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gal: cairo: pixel-align arc endpoints, not center to avoid misalignment with adjacent line segments

This commit is contained in:
Tomasz Włostowski 2019-02-19 00:39:55 +01:00
parent 4597979d18
commit f66baaed8c
1 changed files with 26 additions and 5 deletions
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31
common/gal/cairo/cairo_gal.cpp
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@ -258,19 +258,40 @@ void CAIRO_GAL_BASE::DrawArc( const VECTOR2D& aCenterPoint, double aRadius, doub
{
syncLineWidth();
auto c = roundp( xform( aCenterPoint ) );
auto r = ::roundp( xform( aRadius ) );
SWAP( aStartAngle, >, aEndAngle );
auto startAngleS = angle_xform( aStartAngle );
auto endAngleS = angle_xform( aEndAngle );
SWAP( startAngleS, >, endAngleS );
VECTOR2D startPoint( cos( startAngleS ) * aRadius + aCenterPoint.x,
sin( startAngleS ) * aRadius + aCenterPoint.y );
VECTOR2D endPoint( cos( endAngleS ) * aRadius + aCenterPoint.x,
sin( endAngleS ) * aRadius + aCenterPoint.y );
auto startPointS = roundp( xform ( startPoint ) );
auto endPointS = roundp( xform ( endPoint ) );
double centerAngle = endAngleS - startAngleS;
auto mid = ( startPointS + endPointS ) * 0.5;
auto chord = endPointS - startPointS;
double c = chord.EuclideanNorm() / 2.0;
auto d = chord.Rotate( (centerAngle > M_PI ? -M_PI : M_PI) / 2.0 ).Resize( c );
VECTOR2D centerS;
if( centerAngle == 0.0 )
centerS = mid;
else
centerS = mid + d * ( 1.0 / tan( centerAngle / 2.0 ) );
auto rS = (centerS - startPointS).EuclideanNorm();
cairo_set_line_width( currentContext, lineWidthInPixels );
cairo_new_sub_path( currentContext );
if( isFillEnabled )
cairo_move_to( currentContext, c.x, c.y );
cairo_move_to( currentContext, centerS.x, centerS.y );
cairo_arc( currentContext, c.x, c.y, r, startAngleS, endAngleS );
cairo_arc( currentContext, centerS.x, centerS.y, rS, startAngleS, endAngleS );
if( isFillEnabled )
cairo_close_path( currentContext );