From 6e5489c88eecb1a70feb9b57e779a0ac0b0e07d1 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Tue, 13 Sep 2016 23:16:23 -0400
Subject: [PATCH] do not allow cursor movements for non-valid cursors

---
 src/core/PieceTable.cc | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/core/PieceTable.cc b/src/core/PieceTable.cc
index 9f44107..3ecb5c8 100644
--- a/src/core/PieceTable.cc
+++ b/src/core/PieceTable.cc
@@ -124,6 +124,8 @@ PieceTable::Cursor::Cursor(PieceTable * pt) : iterator(pt)
 
 bool PieceTable::Cursor::go_start_of_line()
 {
+    if (!iterator.valid())
+        return false;
     bool rv = false;
     while (iterator.valid() &&
             (!iterator.piece->prev->eol()) &&
@@ -141,6 +143,8 @@ bool PieceTable::Cursor::go_start_of_line()
 
 bool PieceTable::Cursor::go_end_of_line()
 {
+    if (!iterator.valid())
+        return false;
     bool rv = false;
     while (iterator.valid() &&
             (!iterator.piece->eol()) &&
@@ -159,6 +163,8 @@ bool PieceTable::Cursor::go_end_of_line()
 
 bool PieceTable::Cursor::go_up(int n, uint32_t desired_column)
 {
+    if (!iterator.valid())
+        return false;
     Piece * p = prev_line();
     if (p == nullptr)
     {
@@ -174,6 +180,8 @@ bool PieceTable::Cursor::go_up(int n, uint32_t desired_column)
 
 bool PieceTable::Cursor::go_down(int n, uint32_t desired_column)
 {
+    if (!iterator.valid())
+        return false;
     Piece * p = next_line();
     if (p == nullptr)
     {
@@ -189,6 +197,8 @@ bool PieceTable::Cursor::go_down(int n, uint32_t desired_column)
 
 bool PieceTable::Cursor::go_left(int n)
 {
+    if (!iterator.valid())
+        return false;
     if (is_start_of_line())
     {
         return false;
@@ -209,6 +219,8 @@ bool PieceTable::Cursor::go_left(int n)
 
 bool PieceTable::Cursor::go_right(int n)
 {
+    if (!iterator.valid())
+        return false;
     if (is_end_of_line())
     {
         return false;