From 3e9a4ea234b450f2b7e55362e121ef1e0abad940 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Fri, 29 Dec 2023 12:45:57 -0800
Subject: [PATCH] terminal: cub with reverse wrap consumes pending wrap state
 as one

Related to #1184

See the updated website page and associated test.
---
 src/terminal/Terminal.zig   | 53 ++++++++++++++++++++++++++++++++++---
 website/app/vt/cub/page.mdx | 22 +++++++++++++++
 2 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index f21970424..32f6ced86 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -1564,18 +1564,23 @@ pub fn cursorLeft(self: *Terminal, count_req: usize) void {
         break :wrap_mode .none;
     };
 
-    // Unset the pending wrap state no matter what
-    self.screen.cursor.pending_wrap = false;
-
     var count: usize = @max(count_req, 1);
 
     // If we are in no wrap mode, then we move the cursor left and exit
     // since this is the fastest and most typical path.
     if (wrap_mode == .none) {
         self.screen.cursor.x -|= count;
+        self.screen.cursor.pending_wrap = false;
         return;
     }
 
+    // If we have a pending wrap state and we are in either reverse wrap
+    // modes then we decrement the amount we move by one to match xterm.
+    if (self.screen.cursor.pending_wrap) {
+        count -= 1;
+        self.screen.cursor.pending_wrap = false;
+    }
+
     // The margins we can move to.
     const top = self.scrolling_region.top;
     const bottom = self.scrolling_region.bottom;
@@ -6265,6 +6270,48 @@ test "Terminal: cursorLeft unsets pending wrap state with longer jump" {
     }
 }
 
+test "Terminal: cursorLeft reverse wrap with pending wrap state" {
+    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);
+
+    for ("ABCDE") |c| try t.print(c);
+    try testing.expect(t.screen.cursor.pending_wrap);
+    t.cursorLeft(1);
+    try testing.expect(!t.screen.cursor.pending_wrap);
+    try t.print('X');
+
+    {
+        const str = try t.plainString(testing.allocator);
+        defer testing.allocator.free(str);
+        try testing.expectEqualStrings("ABCDX", str);
+    }
+}
+
+test "Terminal: cursorLeft reverse wrap extended with pending wrap state" {
+    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_extended, true);
+
+    for ("ABCDE") |c| try t.print(c);
+    try testing.expect(t.screen.cursor.pending_wrap);
+    t.cursorLeft(1);
+    try testing.expect(!t.screen.cursor.pending_wrap);
+    try t.print('X');
+
+    {
+        const str = try t.plainString(testing.allocator);
+        defer testing.allocator.free(str);
+        try testing.expectEqualStrings("ABCDX", str);
+    }
+}
+
 test "Terminal: cursorLeft reverse wrap" {
     const alloc = testing.allocator;
     var t = try init(alloc, 5, 5);
diff --git a/website/app/vt/cub/page.mdx b/website/app/vt/cub/page.mdx
index f8c6ff068..4a29d992b 100644
--- a/website/app/vt/cub/page.mdx
+++ b/website/app/vt/cub/page.mdx
@@ -51,6 +51,11 @@ is a remaining value of `n`. If the cursor
 is already on the [top margin](#TODO), do not move the cursor up.
 This wrapping mode does not wrap the cursor row back to the bottom margin.
 
+For **extended reverse wrap** or **reverse wrap** modes, if the pending
+wrap state is set, decrease `n` by 1. In these modes, the initial cursor
+backward count is consumed by the pending wrap state, as if you pressed
+"backspace" on an empty newline and the cursor moved back to the previous line.
+
 ## Validation
 
 ### CUB V-1: Pending Wrap is Unset
@@ -159,3 +164,20 @@ printf "X"
 |__________|
 |Xc________|
 ```
+
+### CUB V-7: Reverse Wrap with Pending Wrap State
+
+```bash
+
+cols=$(tput cols)
+printf "\033[?45h"
+printf "\033[${cols}G"
+printf "\033[4D"
+printf "ABCDE"
+printf "\033[D"
+printf "X"
+```
+
+```
+|_____ABCDX|
+```