Formatting Value Labels in Engeneering Format

Formatting Value Labels in Engeneering Format

Posted by: cpn on 14 September 2021, 7:05 pm EST

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  cpn

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  Posted 14 September 2021, 7:05 pm EST

  For OlectraChart v8 used as a C++/DLL (still beating my .NET/C# collogues in speed and performance
  
  I’m trying to formatting value labels in engineering format (the exponent in a factor of 3, like 31.23E+03, 0.7E-6 etc.) I can’t find a way to do this using the standard formatting #0? using SetXAxisLabelFormat.
  
  But I found that the component is sending and event for the value labels when using SetXAnnotationMethod(XRT_ANNO_VALUES_EVENT).
  
  But the format of the parameters is not documented. I think that this could probably be used to alter a value like 1.5E+04 to 15E+03 on the fly.
  
  Please provide me with the argument of the event.
  
  Thanks cpede

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  cpn

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  Posted 14 September 2021, 10:03 pm EST

  OK, found it myself: XrtFormatAxisAnnoCallbackStruct.

  
  LRESULT CMyChart::OnAxisAnno(WPARAM, LPARAM lData)
  {
  	XrtFormatAxisAnnoCallbackStruct* pData =
  		(XrtFormatAxisAnnoCallbackStruct*)lData;
  	if (pData == NULL) return 0L;
  
  	// for some strange reason adding X after each number string
  	size_t nLen = _tcslen(pData->label->string) + 1; // one X
  	TCHAR *pszText = new TCHAR[nLen + 1];
  	::ZeroMemory(pszText, (nLen + 1)* sizeof(TCHAR));
  	_tcscpy_s(pszText, nLen + 1, pData->label->string);
  	_tcscat_s(pszText, nLen + 1, _T("X"));
  	pData->label->string = pszText;
  	return 0L;
  }
  
  

  The problem is now:
  
  I get assertions in SetRepaint
  
  olch2d8.dll!00007fff273f4047() Unknown

  • Who is responsible for deleting the old pData->label->string, and how should this be deleted?
  • Or should I delete the entire XrtValueLabel pData->label?

  Thanks cpede

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  cpn

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  Posted 26 September 2021, 4:52 pm EST

  Again:
  
  What is the right way of overwriting the pData->label->string?
  
  Who is responsible for deleting the old pData->label->string, and how should this be deleted?