Fix bug #6611. This also gives us a more robust fall-back in case we are

completely unable to load a text class. At least not very long ago, if
we were unable even to load article, we would crash. Not now. We will
ALWAYS have at least a really basic class (nothing but Standard!)
available.


git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@34080 a592a061-630c-0410-9148-cb99ea01b6c8

src/BufferParams.cpp

@@ -1764,10 +1764,11 @@ bool BufferParams::setBaseClass(string const & classname)
 	LayoutFileList & bcl = LayoutFileList::get();
 	if (!bcl.haveClass(classname)) {
 		docstring s = 
-			bformat(_("The document class %1$s could not be found. "
+			bformat(_("The layout file:\n"
-				"A default textclass with default layouts will be used. "
+				"%1$s\n"
-				"LyX might not be able to produce output unless a correct "
+				"could not be found. A default textclass with default\n"
-				"textclass is selected from the document settings dialog."),
+				"layouts will be used. LyX will not be able to produce\n"
+				"correct output."),
 			from_utf8(classname));
 		frontend::Alert::error(_("Document class not found"), s);
 		bcl.addEmptyClass(classname);
@@ -1776,10 +1777,14 @@ bool BufferParams::setBaseClass(string const & classname)
 	bool const success = bcl[classname].load();
 	if (!success) {
 		docstring s = 
-			bformat(_("The document class %1$s could not be loaded."),
+			bformat(_("Due to some error in it, the layout file:\n"
+				"%1$s\n"
+				"could not be loaded. A default textclass with default\n"
+				"layouts will be used. LyX will not be able to produce\n"
+				"correct output."),
 			from_utf8(classname));
 		frontend::Alert::error(_("Could not load class"), s);
-		return false;
+		bcl.addEmptyClass(classname);
 	}
 
 	pimpl_->baseClass_ = classname;

src/LayoutFile.cpp

@@ -204,21 +204,13 @@ void LayoutFileList::reset(LayoutFileIndex const & classname) {
 }
 
 
-LayoutFileIndex LayoutFileList::addEmptyClass(string const & textclass)
+namespace {
-{
-	if (haveClass(textclass))
-		return textclass;
 
-	FileName const tempLayout = FileName::tempName();
+string layoutpost =			
-	ofstream ofs(tempLayout.toFilesystemEncoding().c_str());
+		"Columns      1\n"
-	ofs << "# This layout is automatically generated\n"
+		"Sides        1\n"
-		"# \\DeclareLaTeXClass{" << textclass << "}\n\n"
+		"SecNumDepth  2\n"
-		"Format		7\n"
+		"TocDepth     2\n"
-		"Input stdclass.inc\n\n"
-		"Columns		1\n"
-		"Sides			1\n"
-		"SecNumDepth	2\n"
-		"TocDepth		2\n"
 		"DefaultStyle	Standard\n\n"
 		"Style Standard\n"
 		"	Category              MainText\n"
@@ -231,6 +223,20 @@ LayoutFileIndex LayoutFileList::addEmptyClass(string const & textclass)
 		"	AlignPossible         Block, Left, Right, Center\n"
 		"	LabelType             No_Label\n"
 		"End\n";
+	
+}
+
+LayoutFileIndex LayoutFileList::addEmptyClass(string const & textclass)
+{
+	FileName const tempLayout = FileName::tempName();
+	ofstream ofs(tempLayout.toFilesystemEncoding().c_str());
+	// This writes a very basic class, but it also attempts to include 
+	// stdclass.inc. That would give us something moderately usable.
+	ofs << "# This layout is automatically generated\n"
+	       "# \\DeclareLaTeXClass{" << textclass << "}\n\n"
+	       "Format 26\n"
+	       "Input stdclass.inc\n\n"
+	    << layoutpost;
 	ofs.close();
 
 	// We do not know if a LaTeX class is available for this document, but setting
@@ -238,11 +244,24 @@ LayoutFileIndex LayoutFileList::addEmptyClass(string const & textclass)
 	// tex class.
 	LayoutFile * tc = new LayoutFile(textclass, textclass, 
 			"Unknown text class " + textclass, textclass + ".cls", true);
+
 	if (!tc->load(tempLayout.absFilename())) {
-		// The only way this happens is because the hardcoded layout file above
+		// The only way this happens is because the hardcoded layout file 
-		// is wrong.
+		// aboveis wrong or stdclass.inc cannot be found. So try again 
-		LASSERT(false, /**/);
+		// without stdclass.inc.
+		ofstream ofs2(tempLayout.toFilesystemEncoding().c_str());
+		ofs2 << "# This layout is automatically generated\n"
+		        "# \\DeclareLaTeXClass{" << textclass << "}\n\n"
+		        "Format 26\n"
+		        "Input stdclass.inc\n\n"
+		     << layoutpost;
+		ofs2.close();
+		if (!tc->load(tempLayout.absFilename())) {
+			// This can only happen if the hardcoded file above is wrong.
+			LASSERT(false, /* */);
+		}
 	}
+
 	classmap_[textclass] = tc;
 	return textclass;
 }

src/LayoutFile.h

@@ -115,7 +115,9 @@ public:
 	/// Clears the textclass so as to force it to be reloaded
 	void reset(LayoutFileIndex const & tc);
 
-	/// add a default textclass with all standard layouts.
+	/// Add a default textclass with all standard layouts.
+	/// Note that this will over-write any information we may have
+	/// gotten from textclass.lst about this class.
 	LayoutFileIndex addEmptyClass(std::string const & textclass);
 
 	/// add a textclass from user local directory.