CodeGuru content and product recommendations are editorially independent. We may make money when you click on links to our partners. Learn More.
CFontCombo Overview
The CFontCombo class is a CComboBox-derived class that while
being a simple class is very useful in that it enables
you to display all the fonts on the system in a combo box for the user’s
selection. Obviously, for the curious, you not only get the control itself,
but the source code that shows how to iterate through the system’s fonts and then
how to apply a selected font to a bit of text (you can see this bit in the
article’s demo project shown in the screen shot above).
How it works
The way it works is that when the CFontCombo is subclassed
(as with the MFC DDX mechanism), it calls ProcessFonts.
void CFontCombo::PreSubclassWindow()
{
// call function to get system's fonts when control is subclassed
this->ProcessFonts();
// call base class' implementation
CComboBox::PreSubclassWindow();
}
Once, in the CFontCombo::ProcessFonts member function. As you can
see below, ProcessFonts
calls the Win32 SDK function, ::EnumFontFamiliesEx. A quick peek at the
MSDN Library reveals that “The EnumFontFamiliesEx function
enumerates all fonts in the system that match the font characteristics specified
by the LOGFONT structure.” The main arguments here are the second, third and forth
ones. In those, I specify (in order) the LOGFONT structure (which defines which fonts I
want – I selected all ANSI fonts), a callback function that Windows will call once for each
font found in the system and finally a user supplied pointer to a block of memory.
The first two are pretty much self-explanatory. The last one (the user supplied memory)
works like this. I’m passing the address of a CStringArray
(called fontlist) which will be passed to my callback function
(CFontCombo::EnumFontFamExProc) for each
found font. In that callback function (which you’ll see shortly),
I get the name of a font which I then store in the fontlist. However,
the call to EnumFontFamiliesEx doesn’t return until all fonts have been
enumerated. Therefore, once this call does return, I know that all the fonts are
in my fontlist string array. At this point, I simply iterate
through that list (see the for loop below) and add each string to the
combo box.
void CFontCombo::ProcessFonts(void)
{
LOGFONT lf;
POSITION pos;
lf.lfCharSet = ANSI_CHARSET;
lf.lfFaceName[0]='\0';
::EnumFontFamiliesEx(this->GetParent()->GetDC()->m_hDC,
&lf,
(FONTENUMPROC) CFontCombo::EnumFontFamExProc,
(LPARAM) &fontlist, 0);
for(pos = fontlist.GetHeadPosition(); pos != NULL;)
this->AddString(fontlist.GetNext(pos));
}
The last thing to look at is the callback function
(CFontCombo::EnumFontFamExProc) itself. Here I simply take the
font name (from the first argument) and add it to my string array (passed to
me as an lparam. The last line (where I return 1) simply tells
Windows that I’m not finished and that I want to continue receiving more fonts.
int CALLBACK CFontCombo::EnumFontFamExProc(ENUMLOGFONTEX *lpelfe,
NEWTEXTMETRICEX *lpntme,
int FontType,
LPARAM lParam)
{
CStringList* m_temp = (CStringList*) lParam;
m_temp->AddTail((char*)lpelfe->elfFullName);
return 1; // I want to get all fonts
}
