1 files changed, 50 insertions, 6 deletions

diff --git a/src/pardes.zig b/src/pardes.zig
index ec406094..4bc5829b 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -4555,6 +4555,10 @@ pub const Pardes = struct {
     /// where the shell wrote the last dump (shell reports back after
     /// write_dump); shown in the topbar as `Restore <path>`
     last_dump: ?[]const u8 = null,
+    /// What a session word (Newcol, New, Exit) runs with when no pane is
+    /// there to run it: the window Delcol emptied. Never installed, made the
+    /// first time it is wanted.
+    stand_in: ?*Pane = null,
     /// a Restore builtin wants this dump loaded into the live session; the
     /// shell consumes it via takeRestore each frame (restore contents stay host-fed)
     restore_req: ?[]const u8 = null,
@@ -4780,6 +4784,7 @@ pub const Pardes = struct {
         for (p.panes) |slot| if (slot) |pane| p.noteClosed(pane);
         p.saveRecent();
         p.recent.deinit(p.recentGpa());
+        if (p.stand_in) |pane| p.teardownPane(pane);
         look.cancelLookHover(p);
         if (p.repl_ask) |ask| p.gpa.free(ask.text);
         for (0..MAX_PANES) |id| p.dropPendingWrite(id);
@@ -5024,7 +5029,8 @@ pub const Pardes = struct {
     }
 
     fn newScratch(p: *Pardes, from_id: usize, free: usize, kind: exec.NewPane) !*Pane {
-        const src = p.panes[from_id] orelse return error.MissingPane;
+        // None asking (an empty window): the session's, as pane/new's is.
+        const src_or = p.panes[from_id];
         const content = try p.gpa.dupe(u8, "");
         errdefer p.gpa.free(content);
         // A terminal that has not said where it is yet (the boot layout's)
@@ -5032,10 +5038,10 @@ pub const Pardes = struct {
         // 9P's pane/new, and a New from a column's or the workspace's tag:
         // no pane asked for it, whichever last had the keyboard (acme's new
         // window has acme's directory).
-        const own = kind != .fs and !p.exec_header;
-        const dir = if (own) paneDir(src) else "";
+        const src = if (kind != .fs and !p.exec_header) src_or else null;
+        const dir = if (src) |s| paneDir(s) else "";
         const np = try panes.Output.open(p, free, if (dir.len == 0) p.sessionDir() else dir, .{ .cmd = .New }, "", content);
-        if (own) np.cwd = .{ .inherited = src };
+        if (src) |s| np.cwd = .{ .inherited = s };
         np.body.cur_pinned = true;
         return np;
     }
@@ -5056,6 +5062,8 @@ pub const Pardes = struct {
     /// Newcol: an empty column right of the calling pane's, the keyboard
     /// on its tag, for the next pane made to fill.
     pub fn newColumn(p: *Pardes, from_id: usize) void {
+        // An empty window (Delcol took the last column): its first column.
+        if (layout.firstColumn(p)) |c| return tagline.enterHeader(p, c);
         const col = p.keyboardColumn(from_id) orelse return;
         // Said, not silently nothing: "no space" is 9ns's word for ENOSPC.
         const c = layout.insertColumn(p, col, false) orelse {
@@ -5331,6 +5339,12 @@ pub const Pardes = struct {
         }
     }
 
+    /// The pane a session word runs with in an empty window.
+    pub fn standIn(p: *Pardes) ?*Pane {
+        if (p.stand_in == null) p.stand_in = panes.Terminal.createDoc(p.gpa, p.screen_w, p.screen_h) catch null;
+        return p.stand_in;
+    }
+
     /// Drop a pane's parked bytes: its pty is gone, and the slot it occupied
     /// may be handed to a different pane next frame.
     fn dropPendingWrite(p: *Pardes, id: usize) void {
@@ -6756,7 +6770,9 @@ pub const Pardes = struct {
             p.panes[closed] = null;
         }
         layout.dropColumn(p, col);
-        if (p.panes[p.active] == null) p.active = beside orelse p.anyPane() orelse return p.quitEmpty();
+        // The last column gone, the window stays, empty but for the
+        // workspace tag, as acme's does; Newcol starts again from there.
+        if (p.panes[p.active] == null) p.active = beside orelse p.anyPane() orelse return tagline.enterHeader(p, null);
     }
 
     /// No pane is left: the session is over.
@@ -6798,7 +6814,7 @@ pub const Pardes = struct {
     }
 
     /// Any live pane: the last resort when nothing took the closed one's place.
-    fn anyPane(p: *const Pardes) ?usize {
+    pub fn anyPane(p: *const Pardes) ?usize {
         for (p.panes, 0..) |slot, k| if (slot != null) return k;
         return null;
     }
@@ -8517,3 +8533,31 @@ test "a Save the host could not do logs no save record" {
     p.perform(.{ .save_file = .{ .pane = 0 } });
     try std.testing.expect(th.logHas(p, "\nsave "));
 }
+
+test "Delcol on the last column leaves the window, drawn and typed into, and Newcol starts it again" {
+    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 80, .rows = 24 });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    while (p.ncol > 0) {
+        p.exec_column = 0;
+        _ = p.executeBuiltinLine(p.active, "Delcol");
+        p.exec_column = null;
+        p.sync();
+    }
+    try std.testing.expect(!p.quit);
+    try std.testing.expect(p.anyPane() == null);
+    // Drawn, and keys go to the workspace tag.
+    _ = try p.render(p.frame_arena.allocator());
+    p.update(.{ .key = .{ .cp = 'x', .text = "x" } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    p.sync();
+    _ = try p.render(p.frame_arena.allocator());
+    try std.testing.expect(!p.quit);
+    _ = p.executeBuiltinLine(p.active, "Newcol");
+    p.sync();
+    try std.testing.expectEqual(@as(usize, 1), p.ncol);
+    _ = p.executeBuiltinLine(p.active, "New");
+    p.sync();
+    try std.testing.expect(p.anyPane() != null);
+    _ = try p.render(p.frame_arena.allocator());
+}