[LyX/master] Fix bug #10295.

[Richard Heck]

commit f9835d054d7aac5830ec6bb5a3537c2b4fa2d269
Author: Richard Heck <rgh...@lyx.org>
Date:   Sun Apr 2 20:59:23 2017 -0400

    Fix bug #10295.
    
    As it was, the comparison buffer was sharing a DocumentClass with
    the buffer from which the document settings are taken.
---
 src/Compare.cpp |   22 +++++++++++++++++++---
 1 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/Compare.cpp b/src/Compare.cpp
index b2f6439..6c14616 100644
--- a/src/Compare.cpp
+++ b/src/Compare.cpp
@@ -15,6 +15,8 @@
 #include "Author.h"
 #include "BufferParams.h"
 #include "Changes.h"
+#include "CutAndPaste.h"
+#include "ErrorList.h"
 #include "Font.h"
 
 #include "insets/InsetText.h"
@@ -382,7 +384,6 @@ void Compare::run()
        // Copy the buffer params to the destination buffer
        dest_buffer->params() = options_.settings_from_new
                ? new_buffer->params() : old_buffer->params();
-
        // Copy extra authors to the destination buffer
        AuthorList const & extra_authors = options_.settings_from_new ?
                old_buffer->params().authors() : new_buffer->params().authors();
@@ -390,12 +391,27 @@ void Compare::run()
        for (; it != extra_authors.end(); ++it)
                dest_buffer->params().authors().record(*it);
 
-       doStatusMessage();
+       // We will need this later
+       DocumentClassConstPtr const olddc = 
+               dest_buffer->params().documentClassPtr();
+       // We do not want to share the DocumentClass with the other Buffer.
+       // See bug #10295.
+       dest_buffer->params().makeDocumentClass();
 
-       // do the real work
+       doStatusMessage();
+       // Do the real work
        if (!doCompare())
                return;
 
+       // The comparison routine simply copies the paragraphs over into the
+       // new buffer with the document class from wherever they came from.
+       // So we need to reset the document class of all the paragraphs.
+       // See bug #10295.
+       ErrorList el;
+       cap::switchBetweenClasses(
+                       olddc, dest_buffer->params().documentClassPtr(),
+                       static_cast<InsetText &>(dest_buffer->inset()), el);
+
        finished(pimpl_->abort_);
        return;
 }