gr_basic.cpp

Go to the documentation of this file.

/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright (C) 2015 Jean-Pierre Charras, jp.charras at wanadoo.fr
 * Copyright (C) 2011 Wayne Stambaugh <[email protected]>
 * Copyright (C) 1992-2021 KiCad Developers, see AUTHORS.txt for contributors.
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */

#include <gr_basic.h>
#include <trigo.h>
#include <eda_item.h>
#include <math_for_graphics.h>
#include <wx/graphics.h>
#include <geometry/geometry_utils.h>
#include <math/util.h> // for KiROUND

#include <algorithm>

static const bool FILLED = true;
static const bool NOT_FILLED = false;

/* Important Note:
 * These drawing functions clip draw item before send these items to wxDC draw
 * functions. For guy who asks why i did it, see a sample of problems encountered
 * when pixels
 * coordinates overflow 16 bits values:
 * http://trac.wxwidgets.org/ticket/10446
 * Problems can be found under Windows **and** Linux (mainly when drawing arcs)
 * (mainly at low zoom values (2, 1 or 0.5), in Pcbnew)
 * some of these problems could be now fixed in recent distributions.
 *
 * Currently (feb 2009) there are overflow problems when drawing solid (filled)
 * polygons under linux without clipping
 *
 * So before removing clipping functions, be aware these bug (they are not in
 * KiCad or wxWidgets) are fixed by testing how are drawn complex lines arcs
 * and solid polygons under Windows and Linux and remember users can have old
 * versions with bugs
 */


/* Definitions for enabling and disabling debugging features in gr_basic.cpp.
 * Please remember to set these back to 0 before making LAUNCHPAD commits.
 */
#define DEBUG_DUMP_CLIP_ERROR_COORDS 0 // Set to 1 to dump clip algorithm errors.
#define DEBUG_DUMP_CLIP_COORDS 0 // Set to 1 to dump clipped coordinates.


// For draw mode = XOR GR_XOR or GR_NXOR by background color
GR_DRAWMODE g_XorMode = GR_NXOR;


static void ClipAndDrawPoly( EDA_RECT* ClipBox, wxDC* DC, const wxPoint* Points, int n );

/* These functions are used by corresponding functions
 * ( GRSCircle is called by GRCircle for instance) after mapping coordinates
 * from user units to screen units(pixels coordinates)
 */
static void GRSRect( EDA_RECT* aClipBox, wxDC* aDC, int x1, int y1,
 int x2, int y2, int aWidth, const COLOR4D& aColor );



static int GRLastMoveToX, GRLastMoveToY;
static bool s_ForceBlackPen; /* if true: draws in black instead of
 * color for printing. */
static int xcliplo = 0,
 ycliplo = 0,
 xcliphi = 2000,
 ycliphi = 2000;

static COLOR4D s_DC_lastbrushcolor( 0, 0, 0, 0 );
static bool s_DC_lastbrushfill = false;
static wxDC* s_DC_lastDC = nullptr;

static void WinClipAndDrawLine( EDA_RECT* ClipBox, wxDC* DC, int x1, int y1, int x2, int y2,
 int width )
{
 GRLastMoveToX = x2;
 GRLastMoveToY = y2;

 if( ClipBox )
 {
 EDA_RECT clipbox(*ClipBox);
 clipbox.Inflate(width/2);
 if( ClipLine( &clipbox, x1, y1, x2, y2 ) )
 return;
 }

 DC->DrawLine( x1, y1, x2, y2 );
}


void GRResetPenAndBrush( wxDC* DC )
{
 GRSetBrush( DC, BLACK ); // Force no fill
 s_DC_lastbrushcolor = COLOR4D::UNSPECIFIED;
 s_DC_lastDC = nullptr;
}


void GRSetColorPen( wxDC* DC, const COLOR4D& Color, int width, wxPenStyle style )
{
 COLOR4D color = Color;

 wxDash dots[2] = { 1, 3 };

 // Under OSX and while printing when wxPen is set to 0, renderer follows the request drawing
 // nothing & in the bitmap world the minimum is enough to light a pixel, in vectorial one not
 if( width <= 1 )
 width = DC->DeviceToLogicalXRel( 1 );

 if( s_ForceBlackPen )
 color = COLOR4D::BLACK;

 const wxPen& curr_pen = DC->GetPen();

 if( !curr_pen.IsOk() || curr_pen.GetColour() != color.ToColour()
 || curr_pen.GetWidth() != width || curr_pen.GetStyle() != style )
 {
 wxPen pen;
 pen.SetColour( color.ToColour() );

 if( style == wxPENSTYLE_DOT )
 {
 style = wxPENSTYLE_USER_DASH;
 pen.SetDashes( 2, dots );
 }

 pen.SetWidth( width );
 pen.SetStyle( style );
 DC->SetPen( pen );
 }
 else
 {
 // Should be not needed, but on Linux, in printing process
 // the curr pen settings needs to be sometimes re-initialized
 // Clearly, this is due to a bug, related to SetBrush(),
 // but we have to live with it, at least on wxWidgets 3.0
 DC->SetPen( curr_pen );
 }
}


void GRSetBrush( wxDC* DC, const COLOR4D& Color, bool fill )
{
 COLOR4D color = Color;

 if( s_ForceBlackPen )
 color = COLOR4D::BLACK;

 if( s_DC_lastbrushcolor != color || s_DC_lastbrushfill != fill || s_DC_lastDC != DC )
 {
 wxBrush brush;

 brush.SetColour( color.ToColour() );

 if( fill )
 brush.SetStyle( wxBRUSHSTYLE_SOLID );
 else
 brush.SetStyle( wxBRUSHSTYLE_TRANSPARENT );

 DC->SetBrush( brush );

 s_DC_lastbrushcolor = color;
 s_DC_lastbrushfill = fill;
 s_DC_lastDC = DC;
 }
}


void GRForceBlackPen( bool flagforce )
{
 s_ForceBlackPen = flagforce;
}


bool GetGRForceBlackPenState( void )
{
 return s_ForceBlackPen;
}


void GRLine( EDA_RECT* ClipBox, wxDC* DC, int x1, int y1, int x2, int y2, int width,
 const COLOR4D& Color, wxPenStyle aStyle)
{
 GRSetColorPen( DC, Color, width, aStyle );
 WinClipAndDrawLine( ClipBox, DC, x1, y1, x2, y2, width );
 GRLastMoveToX = x2;
 GRLastMoveToY = y2;
}


void GRLine( EDA_RECT* aClipBox, wxDC* aDC, const wxPoint& aStart, const wxPoint& aEnd, int aWidth,
 const COLOR4D& aColor, wxPenStyle aStyle )
{
 GRLine( aClipBox, aDC, aStart.x, aStart.y, aEnd.x, aEnd.y, aWidth, aColor, aStyle );
}


void GRMoveTo( int x, int y )
{
 GRLastMoveToX = x;
 GRLastMoveToY = y;
}


void GRLineTo( EDA_RECT* ClipBox, wxDC* DC, int x, int y, int width, const COLOR4D& Color )
{
 GRLine( ClipBox, DC, GRLastMoveToX, GRLastMoveToY, x, y, width, Color );
}


void GRCSegm( EDA_RECT* ClipBox, wxDC* DC, int x1, int y1, int x2, int y2, int width,
 int aPenSize, const COLOR4D& Color )
{
 GRLastMoveToX = x2;
 GRLastMoveToY = y2;

 if( ClipBox )
 {
 EDA_RECT clipbox( *ClipBox );
 clipbox.Inflate( width / 2 );

 if( ClipLine( &clipbox, x1, y1, x2, y2 ) )
 return;
 }

 if( width <= 2 ) /* single line or 2 pixels */
 {
 GRSetColorPen( DC, Color, width );
 DC->DrawLine( x1, y1, x2, y2 );
 return;
 }

 GRSetBrush( DC, Color, NOT_FILLED );
 GRSetColorPen( DC, Color, aPenSize );

 int radius = ( width + 1 ) >> 1;
 int dx = x2 - x1;
 int dy = y2 - y1;
 double angle = -ArcTangente( dy, dx );
 wxPoint start;
 wxPoint end;
 wxPoint org( x1, y1 );
 int len = (int) hypot( dx, dy );

 // We know if the DC is mirrored, to draw arcs
 int slx = DC->DeviceToLogicalX( 1 ) - DC->DeviceToLogicalX( 0 );
 int sly = DC->DeviceToLogicalY( 1 ) - DC->DeviceToLogicalY( 0 );
 bool mirrored = ( slx > 0 && sly < 0 ) || ( slx < 0 && sly > 0 );

 // first edge
 start.x = 0;
 start.y = radius;
 end.x = len;
 end.y = radius;
 RotatePoint( &start, angle );
 RotatePoint( &end, angle );

 start += org;
 end += org;

 DC->DrawLine( start, end );

 // first rounded end
 end.x = 0;
 end.y = -radius;
 RotatePoint( &end, angle );
 end += org;

 if( !mirrored )
 DC->DrawArc( end, start, org );
 else
 DC->DrawArc( start, end, org );

 // second edge
 start.x = len;
 start.y = -radius;
 RotatePoint( &start, angle );
 start += org;

 DC->DrawLine( start, end );

 // second rounded end
 end.x = len;
 end.y = radius;
 RotatePoint( &end, angle);
 end += org;

 if( !mirrored )
 DC->DrawArc( end.x, end.y, start.x, start.y, x2, y2 );
 else
 DC->DrawArc( start.x, start.y, end.x, end.y, x2, y2 );
}


void GRCSegm( EDA_RECT* ClipBox, wxDC* DC, int x1, int y1, int x2, int y2, int width,
 const COLOR4D& Color )
{
 GRCSegm( ClipBox, DC, x1, y1, x2, y2, width, 0, Color );
}


void GRCSegm( EDA_RECT* aClipBox, wxDC* aDC, const wxPoint& aStart, const wxPoint& aEnd, int aWidth,
 const COLOR4D& aColor )
{
 GRCSegm( aClipBox, aDC, aStart.x, aStart.y, aEnd.x, aEnd.y, aWidth, 0, aColor );
}


void GRFillCSegm( EDA_RECT* ClipBox, wxDC* DC, int x1, int y1, int x2, int y2, int width,
 const COLOR4D& Color )
{
 GRSetColorPen( DC, Color, width );
 WinClipAndDrawLine( ClipBox, DC, x1, y1, x2, y2, width );
}


void GRFilledSegment( EDA_RECT* aClipBox, wxDC* aDC, const wxPoint& aStart, const wxPoint& aEnd,
 int aWidth, const COLOR4D& aColor )
{
 GRSetColorPen( aDC, aColor, aWidth );
 WinClipAndDrawLine( aClipBox, aDC, aStart.x, aStart.y, aEnd.x, aEnd.y, aWidth );
}

static bool IsGRSPolyDrawable( EDA_RECT* ClipBox, int n, const wxPoint* Points )
{
 if( !ClipBox )
 return true;

 if( n <= 0 )
 return false;

 int Xmin, Xmax, Ymin, Ymax;

 Xmin = Xmax = Points[0].x;
 Ymin = Ymax = Points[0].y;

 for( int ii = 1; ii < n; ii++ ) // calculate rectangle
 {
 Xmin = std::min( Xmin, Points[ii].x );
 Xmax = std::max( Xmax, Points[ii].x );
 Ymin = std::min( Ymin, Points[ii].y );
 Ymax = std::max( Ymax, Points[ii].y );
 }

 xcliplo = ClipBox->GetX();
 ycliplo = ClipBox->GetY();
 xcliphi = ClipBox->GetRight();
 ycliphi = ClipBox->GetBottom();

 if( Xmax < xcliplo )
 return false;
 if( Xmin > xcliphi )
 return false;
 if( Ymax < ycliplo )
 return false;
 if( Ymin > ycliphi )
 return false;

 return true;
}


static void GRSPoly( EDA_RECT* ClipBox, wxDC* DC, int n, const wxPoint* Points, bool Fill,
 int width, const COLOR4D& Color, const COLOR4D& BgColor )
{
 if( !IsGRSPolyDrawable( ClipBox, n, Points ) )
 return;

 if( Fill && ( n > 2 ) )
 {
 GRSetBrush( DC, BgColor, FILLED );
 GRSetColorPen( DC, Color, width );

 /* clip before send the filled polygon to wxDC, because under linux
 * (GTK?) polygons having large coordinates are incorrectly drawn
 * (integer overflow in coordinates, I am guessing)
 */
 ClipAndDrawPoly( ClipBox, DC, Points, n );
 }
 else
 {

 GRMoveTo( Points[0].x, Points[0].y );

 for( int i = 1; i < n; ++i )
 {
 GRLineTo( ClipBox, DC, Points[i].x, Points[i].y, width, Color );
 }
 }
}


static void GRSClosedPoly( EDA_RECT* aClipBox, wxDC* aDC, int aPointCount, const wxPoint* aPoints,
 bool aFill, int aWidth, const COLOR4D& aColor, const COLOR4D& aBgColor )
{
 if( !IsGRSPolyDrawable( aClipBox, aPointCount, aPoints ) )
 return;

 if( aFill && ( aPointCount > 2 ) )
 {
 GRLastMoveToX = aPoints[aPointCount - 1].x;
 GRLastMoveToY = aPoints[aPointCount - 1].y;
 GRSetBrush( aDC, aBgColor, FILLED );
 GRSetColorPen( aDC, aColor, aWidth );
 ClipAndDrawPoly( aClipBox, aDC, aPoints, aPointCount );
 }
 else
 {

 GRMoveTo( aPoints[0].x, aPoints[0].y );

 for( int i = 1; i < aPointCount; ++i )
 {
 GRLineTo( aClipBox, aDC, aPoints[i].x, aPoints[i].y, aWidth, aColor );
 }

 int lastpt = aPointCount - 1;

 // Close the polygon
 if( aPoints[lastpt] != aPoints[0] )
 {
 GRLineTo( aClipBox, aDC, aPoints[0].x, aPoints[0].y, aWidth, aColor );
 }
 }
}


void GRPoly( EDA_RECT* ClipBox, wxDC* DC, int n, const wxPoint* Points, bool Fill, int width,
 const COLOR4D& Color, const COLOR4D& BgColor )
{
 GRSPoly( ClipBox, DC, n, Points, Fill, width, Color, BgColor );
}


void GRClosedPoly( EDA_RECT* ClipBox, wxDC* DC, int n, const wxPoint* Points, bool Fill,
 const COLOR4D& Color, const COLOR4D& BgColor )
{
 GRClosedPoly( ClipBox, DC, n, Points, Fill, 0, Color, BgColor );
}


void GRClosedPoly( EDA_RECT* ClipBox, wxDC* DC, int n, const wxPoint* Points, bool Fill, int width,
 const COLOR4D& Color, const COLOR4D& BgColor )
{
 GRSClosedPoly( ClipBox, DC, n, Points, Fill, width, Color, BgColor );
}


static bool clipCircle( EDA_RECT* aClipBox, int xc, int yc, int r, int aWidth )
{
 // Clip circles that are outside the ClipBox.
 if( aClipBox )
 {
 int x0, y0, xm, ym;
 x0 = aClipBox->GetX();
 y0 = aClipBox->GetY();
 xm = aClipBox->GetRight();
 ym = aClipBox->GetBottom();

 r += aWidth;

 if( xc < ( x0 - r ) )
 return true;

 if( yc < ( y0 - r ) )
 return true;

 if( xc > ( r + xm ) )
 return true;

 if( yc > ( r + ym ) )
 return true;
 }

 return false;
}


void GRCircle( EDA_RECT* ClipBox, wxDC* DC, int xc, int yc, int r, int width, const COLOR4D& Color )
{
 if( clipCircle( ClipBox, xc, yc, r, width ) || r <= 0 )
 return;

 GRSetBrush( DC, Color, NOT_FILLED );
 GRSetColorPen( DC, Color, width );

 // Draw two arcs here to make a circle. Unfortunately, the printerDC doesn't handle
 // transparent brushes when used with circles. It does work for for arcs, however
 DC->DrawArc(xc + r, yc, xc - r, yc, xc, yc);
 DC->DrawArc(xc - r, yc, xc + r, yc, xc, yc);
}


void GRCircle( EDA_RECT* aClipBox, wxDC* aDC, const wxPoint& aPos, int aRadius, int aWidth,
 const COLOR4D& aColor )
{
 GRCircle( aClipBox, aDC, aPos.x, aPos.y, aRadius, aWidth, aColor );
}


void GRFilledCircle( EDA_RECT* ClipBox, wxDC* DC, int x, int y, int r, int width,
 const COLOR4D& Color, const COLOR4D& BgColor )
{
 if( clipCircle( ClipBox, x, y, r, width ) || r <= 0 )
 return;

 GRSetBrush( DC, BgColor, FILLED );
 GRSetColorPen( DC, Color, width );
 DC->DrawEllipse( x - r, y - r, r + r, r + r );
}


void GRFilledCircle( EDA_RECT* aClipBox, wxDC* aDC, const wxPoint& aPos, int aRadius,
 const COLOR4D& aColor )
{
 GRFilledCircle( aClipBox, aDC, aPos.x, aPos.y, aRadius, 0, aColor, aColor );
}


void GRArc1( EDA_RECT* ClipBox, wxDC* DC, int x1, int y1, int x2, int y2, int xc, int yc,
 int width, const COLOR4D& Color )
{
 /* Clip arcs off screen. */
 if( ClipBox )
 {
 int x0, y0, xm, ym, r;
 x0 = ClipBox->GetX();
 y0 = ClipBox->GetY();
 xm = ClipBox->GetRight();
 ym = ClipBox->GetBottom();
 r = KiROUND( Distance( x1, y1, xc, yc ) );

 if( xc < ( x0 - r ) )
 return;

 if( yc < ( y0 - r ) )
 return;

 if( xc > ( r + xm ) )
 return;

 if( yc > ( r + ym ) )
 return;
 }

 GRSetBrush( DC, Color );
 GRSetColorPen( DC, Color, width );
 DC->DrawArc( x1, y1, x2, y2, xc, yc );
}


void GRArc1( EDA_RECT* aClipBox, wxDC* aDC, const wxPoint& aStart, const wxPoint& aEnd,
 const wxPoint& aCenter, int aWidth, const COLOR4D& aColor )
{
 GRArc1( aClipBox, aDC, aStart.x, aStart.y, aEnd.x, aEnd.y, aCenter.x, aCenter.y,
 aWidth, aColor );
}


void GRFilledArc1( EDA_RECT* ClipBox, wxDC* DC, const wxPoint& aStart, const wxPoint& aEnd,
 const wxPoint& aCenter, int width, const COLOR4D& Color, const COLOR4D& BgColor )
{
 /* Clip arcs off screen. */
 if( ClipBox )
 {
 int x0, y0, xm, ym, r;
 x0 = ClipBox->GetX();
 y0 = ClipBox->GetY();
 xm = ClipBox->GetRight();
 ym = ClipBox->GetBottom();
 r = KiROUND( Distance( aStart.x, aStart.y, aCenter.x, aCenter.y ) );

 if( aCenter.x < ( x0 - r ) )
 return;

 if( aCenter.y < ( y0 - r ) )
 return;

 if( aCenter.x > ( r + xm ) )
 return;

 if( aCenter.y > ( r + ym ) )
 return;
 }

 GRSetBrush( DC, BgColor, FILLED );
 GRSetColorPen( DC, Color, width );
 DC->DrawArc( aStart.x, aStart.y, aEnd.x, aEnd.y, aCenter.x, aCenter.y );
}


void GRArc( EDA_RECT* ClipBox, wxDC* DC, int xc, int yc, double StAngle, double EndAngle, int r,
 const COLOR4D& Color )
{
 int x1, y1, x2, y2;

 /* Clip arcs off screen */
 if( ClipBox )
 {
 int radius = r + 1;
 int x0, y0, xm, ym, x, y;
 x0 = ClipBox->GetX();
 y0 = ClipBox->GetY();
 xm = ClipBox->GetRight();
 ym = ClipBox->GetBottom();
 x = xc;
 y = yc;

 if( x < ( x0 - radius ) )
 return;

 if( y < ( y0 - radius ) )
 return;

 if( x > ( xm + radius ) )
 return;

 if( y > ( ym + radius ) )
 return;
 }

 x1 = r;
 y1 = 0;
 RotatePoint( &x1, &y1, EndAngle );

 x2 = r;
 y2 = 0;
 RotatePoint( &x2, &y2, StAngle );

 GRSetBrush( DC, Color, NOT_FILLED );
 GRSetColorPen( DC, Color );
 DC->DrawArc( xc + x1, yc - y1, xc + x2, yc - y2, xc, yc );
}


void GRArc( EDA_RECT* ClipBox, wxDC* DC, int x, int y, double StAngle, double EndAngle, int r,
 int width, const COLOR4D& Color )
{
 int x1, y1, x2, y2;

 /* Clip arcs off screen. */
 if( ClipBox )
 {
 int x0, y0, xm, ym;
 x0 = ClipBox->GetX();
 y0 = ClipBox->GetY();
 xm = ClipBox->GetRight();
 ym = ClipBox->GetBottom();

 if( x < ( x0 - r - width ) )
 return;

 if( y < ( y0 - r - width ) )
 return;

 if( x > ( r + xm + width ) )
 return;

 if( y > ( r + ym + width ) )
 return;
 }

 x1 = r;
 y1 = 0;
 RotatePoint( &x1, &y1, EndAngle );

 x2 = r;
 y2 = 0;
 RotatePoint( &x2, &y2, StAngle );

 GRSetBrush( DC, Color );
 GRSetColorPen( DC, Color, width );
 DC->DrawArc( x + x1, y - y1, x + x2, y - y2, x, y );
}


void GRRect( EDA_RECT* ClipBox, wxDC* DC, int x1, int y1, int x2, int y2, int width,
 const COLOR4D& Color )
{
 GRSRect( ClipBox, DC, x1, y1, x2, y2, width, Color );
}


void GRFilledRect( EDA_RECT* ClipBox, wxDC* DC, int x1, int y1, int x2, int y2,
 const COLOR4D& Color, const COLOR4D& BgColor )
{
 GRSFilledRect( ClipBox, DC, x1, y1, x2, y2, 0, Color, BgColor );
}


void GRFilledRect( EDA_RECT* ClipBox, wxDC* DC, int x1, int y1, int x2, int y2, int width,
 const COLOR4D& Color, const COLOR4D& BgColor )
{
 GRSFilledRect( ClipBox, DC, x1, y1, x2, y2, width, Color, BgColor );
}


void GRSRect( EDA_RECT* aClipBox, wxDC* aDC, int x1, int y1, int x2, int y2, int aWidth,
 const COLOR4D& aColor )
{
 wxPoint points[5];
 points[0] = wxPoint( x1, y1 );
 points[1] = wxPoint( x1, y2 );
 points[2] = wxPoint( x2, y2 );
 points[3] = wxPoint( x2, y1 );
 points[4] = points[0];
 GRSClosedPoly( aClipBox, aDC, 5, points, NOT_FILLED, aWidth, aColor, aColor );
}


void GRSFilledRect( EDA_RECT* aClipBox, wxDC* aDC, int x1, int y1, int x2, int y2, int aWidth,
 const COLOR4D& aColor, const COLOR4D& aBgColor )
{
 wxPoint points[5];
 points[0] = wxPoint( x1, y1 );
 points[1] = wxPoint( x1, y2 );
 points[2] = wxPoint( x2, y2 );
 points[3] = wxPoint( x2, y1 );
 points[4] = points[0];

 GRSetBrush( aDC, aBgColor, FILLED );
 GRSetColorPen( aDC, aBgColor, aWidth );

 if( aClipBox && ( aWidth > 0 ) )
 {
 EDA_RECT clipbox( *aClipBox );
 clipbox.Inflate( aWidth );
 ClipAndDrawPoly( &clipbox, aDC, points, 5 ); // polygon approach is more accurate
 }
 else
 {
 ClipAndDrawPoly(aClipBox, aDC, points, 5 );
 }
}

#include <SutherlandHodgmanClipPoly.h>

void ClipAndDrawPoly( EDA_RECT* aClipBox, wxDC* aDC, const wxPoint* Points, int n )
{
 if( aClipBox == nullptr )
 {
 aDC->DrawPolygon( n, Points );
 return;
 }

 // A clip box exists: clip and draw the polygon.
 static std::vector<wxPoint> clippedPolygon;
 static pointVector inputPolygon, outputPolygon;

 inputPolygon.clear();
 outputPolygon.clear();
 clippedPolygon.clear();

 for( int ii = 0; ii < n; ii++ )
 inputPolygon.push_back( PointF( (REAL) Points[ii].x, (REAL) Points[ii].y ) );

 RectF window( (REAL) aClipBox->GetX(), (REAL) aClipBox->GetY(),
 (REAL) aClipBox->GetWidth(), (REAL) aClipBox->GetHeight() );

 SutherlandHodgman sh( window );
 sh.Clip( inputPolygon, outputPolygon );

 for( cpointIterator cit = outputPolygon.begin(); cit != outputPolygon.end(); ++cit )
 {
 clippedPolygon.emplace_back( KiROUND( cit->X ), KiROUND( cit->Y ) );
 }

 if( clippedPolygon.size() )
 aDC->DrawPolygon( clippedPolygon.size(), &clippedPolygon[0] );
}