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Peg2DPolygon

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Overview Derived from class PegThing The Peg2DPolygon class is an advanced drawing class which can be used to draw, move and rotate two dimensional polygon shapes. This class of objects is suitable for drawing filled polygons, wireframe outlines and geographical maps. Because of the ease with which the objects can be moved and rotated, the class can also be used to create and manipulate sprites, simple outlines which rapidly move about your screen. Unlike the Polygon() function provided by the PegScreen class, the polygon points for a Peg2DPolygon object are specified using offsets from the top, left corner of the object's bounding rectangle instead of absolute screen coordinates. The polygon outline is drawn in the object's normal color as specified by color flag PCI_NTEXT. The polygon will be drawn over the bounding rectangle painted in the object's normal background color as specified by color flag PCI_NORMAL. Alternatively, the polygon outline can float over the parent object if the polygon is given the AF_TRANSPARENT style. In either case, the interior of the polygon can be filled with the object's select color as specified by color flag PCI_STEXT, provided that you enable fill mode with a call to function SetFill(). The Peg2DPolygon object can also be rotated. The geometry used for specifying the angle of rotation is described below. This class does NOT require floating point support. To use the Peg2DPolygon class or its derivatives, your KwikPeg configuration must have the following option enabled:   Drawing: Polygons, circles, ellipses and patterned lines

See Also

PegScreen (Polygon() function)

Polygon Geometry

It is important to understand the geometry which governs the operation of a KwikPeg 2D polygon.

Consider the x-y coordinate system shown in Figures 1 and 2 below. A point P in the x-y plane has coordinates (x,y). Coordinate x is considered positive along OX and negative along OX'. Coordinate y is positive along OY and negative along OY'. Line X'OXis the x; line Y'OY is the y axis.

The angle A (shown red) described counterclockwise from OX is considered positive. If the angle is described clockwise from OX, it is considered negative.

The quadrants denoted by I, II, III and IV are the first, second, third and fourth quadrants, respectively. In Figure 1, the angle shown in red is in the second quadrant. In Figure 2, the angle shown in red is in the third quadrant.

Angles used by the Peg2DPolygon class are defined as follows. 0 degrees is always along line OX. Angle values increase in the counterclockwise direction. Therefore, line OY is at 90 degrees, line OX' is at 180 degrees and line OY' is at 270 degrees.

It is also important to note that the polygon is rotated relative to the center of its bounding rectangle. Hence, you can easily create some very interesting rotational effects.

When rotating the polygon, you must be aware of the distance from the center of the bounding rectangle to each polygon point. If a polygon point lies outside largest concentric circle that will fit within the bounding rectangle, then the line segments joining that point to its neighboring polygon points may be clipped as the polygon is rotated.

Styles

The Peg2DPolygon class supports the following style flags:

Although the Peg2DPolygon class supports the AF_TRANSPARENT style, you must take care when rotating or moving the polygon to ensure that the relic polygon is properly erased. After rotating the polygon, you should force the parent object to redraw itself. Of course, this assumes that you have not set the PSF_VIEWPORT status on the Peg2DPolygon object.

The Peg2DPolygon class also supports the TT_COPY style. When this style flag is used, the Peg2DPolygon copies the array of PegPoints into the Peg2DPolygon object. Therefore, if you have statically allocated your point array or have dynamically created your list of points, you can avoid duplicating your array by not using the TT_COPY style. This style flag is not used unless specified by you.

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Members

Constructors:

	Peg2DPolygon(const PegRect &Rect,
	PegPoint *pPoints, WORD wNumPoints,
	WORD wId = 0, WORD wStyle = FF_NONE)

This constructor creates a 2D polygon in the rectangle specified by parameter Rect.

Parameter iNumPoints specifies the number of PegPoints listed in the array of points referenced by pPoints. The last point in the array will be connected to the first point in the array when the polygon is drawn.

The frame style and polygon characteristics will be governed by the style flags provided by parameter wStyle.

Public Functions:

	void Draw()

The Peg2DPolygon class overrides the Draw() function to draw the 2D polygon.

	SIGNED GetCurAngle() const
	void SetCurAngle(SIGNED iTheta)

These inline functions get or set the current angle of rotation of the polygon. By default, the angle is set to 0 degrees.

	BOOL GetFill() const
	void SetFill(BOOL bFill)

These inline functions get or set the current fill mode. By default, the fill mode is set to FALSE.

If parameter bFill is TRUE, the polygon will be filled with the object's select color as specified by color flag PCI_STEXT.

If parameter bFill is FALSE, the polygon interior will not be filled. In most cases, the interior will be painted in the object's normal color as specified by color flag PCI_NORMAL. However, if style flag AF_TRANSPARENT is set, the polygon interior will be left transparent, allowing the underlying parent object to show through the polygon.

	SIGNED GetLineWidth() const
	void SetLineWidth(SIGNED iWidth)

These inline functions get or set the current width of the lines used to draw the polygon outline. Parameter iWidth specifies the line width in pixels. By default, the line width is set to one pixel.

	WORD GetNumPoints(void) const

This inline function returns the number of points in the array of points used to specify the polygon shape.

	void ParentShift(
	WORD iXOffset, WORD iYOffset)

The Peg2DPolygon class overrides the ParentShift() function to map the polygon coordinates to the correct screen location when the polygon is moved. This function is used only by KwikPeg.

	void Resize(PegRect Rect)

The Peg2DPolygon class overrides the Resize() function to redraw the polygon within the bounding rectangle specified by tRect. Note that the size and location of the bounding rectangle can change but the polygon points relative to the bounding rectangle will not change. Hence, the polygon will not change size, shape or orientation within its bounding rectangle.

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Examples

The following example illustrates a 2D polygon derived from the Peg2DPolygon class and drawn within a decorated window.

 
The Peg2DPolygon object illustrated above was created by the following code fragment:

// Polygon point data
static PegPoint gtPolyPoints[] =
    { {47, 24}, {12, 12}, {24, 22},
      {24, 23}, {31, 19}, {31, 27}, 
      {24, 25}, {12, 35} };


PolygonWindow::PolygonWindow() : PegDecoratedWindow()
{
    mReal.Set(0, 0, 300, 160);
    InitClient();

    SetColor(PCI_NORMAL, LIGHTCYAN);

    Add(new PegTitle("Peg2DPolygon Example"));

    PegRect tRect;
    tRect.Set(mClient.wLeft + 80,
              mClient.wTop + 40,
              mClient.wLeft + 80 + 47,
              mClient.wTop + 40 + 47);

    mpPolygon = new Peg2DPolygon(tRect,
              &gtPolyPoints[0],
              sizeof(gtPolyPoints)/sizeof(PegPoint),
              101, FF_NONE | AF_TRANSPARENT);

    mpPolygon->SetColor(PCI_STEXT, LIGHTRED);
    mpPolygon->SetColor(PCI_NTEXT, WHITE);
    mpPolygon->SetFill(TRUE);
    Add(mpPolygon);
}

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