[LyX/master] Let Tab go out of inset when no cycling is possible

[Jean-Marc Lasgouttes]

commit 85f030a03173252dbb9d3ba75853ad48f43a8a8f
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Thu Oct 21 22:36:29 2021 +0200

    Let Tab go out of inset when no cycling is possible
    
    Adapted patch from Enrico by adding S-Tab handling.
    
    Fixes bug #11085
---
 src/mathed/InsetMathNest.cpp |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/mathed/InsetMathNest.cpp b/src/mathed/InsetMathNest.cpp
index 7e763b7..b62505a 100644
--- a/src/mathed/InsetMathNest.cpp
+++ b/src/mathed/InsetMathNest.cpp
@@ -780,8 +780,12 @@ void InsetMathNest::doDispatch(Cursor & cur, FuncRequest & cmd)
 		cur.clearTargetX();
 		cur.macroModeClose();
 		if (!cur.inset().idxNext(cur)) {
-			cur.idx() = firstIdx();
-			cur.pos() = 0;
+			if (cur.lastidx() == 0)
+				cur.popForward();
+			else {
+				cur.idx() = firstIdx();
+				cur.pos() = 0;
+			}
 		}
 		break;
 
@@ -791,8 +795,12 @@ void InsetMathNest::doDispatch(Cursor & cur, FuncRequest & cmd)
 		cur.clearTargetX();
 		cur.macroModeClose();
 		if (!cur.inset().idxPrev(cur)) {
-			cur.idx() = cur.lastidx();
-			cur.pos() = lyxrc.mac_like_cursor_movement ? cur.lastpos() : 0;
+			if (cur.lastidx() == 0)
+				cur.popBackward();
+			else {
+				cur.idx() = cur.lastidx();
+				cur.pos() = lyxrc.mac_like_cursor_movement ? cur.lastpos() : 0;
+			}
 		}
 		break;