geomobjs(3U) | InterViews Reference Manual | geomobjs(3U) |

# NAME¶

PointObj, LineObj, BoxObj, MultiLineObj, FillPolygonObj, Extent - helper classes that manage geometric information for structured graphics

# SYNOPSIS¶

**#include <Unidraw/Graphic/geomobjs.h>**

# DESCRIPTION¶

Unidraw defines several helper classes that store and manage geometric information. Structured graphics objects may use these helper classes to support their semantics. PointObj stores a point, LineObj stores two points, and MultiLineObj stores any number of points. BoxObj and FillPolygonObj define rectangular and polygonal areas, respectively. Extent stores extent information, that is, the lower left corner and center of a bounding box plus a fixed amount of extra space around the bounding box. All these classes provide operations for computing geometric information.

# POINTOBJ PUBLIC OPERATIONS¶

**PointObj(Coord = 0, Coord = 0)****PointObj(PointObj*)**- Construct a PointObj, supplying either two Coords or another PointObj to
specify the instance's coordinates, which are stored in its
*_x*and*_y*public members. **float Distance(PointObj&)**- Return the distance between
*this*and the given PointObj.

# LINEOBJ PUBLIC OPERATIONS¶

**LineObj(Coord = 0, Coord = 0, Coord = 0, Coord = 0)****LineObj(LineObj*)**- Construct a LineObj, supplying either two coordinate pairs or another
LineObj to specify the instance's endpoints, which are stored in its
*_p1*and*_p2*public members. **boolean Contains(PointObj&)****boolean Intersects(LineObj&)**- Return whether
*this*contains the given point and intersects the given line, respectively. **int Same(PointObj& p1, PointObj& p2)**- A helper function used in Intersects. Same returns a positive value if
*p1*and*p2*fall on the same side of the line, 0 if both points fall on the line, or a negative value if the points are on opposite sides of the line.

# BOXOBJ PUBLIC OPERATIONS¶

**BoxObj(Coord = 0, Coord = 0, Coord = 0, Coord = 0)****BoxObj(BoxObj*)**- Construct a BoxObj, supplying either two coordinate pairs or another
BoxObj to specify the instance's bottom-left and top-right corners, which
are stored in its
*_left*,*_bottom*,*_right*, and*_top*public members. **boolean Contains(PointObj&)****boolean Intersects(BoxObj&)****boolean Intersects(LineObj&)**- Return whether
*this*contains the given point and intersects the given box or line, respectively. **BoxObj operator - (BoxObj&)****BoxObj operator + (BoxObj&)**- Compute the intersection (-) or union (+) of
*this*and the given box, returning the result. These operations do not affect*this*or their argument. **boolean Within(BoxObj&)**- Return
*true*if*this*falls completely within the given box. Within will also return*true*if the boxes are identical.

# MULTILINEOBJ PUBLIC OPERATIONS¶

**MultiLineObj(Coord* = nil, Coord* = nil, int = 0)**- Create a MultiLineObj, optionally supplying coordinate arrays (and their
size) that define the vertices of the multiline. The MultiLineObj does
*not*copy these arrays but stores them directly. The MultiLineObj stores this information in its*_x*,*_y*, and*_count*public members. **void GetBox(BoxObj&)**- Calculate the bounding box circumscribing the MultiLineObj's vertices and store it in the argument.
**boolean Contains(PointObj&)****boolean Intersects(BoxObj&)****boolean Intersects(LineObj&)**- Return whether
*this*contains the given point and intersects the given box or line, respectively. **boolean Within(BoxObj&)**- Return
*true*if*this*falls completely within the MultiLineObj's bounding box. Within will also return*true*if the boxes are identical. **void SplineToMultiLine(Coord* cpx, Coord* cpy, int count)****void ClosedSplineToMultiLine(Coord* cpx, Coord* cpy, int count)**- Linearize the open or closed B-Spline defined by the given set of control
points and store the result in
*this*. These operations store the linearized result in internal buffers and assign the addresses of these buffers to*_x*and*_y*; they do*not*delete*_x*and*_y*if they are non-nil prior to assignment.

# MULTILINEOBJ PROTECTED OPERATIONS¶

**void GrowBuf()**- Increase the size of the internal buffers used to store linearized splines.
**boolean CanApproxWithLine(****double x0, double, y0,****double x1, double y1,****double x2, double y2****)**-

Return whether two connected line segments defined by the given three points can be approximated visually with a single line between the endpoints. **void AddLine(double x0, double y0, double x1, double y1)**- Add a line to the internal buffer of vertices.
**void AddBezierArc(****double x0, double y0, double x1, double y1,****double x2, double y2, double x3, double y3****)**-

Add lines approximating the appearance of a Bezier arc defined by the given points to the internal buffer of vertices. **void CalcSection(****Coord cminus1x, Coord cminus1y, Coord cx, Coord cy,****Coord cplus1x, Coord cplus1y, Coord cplus2x, Coord cplus2y****)**-

Add a Bezier arc to the internal buffer of vertices based on a series of four B-spline control points, the one before and the two after (*cx, cy*).

# FILLPOLYGONOBJ PUBLIC OPERATIONS¶

**FillPolygonObj(Coord* = nil, Coord* = nil, int = 0)**- Create a new FillPolygonObj, optionally specifying its vertices. If
vertices are supplied, then the constructor uses Normalize (described
below) to store a normalized set of vertices in the FillPolygonObj's
*_normx*,*_normy*, and*_normCount*public members. FillPolygonObj is a subclass of MultiLineObj; thus it stores the constructor arguments in its*_x*,*_y*, and*_count*public members. **virtual ~FillPolygonObj()**- The destructor deletes the
*_normx*and*_normy*arrays. **boolean Contains(PointObj&)****boolean Intersects(BoxObj&)****boolean Intersects(LineObj&)**- Return whether
*this*contains the given point and intersects the given box or line, respectively.

# FILLPOLYGONOBJ PROTECTED OPERATIONS¶

**void Normalize()**- Copy the vertices defined by
*_x*,*_y*, and*_count*into*_normx*,*_normy*, and*_normCount*such that (*_normx[0], _normy[0]*) is the lower-leftmost vertex and there are no redundant vertices.

# EXTENT PUBLIC OPERATIONS¶

**Extent(****float left = 0, float bottom = 0,****float cx = 0, float cy = 0, float tol = 0****)****Extent(Extent&)**- Construct a new Extent, optionally supplying its parameters explicitly or
providing a existing Extent to copy. The parameters are stored in the
Extent's
*_left*,*_bottom*,*_cx*,*_cy*, and*_tol*public members. **boolean Undefined()**- Return whether the extent is undefined, that is, if (
*_left,**_bottom*) and (*_cx, _cy*) are the same point. **boolean Within(Extent&)**- Return
*true*if the given extent circumscribes*this*. Within will also return*true*if the extents are identical. **void Merge(Extent&)**- Enlarge this extent to subsume area of the given extent.

# SEE ALSO¶

Graphic(3U)

2 February 1991 | Unidraw |