terminal: add protected mode flag to cursor pen

src/terminal/Screen.zig

@@ -232,6 +232,7 @@ pub const Cell = struct {
         strikethrough: bool = false,
         underline: sgr.Attribute.Underline = .none,
         underline_color: bool = false,
+        protected: bool = false,
 
         /// True if this is a wide character. This char takes up
         /// two cells. The following cell ALWAYS is a space.

src/terminal/Terminal.zig

@@ -1728,6 +1728,24 @@ pub fn kittyGraphics(
     return kitty.graphics.execute(alloc, self, cmd);
 }
 
+/// Set the character protection mode for the terminal.
+pub fn setProtectedMode(self: *Terminal, mode: ansi.ProtectedMode) void {
+    switch (mode) {
+        .off => {
+            self.screen.cursor.pen.attrs.protected = false;
+        },
+
+        // TODO: ISO/DEC have very subtle differences, so we should track that.
+        .iso => {
+            self.screen.cursor.pen.attrs.protected = true;
+        },
+
+        .dec => {
+            self.screen.cursor.pen.attrs.protected = true;
+        },
+    }
+}
+
 /// Full reset
 pub fn fullReset(self: *Terminal, alloc: Allocator) void {
     self.primaryScreen(alloc, .{ .clear_on_exit = true, .cursor_save = true });
@@ -2953,3 +2971,19 @@ test "Terminal: saveCursor with screen change" {
     try testing.expect(t.screen.charset.gr == .G3);
     try testing.expect(t.modes.get(.origin));
 }
+
+test "Terminal: setProtectedMode" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 3, 3);
+    defer t.deinit(alloc);
+
+    try testing.expect(!t.screen.cursor.pen.attrs.protected);
+    t.setProtectedMode(.off);
+    try testing.expect(!t.screen.cursor.pen.attrs.protected);
+    t.setProtectedMode(.iso);
+    try testing.expect(t.screen.cursor.pen.attrs.protected);
+    t.setProtectedMode(.dec);
+    try testing.expect(t.screen.cursor.pen.attrs.protected);
+    t.setProtectedMode(.off);
+    try testing.expect(!t.screen.cursor.pen.attrs.protected);
+}

src/terminal/ansi.zig

@@ -111,3 +111,11 @@ pub const ModifyKeyFormat = union(enum) {
     function_keys: void,
     other_keys: enum { none, numeric_except, numeric },
 };
+
+/// The protection modes that can be set for the terminal. See DECSCA and
+/// ESC V, W.
+pub const ProtectedMode = enum {
+    off,
+    iso, // ESC V, W
+    dec, // CSI Ps " q
+};

src/terminal/main.zig

@@ -28,6 +28,7 @@ pub const DeviceAttributeReq = ansi.DeviceAttributeReq;
 pub const DeviceStatusReq = ansi.DeviceStatusReq;
 pub const Mode = modes.Mode;
 pub const ModifyKeyFormat = ansi.ModifyKeyFormat;
+pub const ProtectedMode = ansi.ProtectedMode;
 pub const StatusLineType = ansi.StatusLineType;
 pub const StatusDisplay = ansi.StatusDisplay;
 pub const EraseDisplay = csi.EraseDisplay;