>  Hello All,

> I have been trying to use a graphing component from National Instruments
> to plot data.  I installed it into my project, and it seems to work
> find, except for one little thing.  The more data I plot, the slower it
> goes.  In other words, if I plot one set of points, it might take 1ms.
> If I press a button and plot the same set of points again, it might take
> 1.05ms.  Then 1.1ms, 1.15ms, and so on forever.  This makes the control
> useless after a few thousand plots.

>  I thought this was a problem with National Instruments' control,
> except:

> 1) I can run the same code in VC++ 6.0, and it works fine (no slowdown)
> 2) I can run the same code (ported) in VB, and it works fine
> 3) I have had the same problem with other controls

> I also tried switching to a strip chart control from General Majic Corp
> (yes, that's how they spell "Majic").  I get the same problem with a
> GreenLeaf serial port control ActiveX library when flipping bits on the
> serial port (see code snippet below).

> Here is a simple code example using the GreenLeaf serial port control to
> flip the DTR bit on COMM1 (you can ignore my DebugTimer calls, as the
> problem is the same even when they are removed):

> void __fastcall TForm1::BitBtn1Click(TObject *Sender)
> {
>    PortCtl1->Open(); // this function opens the serial port

>    DebugTimer profiler;
>    profiler.Start("Beginning loop");  // log the current time

>    int state = 0;
>    for (int i = 0; i < 200; i++)
>    { // THIS LOOP TAKES LONGER AND LONGER EACH TIME THROUGH!

>       state = !state;
>       PortCtl1->Dtr = state;  // <<== set a property on the activeX
> control, this line Gets SLOW
>       profiler.TimeCheck("in loop");  // log how long it took for this
> iteration

>    }

>    profiler.TimeCheckAndStop("Done loop"); // log the end time
>    PortCtl1->Close(); // close the serial port
> }

> When I re-wrote this code using the windows API functions to set the DTR
> bit, it ran at the same speed the first time through the loop, but was
> going 100x faster by the last iteration.

> I would be VERY appreciative if anybody has any suggestions.  Right now,
> it looks like I may have to reimplement my application in visual
> basic... not a pretty thought.

> I did try an example like the one above with some of the chart and
> spreadsheet controls that come with Builder, and did not get the same
> slowdown.  I am using Windows2000 with service pack1, and C++Builder
> version 5 with the latest patches.

> Please help!

> -Peter