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Guest
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 Posted: Tue May 01, 2007 11:57 pm Post subject: Strange Error when plotting data with TChart |
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I have a TChart and one button in a project. The button just plots
points to the chart. If I call the AddXY() function it bombs if the
data is from an array created outside this routine or it bombs if the
"Y" data is a constant like dVal = 18100. NOTE: If the dVal = 1817 it
won't bomb, if dVal = 1818 it will bomb.
( dVal = 0x71A; //0x71A (1818)fails //0x719 (1817) passes )
Any ideas why this occurs? The only difference I can see is that one
is calculated on the fly and the other is known by the compiler at
compile time(this doesn't explain why dVal < 1817 passes but dVal >=
1818 fails though)
Thanks...
void __fastcall TForm1::Button2Click(TObject *Sender)
{
int i;
int iVal;
double dVal;
//dVal = 18180; // Bombs, when used
for(i=0;i<10000;i++)
{
//dVal = 8000; // Bombs, when used
//dVal = i*sin(i*3.14/360); // Works, when used
tcDataPlot->Series[0]->AddXY(i,dVal,"",clBlue); //i,10000,"",
clBlack);
}
}
//---------------------------------------------------------------------------
"Access violation at address 40901083 in module 'tee60.bpl'. Write of
address 01754000"
"Project test.exe raised exception class EInvalidPointer with message
'Invalid pointer operation'. Process stopped" |
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Oliver Rutsch
Guest
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| Posted: Wed May 02, 2007 8:10 am Post subject: Re: Strange Error when plotting data with TChart |
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Hi,
| Quote: | I have a TChart and one button in a project. The button just plots
points to the chart. If I call the AddXY() function it bombs if the
data is from an array created outside this routine or it bombs if the
"Y" data is a constant like dVal = 18100. NOTE: If the dVal = 1817 it
won't bomb, if dVal = 1818 it will bomb.
( dVal = 0x71A; //0x71A (1818)fails //0x719 (1817) passes )
|
I think you're using BCB6, right? In BCB5 there was a serious problem in
the TChart component when you're using Y-axis autoscaling. The problem
was that the autoscaling algorithm failed with an AV when ALL Y-values
in the diagram had the same value. What you can try is:
1. Disable autoscaling for the Y-axis.
2. Make sure that you have at least two different y-values in the
diagram. The AV occurs when the diagram repaints, so make sure that you
add your values without interruption.
3. Try this workaround:
Add in the constructor of your form:
MySeries->OnAfterAdd=AfterAdd;
Add this event in your form:
void __fastcall TMyForm::AfterAdd(TChartSeries * Sender, int ValueIndex)
{
TCustomAxisPanel * Parent=Sender->ParentChart;
if (!Parent)
return;
// not if zoomed!
if (Parent->Zoomed)
return;
// Workaround to prevent access violation in TChart when
// Min/Max values are the same.
const double tmpVal = Sender->YValues->MaxValue;
// remember initial value of the Automatic property
const static bool y_auto=Sender->GetVertAxis->Automatic;
if (tmpVal!=Sender->YValues->MinValue)
{
// already different min/max values
Sender->GetVertAxis->Automatic = y_auto;
return;
}
bool SameVal=true;
for (int i=0;i<Parent->SeriesList->Count;i++)
{
const double SeriesMin=Parent->Series[i]->YValues->MinValue;
const double SeriesMax=Parent->Series[i]->YValues->MaxValue;
if (Parent->Series[i]->Count() && (tmpVal!=SeriesMin ||
tmpVal!=SeriesMax))
{
SameVal=false;
break;
}
}
if (SameVal)
{
// Set Automatic to false to prevent AV in TChart
Sender->GetVertAxis->Automatic = false;
Sender->GetVertAxis->SetMinMax(tmpVal-1, tmpVal+1);
}
else
Sender->GetVertAxis->Automatic = y_auto; // set to initial value
}
Bye,
--
Dipl. Ing. Oliver Rutsch
EMail: orutsch (AT) sympatec (DOT) com
Sympatec GmbH |
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