[LyX/master] Fix cursor navigation in \overbrace and \underbrace

[Enrico Forestieri]

commit c2facb8c565610d6a702c39b2f95572551f624be
Author: Enrico Forestieri <forenr at lyx.org>
Date:   Fri Feb 26 20:30:41 2021 +0100

    Fix cursor navigation in \overbrace and \underbrace
    
    Due to the way these decorations are implemented, entering
    them with the cursor (either form right or left) required
    pressing two times cursor left or right.
    
    Fixes #2264
---
 src/Cursor.cpp |   47 +++++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/src/Cursor.cpp b/src/Cursor.cpp
index fae9d85..1d492d2 100644
--- a/src/Cursor.cpp
+++ b/src/Cursor.cpp
@@ -2037,20 +2037,39 @@ bool Cursor::mathForward(bool word)
 					posForward();
 				while (pos() < lastpos() && mc == nextMath().mathClass());
 		} else if (openable(nextAtom())) {
+			InsetMathScript const * n = nextMath().asScriptInset();
+			bool to_brace_deco = n
+				&& n->nuc().back()->lyxCode() == MATH_DECORATION_CODE
+				&& n->nuc().back()->mathClass() == MC_OP;
 			// single step: try to enter the next inset
 			pushBackward(nextMath());
 			inset().idxFirst(*this);
+			// Make sure the cursor moves directly to an
+			// \overbrace or \underbrace inset (bug 2264)
+			if (to_brace_deco) {
+				pushBackward(nextMath());
+				inset().idxFirst(*this);
+			}
 		} else
 			posForward();
 		return true;
 	}
 	if (inset().idxForward(*this))
 		return true;
+	InsetMath const * m = inset().asInsetMath();
+	bool from_brace_deco = m
+		&& m->lyxCode() == MATH_DECORATION_CODE
+		&& m->mathClass() == MC_OP;
 	// try to pop forwards --- but don't pop out of math! leave that to
 	// the FINISH lfuns
 	int s = depth() - 2;
-	if (s >= 0 && operator[](s).inset().asInsetMath())
-		return popForward();
+	if (s >= 0 && operator[](s).inset().asInsetMath() && popForward()) {
+		// Make sure the cursor moves directly to an
+		// \overbrace or \underbrace inset (bug 2264)
+		bool to_script = inset().asInsetMath()
+			&& inset().asInsetMath()->asScriptInset();
+		return from_brace_deco && to_script ? mathForward(word) : true;
+	}
 	return false;
 }
 
@@ -2072,21 +2091,41 @@ bool Cursor::mathBackward(bool word)
 				while (pos() > 0 && mc == prevMath().mathClass());
 			}
 		} else if (openable(prevAtom())) {
+			InsetMathScript const * p = prevMath().asScriptInset();
+			bool to_brace_deco = p
+				&& p->nuc().back()->lyxCode() == MATH_DECORATION_CODE
+				&& p->nuc().back()->mathClass() == MC_OP;
 			// single step: try to enter the preceding inset
 			posBackward();
 			push(nextMath());
 			inset().idxLast(*this);
+			// Make sure the cursor moves directly to an
+			// \overbrace or \underbrace inset (bug 2264)
+			if (to_brace_deco) {
+				posBackward();
+				push(nextMath());
+				inset().idxLast(*this);
+			}
 		} else
 			posBackward();
 		return true;
 	}
 	if (inset().idxBackward(*this))
 		return true;
+	InsetMath const * m = inset().asInsetMath();
+	bool from_brace_deco = m
+		&& m->lyxCode() == MATH_DECORATION_CODE
+		&& m->mathClass() == MC_OP;
 	// try to pop backwards --- but don't pop out of math! leave that to
 	// the FINISH lfuns
 	int s = depth() - 2;
-	if (s >= 0 && operator[](s).inset().asInsetMath())
-		return popBackward();
+	if (s >= 0 && operator[](s).inset().asInsetMath() && popBackward()) {
+		// Make sure the cursor moves directly to an
+		// \overbrace or \underbrace inset (bug 2264)
+		bool to_script = inset().asInsetMath()
+			&& inset().asInsetMath()->asScriptInset();
+		return from_brace_deco && to_script ? mathBackward(word) : true;
+	}
 	return false;
 }