terminal: save cursor and restore cursor xterm audit

src/terminal/Screen.zig

@@ -57,6 +57,7 @@ const Allocator = std.mem.Allocator;
 const utf8proc = @import("utf8proc");
 const trace = @import("tracy").trace;
 const ansi = @import("ansi.zig");
+const modes = @import("modes.zig");
 const sgr = @import("sgr.zig");
 const color = @import("color.zig");
 const kitty = @import("kitty.zig");
@@ -107,6 +108,17 @@ pub const Cursor = struct {
     /// is determined by mode 12 (modes.zig). This mode is synchronized
     /// with CSI q, the same as xterm.
     pub const Style = enum { bar, block, underline };
+
+    /// Saved cursor state. This contains more than just Cursor members
+    /// because additional state is stored.
+    pub const Saved = struct {
+        x: usize,
+        y: usize,
+        pen: Cell,
+        pending_wrap: bool,
+        origin: bool,
+        charset: CharsetState,
+    };
 };
 
 /// This is a single item within the storage buffer. We use a union to
@@ -931,7 +943,7 @@ history: usize,
 cursor: Cursor = .{},
 
 /// Saved cursor saved with DECSC (ESC 7).
-saved_cursor: Cursor = .{},
+saved_cursor: ?Cursor.Saved = null,
 
 /// The selection for this screen (if any).
 selection: ?Selection = null,
@@ -945,15 +957,6 @@ kitty_images: kitty.graphics.ImageStorage = .{},
 /// The charset state
 charset: CharsetState = .{},
 
-/// The saved charset state. This state is saved / restored along with the
-/// cursor state
-saved_charset: CharsetState = .{},
-
-/// The saved state of origin mode. This mode gets special handling in Screen
-/// because it's state is saved/restored with the cursor and must have a state
-/// independent to each screen (primary and alternate)
-saved_origin_mode: bool = false,
-
 /// The current or most recent protected mode. Once a protection mode is
 /// set, this will never become "off" again until the screen is reset.
 /// The current state of whether protection attributes should be set is

src/terminal/Terminal.zig

@@ -416,9 +416,14 @@ fn plainString(self: *Terminal, alloc: Allocator) ![]const u8 {
 /// is kept per screen (main / alternative). If for the current screen state
 /// was already saved it is overwritten.
 pub fn saveCursor(self: *Terminal) void {
-    self.screen.saved_cursor = self.screen.cursor;
+    self.screen.saved_cursor = .{
-    self.screen.saved_charset = self.screen.charset;
+        .x = self.screen.cursor.x,
-    self.screen.saved_origin_mode = self.modes.get(.origin);
+        .y = self.screen.cursor.y,
+        .pen = self.screen.cursor.pen,
+        .pending_wrap = self.screen.cursor.pending_wrap,
+        .origin = self.modes.get(.origin),
+        .charset = self.screen.charset,
+    };
 }
 
 /// Restore cursor position and other state.
@@ -426,9 +431,21 @@ pub fn saveCursor(self: *Terminal) void {
 /// The primary and alternate screen have distinct save state.
 /// If no save was done before values are reset to their initial values.
 pub fn restoreCursor(self: *Terminal) void {
-    self.screen.cursor = self.screen.saved_cursor;
+    const saved: Screen.Cursor.Saved = self.screen.saved_cursor orelse .{
-    self.screen.charset = self.screen.saved_charset;
+        .x = 0,
-    self.modes.set(.origin, self.screen.saved_origin_mode);
+        .y = 0,
+        .pen = .{},
+        .pending_wrap = false,
+        .origin = false,
+        .charset = .{},
+    };
+
+    self.screen.cursor.pen = saved.pen;
+    self.screen.charset = saved.charset;
+    self.modes.set(.origin, saved.origin);
+    self.screen.cursor.x = saved.x;
+    self.screen.cursor.y = saved.y;
+    self.screen.cursor.pending_wrap = saved.pending_wrap;
 }
 
 /// TODO: test
@@ -1993,7 +2010,7 @@ pub fn fullReset(self: *Terminal, alloc: Allocator) void {
     self.flags = .{};
     self.tabstops.reset(TABSTOP_INTERVAL);
     self.screen.cursor = .{};
-    self.screen.saved_cursor = .{};
+    self.screen.saved_cursor = null;
     self.screen.selection = null;
     self.screen.kitty_keyboard = .{};
     self.screen.protected_mode = .off;
@@ -4760,6 +4777,66 @@ test "Terminal: saveCursor with screen change" {
     try testing.expect(t.modes.get(.origin));
 }
 
+test "Terminal: saveCursor position" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 10, 5);
+    defer t.deinit(alloc);
+
+    t.setCursorPos(1, 5);
+    try t.print('A');
+    t.saveCursor();
+    t.setCursorPos(1, 1);
+    try t.print('B');
+    t.restoreCursor();
+    try t.print('X');
+
+    {
+        var str = try t.plainString(testing.allocator);
+        defer testing.allocator.free(str);
+        try testing.expectEqualStrings("B   AX", str);
+    }
+}
+
+test "Terminal: saveCursor pending wrap state" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 5, 5);
+    defer t.deinit(alloc);
+
+    t.setCursorPos(1, 5);
+    try t.print('A');
+    t.saveCursor();
+    t.setCursorPos(1, 1);
+    try t.print('B');
+    t.restoreCursor();
+    try t.print('X');
+
+    {
+        var str = try t.plainString(testing.allocator);
+        defer testing.allocator.free(str);
+        try testing.expectEqualStrings("B   A\nX", str);
+    }
+}
+
+test "Terminal: saveCursor origin mode" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 10, 5);
+    defer t.deinit(alloc);
+
+    t.modes.set(.origin, true);
+    t.saveCursor();
+    t.modes.set(.enable_left_and_right_margin, true);
+    t.setLeftAndRightMargin(3, 5);
+    t.setTopAndBottomMargin(2, 4);
+    t.restoreCursor();
+    try t.print('X');
+
+    {
+        var str = try t.plainString(testing.allocator);
+        defer testing.allocator.free(str);
+        try testing.expectEqualStrings("X", str);
+    }
+}
+
 test "Terminal: setProtectedMode" {
     const alloc = testing.allocator;
     var t = try init(alloc, 3, 3);

src/terminal/modes.zig

@@ -162,7 +162,13 @@ const ModeEntry = struct {
     name: []const u8,
     value: comptime_int,
     default: bool = false,
+
+    /// True if this is an ANSI mode, false if its a DEC mode (?-prefixed).
     ansi: bool = false,
+
+    /// If true, this mode is disabled and Ghostty will not allow it to be
+    /// set or queried. The mode enum still has it, allowing Ghostty developers
+    /// to develop a mode without exposing it to real users.
     disabled: bool = false,
 };
 

website/app/vt/decrc/page.mdx

@@ -0,0 +1,14 @@
+import VTSequence from "@/components/VTSequence";
+
+# Restore Cursor (DECRC)
+
+<VTSequence sequence={["ESC", "8"]} />
+
+Restore the cursor-related state saved via [Save Cursor (DECSC)](/vt/decsc).
+
+If a cursor was never previously saved, this sets all the typically saved
+values to their default values.
+
+## Validation
+
+Validation is shared with [Save Cursor (DECSC)](/vt/decsc).

website/app/vt/decsc/page.mdx

@@ -0,0 +1,83 @@
+import VTSequence from "@/components/VTSequence";
+
+# Save Cursor (DECSC)
+
+<VTSequence sequence={["ESC", "7"]} />
+
+Save various cursor-related state that can be restored with
+[Restore Cursor (DECRC)](/vt/decrc).
+
+The following attributes are saved:
+
+- Cursor row and column in absolute screen coordinates
+- Character sets
+- Pending wrap state
+- SGR attributes
+- [Origin mode (DEC Mode 6)](/vt/modes/origin)
+
+Only one cursor can be saved at any time. If save cursor is repeated, the
+previously save cursor is overwritten.
+
+Primary and alternate screens have separate saved cursor state. A cursor
+saved on the primary screen is inaccessible from the alternate screen
+and vice versa.
+
+## Validation
+
+### SC V-1: Cursor Position
+
+```bash
+printf "\033[1;1H" # move to top-left
+printf "\033[0J" # clear screen
+printf "\033[1;5H"
+printf "A"
+printf "\0337" # Save Cursor
+printf "\033[1;1H"
+printf "B"
+printf "\0338" # Restore Cursor
+printf "X"
+```
+
+```
+|B___AX____|
+```
+
+### SC V-2: Pending Wrap State
+
+```bash
+cols=$(tput cols)
+printf "\033[1;1H" # move to top-left
+printf "\033[0J" # clear screen
+printf "\033[${cols}G"
+printf "A"
+printf "\0337" # Save Cursor
+printf "\033[1;1H"
+printf "B"
+printf "\0338" # Restore Cursor
+printf "X"
+```
+
+```
+|B________A|
+|X_________|
+```
+
+### SC V-3: SGR Attributes
+
+```bash
+printf "\033[1;1H" # move to top-left
+printf "\033[0J" # clear screen
+printf "\033[1;4;33;44m"
+printf "A"
+printf "\0337" # Save Cursor
+printf "\033[0m"
+printf "B"
+printf "\0338" # Restore Cursor
+printf "X"
+```
+
+```
+|AX________|
+```
+
+The "A" and "X" should have identical styling.