[LyX/2.1.x] Make preview filename generation threadsafe

[Georg Baum]

commit 7f1fa090e3a2fcde49c8bf06440520ff57fd8331
Author: Georg Baum <b...@lyx.org>
Date:   Mon Jul 7 21:58:24 2014 +0200

    Make preview filename generation threadsafe
    
    Threadsafety is ensured by the atomic file name generation in TempFile.

diff --git a/src/graphics/PreviewLoader.cpp b/src/graphics/PreviewLoader.cpp
index b4d78e0..b5d464d 100644
--- a/src/graphics/PreviewLoader.cpp
+++ b/src/graphics/PreviewLoader.cpp
@@ -38,6 +38,7 @@
 #include "support/lstrings.h"
 
 #include "support/bind.h"
+#include "support/TempFile.h"
 
 #include <sstream>
 #include <fstream>
@@ -59,11 +60,11 @@ typedef list<string> PendingSnippets;
 typedef vector<SnippetPair> BitmapFile;
 
 
-string const unique_filename(string const & bufferpath)
+FileName const unique_tex_filename(FileName const & bufferpath)
 {
-       static int theCounter = 0;
-       string const filename = lyx::convert<string>(theCounter++) + 
"lyxpreview";
-       return addName(bufferpath, filename);
+       TempFile tempfile(bufferpath, "lyxpreviewXXXXXX.tex");
+       tempfile.setAutoRemove(false);
+       return tempfile.name();
 }
 
 
@@ -529,9 +530,10 @@ void PreviewLoader::Impl::startLoading(bool wait)
        LYXERR(Debug::GRAPHICS, "PreviewLoader::startLoading()");
 
        // As used by the LaTeX file and by the resulting image files
-       string const directory = buffer_.temppath();
+       FileName const directory(buffer_.temppath());
 
-       string const filename_base = unique_filename(directory);
+       FileName const latexfile = unique_tex_filename(directory);
+       string const filename_base = removeExtension(latexfile.absFileName());
 
        // Create an InProgress instance to place in the map of all
        // such processes if it starts correctly.
@@ -541,8 +543,6 @@ void PreviewLoader::Impl::startLoading(bool wait)
        pending_.clear();
 
        // Output the LaTeX file.
-       FileName const latexfile(filename_base + ".tex");
-
        // we use the encoding of the buffer
        Encoding const & enc = buffer_.params().encoding();
        ofdocstream of;