shorten filenames a bit

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@4497 a592a061-630c-0410-9148-cb99ea01b6c8

diff --git a/src/mathed/formula.C b/src/mathed/formula.C
index 88dea2d1ec0c17ce046cb9595986d01cd74511f3..01c3f227e37083b7c610711a5e2a9a4c6bd81cf5 100644 (file)
--- a/src/mathed/formula.C
+++ b/src/mathed/formula.C
@@ -460,6 +460,26 @@ void InsetFormula::init()
 }
 
 
+// built some unique filename
+string constructFileName(string const & data)
+{
+       typedef std::map<string, int> cache_type;
+       static cache_type theCache;
+       static int theCounter = 0;
+
+       int number;
+       cache_type::const_iterator it = theCache.find(data);
+       if (it == theCache.end()) 
+               number = theCache[data] = theCounter++;
+       else
+               number = it->second;
+       
+       ostringstream os;
+       os << number;
+       return os.str();
+}
+
+
 void InsetFormula::updatePreview() const
 {
        // nothing to be done if no preview requested
@@ -472,21 +492,16 @@ void InsetFormula::updatePreview() const
        WriteStream wi(ls, false, false);
        par_->write(wi);
        string const data = ls.str();
-
-       // built some unique filename
-       ostringstream os;
-       os << "preview_";
-       for (string::const_iterator it = data.begin(); it != data.end(); ++it) 
-               os << char('A' + (*it & 15)) << char('a' + (*it >> 4));
-       string base = os.str();
-       string dir  = OnlyPath(lyx::tempName());
-       string file = dir + base + ".lyxpreview";
+       string const base = constructFileName(data);
+       string const dir  = OnlyPath(lyx::tempName());
+       string const file = dir + base + ".lyxpreview";
 
        // everything is fine already
        if (loader_.filename() == file)
                return;
 
        // the real work starts
+       //lyxerr << "### updatePreview() called for " << file << "\n";
        std::ofstream of(file.c_str());
        of << "\\batchmode"
           << "\\documentclass{article}"
@@ -500,4 +515,6 @@ void InsetFormula::updatePreview() const
 
        // now we are done, start actual loading we will get called back via
        // InsetFormula::statusChanged() if this is finished
-       loader_.reset(file); }
+       loader_.reset(file);
+}
+