Tab N sets a tab's width in cells, 1 through 16, in every pane, drawn and counted (wrapping, clicks, the cursor); bare Tab says it; the ctl read and a Dump keep it

A session setting, not acme's per window: the width is read by File's pure
width functions (~130 callers that are given no pane), so it is one value,
config.tab_now, that Runtime.apply sets and a new session resets. A file:L:C
column counts runes, as compilers do, and never depended on it.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 8 insertions, 2 deletions

diff --git a/src/exec.zig b/src/exec.zig
index 4bdb2584..1ee57520 100644
--- a/src/exec.zig
+++ b/src/exec.zig
@@ -953,7 +953,6 @@ pub const acme_words = [_]struct { acme: []const u8, pardes: ?[]const u8, hint:
     .{ .acme = "Load", .pardes = "Restore" },
     .{ .acme = "ID", .pardes = null },
     .{ .acme = "Send", .pardes = null },
-    .{ .acme = "Tab", .pardes = null },
     .{ .acme = "Indent", .pardes = null, .hint = ": Enter, o and O keep the indent always" },
     .{ .acme = "Local", .pardes = null },
     .{ .acme = "Abort", .pardes = null, .hint = ": a debugging word that crashes acme" },
@@ -1120,6 +1119,13 @@ pub fn applySettingBuiltin(p: *Pardes, setting: config.Runtime.Setting, arg: ?[]
             }
             if (!p.settings.apply(setting, want)) p.reportFailure(p.active, "Shell: takes " ++ comptime config.Runtime.takes(.shell).?);
         },
+        // Bare, it says the width, as acme's Tab does.
+        .tab => if (arg == null) {
+            var said: [32]u8 = undefined;
+            return p.setMessage(p.active, std.fmt.bufPrint(&said, "Tab {d}", .{p.settings.tab}) catch "Tab");
+        } else if (!p.settings.apply(setting, arg)) {
+            p.reportFailure(p.active, "Tab: takes " ++ comptime config.Runtime.takes(.tab).?);
+        },
         // Said with what it takes: its words, its range.
         else => if (!p.settings.apply(setting, arg)) {
             var text: [160]u8 = undefined;
@@ -1133,7 +1139,7 @@ pub fn applySettingBuiltin(p: *Pardes, setting: config.Runtime.Setting, arg: ?[]
             if (pane.file) |*file| file.syntax_dirty = true;
         }
     }
-    if (p.settings.tree_context_tag_style != previous_context_style) {
+    if (p.settings.tree_context_tag_style != previous_context_style or setting.action == .tab) {
         for (p.panes, 0..) |slot, id| {
             p.surface.body_layers[id].rows = 0;
             const pane = slot orelse continue;