Added a hopeful quit blocking dialog.

src/Settings.zig

@@ -128,6 +128,15 @@ arena: std.heap.ArenaAllocator,
 
 theme: Theme = .system,
 
+/// Whether closing the window asks first.
+///
+/// On by default, which is the opposite of what a terminal usually does — and
+/// deliberately so. A window here is not one shell but a whole arrangement of
+/// them, and under a tiling compositor the binding that closes it sits a
+/// modifier away from the ones that move focus. There is nothing else between
+/// a mistyped chord and every shell in every tab exiting.
+confirm_quit: bool = true,
+
 /// Changes to the palette. Empty means every colour is at its default, which is
 /// the state anyone who never opens the colour editor stays in — and it is the
 /// reason the defaults can be retuned in a later version and still reach them.
@@ -246,6 +255,10 @@ fn parse(self: *Settings, text: []const u8) ParseError!void {
         }
     }
 
+    if (root.get("confirm_quit")) |value| {
+        if (value == .bool) self.confirm_quit = value.bool;
+    }
+
     if (root.get("colors")) |value| self.parseColors(value);
 
     if (root.get("tint")) |value| self.parseTint(value);
@@ -595,6 +608,8 @@ fn serialize(self: *Settings) SaveError![]u8 {
     try json.write(format_version);
     try json.objectField("theme");
     try json.write(@tagName(self.theme));
+    try json.objectField("confirm_quit");
+    try json.write(self.confirm_quit);
 
     // Only the colours that have been changed, and only the schemes that have
     // any. The object itself is written even when empty, for the same reason
@@ -731,6 +746,42 @@ fn forTesting() Settings {
     return .{ .arena = .init(std.testing.allocator) };
 }
 
+test "confirming a quit is on unless the file turns it off" {
+    var settings = forTesting();
+    defer settings.arena.deinit();
+
+    // Nothing said about it: on. That is what anyone who never opens the
+    // settings page gets, and it is the half of this that has to be right.
+    try std.testing.expect(settings.confirm_quit);
+
+    try settings.parse(
+        \\{"theme": "dark", "confirm_quit": false}
+    );
+    try std.testing.expect(!settings.confirm_quit);
+
+    // And it goes back out. Saving rewrites the whole file, so a flag that
+    // didn't come out of `serialize` would be handed back by the next theme
+    // change — with a confirmation dialog someone had switched off.
+    const text = try settings.serialize();
+    defer std.testing.allocator.free(text);
+
+    try std.testing.expect(std.mem.indexOf(u8, text, "\"confirm_quit\": false") != null);
+}
+
+test "a confirm_quit we can't read leaves the confirmation up" {
+    var settings = forTesting();
+    defer settings.arena.deinit();
+
+    try settings.parse(
+        \\{"confirm_quit": "no", "theme": "dark"}
+    );
+
+    // Failing safe is the only direction worth failing in here, and the rest of
+    // the file still lands.
+    try std.testing.expect(settings.confirm_quit);
+    try std.testing.expectEqual(Theme.dark, settings.theme);
+}
+
 test "palette overrides are read per scheme" {
     var settings = forTesting();
     defer settings.arena.deinit();