Syntax Highlighting: What every parent should know
So, with only one post in between my admitted dislike for implementing FSAs, what do I do but go out and volunteer to implement one in one of my comments.
If you are too lazy to follow the links, I don't blame you. But the jist of it is that gus complained about the lack of syntax highlighting in all the code I have been posting lately.
I can't blame him. I have been a huge Larry Osterman fan since the Channel 9 post about the completion of his twentieth year at Microsoft. But the one complaint, well, not really complaint, but suggestion for improvement I would make for his blog is syntax highlighting.
So now I have written a small, quick and dirty MFC app to turn code snippets into syntax highlighted HTML. I am sure others have done this before me, but I thought it would be more interesting to write the app, than Googling until I found one. Being a quick and dirty app, I implemented the source to HTMLized functions as members of the main window class. Let's have a look at the definition of the class, syntax highlighted with my new tool:
///
/// <summary>
/// This class models the main window of the Snippet2Html application
/// </summary>
/// <author>Jim Barnett</author>
/// <date>3/18/2005</date>
///
class CMainWindow : public CDialog
{
public:
CMainWindow(CWnd* pParent = 0);
afx_msg void OnBnClickedCopyToClipboard();
afx_msg void OnBnClickedHtmlify();
static const int NONE = 0;
static const int SLASH = 1;
static const int SLASHSLASH = 2;
static const int SLASHSTAR = 3;
static const int SLASHSTARSTAR = 4;
static const int LITERAL = 5;
static const int LITERALESCAPE = 6;
static const int CHARLITERAL = 7;
static const int CHARLITERALESCAPE = 8;
static const CString COMMENTHTML;
static const CString ENDCOMMENT;
static const CString ENDSPECIAL;
static const CString SPECIALHTML;
static const CString INITHTML;
static const CString ENDHTML;
enum { IDD = IDD_SNIPPET2HTML_DIALOG };
protected:
bool CheckForReservedWord(int nState, int& nPos, CString& sHtmlified) const;
virtual void DoDataExchange(CDataExchange* pDX);
int HandleReservedWord(int nPos, CString sToken, CString& sCode) const;
void HtmlifyCode();
bool IgnoreReserved(int nState) const;
bool IsSpecial(CString sToken) const;
virtual BOOL OnInitDialog();
afx_msg void OnPaint();
afx_msg HCURSOR OnQueryDragIcon();
HACCEL m_hAccel;
HICON m_hIcon;
CString m_sCode;
static CStringArray m_sReservedOrDirective;
BOOL m_fWebForm;
DECLARE_MESSAGE_MAP()
};Not terribly interesting by itself, so lets move on to the main function of interest and its helpers:
void CMainWindow::HtmlifyCode()
{
/*
* Comment to prove multiline comments do not always fail :)
*/
VERIFY(UpdateData(true));
CString sHtmlified = _T("");
TCHAR chCurrent;
int nState = NONE;
int nCurPos = 0;
CString sToken;
for (int i = 0; i < m_sCode.GetLength(); ++i)
{
chCurrent = m_sCode.GetAt(i);
switch (chCurrent)
{
case _T(' '):
sHtmlified += _T(" ");
if (nState == SLASH) nState = NONE;
break;
case _T('\t'):
sHtmlified += _T(" ");
if (nState == SLASH) nState = NONE;
break;
case _T('\n'):
if (nState == SLASHSLASH)
{
sHtmlified += ENDCOMMENT;
nState = NONE;
}
else if (nState == SLASH) nState = NONE;
sHtmlified += _T("<br>");
if (!m_fWebForm) sHtmlified += _T("\r\n");
break;
case _T('/'):
switch (nState)
{
case NONE:
sHtmlified += chCurrent;
nState = SLASH;
break;
case SLASH:
nState = SLASHSLASH;
sHtmlified += chCurrent;
sHtmlified.Insert(sHtmlified.GetLength()-2, COMMENTHTML);
break;
case SLASHSTARSTAR:
nState = NONE;
sHtmlified += chCurrent;
sHtmlified += ENDCOMMENT;
break;
default:
sHtmlified += chCurrent;
break;
}
break;
case _T('*'):
switch (nState)
{
case SLASH:
nState = SLASHSTAR;
sHtmlified += chCurrent;
sHtmlified.Insert(sHtmlified.GetLength()-2, COMMENTHTML);
break;
case SLASHSTAR:
nState = SLASHSTARSTAR;
sHtmlified += chCurrent;
break;
default:
sHtmlified += chCurrent;
break;
}
break;
case _T('\r'):
break; // eat it
case _T('"'):
switch (nState)
{
case LITERAL:
nState = NONE;
break;
case LITERALESCAPE:
nState = LITERAL;
break;
}
if (nState == SLASH) nState = NONE;
sHtmlified += chCurrent;
break;
case _T('\''):
switch (nState)
{
case CHARLITERAL:
nState = NONE;
break;
case NONE:
nState = CHARLITERAL;
break;
case CHARLITERALESCAPE:
nState = CHARLITERAL;
break;
}
if (nState == SLASH) nState = NONE;
sHtmlified += chCurrent;
break;
case _T('<'):
if (nState == SLASH) nState = NONE;
sHtmlified += _T("<");
break;
case _T('>'):
if (nState == SLASH) nState = NONE;
sHtmlified += _T(">");
break;
case _T('&'):
if (nState == SLASH) nState = NONE;
sHtmlified += _T("&");
break;
case _T('\\'):
switch (nState)
{
case LITERAL:
nState = LITERALESCAPE;
break;
case CHARLITERAL:
nState = CHARLITERALESCAPE;
break;
case LITERALESCAPE:
nState = LITERAL;
break;
case CHARLITERALESCAPE:
nState = CHARLITERAL;
break;
}
if (nState == SLASH) nState = NONE;
sHtmlified += chCurrent;
break;
default:
if (!CheckForReservedWord(nState, i, sHtmlified))
sHtmlified += chCurrent;
if (nState == SLASH) nState = NONE;
else if (nState == CHARLITERALESCAPE) nState = CHARLITERAL;
break;
}
}
sHtmlified = INITHTML + sHtmlified;
sHtmlified += ENDHTML;
m_sCode = sHtmlified;
UpdateData(false);
}
bool CMainWindow::IgnoreReserved(int nState) const
{
if ((nState == SLASHSLASH) || (nState == SLASHSTAR)
|| (nState == SLASHSTARSTAR) || (nState == LITERAL)
|| (nState == LITERALESCAPE))
return true;
else
return false;
}
bool CMainWindow::IsSpecial(CString sToken) const
{
for (INT_PTR i = 0; i < m_sReservedOrDirective.GetCount(); ++i)
{
if (sToken == m_sReservedOrDirective[i]) return true;
}
return false;
}
void CMainWindow::HtmlifyCode()
{
/*
* Comment to prove multiline comments do not always fail :)
*/
VERIFY(UpdateData(true));
CString sHtmlified = _T("");
TCHAR chCurrent;
int nState = NONE;
int nCurPos = 0;
CString sToken;
for (int i = 0; i < m_sCode.GetLength(); ++i)
{
chCurrent = m_sCode.GetAt(i);
switch (chCurrent)
{
case _T(' '):
sHtmlified += _T(" ");
if (nState == SLASH) nState = NONE;
break;
case _T('\t'):
sHtmlified += _T(" ");
if (nState == SLASH) nState = NONE;
break;
case _T('\n'):
if (nState == SLASHSLASH)
{
sHtmlified += ENDCOMMENT;
nState = NONE;
}
else if (nState == SLASH) nState = NONE;
sHtmlified += _T("<br>");
if (!m_fWebForm) sHtmlified += _T("\r\n");
break;
case _T('/'):
switch (nState)
{
case NONE:
sHtmlified += chCurrent;
nState = SLASH;
break;
case SLASH:
nState = SLASHSLASH;
sHtmlified += chCurrent;
sHtmlified.Insert(sHtmlified.GetLength()-2, COMMENTHTML);
break;
case SLASHSTARSTAR:
nState = NONE;
sHtmlified += chCurrent;
sHtmlified += ENDCOMMENT;
break;
default:
sHtmlified += chCurrent;
break;
}
break;
case _T('*'):
switch (nState)
{
case SLASH:
nState = SLASHSTAR;
sHtmlified += chCurrent;
sHtmlified.Insert(sHtmlified.GetLength()-2, COMMENTHTML);
break;
case SLASHSTAR:
nState = SLASHSTARSTAR;
sHtmlified += chCurrent;
break;
default:
sHtmlified += chCurrent;
break;
}
break;
case _T('\r'):
break; // eat it
case _T('"'):
switch (nState)
{
case LITERAL:
nState = NONE;
break;
case LITERALESCAPE:
nState = LITERAL;
break;
}
if (nState == SLASH) nState = NONE;
sHtmlified += chCurrent;
break;
case _T('\''):
switch (nState)
{
case CHARLITERAL:
nState = NONE;
break;
case NONE:
nState = CHARLITERAL;
break;
case CHARLITERALESCAPE:
nState = CHARLITERAL;
break;
}
if (nState == SLASH) nState = NONE;
sHtmlified += chCurrent;
break;
case _T('<'):
if (nState == SLASH) nState = NONE;
sHtmlified += _T("<");
break;
case _T('>'):
if (nState == SLASH) nState = NONE;
sHtmlified += _T(">");
break;
case _T('&'):
if (nState == SLASH) nState = NONE;
sHtmlified += _T("&");
break;
case _T('\\'):
switch (nState)
{
case LITERAL:
nState = LITERALESCAPE;
break;
case CHARLITERAL:
nState = CHARLITERALESCAPE;
break;
case LITERALESCAPE:
nState = LITERAL;
break;
case CHARLITERALESCAPE:
nState = CHARLITERAL;
break;
}
if (nState == SLASH) nState = NONE;
sHtmlified += chCurrent;
break;
default:
if (!CheckForReservedWord(nState, i, sHtmlified))
sHtmlified += chCurrent;
if (nState == SLASH) nState = NONE;
else if (nState == CHARLITERALESCAPE) nState = CHARLITERAL;
break;
}
}
sHtmlified = INITHTML + sHtmlified;
sHtmlified += ENDHTML;
m_sCode = sHtmlified;
UpdateData(false);
}
bool CMainWindow::IgnoreReserved(int nState) const
{
if ((nState == SLASHSLASH) || (nState == SLASHSTAR)
|| (nState == SLASHSTARSTAR) || (nState == LITERAL)
|| (nState == LITERALESCAPE))
return true;
else
return false;
}
bool CMainWindow::IsSpecial(CString sToken) const
{
for (INT_PTR i = 0; i < m_sReservedOrDirective.GetCount(); ++i)
{
if (sToken == m_sReservedOrDirective[i]) return true;
}
return false;
}
bool CMainWindow::CheckForReservedWord(int nState, int& nPos,
CString& sHtmlified) const
{
int nOrigPos = nPos;
const CString sDelimiters = _T(" \n\t+-\\*~<>!=&;:.{}[]()|^%\\/?',=");
// Get the next token
CString sToken = m_sCode.Tokenize(
_T(" \n\t+-\\*~<>!=&;:.{}[]()|^%\\/?',="), nOrigPos);
CString sNextChars = (m_sCode.Left(nPos+sToken.GetLength())).Right(
sToken.GetLength());
bool fAtTokenStart = (nPos == 0) ? true
: (sDelimiters.Find(m_sCode.GetAt(nPos-1)) != -1);
if (IsSpecial(sToken) && !IgnoreReserved(nState)
&& (sToken == sNextChars) && fAtTokenStart)
{
nPos += HandleReservedWord(nPos, sToken, sHtmlified);
return true;
}
return false;
}I guess you could say I cheated a little since I only used the automaton to do the highlighting of comments and wrote some helper functions to deal with the keywords/preprocessor directives. One of the main shortcomings of my simple approach is that context senstive preprocessor directives are not supported (such as the the
#pragma once directive, particularly the "once" token. You could criticize the memory usage of this algorithm since I used another CString to insert the HTML rather than just inserting the HTML right into m_sCode. I think that would have been messier, and it would have been an unnecessary performance hack.A lot of these web form interfaces don't let you have decently formatted HTML without screwing up your original intention. They tend to interpret <br>\n as two lines, which kept double spacing my code. The m_fWebForm boolean variable indicates wherther you want one big nasty line of HTML if true, or you want decently formatted, somewhat human readable HTML if false. It took a fair amount of work to figure out what truly caused the double-spaced code. This task proved to be much more of a learning experience than I intended, but I guess that could be a good thing.
I am already planning on some improvements. It would be really easy to add highlighting to string and char literals. If I modified it to read values from a file for some variables that are currently hard-coded, this app could be made language agnostic. I may do that just for the fun of it, but I am self-admitted C++ elitist.
So, that is it. Is this any better, gus?
posted by Jim B @ 8:41 PM
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