Creating font for a different dpi

Question

Using Visual Studio 2008 for our project C++.. 
Trying to create/select a font at a different dot per inch (dpi) .
We calculate the font height with this line..    dot per mm * 25.4 = dpi.
m_pLF->lfHeight = (long)(-item.GetFontSize() * theMachine.GetDotsPerMm()) * 25.4 / 72;
The font is drawn on a bitmap and then viewed. The problem is that the font seems to come out too small ?
About 30% too small
Full font selection routine is here.
void CLibraryBase::SelectFont(CItem &item, CLabel &label)
//choose the font
m_pLF=(LOGFONT*)calloc(1,sizeof(LOGFONT));
CString szFontName = item.GetFontName();
wcsncpy(m_pLF->lfFaceName,szFontName,szFontName.GetLength());
m_pLF->lfHeight = (long)(-item.GetFontSize() * theMachine.GetDotsPerMm()) * 25.4 / 72;
m_pLF->lfWeight = FW_NORMAL;
if(item.GetBold())
m_pLF->lfWeight = FW_BOLD;
if((szFontName.MakeUpper() == "WINGDINGS")||(szFontName.MakeUpper() == "SYMBOL")||(szFontName.MakeUpper() == "WEBDINGS"))
m_pLF->lfCharSet = SYMBOL_CHARSET;
m_pLF->lfItalic = item.GetItalic();
m_pLF->lfUnderline = item.GetUnderline();
m_pLF->lfStrikeOut = item.GetStrikeout();
m_pLF->lfQuality = ANTIALIASED_QUALITY;
m_pLF->lfPitchAndFamily = VARIABLE_PITCH | FF_DONTCARE;
m_Font.CreateFontIndirect(m_pLF);

Answer 1

Please show the code of GetFontSize and GetDotsPerMm function.
Think about using GetTextMetrics() function, like this.
https://msdn.microsoft.com/en-us/library/dd144941(v=vs.85).aspx
GetTextMetrics(hdc, &tm); m_pLF->lfHeight= tm.tmHeight + tm.tmExternalLeading;
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