ref: 6e88087d6962714e2cf1d1ddba56cfeb2cf9c02c
parent: 0b3cb8a8afb15247ee55477f73e25e0ca3038e5b
author: Alexei Podtelezhnikov <[email protected]>
date: Thu May 5 19:41:03 EDT 2016
[smooth] More efficient accounting of conic splits and draws. A single decrement counter of segments to draw, instead of an array, contains all the information necessary to decide when to split and when to draw a conic segment. The number of splits before each draw is equal to the number of trailing zeros in the counter. * src/smooth/ftgrays.c (gray_TWorker): Remove `lev_stack'. (gray_render_conic): Updated to use decrement counter of segments.
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2016-05-05 Alexei Podtelezhnikov <[email protected]>
+
+ [smooth] More efficient accounting of conic splits and draws.
+
+ A single decrement counter of segments to draw, instead of an array,
+ contains all the information necessary to decide when to split and
+ when to draw a conic segment. The number of splits before each draw is
+ equal to the number of trailing zeros in the counter.
+
+ * src/smooth/ftgrays.c (gray_TWorker): Remove `lev_stack'.
+ (gray_render_conic): Updated to use decrement counter of segments.
+
2016-05-05 Werner Lemberg <[email protected]>
[cff, truetype] Fix logic for `FT_Property_Set'.
--- a/src/smooth/ftgrays.c
+++ b/src/smooth/ftgrays.c
@@ -369,7 +369,7 @@
/* These macros speed up repetitive divisions by replacing them */
- /* with multiplications and right shifts. */
+ /* with multiplications and right shifts. */
#define FT_UDIVPREP( b ) \
long b ## _r = (long)( FT_ULONG_MAX >> PIXEL_BITS ) / ( b )
#define FT_UDIV( a, b ) \
@@ -435,7 +435,6 @@
TPos x, y;
FT_Vector bez_stack[32 * 3 + 1];
- int lev_stack[32];
FT_Outline outline;
FT_Bitmap target;
@@ -1068,50 +1067,44 @@
gray_render_conic( RAS_ARG )
{TPos dx, dy;
- int top, level;
- int* levels = ras.lev_stack;
+ int draw, split, level;
FT_Vector* arc = ras.bez_stack;
- top = 0;
-
dx = FT_ABS( arc[2].x + arc[0].x - 2 * arc[1].x );
dy = FT_ABS( arc[2].y + arc[0].y - 2 * arc[1].y );
if ( dx < dy )
dx = dy;
- if ( dx < ONE_PIXEL / 4 )
- goto Draw;
+ /* We can calculate the number of necessary bisections because */
+ /* each bisection predictably reduces deviation exactly 4-fold. */
- /* we can calculate the number of necessary bisections because */
- /* each bisection predictably reduces deviation at least 4-fold */
level = 0;
- do
+ while ( dx > ONE_PIXEL / 4 )
{dx >>= 2;
level++;
- } while ( dx > ONE_PIXEL / 4 );
+ }
- levels[0] = level;
+ /* We use decrement counter to count the total number of segments */
+ /* to draw starting from 2^level. Before each draw we split as */
+ /* many times as there are trailing zeros in the counter. */
+ draw = 1 << level;
do
{- level = levels[top];
- if ( level > 0 )
+ split = 1;
+ while ( ( draw & split ) == 0 )
{gray_split_conic( arc );
arc += 2;
- top++;
- levels[top] = levels[top - 1] = level - 1;
- continue;
+ split <<= 1;
}
- Draw:
gray_render_line( RAS_VAR_ arc[0].x, arc[0].y );
- top--;
arc -= 2;
- } while ( top >= 0 );
+ } while ( --draw );
}