[LyX/master] Output default mathindent value as "default"

[Jean-Marc Lasgouttes]

commit 83cd3f4293a3a17f09abfbe55fd4a30418a6ba9d
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Wed May 24 15:40:36 2017 +0200

    Output default mathindent value as "default"
    
    This is like parindent now. The old code would avoid outputing the
    value when it was empty (default indentation).
    
    Fixes bug #10657.
---
 src/BufferParams.cpp |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/BufferParams.cpp b/src/BufferParams.cpp
index 24aaf02..38ca643 100644
--- a/src/BufferParams.cpp
+++ b/src/BufferParams.cpp
@@ -866,7 +866,11 @@ string BufferParams::readToken(Lexer & lex, string const & 
token,
                lex >> is_math_indent;
        } else if (token == "\\math_indentation") {
                lex.next();
-               pimpl_->mathindent = Length(lex.getString());
+               string mathindent = lex.getString();
+               if (mathindent == "default")
+                       pimpl_->mathindent = Length();
+               else
+                       pimpl_->mathindent = Length(mathindent);
        } else if (token == "\\math_numbering_side") {
                string tmp;
                lex >> tmp;
@@ -1377,8 +1381,9 @@ void BufferParams::writeFile(ostream & os, Buffer const * 
buf) const
        else
                os << "\n\\defskip " << getDefSkip().asLyXCommand();
        os << "\n\\is_math_indent " << is_math_indent;
-       if (is_math_indent && !getMathIndent().empty())
-               os << "\n\\math_indentation " << getMathIndent().asString();
+       if (is_math_indent)
+               os << "\n\\math_indentation "
+                  << (getMathIndent().empty() ? "default" : 
getMathIndent().asString());
        os << "\n\\math_numbering_side ";
        switch(math_numbering_side) {
        case LEFT: