From 578dd730f9a81580376c1423ae60f2009cc2d267 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Thu, 26 Oct 2023 23:01:55 -0700
Subject: [PATCH] terminal: CUB with reverse wrap on first row should not crash

---
 src/terminal/Terminal.zig | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index 9f45aebdc..05e0f0d59 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -1464,12 +1464,6 @@ pub fn cursorLeft(self: *Terminal, count_req: usize) void {
             continue;
         }
 
-        // If our previous line is not wrapped then we are done.
-        if (wrap_mode != .reverse_extended) {
-            const row = self.screen.getRow(.{ .active = self.screen.cursor.y - 1 });
-            if (!row.isWrapped()) break;
-        }
-
         // UNDEFINED TERMINAL BEHAVIOR. This situation is not handled in xterm
         // and currently results in a crash in xterm. Given no other known
         // terminal [to me] implements XTREVWRAP2, I decided to just mimick
@@ -1482,6 +1476,12 @@ pub fn cursorLeft(self: *Terminal, count_req: usize) void {
             break;
         }
 
+        // If our previous line is not wrapped then we are done.
+        if (wrap_mode != .reverse_extended) {
+            const row = self.screen.getRow(.{ .active = self.screen.cursor.y - 1 });
+            if (!row.isWrapped()) break;
+        }
+
         self.screen.cursor.y -= 1;
         self.screen.cursor.x = right_margin;
         count -= 1;
@@ -6154,6 +6154,22 @@ test "Terminal: cursorLeft extended reverse wrap above top scroll region" {
     try testing.expectEqual(@as(usize, 0), t.screen.cursor.y);
 }
 
+test "Terminal: cursorLeft reverse wrap on first row" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 5, 5);
+    defer t.deinit(alloc);
+
+    t.modes.set(.wraparound, true);
+    t.modes.set(.reverse_wrap, true);
+
+    t.setTopAndBottomMargin(3, 0);
+    t.setCursorPos(1, 2);
+    t.cursorLeft(1000);
+
+    try testing.expectEqual(@as(usize, 0), t.screen.cursor.x);
+    try testing.expectEqual(@as(usize, 0), t.screen.cursor.y);
+}
+
 test "Terminal: cursorDown basic" {
     const alloc = testing.allocator;
     var t = try init(alloc, 5, 5);