[LyX/master] Fix bug #8999 by locking math macros while they are updating.

[Richard Heck]

commit e86cdc4020bad2015e0b5bd8e7b9b683b9661035
Author: Richard Heck <rgh...@lyx.org>
Date:   Wed Mar 5 18:45:42 2014 -0500

    Fix bug #8999 by locking math macros while they are updating.

diff --git a/src/mathed/MathMacro.cpp b/src/mathed/MathMacro.cpp
index 2f0241b..e536af5 100644
--- a/src/mathed/MathMacro.cpp
+++ b/src/mathed/MathMacro.cpp
@@ -312,9 +312,27 @@ void MathMacro::updateMacro(MacroContext const & mc)
 }
 
 
+class MathMacro::UpdateLocker
+{
+public:
+       explicit UpdateLocker(MathMacro & mm) : mac(mm)
+       {
+               mac.isUpdating_ = true;
+       }
+       ~UpdateLocker() { mac.isUpdating_ = false; }
+private:
+       MathMacro & mac;
+};
+
+
 void MathMacro::updateRepresentation(Cursor * cur, MacroContext const & mc,
                UpdateType utype)
 {
+       if (isUpdating_)
+               return;
+
+       UpdateLocker(*this);
+
        // known macro?
        if (macro_ == 0)
                return;
diff --git a/src/mathed/MathMacro.h b/src/mathed/MathMacro.h
index b730856..b2d7553 100644
--- a/src/mathed/MathMacro.h
+++ b/src/mathed/MathMacro.h
@@ -183,6 +183,10 @@ private:
        std::string requires_;
        /// update macro representation
        bool needsUpdate_;
+       /// update lock to avoid loops
+       class UpdateLocker;
+       friend class UpdateLocker;
+       bool isUpdating_;
        /// maximal number of arguments the macro is greedy for
        size_t appetite_;