/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright (C) 2014 CERN
 * Copyright (C) 2018-2021 KiCad Developers, see AUTHORS.txt for contributors.
 * @author Tomasz Wlostowski <tomasz.wlostowski@cern.ch>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you may find one here:
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * or you may search the http://www.gnu.org website for the version 2 license,
 * or you may write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */

#include <functional>
#include <board.h>
#include <dimension.h>
#include <fp_shape.h>
#include <footprint.h>
#include <track.h>
#include <zone.h>
#include <geometry/shape_circle.h>
#include <geometry/shape_line_chain.h>
#include <geometry/shape_rect.h>
#include <geometry/shape_segment.h>
#include <geometry/shape_simple.h>
#include <macros.h>
#include <math/util.h> // for KiROUND
#include <painter.h>
#include <pcbnew_settings.h>
#include <tool/tool_manager.h>
#include <tools/pcb_tool_base.h>
#include <view/view.h>
#include "pcb_grid_helper.h"


PCB_GRID_HELPER::PCB_GRID_HELPER( TOOL_MANAGER* aToolMgr, MAGNETIC_SETTINGS* aMagneticSettings ) :
    GRID_HELPER( aToolMgr ),
    m_magneticSettings( aMagneticSettings )
{
    KIGFX::VIEW*            view = m_toolMgr->GetView();
    KIGFX::RENDER_SETTINGS* settings = view->GetPainter()->GetSettings();
    KIGFX::COLOR4D          auxItemsColor = settings->GetLayerColor( LAYER_AUX_ITEMS );
    KIGFX::COLOR4D          umbilicalColor = settings->GetLayerColor( LAYER_ANCHOR );

    m_viewAxis.SetSize( 20000 );
    m_viewAxis.SetStyle( KIGFX::ORIGIN_VIEWITEM::CROSS );
    m_viewAxis.SetColor( auxItemsColor.WithAlpha( 0.4 ) );
    m_viewAxis.SetDrawAtZero( true );
    view->Add( &m_viewAxis );
    view->SetVisible( &m_viewAxis, false );

    m_viewSnapPoint.SetStyle( KIGFX::ORIGIN_VIEWITEM::CIRCLE_CROSS );
    m_viewSnapPoint.SetColor( auxItemsColor );
    m_viewSnapPoint.SetDrawAtZero( true );
    view->Add( &m_viewSnapPoint );
    view->SetVisible( &m_viewSnapPoint, false );

    m_viewSnapLine.SetStyle( KIGFX::ORIGIN_VIEWITEM::DASH_LINE );
    m_viewSnapLine.SetColor( umbilicalColor );
    m_viewSnapLine.SetDrawAtZero( true );
    view->Add( &m_viewSnapLine );
    view->SetVisible( &m_viewSnapLine, false );
}


VECTOR2I PCB_GRID_HELPER::AlignToSegment( const VECTOR2I& aPoint, const SEG& aSeg )
{
    OPT_VECTOR2I pts[6];

    if( !m_enableSnap )
        return aPoint;

    const VECTOR2D gridOffset( GetOrigin() );
    const VECTOR2D gridSize( GetGrid() );

    VECTOR2I nearest( KiROUND( ( aPoint.x - gridOffset.x ) / gridSize.x ) * gridSize.x + gridOffset.x,
                      KiROUND( ( aPoint.y - gridOffset.y ) / gridSize.y ) * gridSize.y + gridOffset.y );

    pts[0] = aSeg.A;
    pts[1] = aSeg.B;
    pts[2] = aSeg.IntersectLines( SEG( nearest + VECTOR2I( -1, 1 ), nearest + VECTOR2I( 1, -1 ) ) );
    pts[3] = aSeg.IntersectLines( SEG( nearest + VECTOR2I( -1, -1 ), nearest + VECTOR2I( 1, 1 ) ) );

    int min_d = std::numeric_limits<int>::max();

    for( int i = 0; i < 4; i++ )
    {
        if( pts[i] && aSeg.Contains( *pts[i] ) )
        {
            int d = (*pts[i] - aPoint).EuclideanNorm();

            if( d < min_d )
            {
                min_d = d;
                nearest = *pts[i];
            }
        }
    }

    return nearest;
}


VECTOR2I PCB_GRID_HELPER::AlignToArc( const VECTOR2I& aPoint, const SHAPE_ARC& aArc )
{
    if( !m_enableSnap )
        return aPoint;

    const VECTOR2D gridOffset( GetOrigin() );
    const VECTOR2D gridSize( GetGrid() );

    VECTOR2I nearest( KiROUND( ( aPoint.x - gridOffset.x ) / gridSize.x ) * gridSize.x + gridOffset.x,
                      KiROUND( ( aPoint.y - gridOffset.y ) / gridSize.y ) * gridSize.y + gridOffset.y );

    int min_d = std::numeric_limits<int>::max();

    for( auto pt : { aArc.GetP0(), aArc.GetP1() } )
    {
        int d = ( pt - aPoint ).EuclideanNorm();

        if( d < min_d )
        {
            min_d = d;
            nearest = pt;
        }
        else
            break;
    }

    return nearest;
}


VECTOR2I PCB_GRID_HELPER::BestDragOrigin( const VECTOR2I &aMousePos,
                                          std::vector<BOARD_ITEM*>& aItems )
{
    clearAnchors();

    for( BOARD_ITEM* item : aItems )
        computeAnchors( item, aMousePos, true );

    double worldScale = m_toolMgr->GetView()->GetGAL()->GetWorldScale();
    double lineSnapMinCornerDistance = 50.0 / worldScale;

    ANCHOR* nearestOutline = nearestAnchor( aMousePos, OUTLINE, LSET::AllLayersMask() );
    ANCHOR* nearestCorner = nearestAnchor( aMousePos, CORNER, LSET::AllLayersMask() );
    ANCHOR* nearestOrigin = nearestAnchor( aMousePos, ORIGIN, LSET::AllLayersMask() );
    ANCHOR* best = NULL;
    double minDist = std::numeric_limits<double>::max();

    if( nearestOrigin )
    {
        minDist = nearestOrigin->Distance( aMousePos );
        best = nearestOrigin;
    }

    if( nearestCorner )
    {
        double dist = nearestCorner->Distance( aMousePos );

        if( dist < minDist )
        {
            minDist = dist;
            best = nearestCorner;
        }
    }

    if( nearestOutline )
    {
        double dist = nearestOutline->Distance( aMousePos );

        if( minDist > lineSnapMinCornerDistance && dist < minDist )
            best = nearestOutline;
    }

    return best ? best->pos : aMousePos;
}


VECTOR2I PCB_GRID_HELPER::BestSnapAnchor( const VECTOR2I& aOrigin, BOARD_ITEM* aReferenceItem )
{
    LSET layers;
    std::vector<BOARD_ITEM*> item;

    if( aReferenceItem )
    {
        layers = aReferenceItem->GetLayerSet();
        item.push_back( aReferenceItem );
    }
    else
        layers = LSET::AllLayersMask();

    return BestSnapAnchor( aOrigin, layers, item );
}


VECTOR2I PCB_GRID_HELPER::BestSnapAnchor( const VECTOR2I& aOrigin, const LSET& aLayers,
                                          const std::vector<BOARD_ITEM*>& aSkip )
{
    // Tuning constant: snap radius in screen space
    const int snapSize = 25;

    // Snapping distance is in screen space, clamped to the current grid to ensure that the grid
    // points that are visible can always be snapped to.
    // see https://gitlab.com/kicad/code/kicad/-/issues/5638
    // see https://gitlab.com/kicad/code/kicad/-/issues/7125
    double snapScale = snapSize / m_toolMgr->GetView()->GetGAL()->GetWorldScale();
    int    snapRange = std::min( KiROUND( snapScale ), GetGrid().x );
    int    snapDist  = snapRange;

    BOX2I bb( VECTOR2I( aOrigin.x - snapRange / 2, aOrigin.y - snapRange / 2 ),
              VECTOR2I( snapRange, snapRange ) );

    clearAnchors();

    for( BOARD_ITEM* item : queryVisible( bb, aSkip ) )
        computeAnchors( item, aOrigin );

    ANCHOR*  nearest = nearestAnchor( aOrigin, SNAPPABLE, aLayers );
    VECTOR2I nearestGrid = Align( aOrigin );

    if( nearest )
        snapDist = nearest->Distance( aOrigin );

    // Existing snap lines need priority over new snaps
    if( m_snapItem && m_enableSnapLine && m_enableSnap )
    {
        bool snapLine = false;
        int x_dist = std::abs( m_viewSnapLine.GetPosition().x - aOrigin.x );
        int y_dist = std::abs( m_viewSnapLine.GetPosition().y - aOrigin.y );

        /// Allows de-snapping from the line if you are closer to another snap point
        if( x_dist < snapRange && ( !nearest || snapDist > snapRange ) )
        {
            nearestGrid.x = m_viewSnapLine.GetPosition().x;
            snapLine      = true;
        }

        if( y_dist < snapRange && ( !nearest || snapDist > snapRange ) )
        {
            nearestGrid.y = m_viewSnapLine.GetPosition().y;
            snapLine      = true;
        }

        if( snapLine && m_skipPoint != VECTOR2I( m_viewSnapLine.GetPosition() ) )
        {
            m_viewSnapLine.SetEndPosition( nearestGrid );

            if( m_toolMgr->GetView()->IsVisible( &m_viewSnapLine ) )
                m_toolMgr->GetView()->Update( &m_viewSnapLine, KIGFX::GEOMETRY );
            else
                m_toolMgr->GetView()->SetVisible( &m_viewSnapLine, true );

            return nearestGrid;
        }
    }

    if( nearest && m_enableSnap )
    {
        if( nearest->Distance( aOrigin ) <= snapRange )
        {
            m_viewSnapPoint.SetPosition( wxPoint( nearest->pos ) );
            m_viewSnapLine.SetPosition( wxPoint( nearest->pos ) );
            m_toolMgr->GetView()->SetVisible( &m_viewSnapLine, false );

            if( m_toolMgr->GetView()->IsVisible( &m_viewSnapPoint ) )
                m_toolMgr->GetView()->Update( &m_viewSnapPoint, KIGFX::GEOMETRY);
            else
                m_toolMgr->GetView()->SetVisible( &m_viewSnapPoint, true );

            m_snapItem = nearest;
            return nearest->pos;
        }
    }

    m_snapItem = nullptr;
    m_toolMgr->GetView()->SetVisible( &m_viewSnapPoint, false );
    m_toolMgr->GetView()->SetVisible( &m_viewSnapLine, false );
    return nearestGrid;
}


BOARD_ITEM* PCB_GRID_HELPER::GetSnapped() const
{
    if( !m_snapItem )
        return nullptr;

    return static_cast<BOARD_ITEM*>( m_snapItem->item );
}


std::set<BOARD_ITEM*> PCB_GRID_HELPER::queryVisible( const BOX2I& aArea,
                                                     const std::vector<BOARD_ITEM*>& aSkip ) const
{
    std::set<BOARD_ITEM*> items;
    std::vector<KIGFX::VIEW::LAYER_ITEM_PAIR> selectedItems;

    KIGFX::VIEW*                  view = m_toolMgr->GetView();
    RENDER_SETTINGS*              settings = view->GetPainter()->GetSettings();
    const std::set<unsigned int>& activeLayers = settings->GetHighContrastLayers();
    bool                          isHighContrast = settings->GetHighContrast();

    view->Query( aArea, selectedItems );

    for( const KIGFX::VIEW::LAYER_ITEM_PAIR& it : selectedItems )
    {
        BOARD_ITEM* item = static_cast<BOARD_ITEM*>( it.first );

        // If we are in the footprint editor, don't use the footprint itself
        if( static_cast<PCB_TOOL_BASE*>( m_toolMgr->GetCurrentTool() )->IsFootprintEditor()
                && item->Type() == PCB_FOOTPRINT_T )
        {
            continue;
        }

        // The item must be visible and on an active layer
        if( view->IsVisible( item )
                && ( !isHighContrast || activeLayers.count( it.second ) )
                && item->ViewGetLOD( it.second, view ) < view->GetScale() )
        {
            items.insert ( item );
        }
    }

    for( BOARD_ITEM* skipItem : aSkip )
        items.erase( skipItem );

    return items;
}


void PCB_GRID_HELPER::computeAnchors( BOARD_ITEM* aItem, const VECTOR2I& aRefPos, bool aFrom )
{
    KIGFX::VIEW*                  view = m_toolMgr->GetView();
    RENDER_SETTINGS*              settings = view->GetPainter()->GetSettings();
    const std::set<unsigned int>& activeLayers = settings->GetHighContrastLayers();
    bool                          isHighContrast = settings->GetHighContrast();

    auto handlePadShape =
            [&]( PAD* aPad )
            {
                addAnchor( aPad->GetPosition(), ORIGIN | SNAPPABLE, aPad );

                /// If we are getting a drag point, we don't want to center the edge of pads
                if( aFrom )
                    return;

                const std::shared_ptr<SHAPE> eshape = aPad->GetEffectiveShape( aPad->GetLayer() );

                wxASSERT( eshape->Type() == SH_COMPOUND );
                const std::vector<SHAPE*> shapes =
                        static_cast<const SHAPE_COMPOUND*>( eshape.get() )->Shapes();

                for( const SHAPE* shape : shapes )
                {
                    switch( shape->Type() )
                    {
                    case SH_RECT:
                    {
                        const SHAPE_RECT* rect    = static_cast<const SHAPE_RECT*>( shape );
                        SHAPE_LINE_CHAIN  outline = rect->Outline();

                        for( int i = 0; i < outline.SegmentCount(); i++ )
                        {
                            const SEG& seg = outline.CSegment( i );
                            addAnchor( seg.A,         OUTLINE | SNAPPABLE, aPad );
                            addAnchor( seg.Center(),  OUTLINE | SNAPPABLE, aPad );
                        }

                        break;
                    }

                    case SH_SEGMENT:
                    {
                        const SHAPE_SEGMENT* segment = static_cast<const SHAPE_SEGMENT*>( shape );

                        int offset = segment->GetWidth() / 2;
                        SEG seg    = segment->GetSeg();
                        VECTOR2I normal = ( seg.B - seg.A ).Resize( offset ).Rotate( -M_PI_2 );

                        /*
                         * TODO: This creates more snap points than necessary for rounded rect pads
                         * because they are built up of overlapping segments.  We could fix this if
                         * desired by testing these to see if they are "inside" the pad.
                         */

                        addAnchor( seg.A + normal, OUTLINE | SNAPPABLE, aPad );
                        addAnchor( seg.A - normal, OUTLINE | SNAPPABLE, aPad );
                        addAnchor( seg.B + normal, OUTLINE | SNAPPABLE, aPad );
                        addAnchor( seg.B - normal, OUTLINE | SNAPPABLE, aPad );
                        addAnchor( seg.Center() + normal, OUTLINE | SNAPPABLE, aPad );
                        addAnchor( seg.Center() - normal, OUTLINE | SNAPPABLE, aPad );

                        normal = normal.Rotate( M_PI_2 );

                        addAnchor( seg.A - normal, OUTLINE | SNAPPABLE, aPad );
                        addAnchor( seg.B + normal, OUTLINE | SNAPPABLE, aPad );
                        break;
                    }

                    case SH_CIRCLE:
                    {
                        const SHAPE_CIRCLE* circle = static_cast<const SHAPE_CIRCLE*>( shape );

                        int      r     = circle->GetRadius();
                        VECTOR2I start = circle->GetCenter();

                        addAnchor( start + VECTOR2I( -r, 0 ), OUTLINE | SNAPPABLE, aPad );
                        addAnchor( start + VECTOR2I( r, 0 ), OUTLINE | SNAPPABLE, aPad );
                        addAnchor( start + VECTOR2I( 0, -r ), OUTLINE | SNAPPABLE, aPad );
                        addAnchor( start + VECTOR2I( 0, r ), OUTLINE | SNAPPABLE, aPad );
                        break;
                    }

                    case SH_ARC:
                    {
                        const SHAPE_ARC* arc = static_cast<const SHAPE_ARC*>( shape );

                        addAnchor( arc->GetP0(), OUTLINE | SNAPPABLE, aPad );
                        addAnchor( arc->GetP1(), OUTLINE | SNAPPABLE, aPad );
                        addAnchor( arc->GetArcMid(), OUTLINE | SNAPPABLE, aPad );
                        break;
                    }

                    case SH_SIMPLE:
                    {
                        const SHAPE_SIMPLE* poly = static_cast<const SHAPE_SIMPLE*>( shape );

                        for( size_t i = 0; i < poly->GetSegmentCount(); i++ )
                        {
                            const SEG& seg = poly->GetSegment( i );

                            addAnchor( seg.A, OUTLINE | SNAPPABLE, aPad );
                            addAnchor( seg.Center(), OUTLINE | SNAPPABLE, aPad );

                            if( i == poly->GetSegmentCount() - 1 )
                                addAnchor( seg.B, OUTLINE | SNAPPABLE, aPad );
                        }

                        break;
                    }

                    case SH_POLY_SET:
                    case SH_LINE_CHAIN:
                    case SH_COMPOUND:
                    case SH_POLY_SET_TRIANGLE:
                    case SH_NULL:
                    default:
                        break;
                    }
                }
            };

    switch( aItem->Type() )
    {
        case PCB_FOOTPRINT_T:
        {
            FOOTPRINT* footprint = static_cast<FOOTPRINT*>( aItem );

            for( PAD* pad : footprint->Pads() )
            {
                // Getting pads from the footprint requires re-checking that the pad is shown
                if( ( aFrom || m_magneticSettings->pads == MAGNETIC_OPTIONS::CAPTURE_ALWAYS )
                    && pad->GetBoundingBox().Contains( wxPoint( aRefPos.x, aRefPos.y ) )
                    && view->IsVisible( pad )
                    && ( !isHighContrast || activeLayers.count( pad->GetLayer() ) )
                    && pad->ViewGetLOD( pad->GetLayer(), view ) < view->GetScale() )
                {
                    handlePadShape( pad );
                    break;
                }
            }

            // if the cursor is not over a pad, then drag the footprint by its origin
            VECTOR2I position = footprint->GetPosition();
            addAnchor( position, ORIGIN | SNAPPABLE, footprint );

            // Add the footprint center point if it is markedly different from the origin
            VECTOR2I center = footprint->GetFootprintRect().Centre();
            VECTOR2I grid( GetGrid() );

            if( ( center - position ).SquaredEuclideanNorm() > grid.SquaredEuclideanNorm() )
                addAnchor( footprint->GetFootprintRect().Centre(), ORIGIN | SNAPPABLE, footprint );

            break;
        }

        case PCB_PAD_T:
        {
            if( aFrom || m_magneticSettings->pads == MAGNETIC_OPTIONS::CAPTURE_ALWAYS )
            {
                PAD* pad = static_cast<PAD*>( aItem );
                handlePadShape( pad );
            }

            break;
        }

        case PCB_FP_SHAPE_T:
        case PCB_SHAPE_T:
        {
            if( !m_magneticSettings->graphics )
                break;

            PCB_SHAPE* shape = static_cast<PCB_SHAPE*>( aItem );
            VECTOR2I   start = shape->GetStart();
            VECTOR2I   end = shape->GetEnd();

            switch( shape->GetShape() )
            {
                case S_CIRCLE:
                {
                    int r = ( start - end ).EuclideanNorm();

                    addAnchor( start, ORIGIN | SNAPPABLE, shape );
                    addAnchor( start + VECTOR2I( -r, 0 ), OUTLINE | SNAPPABLE, shape );
                    addAnchor( start + VECTOR2I( r, 0 ), OUTLINE | SNAPPABLE, shape );
                    addAnchor( start + VECTOR2I( 0, -r ), OUTLINE | SNAPPABLE, shape );
                    addAnchor( start + VECTOR2I( 0, r ), OUTLINE | SNAPPABLE, shape );
                    break;
                }

                case S_ARC:
                    addAnchor( shape->GetArcStart(), CORNER | SNAPPABLE, shape );
                    addAnchor( shape->GetArcEnd(), CORNER | SNAPPABLE, shape );
                    addAnchor( shape->GetArcMid(), CORNER | SNAPPABLE, shape );
                    addAnchor( shape->GetCenter(), ORIGIN | SNAPPABLE, shape );
                    break;

                case S_RECT:
                {
                    VECTOR2I point2( end.x, start.y );
                    VECTOR2I point3( start.x, end.y );
                    SEG first( start, point2 );
                    SEG second( point2, end );
                    SEG third( end, point3 );
                    SEG fourth( point3, start );

                    addAnchor( first.A,         CORNER | SNAPPABLE, shape );
                    addAnchor( first.Center(),  CORNER | SNAPPABLE, shape );
                    addAnchor( second.A,        CORNER | SNAPPABLE, shape );
                    addAnchor( second.Center(), CORNER | SNAPPABLE, shape );
                    addAnchor( third.A,         CORNER | SNAPPABLE, shape );
                    addAnchor( third.Center(),  CORNER | SNAPPABLE, shape );
                    addAnchor( fourth.A,        CORNER | SNAPPABLE, shape );
                    addAnchor( fourth.Center(), CORNER | SNAPPABLE, shape );
                    break;
                }

                case S_SEGMENT:
                    addAnchor( start, CORNER | SNAPPABLE, shape );
                    addAnchor( end, CORNER | SNAPPABLE, shape );
                    addAnchor( shape->GetCenter(), CORNER | SNAPPABLE, shape );
                    break;

                case S_POLYGON:
                    for( const wxPoint& p : shape->BuildPolyPointsList() )
                        addAnchor( p, CORNER | SNAPPABLE, shape );

                    break;

                case S_CURVE:
                    addAnchor( start, CORNER | SNAPPABLE, shape );
                    addAnchor( end, CORNER | SNAPPABLE, shape );
                    KI_FALLTHROUGH;

                default:
                    addAnchor( shape->GetStart(), ORIGIN | SNAPPABLE, shape );
                    break;
            }
            break;
        }

        case PCB_TRACE_T:
        case PCB_ARC_T:
        {
            if( aFrom || m_magneticSettings->tracks == MAGNETIC_OPTIONS::CAPTURE_ALWAYS )
            {
                TRACK* track = static_cast<TRACK*>( aItem );

                addAnchor( track->GetStart(), CORNER | SNAPPABLE, track );
                addAnchor( track->GetEnd(), CORNER | SNAPPABLE, track );
                addAnchor( track->GetCenter(), ORIGIN, track);
            }

            break;
        }

        case PCB_MARKER_T:
        case PCB_TARGET_T:
            addAnchor( aItem->GetPosition(), ORIGIN | CORNER | SNAPPABLE, aItem );
            break;

        case PCB_VIA_T:
        {
            if( aFrom || m_magneticSettings->tracks == MAGNETIC_OPTIONS::CAPTURE_ALWAYS )
                addAnchor( aItem->GetPosition(), ORIGIN | CORNER | SNAPPABLE, aItem );

            break;
        }

        case PCB_ZONE_T:
        {
            const SHAPE_POLY_SET* outline = static_cast<const ZONE*>( aItem )->Outline();

            SHAPE_LINE_CHAIN lc;
            lc.SetClosed( true );

            for( auto iter = outline->CIterateWithHoles(); iter; iter++ )
            {
                addAnchor( *iter, CORNER, aItem );
                lc.Append( *iter );
            }

            addAnchor( lc.NearestPoint( aRefPos ), OUTLINE, aItem );

            break;
        }

        case PCB_DIM_ALIGNED_T:
        case PCB_DIM_ORTHOGONAL_T:
        {
            const ALIGNED_DIMENSION* dim = static_cast<const ALIGNED_DIMENSION*>( aItem );
            addAnchor( dim->GetCrossbarStart(), CORNER | SNAPPABLE, aItem );
            addAnchor( dim->GetCrossbarEnd(), CORNER | SNAPPABLE, aItem );
            addAnchor( dim->GetStart(), CORNER | SNAPPABLE, aItem );
            addAnchor( dim->GetEnd(), CORNER | SNAPPABLE, aItem );
            break;
        }

        case PCB_DIM_CENTER_T:
        {
            const CENTER_DIMENSION* dim = static_cast<const CENTER_DIMENSION*>( aItem );
            addAnchor( dim->GetStart(), CORNER | SNAPPABLE, aItem );
            addAnchor( dim->GetEnd(), CORNER | SNAPPABLE, aItem );

            VECTOR2I start( dim->GetStart() );
            VECTOR2I radial( dim->GetEnd() - dim->GetStart() );

            for( int i = 0; i < 2; i++ )
            {
                radial = radial.Rotate( DEG2RAD( 90 ) );
                addAnchor( start + radial, CORNER | SNAPPABLE, aItem );
            }

            break;
        }

        case PCB_DIM_LEADER_T:
        {
            const LEADER* leader = static_cast<const LEADER*>( aItem );
            addAnchor( leader->GetStart(), CORNER | SNAPPABLE, aItem );
            addAnchor( leader->GetEnd(), CORNER | SNAPPABLE, aItem );
            addAnchor( leader->Text().GetPosition(), CORNER | SNAPPABLE, aItem );
            break;
        }

        case PCB_FP_TEXT_T:
        case PCB_TEXT_T:
            addAnchor( aItem->GetPosition(), ORIGIN, aItem );
            break;

        default:
            break;
   }
}


PCB_GRID_HELPER::ANCHOR* PCB_GRID_HELPER::nearestAnchor( const VECTOR2I& aPos, int aFlags,
                                                         LSET aMatchLayers )
{
    double  minDist = std::numeric_limits<double>::max();
    ANCHOR* best = NULL;

    for( ANCHOR& a : m_anchors )
    {
        BOARD_ITEM* item = static_cast<BOARD_ITEM*>( a.item );

        if( ( aMatchLayers & item->GetLayerSet() ) == 0 )
            continue;

        if( ( aFlags & a.flags ) != aFlags )
            continue;

        double dist = a.Distance( aPos );

        if( dist < minDist )
        {
            minDist = dist;
            best = &a;
        }
    }

    return best;
}