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PegLineChart

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Overview Derived from class PegChart The PegLineChart class provides a simple, single line, two dimensional chart for plotting one data variable as a function of another. The chart is drawn as a series of straight line segments joining the data points. The chart has all of the characteristics provided by the PegChart base class from which it is derived. The PegLineChart class maintains a linked list of the data points which make up the line chart. The data points are joined by straight line segments. The line segments are drawn from point to point in the order in which the data points appear in the list. Each data point is recorded in its own PegChartPoint structure maintained by the PegLineChart class. These private structures are used to identify data points and control their position on the screen. The pointer to such a data point structure is called a data point handle. Your application will have access to these handles as you add, insert or remove the data points which form your line chart. To use the PegLineChart class or its derivatives, your KwikPeg configuration must have the following option enabled:   Drawing: Charts

See Also

PegMultiLineChart

PegStripChart

Styles

The PegLineChart class supports the following extended style flags:

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Members

Constructors:

	PegLineChart(const PegRect &Rect,
	LONG lMinX, LONG lMaxX,
	LONG lMinY, LONG lMaxY,
	WORD wXMajorScale = 0,
	WORD wYMajorScale = 0)

This constructor creates a single line chart in the rectangle specified by parameter Rect. If style flag CS_AUTOSIZE is to be used (see function SetExStyle()), you may want to draw the chart in the parent's mClient rectangle.

Parameters lMinX and lMaxX specify the minimum and maximum X (horizontal) values. Parameters lMinY and lMaxY specify the minimum and maximum Y (vertical) values. Data points which lie outside these ranges, although not rejected, will not be viewable in the chart rectangle.

Parameters wXMajorScale and wYMajorScale define the intervals along the X and Y axes respectively at which major tick marks will be drawn. Of course, tick marks are only drawn if the object's CS_DRAWXTICS or CS_DRAWYTICS extended style flag is set.

For example, if the minimum Y value is -100, the maximum Y value is 900, the Y scale is 100 and the CS_DRAWYTICS extended style flag is set, then tick marks will be drawn on the Y axis at intervals of 100 starting at -100 and ending at 900. Consequently, there will be 11 tick marks drawn on the Y axis. If the CS_DRAWYGRID extended style flag is also set, horizontal grid lines will also be drawn at the same tick mark intervals.

The interval at which axis label values are drawn is independent of the tick mark/grid line scaling interval. Hence, tick marks might appear at intervals of 100 with the axis values labeled at intervals of 200.

Public Functions:

	PegChartPoint *AddPoint(
	LONG lX, LONG lY)

This function adds a new data point (lX,lY) to the end of the data point list maintained by the line chart. The function returns a data point handle which the chart will use to identify the new data point and control its position on the screen. Rarely will there be a need for you to use the handle.

Use this procedure to add data points to the line chart in the order in which you want the line segments drawn. Each data point added using this function will be joined by a straight line segment to the data point previously at the end of the data point list. In most cases, data points should be added such that the X values are monotonically increasing.

	virtual void Draw(void)

The PegLineChart class overrides the Draw() function to draw the straight line segments that join each data point to make up the line chart.

	PegChartPoint *GetFirstPoint(void) const

This function returns the data point handle for the first data point of the line chart.

	COLORVAL GetLineColor(void) const

This function returns the KwikPeg COLORVAL value which defines the color of the line segments.

	PegChartPoint *InsertPoint(
	PegChartPoint *pPoint,
	LONG lX, LONG lY)

This function inserts a new data point (lX,lY) into the data point list maintained by the line chart. The data point is inserted following the data point referenced by the handle pPoint. The function returns a new data point handle which the chart will use to identify the new data point and control its position on the screen.

	virtual SIGNED Message(const PegMessage &Mesg)

The PegLineChart class overrides the Message() function to recalculate the chart location or layout when its parent is moved or resized.

	void RecalcLine(void)

This function recalculates the screen coordinates for every data point in the line chart. This function is used privately by this chart class.

	virtual void RecalcSize(
	const PegRect &NewRect,
	BOOL bRedraw = TRUE)

The PegLineChart class overrides the RecalcSize() function to adjust the line chart's location and size as specified by the rectangle NewRect. This function is used privately to redraw the line chart if it is moved or resized. The function uses the Resize() function to update the screen coordinates of all the line data points. If the bRedraw flag is TRUE, the chart is redrawn.

	PegChartPoint *RemovePoint(PegChartPoint *pPoint)

This function removes the data point referenced by the handle pPoint from the line chart. The function returns the handle of the data point which preceded the removed data point. The function returns NULL if the removed data point was at the head of the line chart data point list.

	void ResetLine(void)

This function removes all data points, if any, from the line chart. All data point handles in your possession will be invalid after this function is called.

	virtual void Resize(PegRect NewRect)

The PegLineChart class overrides the Resize() function to adjust the line chart's location and size as specified by the rectangle NewRect. The function calls the PegChart base class RecalcLayout() function but inhibits redrawing of the chart. Function RecalcLine() is then used to reposition all line data points within the revised chart. This function is used privately by this chart class.

	COLORVAL SetLineColor(COLORVAL Color)

This function sets the color to be used for drawing line segments to the color defined by the COLORVAL value referenced by Color. The function returns the color that was previously being used to draw chart lines.

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Examples

The following code fragment illustrates the use of a PegLineChart object to generate the line chart pictured below.

    PegRect Rect;
    Rect.Set(20, 20, 600, 440);

    PegLineChart *pLineChart =
        new PegLineChart(Rect, 0, 1000, 0, 1000, 100, 100);

    pLineChart->SetXLabelScale(200);

    pLineChart->SetExStyle(
        CS_DRAWXTICS | CS_DRAWYTICS |
        CS_DRAWXGRID | CS_DRAWYGRID | CS_AUTOSIZE |
        CS_DRAWYLABELS | CS_DRAWXLABELS);

    pLineChart->AddPoint(100, 100);
    pLineChart->AddPoint(200, 200);
    pLineChart->AddPoint(300, 300);

    PegChartPoint *pPoint = pLineChart->AddPoint(400, 400);

    pLineChart->AddPoint(500, 500);
    pLineChart->AddPoint(600, 600);
    pLineChart->AddPoint(700, 800);

    pLineChart->InsertPoint(pPoint, 450, 0);

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