Commit f8efbcfb8ef77797f5f2c7095a6030080e4c0855
2014-08-12T23:22:17
[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.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174
diff --git a/ChangeLog b/ChangeLog
index 48e3115..b6c5228 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2014-08-12 Alexei Podtelezhnikov <apodtele@gmail.com>
+
+ [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 <apodtele@gmail.com>
[base] Handle collapsed outlines to avoid undefined FT_MSB.
diff --git a/src/base/ftbbox.c b/src/base/ftbbox.c
index 8d3f383..54531c6 100644
--- 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. */
-
- shift = 27 - FT_MSB( FT_ABS( p2 ) | FT_ABS( p3 ) );
+ /* 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. */
- 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 );
+ if ( p2 > *max || p3 > *max )
+ *max += cubic_peak( p1 - *max, p2 - *max, p3 - *max, p4 - *max );
/* now flip the signs to update the minimum */
- nmin = -update_cubic_max( -p1, -p2, -p3, -p4, -nmin );
-
- if ( shift > 0 )
- {
- nmin >>= shift;
- nmax >>= shift;
- }
- else
- {
- nmin <<= -shift;
- nmax <<= -shift;
- }
+ if ( p2 < *min || p3 < *min )
+ *min -= cubic_peak( *min - p1, *min - p2, *min - p3, *min - p4 );
- if ( nmin < *min )
- *min = nmin;
- if ( nmax > *max )
- *max = nmax;
}