nmax >>= shift;
- }
- else
- {- nmin <<= -shift;
- nmax <<= -shift;
- }
-
- if ( nmin < *min )
- *min = nmin;
- if ( nmax > *max )
- *max = nmax;
}