Blank lines open above a selection's first line and below its last

[<space> and ]<space> measured from the cursor's line, so over a selection of
several lines whose head was at the bottom, [<space> opened a line INSIDE the
selection. helix takes the range's line_range: above its start, below its end.
helix-golf's export_from_mod (yp[<space>) is where it showed.

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

4 files changed, 20 insertions, 7 deletions

diff --git a/docs/helix-keys.md b/docs/helix-keys.md
index 816010a6..f6880f33 100644
--- a/docs/helix-keys.md
+++ b/docs/helix-keys.md
@@ -301,7 +301,7 @@ keeps the matches it found so far.
 | Key | Behavior | Notes | Status |
 | --- | --- | --- | --- |
 | `]p` / `[p` | next / prev paragraph (+ count) | helix `goto_next/prev_paragraph`: selects to the boundary (anchor at the origin), blank-line-delimited blocks, count iterates | helix-verified (phase 5) |
-| `]Space` / `[Space` | add `<n>` blank lines below / above, cursor staying on its text line | file panes only (shell output immutable) | helix-verified (phase 5) |
+| `]Space` / `[Space` | add `<n>` blank lines below the selection's last line / above its first, the selection staying on its text | file panes only (shell output immutable) | helix-verified (phase 5) |
 
 ### Insert mode
 
diff --git a/src/edit.zig b/src/edit.zig
index fb8681d8..b548c7c6 100644
--- a/src/edit.zig
+++ b/src/edit.zig
@@ -1452,9 +1452,12 @@ pub fn normalAdjustNumber(p: *Pardes, t: *Text, delta: i64) void {
 /// `]Space` / `[Space`: add blank lines below/above, the cursor staying
 /// on its text line (the selection rides along)
 pub fn addNewline(p: *Pardes, t: *Text, below: bool, cnt: usize) void {
-    const eb = editText(p, t, t.cur_row, t.cur_row, -1) orelse return;
+    // above the selection's first line, below its last (helix line_range)
+    const sr = selRows(t);
+    const at = if (below) sr.hi_row else sr.lo_row;
+    const eb = editText(p, t, at, at, -1) orelse return;
     pushUndo(p, t);
-    const row: usize = @intCast(@max(0, t.cur_row - eb.row0));
+    const row: usize = @intCast(@max(0, at - eb.row0));
     const arena = p.scratch.allocator();
     const nl = arena.alloc(u8, cnt) catch return;
     @memset(nl, '\n');
@@ -1462,10 +1465,14 @@ pub fn addNewline(p: *Pardes, t: *Text, below: bool, cnt: usize) void {
     const new = modal.insertAt(p.gpa, eb.text, .{ .row = row, .col = if (below) llen else 0 }, nl) catch return;
     setEditText(p, t, new);
     if (!below) {
-        t.cur_row += @intCast(cnt); // the line moved down; stay on it
-        if (t.vsel.active and t.vsel.row >= @as(i32, @intCast(row))) t.vsel.row += @intCast(cnt);
-    } else if (t.vsel.active and t.vsel.row > @as(i32, @intCast(row))) {
-        t.vsel.row += @intCast(cnt);
+        // the whole selection moved down; stay on it
+        const n: i32 = @intCast(cnt);
+        t.cur_row += n;
+        if (t.vsel.active) t.vsel.row += n;
+        if (t.msel.active) {
+            t.msel.r0 += n;
+            t.msel.r1 += n;
+        }
     }
     t.cur_pinned = true;
     t.show();
diff --git a/test/hxcases/cases.jsonl b/test/hxcases/cases.jsonl
index 6e1b8188..ada7363b 100644
--- a/test/hxcases/cases.jsonl
+++ b/test/hxcases/cases.jsonl
@@ -252,6 +252,9 @@
 {"name": "add-nl-below", "pane": "file", "text": "aa\nbb\n", "keys": "]<space>"}
 {"name": "add-nl-above", "pane": "file", "text": "aa\nbb\n", "keys": "j[<space>"}
 {"name": "add-nl-count", "pane": "file", "text": "aa\nbb\n", "keys": "2]<space>"}
+{"name": "add-nl-above-sel", "pane": "file", "text": "aa\nbb\ncc\n", "keys": "vj[<space>"}
+{"name": "add-nl-below-sel", "pane": "file", "text": "aa\nbb\ncc\n", "keys": "jvk]<space>"}
+{"name": "add-nl-above-lines", "pane": "file", "text": "aa\nbb\ncc\n", "keys": "jxx[<space>"}
 {"name": "d-word", "pane": "file", "text": "alpha beta\n", "keys": "wd"}
 {"name": "d-bare-char", "pane": "file", "text": "abc\n", "keys": "d"}
 {"name": "d-on-nl-joins", "pane": "file", "text": "ab\ncd\n", "keys": "lld"}
diff --git a/test/hxcases/goldens.jsonl b/test/hxcases/goldens.jsonl
index 8ac110e6..51ab8939 100644
--- a/test/hxcases/goldens.jsonl
+++ b/test/hxcases/goldens.jsonl
@@ -252,6 +252,9 @@
 {"name":"add-nl-below","text":"aa\n\nbb\n","mode":"normal","cursor":{"row":0,"col":0},"anchor":{"row":0,"col":0}}
 {"name":"add-nl-above","text":"aa\n\nbb\n","mode":"normal","cursor":{"row":2,"col":0},"anchor":{"row":2,"col":0}}
 {"name":"add-nl-count","text":"aa\n\n\nbb\n","mode":"normal","cursor":{"row":0,"col":0},"anchor":{"row":0,"col":0}}
+{"name":"add-nl-above-sel","text":"\naa\nbb\ncc\n","mode":"select","cursor":{"row":2,"col":0},"anchor":{"row":1,"col":0}}
+{"name":"add-nl-below-sel","text":"aa\nbb\n\ncc\n","mode":"select","cursor":{"row":0,"col":0},"anchor":{"row":1,"col":0}}
+{"name":"add-nl-above-lines","text":"aa\n\nbb\ncc\n","mode":"normal","cursor":{"row":3,"col":2},"anchor":{"row":2,"col":0}}
 {"name":"d-word","text":"beta\n","mode":"normal","cursor":{"row":0,"col":0},"anchor":{"row":0,"col":0}}
 {"name":"d-bare-char","text":"bc\n","mode":"normal","cursor":{"row":0,"col":0},"anchor":{"row":0,"col":0}}
 {"name":"d-on-nl-joins","text":"abcd\n","mode":"normal","cursor":{"row":0,"col":2},"anchor":{"row":0,"col":2}}