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Replace buggy code in TestSegmentHit() with call to SEG::PointCloserThan() 

Fixes: lp:1843101
* https://bugs.launchpad.net/kicad/+bug/1843101
This commit is contained in:
Jeff Young 2019-09-07 23:16:40 +01:00
parent 0ff20c18a3
commit 6f0d8c3eac
1 changed files with 3 additions and 26 deletions
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29
common/geometry/trigo.cpp
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@ -32,6 +32,7 @@
#include <trigo.h>
#include <common.h>
#include <math_for_graphics.h>
#include <geometry/seg.h>
// Returns true if the point P is on the segment S.
// faster than TestSegmentHit() because P should be exactly on S
@ -151,32 +152,8 @@ bool TestSegmentHit( const wxPoint &aRefPoint, wxPoint aStart, wxPoint aEnd, int
if( aStart.y == aEnd.y && aRefPoint.x > xmin && aRefPoint.x < xmax )
return std::abs( delta.y ) <= aDist;
// Special case for a segment with start == end (equal to a circle)
if ( aStart == aEnd )
{
long double length_square = (long double) delta.x * delta.x + (long double) delta.y * delta.y;
long double dist_square = (long double) aDist * aDist;
return ( length_square <= dist_square );
}
wxPoint len = aEnd - aStart;
// Precision note here:
// These are 32-bit integers, so squaring requires 64 bits to represent
// exactly. 64-bit Doubles have only 52 bits in the mantissa, so we start to lose
// precision at 2^53, which corresponds to ~ ±1nm @ 9.5cm, 2nm at 90cm, etc...
// Long doubles avoid this ambiguity as well as the more expensive denormal double calc
// Long doubles usually (sometimes more if SIMD) have at least 64 bits in the mantissa
long double length_square = (long double) len.x * len.x + (long double) len.y * len.y;
long double cross = std::abs( (long double) len.x * delta.y - (long double) len.y * delta.x );
long double dist_square = (long double) aDist * aDist;
// The perpendicular distance to a line is the vector magnitude of the line from
// a test point to the test line. That is the 2d determinant. Because we handled
// the zero length case above, so we are guaranteed a unique solution.
return ( ( length_square >= cross && dist_square >= cross ) ||
( length_square * dist_square >= cross * cross ) );
SEG segment( aStart, aEnd );
return segment.PointCloserThan( aRefPoint, aDist );
}