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Additional series for <a HREF="sgraph.htm">SGraph</a>.
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<P>For my own use I wrote series which get data from external data storage and draw it. I was going to develop this series, unfortunately I still have not time and it works. Because of I received request for series like this I decide to publish current version.
There are 2 class: <BR>
<B>Tsp_DrawPoints</B>=class(Tsp_DataSeries) and <BR>
<B>Tsp_ndsXYLine</B>=class(Tsp_DrawPoints). <BR>
Tsp_DrawPoints can be used to derive new series, it
contains all draw primitives and main functionality, from this one you can
derive new series with arbitrary data storage engine. Tsp_ndsXYLine source
is example how to do this. Tsp_ndsXYLine itself permits you
keep data separately from series in your own variables (or may be files) and
draw it through callback functions (events) interface. </P>
<H4>How it works?</H4>
<P>Tsp_ndsXYLine in sense of drawing is same to Tsp_XYLine (see
sgr_def.hlp for draw properties of Tsp_XYLine). But
Tsp_ndsXYLine has not internal data storage, it uses callback functions
(events) to receive date for drawing. There are several events</P>
<P>TspGetXYCountEvent=procedure(DS:Tsp_ndsXYLine) of object;<BR>
TspGetXYEvent=procedure(DS:Tsp_ndsXYLine; idx:integer) of object;<BR>
TspGetMinMaxEvent=function(DS:Tsp_ndsXYLine; var
V:double):boolean of object;</P>
<P>and they published in Tsp_ndsXYLine as next properties</P>
<P>published<BR>property OnGetXYCount: TspGetXYCountEvent read
FOnGetXYCount write FOnGetXYCount;<BR>property OnGetXY:
TspGetXYEvent read fOnGetXY write fOnGetXY;<BR>
property OnGetXMin: TspGetMinMaxEvent read fOnGetXMin write fOnGetXMin;<BR>
property OnGetXMax: TspGetMinMaxEvent read fOnGetXMax write fOnGetXMax;<BR>
property OnGetYMin: TspGetMinMaxEvent read fOnGetYMin write fOnGetYMin;<BR>
property OnGetYMax: TspGetMinMaxEvent read fOnGetYMax write fOnGetYMax;<BR>
end;<BR>
You write handlers for this events where inform series about data. Number of
points and current point value are set in handlers as values for public series
fields Count and XV,YV. </P>
<P>Here simple demo program eds_demo is included. In this program we place data
in array Data[0..maxi-1,xi..yi] and write handlers which connect series with
this data storage. When series begin to draw data it call OnGetXYCount where we
define how many times it will call for the data points</P>
<PRE>procedure TForm1.sp_ndsXYLine1GetXYCount(DS: Tsp_ndsXYLine);
begin
DS.Count:=maxi;
end;</PRE>
<P>Then series call <B>Count</B> times this handler </P>
<PRE>procedure TForm1.sp_ndsXYLine1GetXY(DS: Tsp_ndsXYLine; idx: Integer);
begin
DS.XV:=Data[idx,xi];
DS.YV:=Data[idx,yi];
end;</PRE>
<P>to receive data. If series has marker and lines it call this twice for every
points. idx are changed from 0 to Count-1 and
indicate current point number. </P>
<P>When series begin to draw or when plot is making autoscaling and ask series
for limits, series need information about max and min of data values. For that
it calls handlers like this one (see more in help file for the function
GetXMax)</P>
<PRE>function TForm1.sp_ndsXYLine1GetXMax(DS: Tsp_ndsXYLine;
var V: Double): Boolean;
begin
Result:=True; //True because we have info about Max of X data
V:=MaxX;
end;</PRE>
<P>For information about series and plot see sgr_def.hlp file. </P>
<p>Sergei P. Pod'yachev. Novosibirsk, Russia. <br>
WWW: <a HREF="http://pod0.chat.ru">pod0.chat.ru</a> <br>
<a HREF="http://www.iae.nsk.su/~lab12/pod"><FONT SIZE="2" COLOR="">www.iae.nsk.su/~lab12/pod</FONT></a> </p>
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