int PCBNEW_CONTROL::ZoomPreset( const TOOL_EVENT& aEvent )
{
    unsigned int idx = aEvent.Parameter<long>();
    std::vector<double>& zoomList = m_frame->GetScreen()->m_ZoomList;
    KIGFX::VIEW* view = m_frame->GetGalCanvas()->GetView();
    KIGFX::GAL* gal = m_frame->GetGalCanvas()->GetGAL();

    m_frame->SetPresetZoom( idx );

    if( idx == 0 )      // Zoom Auto
    {
        return ZoomFitScreen( aEvent );
    }
    else if( idx >= zoomList.size() )
    {
        assert( false );
        return 0;
    }

    double selectedZoom = zoomList[idx];
    double zoomFactor = gal->GetWorldScale() / gal->GetZoomFactor();
    view->SetScale( 1.0 / ( zoomFactor * selectedZoom ) );

    return 0;
}

void EDA_DRAW_FRAME::UseGalCanvas()
{
    KIGFX::GAL* gal = GetGalCanvas()->GetGAL();

    // Set up grid settings
    gal->SetGridVisibility( IsGridVisible() );
    gal->SetGridSize( VECTOR2D( GetScreen()->GetGridSize() ) );
    gal->SetGridOrigin( VECTOR2D( GetGridOrigin() ) );

    // Transfer EDA_DRAW_PANEL settings
    KIGFX::VIEW_CONTROLS* viewControls = GetGalCanvas()->GetViewControls();
    viewControls->EnableCursorWarping( !m_canvas->GetEnableZoomNoCenter() );
    viewControls->EnableMousewheelPan( m_canvas->GetEnableMousewheelPan() );
    viewControls->EnableAutoPan( m_canvas->GetEnableAutoPan() );

    m_canvas->SetEvtHandlerEnabled( false );
    GetGalCanvas()->SetEvtHandlerEnabled( true );

    GetGalCanvas()->StartDrawing();

    // Switch panes
    // JEY TODO: drop down to a single pane....
    m_auimgr.GetPane( "DrawFrame" ).Show( false );
    m_auimgr.GetPane( "DrawFrameGal" ).Show( true );
    m_auimgr.Update();

    // Reset current tool on switch();
    SetNoToolSelected();
}

int PCBNEW_CONTROL::ZoomFitScreen( const TOOL_EVENT& aEvent )
{
    KIGFX::VIEW* view = m_frame->GetGalCanvas()->GetView();
    KIGFX::GAL* gal = m_frame->GetGalCanvas()->GetGAL();
    BOARD* board = getModel<BOARD>();
    board->ComputeBoundingBox();
    BOX2I boardBBox = board->ViewBBox();
    VECTOR2I screenSize = gal->GetScreenPixelSize();

    if( boardBBox.GetSize().x == 0 || boardBBox.GetSize().y == 0 )
    {
        // Empty view
        view->SetCenter( view->ToWorld( VECTOR2D( screenSize.x / 2, screenSize.y / 2 ) ) );
        view->SetScale( 17.0 );
    }
    else
    {
        // Autozoom to board
        double iuPerX = screenSize.x ? boardBBox.GetWidth() / screenSize.x : 1.0;
        double iuPerY = screenSize.y ? boardBBox.GetHeight() / screenSize.y : 1.0;

        double bestZoom = std::max( iuPerX, iuPerY );
        double zoomFactor = gal->GetWorldScale() / gal->GetZoomFactor();
        double zoom = 1.0 / ( zoomFactor * bestZoom );

        view->SetCenter( boardBBox.Centre() );
        view->SetScale( zoom );
    }

    return 0;
}

void SIMPLE_OVERLAY_ITEM::setupGal( KIGFX::GAL& aGal ) const
{
    // default impl: set up the GAL options we have - the
    // overriding class can add to this if needed
    aGal.SetLineWidth( m_lineWidth );
    aGal.SetStrokeColor( m_strokeColor );
    aGal.SetFillColor( m_fillColor );
    aGal.SetIsStroke( true );
    aGal.SetIsFill( true );
}

int PCBNEW_CONTROL::SwitchCursor( const TOOL_EVENT& aEvent )
{
    const unsigned int BIG_CURSOR = 8000;
    const unsigned int SMALL_CURSOR = 80;

    PCB_BASE_FRAME* frame = getEditFrame<PCB_BASE_FRAME>();
    KIGFX::GAL* gal = frame->GetGalCanvas()->GetGAL();
    gal->SetCursorSize( frame->GetCursorShape() ? BIG_CURSOR : SMALL_CURSOR );

    return 0;
}

int PCBNEW_CONTROL::SwitchCursor( const TOOL_EVENT& aEvent )
{
    const unsigned int BIG_CURSOR = 4000;
    const unsigned int SMALL_CURSOR = 80;

    KIGFX::GAL* gal = getEditFrame<PCB_BASE_FRAME>()->GetGalCanvas()->GetGAL();

    if( gal->GetCursorSize() == BIG_CURSOR )
        gal->SetCursorSize( SMALL_CURSOR );
    else
        gal->SetCursorSize( BIG_CURSOR );

    return 0;
}

void EDA_DRAW_FRAME::UseGalCanvas( bool aEnable )
{
    KIGFX::VIEW* view = GetGalCanvas()->GetView();
    KIGFX::GAL* gal = GetGalCanvas()->GetGAL();

    // Display the same view after canvas switching
    if( aEnable )
    {
        // Switch to GAL renderer from legacy
        if( !m_galCanvasActive )
        {
            // Set up viewport
            double zoomFactor = gal->GetWorldScale() / gal->GetZoomFactor();
            double zoom = 1.0 / ( zoomFactor * m_canvas->GetZoom() );
            view->SetScale( zoom );
            view->SetCenter( VECTOR2D( m_canvas->GetScreenCenterLogicalPosition() ) );
        }

        // Set up grid settings
        gal->SetGridVisibility( IsGridVisible() );
        gal->SetGridSize( VECTOR2D( GetScreen()->GetGridSize() ) );
        gal->SetGridOrigin( VECTOR2D( GetGridOrigin() ) );

        // Transfer EDA_DRAW_PANEL settings
        GetGalCanvas()->GetViewControls()->EnableCursorWarping( !m_canvas->GetEnableZoomNoCenter() );
        GetGalCanvas()->GetViewControls()->EnableMousewheelPan( m_canvas->GetEnableMousewheelPan() );
        GetGalCanvas()->GetViewControls()->EnableAutoPan( m_canvas->GetEnableAutoPan() );
    }
    else if( m_galCanvasActive )
    {
        // Switch to legacy renderer from GAL
        double zoomFactor = gal->GetWorldScale() / gal->GetZoomFactor();
        // TODO replace it with EDA_DRAW_PANEL_GAL::GetLegacyZoom
        m_canvas->SetZoom( 1.0 / ( zoomFactor * view->GetScale() ) );
        VECTOR2D center = view->GetCenter();
        AdjustScrollBars( wxPoint( center.x, center.y ) );
    }

    m_canvas->SetEvtHandlerEnabled( !aEnable );
    GetGalCanvas()->SetEvtHandlerEnabled( aEnable );

    // Switch panes
    m_auimgr.GetPane( wxT( "DrawFrame" ) ).Show( !aEnable );
    m_auimgr.GetPane( wxT( "DrawFrameGal" ) ).Show( aEnable );
    m_auimgr.Update();

    // Reset current tool on switch();
    SetNoToolSelected();

    m_galCanvasActive = aEnable;
}

/**
 * Draw simple ticks on the back of a line such that the line is
 * divided into n parts.
 *
 * @param aGal the GAL to draw on
 * @param aOrigin start of line to draw ticks on
 * @param aLine line vector
 * @param aTickLen length of ticks in IU
 * @param aNumDivisions number of parts to divide the line into
 */
void drawBacksideTicks( KIGFX::GAL& aGal, const VECTOR2D& aOrigin,
        const VECTOR2D& aLine, double aTickLen, int aNumDivisions )
{
    const double backTickSpace = aLine.EuclideanNorm() / aNumDivisions;
    const auto backTickVec = aLine.Rotate( M_PI_2 ).Resize( aTickLen );

    for( int i = 0; i < aNumDivisions + 1; ++i )
    {
        const auto backTickPos = aOrigin + aLine.Resize( backTickSpace * i );
        aGal.DrawLine( backTickPos, backTickPos + backTickVec );
    }
}

/**
 * Draw labelled ticks on a line. Ticks are spaced according to a
 * maximum density. Miror ticks are not labelled.
 *
 * @param aGal the GAL to draw on
 * @param aOrigin start of line to draw ticks on
 * @param aLine line vector
 * @param aMinorTickLen length of minor ticks in IU
 */
void drawTicksAlongLine( KIGFX::GAL& aGal, const VECTOR2D& aOrigin,
        const VECTOR2D& aLine, double aMinorTickLen )
{
    VECTOR2D tickLine = aLine.Rotate( -M_PI_2 );

    double tickSpace;
    TICK_FORMAT tickF = getTickFormatForScale( aGal.GetWorldScale(), tickSpace );

    // number of ticks in whole ruler
    int numTicks = (int) std::ceil( aLine.EuclideanNorm() / tickSpace );

    // work out which way up the tick labels go
    double labelAngle = -tickLine.Angle();

    if( aLine.Angle() > 0 )
    {
        aGal.SetHorizontalJustify( GR_TEXT_HJUSTIFY_LEFT );
    }
    else
    {
        aGal.SetHorizontalJustify( GR_TEXT_HJUSTIFY_RIGHT );
        labelAngle += M_PI;
    }

    // text and ticks are dimmed
    aGal.SetStrokeColor( PreviewOverlayDefaultColor().WithAlpha( PreviewOverlayDeemphAlpha( true ) ) );

    const auto labelOffset = tickLine.Resize( aMinorTickLen * ( majorTickLengthFactor + 1 ) );

    for( int i = 0; i < numTicks; ++i )
    {
        const auto tickPos = aOrigin + aLine.Resize( tickSpace * i );

        double length = aMinorTickLen;
        bool drawLabel = false;

        if( i % tickF.majorStep == 0)
        {
            drawLabel = true;
            length *= majorTickLengthFactor;
        }
        else if( tickF.midStep && i % tickF.midStep == 0 )
        {
            drawLabel = true;
            length *= midTickLengthFactor;
        }

        aGal.DrawLine( tickPos, tickPos + tickLine.Resize( length ) );

        if( drawLabel )
        {
            wxString label = DimensionLabel( "", tickSpace * i, g_UserUnit );

            // FIXME: spaces choke OpenGL lp:1668455
            label.erase( std::remove( label.begin(), label.end(), ' ' ), label.end() );

            aGal.BitmapText( label, tickPos + labelOffset, labelAngle );
        }
    }
}

void EDA_DRAW_FRAME::OnSelectZoom( wxCommandEvent& event )
{
    if( m_zoomSelectBox == NULL )
        return;                        // Should not happen!

    int id = m_zoomSelectBox->GetCurrentSelection();

    if( id < 0 || !( id < (int)m_zoomSelectBox->GetCount() ) )
        return;

    if( id == 0 )                      // Auto zoom (Fit in Page)
    {
        Zoom_Automatique( true );
    }
    else
    {
        id--;
        double selectedZoom = GetScreen()->m_ZoomList[id];

        if( GetScreen()->GetZoom() == selectedZoom )
            return;

        GetScreen()->SetZoom( selectedZoom );

        if( IsGalCanvasActive() )
        {
            // Apply computed view settings to GAL
            KIGFX::VIEW* view = GetGalCanvas()->GetView();
            KIGFX::GAL* gal = GetGalCanvas()->GetGAL();

            double zoomFactor = gal->GetWorldScale() / gal->GetZoomFactor();
            double zoom = 1.0 / ( zoomFactor * GetZoom() );

            view->SetScale( zoom );
            GetGalCanvas()->Refresh();
        }
        else
            RedrawScreen( GetScrollCenterPosition(), false );
    }
}

const wxString EDA_DRAW_FRAME::GetZoomLevelIndicator() const
{
    wxString Line;
    double level = 0.0;

    if( IsGalCanvasActive() )
    {
        KIGFX::GAL* gal = m_galCanvas->GetGAL();
        KIGFX::VIEW* view = m_galCanvas->GetView();
        double zoomFactor = gal->GetWorldScale() / gal->GetZoomFactor();
        level = m_zoomLevelCoeff * zoomFactor * view->GetScale();
    }
    else if( BASE_SCREEN* screen = GetScreen() )
    {
        level = m_zoomLevelCoeff / (double) screen->GetZoom();
    }

    // returns a human readable value which can be displayed as zoom
    // level indicator in dialogs.
    Line.Printf( wxT( "Z %.2f" ), level );

    return Line;
}

void EDA_DRAW_FRAME::UseGalCanvas( bool aEnable )
{
    KIGFX::VIEW* view = GetGalCanvas()->GetView();
    KIGFX::GAL* gal = GetGalCanvas()->GetGAL();

    double zoomFactor = gal->GetWorldScale() / gal->GetZoomFactor();

    // Display the same view after canvas switching
    if( aEnable )
    {
        BASE_SCREEN* screen = GetScreen();

        // Switch to GAL rendering
        if( !IsGalCanvasActive() )
        {
            // Set up viewport
            double zoom = 1.0 / ( zoomFactor * m_canvas->GetZoom() );
            view->SetScale( zoom );
            view->SetCenter( VECTOR2D( m_canvas->GetScreenCenterLogicalPosition() ) );
        }

        // Set up grid settings
        gal->SetGridVisibility( IsGridVisible() );
        gal->SetGridSize( VECTOR2D( screen->GetGridSize().x, screen->GetGridSize().y ) );
        gal->SetGridOrigin( VECTOR2D( GetGridOrigin() ) );
    }
    else
    {
        // Switch to standard rendering
        if( IsGalCanvasActive() )
        {
            // Change view settings only if GAL was active previously
            double zoom = 1.0 / ( zoomFactor * view->GetScale() );
            m_canvas->SetZoom( zoom );

            VECTOR2D center = view->GetCenter();
            RedrawScreen( wxPoint( center.x, center.y ), false );
        }
    }

    m_canvas->SetEvtHandlerEnabled( !aEnable );
    GetGalCanvas()->SetEvtHandlerEnabled( aEnable );

    // Switch panes
    m_auimgr.GetPane( wxT( "DrawFrame" ) ).Show( !aEnable );
    m_auimgr.GetPane( wxT( "DrawFrameGal" ) ).Show( aEnable );
    m_auimgr.Update();

    // Reset current tool on switch();
    SetToolID( ID_NO_TOOL_SELECTED, wxCURSOR_DEFAULT, wxEmptyString );

    m_galCanvasActive = aEnable;
}

void VIEW_GROUP::ViewDraw( int aLayer, VIEW* aView ) const
{
    KIGFX::GAL* gal = aView->GetGAL();
    PAINTER*    painter = aView->GetPainter();
    bool        isSelection = m_layer == LAYER_SELECT_OVERLAY;
    const auto  drawList = updateDrawList();

    std::unordered_map<int, std::vector<VIEW_ITEM*>> layer_item_map;

    // Build a list of layers used by the items in the group
    for( auto item : drawList )
    {
        int item_layers[VIEW::VIEW_MAX_LAYERS], item_layers_count;
        item->ViewGetLayers( item_layers, item_layers_count );

        for( int i = 0; i < item_layers_count; i++ )
        {
            if( layer_item_map.count( item_layers[i] ) == 0 )
            {
                layer_item_map.emplace( std::make_pair( item_layers[i],
                                                        std::vector<VIEW_ITEM*>() ) );
            }

            layer_item_map[ item_layers[i] ].push_back( item );
        }
    }

    int layers[VIEW::VIEW_MAX_LAYERS] = { 0 };
    int layers_count = 0;

    for( const auto& entry : layer_item_map )
    {
        layers[ layers_count++ ] = entry.first;
    }

    aView->SortLayers( layers, layers_count );

    // Now draw the layers in sorted order

    gal->PushDepth();

    for( int i = 0; i < layers_count; i++ )
    {
        int  layer = layers[i];
        bool draw = aView->IsLayerVisible( layer );

        if( isSelection )
        {
            switch( layer )
            {
            case LAYER_PADS_TH:
            case LAYER_PADS_PLATEDHOLES:
            case LAYER_PAD_FR:
            case LAYER_PAD_BK:
                draw = true;
                break;
            default:
                break;
            }
        }

        if( draw )
        {
            gal->AdvanceDepth();

            for( auto item : layer_item_map[ layers[i] ] )
            {
                if( !painter->Draw( item, layers[i] ) )
                    item->ViewDraw( layers[i], aView ); // Alternative drawing method
            }
        }
    }

    gal->PopDepth();
}