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Add comments to `ft_corner_is_flat'.

This commit is contained in:
Werner Lemberg 2013-08-04 18:24:02 +02:00
parent b8bf8b54e5
commit fb09a51f0f
1 changed files with 23 additions and 3 deletions
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26
src/base/ftcalc.c
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@ -945,11 +945,27 @@
FT_Pos d_in, d_out, d_corner;
/* We approximate the Euclidean metric (sqrt(x^2 + y^2)) with */
/* the Taxicab metric (x + y), which can be computed much */
/* faster. If one of the two vectors is much longer than the */
/* other one, the direction of the shorter vector doesn't */
/* influence the result any more. */
/* */
/* corner */
/* x---------------------------x */
/* \ / */
/* \ / */
/* in \ / out */
/* \ / */
/* o */
/* Point */
/* */
if ( ax < 0 )
ax = -ax;
if ( ay < 0 )
ay = -ay;
d_in = ax + ay;
d_in = ax + ay; /* d_in = || in || */
ax = out_x;
if ( ax < 0 )
@ -957,7 +973,7 @@
ay = out_y;
if ( ay < 0 )
ay = -ay;
d_out = ax + ay;
d_out = ax + ay; /* d_out = || out || */
ax = out_x + in_x;
if ( ax < 0 )
@ -965,7 +981,11 @@
ay = out_y + in_y;
if ( ay < 0 )
ay = -ay;
d_corner = ax + ay;
d_corner = ax + ay; /* d_corner = || in + out || */
/* now do a simple length comparison: */
/* */
/* d_in + d_out < 17/16 d_corner */
return ( d_in + d_out - d_corner ) < ( d_corner >> 4 );
}