A pane tag wraps onto rows and can collapse to one, as acme's does

acme's frame wraps a tag at its right edge and the window grows to show
every row (wind.c wintaglines); Tagup/Tagdown shrink it to one row and back.
Pane tags used to be one row, scrolled sideways to the caret. Now a tag's
lines wrap at its width (one cell kept for the caret past a full row) and it
starts expanded; insert-mode Up on the first row collapses it, Down on the
last row expands it, and Alt-Up/Alt-Down do so in either mode. A word the
wrap breaks across rows is still one word to a click and a selection.
Column and workspace tags keep scrolling sideways.

Tests read body rows relative to the body's first row; the 41 snapshot
goldens that moved were re-recorded by name after a programmatic check that
each differs only by body rows shifting under the taller tags, and twelve
scripts whose clicks targeted fixed rows now click the same text.

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

1 files changed, 22 insertions, 2 deletions

diff --git a/src/edit.zig b/src/edit.zig
index 1e480785..a194ef48 100644
--- a/src/edit.zig
+++ b/src/edit.zig
@@ -202,7 +202,7 @@ pub fn clipYank(p: *Pardes, pane: *Pane, main_only: bool) void {
 /// (the tag's lines first, the ones it shows)
 pub fn paneText(p: *Pardes, pane: *Pane) ![]u8 {
     const arena = p.scratch.allocator();
-    const tag = try tagline.tagText(p, arena, pane);
+    const tag = (try tagline.shownTag(p, arena, pane)).text;
     const from = modal.lineStartOffset(tag, pane.tag_top);
     const cut = modal.lineStartOffset(tag, pane.tag_top + pane.tag_rows);
     const shown = if (cut < tag.len) tag[from .. cut - 1] else tag[from..];
@@ -299,13 +299,20 @@ pub fn selectionText(p: *Pardes, pane: *Pane, sl: Pane.Sel) ![]const u8 {
         return result;
     }
     const text = try paneText(p, pane);
+    const shown = try tagline.shownTag(p, arena, pane);
     var out: std.ArrayList(u8) = .empty;
     var it = std.mem.splitAny(u8, text, "\n");
     var v: i32 = 0;
     var first = true;
     while (it.next()) |line| : (v += 1) {
         const cols = sweepCols(sl, v) orelse continue;
-        if (!first) try out.append(arena, '\n');
+        // A row the tag's wrapping began carries on its text: no newline.
+        const soft = v > 0 and v < pane.tag_rows and std.mem.indexOfScalar(
+            usize,
+            shown.soft,
+            modal.lineStartOffset(shown.text, @as(usize, @intCast(v)) + pane.tag_top) -| 1,
+        ) != null;
+        if (!first and !soft) try out.append(arena, '\n');
         first = false;
         // Past the first row a body row starts after its line numbers.
         const gutter: i32 = if (pane.file != null and v >= pane.tag_rows) panes.File.gutterWidth(pane) else 0;
@@ -750,6 +757,19 @@ fn insertEdit(p: *Pardes, t: *Text, key: Key) void {
         Key.left, Key.right, Key.up, Key.down => {
             const lines = paneCursorLines(p, t) catch return;
             const cur0 = t.toModalCursor();
+            // In a pane's tag, Up on its first line collapses it and Down
+            // on its last expands it, where they would move nothing; acme's
+            // arrows in a tag always do (plan9port text.c:776, Tagdown/Tagup).
+            if (t.what == .tag) if (t.pane()) |pane| {
+                if (key.cp == Key.up and cur0.row == 0) {
+                    pane.tag_expanded = false;
+                    return;
+                }
+                if (key.cp == Key.down and cur0.row + 1 >= lines.len) {
+                    pane.tag_expanded = true;
+                    return;
+                }
+            };
             const nc = switch (key.cp) {
                 Key.left => modal.charLeft(lines, cur0),
                 Key.right => modal.charRight(lines, cur0),