#include <InstrumentUtil.h>

Static Public Member Functions
static bool	CohenSutherlandLineClip (double &x0, double &y0, double &x1, double &y1, double xmin, double xmax, double ymin, double ymax)
	Cohen–Sutherland clipping algorithm clips a line from P0 = (x0, y0) to P1 = (x1, y1) against a rectangle with diagonal from (xmin, ymin) to (xmax, ymax). More...

Private Types
typedef int	OutCode

Static Private Member Functions
static OutCode	ComputeOutCode (double x, double y, double xmin, double xmax, double ymin, double ymax)

Static Private Attributes
static const int	INSIDE = 0

static const int	LEFT = 1

static const int	RIGHT = 2

static const int	BOTTOM = 4

static const int	TOP = 8

Member Typedef Documentation

typedef int InstrumentUtil::OutCode

private

Member Function Documentation

bool InstrumentUtil::CohenSutherlandLineClip	(	double &	x0,
		double &	y0,
		double &	x1,
		double &	y1,
		double	xmin,
		double	xmax,
		double	ymin,
		double	ymax
	)

static

Cohen–Sutherland clipping algorithm clips a line from P0 = (x0, y0) to P1 = (x1, y1) against a rectangle with diagonal from (xmin, ymin) to (xmax, ymax).

Returns true if the line segment is intersecting with the rectangle, false otherwise.

Referenced by PlotFigure::refresh().

 {
     // compute outcodes for P0, P1, and whatever point lies outside the clip rectangle
     OutCode outcode0 = ComputeOutCode(x0, y0, xmin, xmax, ymin, ymax);
     OutCode outcode1 = ComputeOutCode(x1, y1, xmin, xmax, ymin, ymax);
     bool accept = false;
 
     while (true) {
         if (!(outcode0 | outcode1)) { // Bitwise OR is 0. Trivially accept and get out of loop
             accept = true;
             break;
         } else if (outcode0 & outcode1) { // Bitwise AND is not 0. Trivially reject and get out of loop
             break;
         } else {
             // failed both tests, so calculate the line segment to clip
             // from an outside point to an intersection with clip edge
             double x, y;
 
             // At least one endpoint is outside the clip rectangle; pick it.
             OutCode outcodeOut = outcode0 ? outcode0 : outcode1;
 
             // Now find the intersection point;
             // use formulas y = y0 + slope * (x - x0), x = x0 + (1 / slope) * (y - y0)
             if (outcodeOut & TOP) {           // point is above the clip rectangle
                 x = x0 + (x1 - x0) * (ymax - y0) / (y1 - y0);
                 y = ymax;
             } else if (outcodeOut & BOTTOM) { // point is below the clip rectangle
                 x = x0 + (x1 - x0) * (ymin - y0) / (y1 - y0);
                 y = ymin;
             } else if (outcodeOut & RIGHT) {  // point is to the right of clip rectangle
                 y = y0 + (y1 - y0) * (xmax - x0) / (x1 - x0);
                 x = xmax;
             } else if (outcodeOut & LEFT) {   // point is to the left of clip rectangle
                 y = y0 + (y1 - y0) * (xmin - x0) / (x1 - x0);
                 x = xmin;
             }
 
             // Now we move outside point to intersection point to clip
             // and get ready for next pass.
             if (outcodeOut == outcode0) {
                 x0 = x;
                 y0 = y;
                 outcode0 = ComputeOutCode(x0, y0, xmin, xmax, ymin, ymax);
             } else {
                 x1 = x;
                 y1 = y;
                 outcode1 = ComputeOutCode(x1, y1, xmin, xmax, ymin, ymax);
             }
         }
     }
     return accept;
 }

InstrumentUtil::OutCode InstrumentUtil::ComputeOutCode	(	double	x,
		double	y,
		double	xmin,
		double	xmax,
		double	ymin,
		double	ymax
	)

staticprivate

Referenced by CohenSutherlandLineClip().

 {
     OutCode code;
 
     code = INSIDE;          // initialised as being inside of [[clip window]]
 
     if (x < xmin)           // to the left of clip window
         code |= LEFT;
     else if (x > xmax)      // to the right of clip window
         code |= RIGHT;
     if (y < ymin)           // below the clip window
         code |= BOTTOM;
     else if (y > ymax)      // above the clip window
         code |= TOP;
 
     return code;
 }