Give a pane's body its own Text holding the cursor, selections, mode and undo

acme keeps what edits a text in its Text (dat.h:171-190) and the window
holds a body and a tag of that type. The cursor, the selections, the modal
state and the edit-buffer undo move off Pane into Text.zig, Pane holds
them as its body, and the edit and normal-mode operations take the Text
they edit. Nothing changes in behaviour; this is the step that lets the
tag become a second Text.

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

1 files changed, 606 insertions, 0 deletions

diff --git a/src/Text.zig b/src/Text.zig
new file mode 100644
index 00000000..ad5aa186
--- /dev/null
+++ b/src/Text.zig
@@ -0,0 +1,606 @@
+//! One editable text, acme's Text (editors/acme/dat.h:171-190, text.c): the
+//! cursor, the selections and the modal state that edit it, and the undo of
+//! an edit buffer. A pane's body is one. Where its characters come from -- a
+//! file's content, a terminal's edit overlay, a PDF's text -- is the window's
+//! business (edit.zig's editText and flatSurface), the way acme's Text reads
+//! its File; everything here works on the flat text it is handed.
+const std = @import("std");
+const panes = @import("panes.zig");
+const modal = @import("modal.zig");
+const config = @import("config.zig");
+const Pane = panes.Pane;
+const File = panes.File;
+const Terminal = panes.Terminal;
+const Text = @This();
+
+pub const Mode = enum { normal, insert, tty };
+
+/// A modal line selection (helix `x`): whole rows [r0, r1], absolute.
+pub const LineSel = struct {
+    active: bool = false,
+    r0: i32 = 0,
+    r1: i32 = 0,
+};
+
+pub const CharSel = struct {
+    active: bool = false,
+    row: i32 = 0,
+    col: i32 = 0,
+    explicit: bool = false,
+};
+
+pub const max_selections = 64;
+
+pub const SelRange = struct {
+    row: i32,
+    col: i32,
+    arow: i32,
+    acol: i32,
+    /// this range's own j/k goal column (helix Range::old_visual_position);
+    /// the PRIMARY's copy is Text.sticky_col
+    sticky: i32 = -1,
+};
+
+mode: Mode = .normal,
+cur_pinned: bool = false,
+cur_row: i32 = 0,
+cur_col: i32 = 0,
+msel: LineSel = .{},
+vsel: CharSel = .{},
+sels: [max_selections - 1]SelRange = undefined,
+nsel: u8 = 0,
+select: bool = false,
+/// sticky goal column for j/k runs (helix old_visual_position): any
+/// non-vertical range write resets it to -1.
+sticky_col: i32 = -1,
+append_at: ?struct { row: i32, col: i32 } = null,
+normal: modal.Normal.State = .{},
+/// last f/F/t/T motion, for Alt-. repeat
+find_op: u8 = 0,
+find_ch: u21 = 0,
+ed_undo: [Terminal.history_max]Terminal.Snapshot = undefined,
+ed_undo_len: usize = 0,
+ed_redo: [Terminal.history_max]Terminal.Snapshot = undefined,
+ed_redo_len: usize = 0,
+
+/// The window this text belongs to (acme's t->w).
+pub fn pane(t: *Text) *Pane {
+    return @alignCast(@fieldParentPtr("body", t));
+}
+
+pub fn toModalCursor(t: *Text) modal.Cursor {
+    return .{ .row = @intCast(@max(0, t.cur_row)), .col = @intCast(@max(0, t.cur_col)) };
+}
+
+pub fn fromModalCursor(t: *Text, c: modal.Cursor) void {
+    t.cur_row = @as(i32, @intCast(c.row));
+    t.cur_col = @intCast(c.col);
+    t.cur_pinned = true;
+}
+
+pub fn insertVerticalCursor(lines: []const []const u8, c: modal.Cursor, down: bool) modal.Cursor {
+    if (lines.len == 0) return c;
+    const row = if (down) @min(c.row + 1, lines.len - 1) else c.row -| 1;
+    const target = lines[row];
+    if (target.len == 0) return .{ .row = row, .col = 0 };
+    const source = if (c.row < lines.len) lines[c.row] else "";
+    const goal = File.rawDisplayCol(source, c.col);
+    const mapped = File.rawAtDisplay(target, goal);
+    const last = modal.prevGrapheme(target, target.len);
+    return .{ .row = row, .col = modal.graphemeStart(target, @min(mapped, last)) };
+}
+
+pub fn primaryRange(t: *Text, text: []const u8, row0: i32) modal.Selection {
+    const c = File.textOffset(t, text, .{ .row = @intCast(@max(0, t.cur_row - row0)), .col = @intCast(@max(0, t.cur_col)) });
+    if (t.msel.active) {
+        // legacy line selection (file-search results highlight): linewise
+        const r0: usize = @intCast(@max(0, @min(t.msel.r0, t.msel.r1) - row0));
+        const r1: usize = @intCast(@max(0, @max(t.msel.r0, t.msel.r1) - row0));
+        const s = modal.lineStartOffset(text, r0);
+        const e = if (r1 + 1 >= modal.cursorLineCount(text)) text.len else modal.lineStartOffset(text, r1 + 1);
+        return .{ .anchor = s, .head = @max(e, modal.nextGrapheme(text, c)) };
+    }
+    if (t.vsel.active) return cellRange(text, t.vsel.row - row0, t.vsel.col, t.cur_row - row0, t.cur_col);
+    return .{ .anchor = c, .head = modal.nextGrapheme(text, c) };
+}
+
+pub fn cellRange(text: []const u8, arow: i32, acol: i32, hrow: i32, hcol: i32) modal.Selection {
+    const a = modal.offsetAt(text, .{ .row = @intCast(@max(0, arow)), .col = @intCast(@max(0, acol)) });
+    const c = modal.offsetAt(text, .{ .row = @intCast(@max(0, hrow)), .col = @intCast(@max(0, hcol)) });
+    return cellOffRange(text, a, c);
+}
+
+/// the same, from the two cells' gap offsets
+pub fn cellOffRange(text: []const u8, a: usize, c: usize) modal.Selection {
+    if (a <= c) return .{ .anchor = a, .head = modal.nextGrapheme(text, c) };
+    return .{ .anchor = modal.nextGrapheme(text, a), .head = c };
+}
+
+pub fn rangeCells(text: []const u8, r: modal.Selection) struct { cur: usize, anc: usize } {
+    if (r.head > r.anchor) return .{ .cur = modal.prevGrapheme(text, r.head), .anc = r.anchor };
+    if (r.head < r.anchor) return .{ .cur = r.head, .anc = modal.prevGrapheme(text, r.anchor) };
+    return .{ .cur = r.head, .anc = r.head };
+}
+
+pub fn setRange(t: *Text, text: []const u8, row0: i32, r0: modal.Selection, explicit: bool) void {
+    var r = r0;
+    if (r.anchor == r.head) r.head = modal.nextGrapheme(text, r.head); // min_width_1
+    const off = rangeCells(text, r);
+    const cc = File.textPosition(t, text, off.cur);
+    // a bare block cursor has both cells on the same offset — the common
+    // case by far — and this conversion is not free even indexed
+    const ac = if (off.anc == off.cur) cc else File.textPosition(t, text, off.anc);
+    t.cur_row = @as(i32, @intCast(cc.row)) + row0;
+    t.cur_col = @intCast(cc.col);
+    t.vsel = .{
+        .active = off.anc != off.cur or t.select,
+        .row = @as(i32, @intCast(ac.row)) + row0,
+        .col = @intCast(ac.col),
+        .explicit = explicit or t.select,
+    };
+    t.msel.active = false;
+    t.nsel = 0; // writing ONE range means the selection IS that range
+    t.cur_pinned = true;
+    t.sticky_col = -1;
+    t.normal.clear();
+    t.pane().ensureCursorVisible();
+}
+
+pub fn ranges(t: *Text, text: []const u8, row0: i32, out: *[max_selections]modal.Selection) struct { n: usize, pri: usize } {
+    const pr = primaryRange(t, text, row0);
+    var n: usize = 0;
+    var pri: usize = 0;
+    var placed = false;
+    for (t.sels[0..t.nsel]) |s| {
+        const r = cellRange(text, s.arow - row0, s.acol, s.row - row0, s.col);
+        if (!placed and @min(pr.anchor, pr.head) <= @min(r.anchor, r.head)) {
+            pri = n;
+            out[n] = pr;
+            n += 1;
+            placed = true;
+        }
+        out[n] = r;
+        n += 1;
+    }
+    if (!placed) {
+        pri = n;
+        out[n] = pr;
+        n += 1;
+    }
+    return .{ .n = n, .pri = pri };
+}
+
+pub fn setRanges(t: *Text, text: []const u8, in: []const modal.Selection, sticky: []const i32, pri0: usize, explicit: bool) void {
+    if (in.len == 0) return; // helix asserts non-empty; here it just means "no change"
+    var r: [max_selections]modal.Selection = undefined;
+    var st: [max_selections]i32 = undefined;
+    var n: usize = @min(in.len, max_selections);
+    var pri: usize = @min(pri0, n - 1);
+    for (in[0..n], 0..) |x, i| {
+        r[i] = x;
+        if (r[i].anchor == r[i].head) r[i].head = modal.nextGrapheme(text, r[i].head);
+        st[i] = if (i < sticky.len) sticky[i] else -1;
+    }
+    // insertion sort by start — n is tiny and usually already ordered
+    var i: usize = 1;
+    while (i < n) : (i += 1) {
+        var j = i;
+        while (j > 0 and @min(r[j].anchor, r[j].head) < @min(r[j - 1].anchor, r[j - 1].head)) : (j -= 1) {
+            std.mem.swap(modal.Selection, &r[j], &r[j - 1]);
+            std.mem.swap(i32, &st[j], &st[j - 1]);
+            if (pri == j) pri = j - 1 else if (pri == j - 1) pri = j;
+        }
+    }
+    var k: usize = 0;
+    i = 1;
+    while (i < n) : (i += 1) {
+        const a = r[k];
+        const b = r[i];
+        const af = @min(a.anchor, a.head);
+        const at = @max(a.anchor, a.head);
+        const bf = @min(b.anchor, b.head);
+        const bt = @max(b.anchor, b.head);
+        if (af == bf or (at > bf and bt > af)) {
+            r[k] = if (a.anchor > a.head and b.anchor > b.head)
+                .{ .anchor = @max(a.anchor, b.anchor), .head = @min(a.head, b.head) }
+            else
+                .{ .anchor = @min(af, bf), .head = @max(at, bt) };
+            if (pri == i) pri = k;
+            if (st[k] < 0) st[k] = st[i];
+            continue;
+        }
+        k += 1;
+        r[k] = b;
+        st[k] = st[i];
+        if (pri == i) pri = k;
+    }
+    n = k + 1;
+    setRange(t, text, 0, r[pri], explicit);
+    t.sticky_col = st[pri];
+    var w: usize = 0;
+    for (r[0..n], 0..) |x, idx| {
+        if (idx == pri) continue;
+        const c = rangeCells(text, x);
+        const cc = modal.positionAt(text, c.cur);
+        const ac = modal.positionAt(text, c.anc);
+        t.sels[w] = .{
+            .row = @as(i32, @intCast(cc.row)),
+            .col = @intCast(cc.col),
+            .arow = @as(i32, @intCast(ac.row)),
+            .acol = @intCast(ac.col),
+            .sticky = st[idx],
+        };
+        w += 1;
+    }
+    t.nsel = @intCast(w);
+}
+
+pub fn multiSelAction(t: *Text, text: []const u8, kind: modal.Normal.Multi, cnt: usize) void {
+    var rs: [max_selections]modal.Selection = undefined;
+    const got = ranges(t, text, 0, &rs);
+    const n = got.n;
+    const expl = (t.vsel.active and t.vsel.explicit) or t.msel.active;
+    if (kind == .remove_primary) {
+        if (n < 2) return; // helix: "no selections remaining"
+        var out: [max_selections]modal.Selection = undefined;
+        var m: usize = 0;
+        for (rs[0..n], 0..) |r, i| {
+            if (i == got.pri) continue;
+            out[m] = r;
+            m += 1;
+        }
+        // helix Selection::remove: the NEXT range takes over, or the
+        // previous one when the primary was last
+        return setRanges(t, text, out[0..m], &.{}, @min(got.pri, m - 1), expl);
+    }
+    if (kind == .rotate_forward or kind == .rotate_backward) {
+        const step = cnt % n;
+        const pri = if (kind == .rotate_forward) (got.pri + step) % n else (got.pri + (n - step)) % n;
+        return setRanges(t, text, rs[0..n], &.{}, pri, expl);
+    }
+    if (kind == .merge) {
+        // helix merge_selections: first.merge(last) — the ranges are
+        // sorted, so that is simply the whole span
+        const lo = @min(rs[0].anchor, rs[0].head);
+        const hi = @max(rs[n - 1].anchor, rs[n - 1].head);
+        const rev = rs[0].anchor > rs[0].head and rs[n - 1].anchor > rs[n - 1].head;
+        const one: modal.Selection = if (rev) .{ .anchor = hi, .head = lo } else .{ .anchor = lo, .head = hi };
+        return setRanges(t, text, &.{one}, &.{}, 0, expl);
+    }
+    if (kind == .merge_consecutive) {
+        var out: [max_selections]modal.Selection = undefined;
+        var m: usize = 0;
+        var pri: usize = 0;
+        for (rs[0..n], 0..) |r, i| {
+            if (m > 0 and @min(r.anchor, r.head) == @max(out[m - 1].anchor, out[m - 1].head)) {
+                const lo = @min(@min(out[m - 1].anchor, out[m - 1].head), @min(r.anchor, r.head));
+                const hi = @max(@max(out[m - 1].anchor, out[m - 1].head), @max(r.anchor, r.head));
+                out[m - 1] = .{ .anchor = lo, .head = hi };
+                if (i == got.pri) pri = m - 1;
+                continue;
+            }
+            if (i == got.pri) pri = m;
+            out[m] = r;
+            m += 1;
+        }
+        return setRanges(t, text, out[0..m], &.{}, pri, expl);
+    }
+    if (kind == .split_newline) {
+        // helix selection::split_on_newline — one range per line the
+        // selection covers, the newlines themselves left out
+        var out: [max_selections]modal.Selection = undefined;
+        var m: usize = 0;
+        for (rs[0..n]) |r| {
+            const from = @min(r.anchor, r.head);
+            const to = @max(r.anchor, r.head);
+            if (from == to) {
+                if (m < max_selections) {
+                    out[m] = r;
+                    m += 1;
+                }
+                continue;
+            }
+            var start = from;
+            while (start < to and m < max_selections) {
+                const eol = modal.lineEndOffset(text, modal.lineAtOffset(text, start));
+                if (eol >= to) {
+                    out[m] = .{ .anchor = start, .head = to };
+                    m += 1;
+                    break;
+                }
+                out[m] = .{ .anchor = start, .head = eol };
+                m += 1;
+                start = eol + 1;
+            }
+        }
+        if (m == 0) return;
+        return setRanges(t, text, out[0..m], &.{}, 0, true); // helix keeps primary 0
+    }
+    if (kind == .trim) {
+        // helix trim_selections: whitespace off both ends; ranges that are
+        // empty or all whitespace are dropped entirely
+        var out: [max_selections]modal.Selection = undefined;
+        var m: usize = 0;
+        for (rs[0..n]) |r| {
+            var from = @min(r.anchor, r.head);
+            var to = @max(r.anchor, r.head);
+            while (from < to and std.ascii.isWhitespace(text[from])) from += 1;
+            while (to > from and std.ascii.isWhitespace(text[to - 1])) to -= 1;
+            if (from >= to) continue;
+            out[m] = if (r.anchor > r.head) .{ .anchor = to, .head = from } else .{ .anchor = from, .head = to };
+            m += 1;
+        }
+        if (m == 0) { // helix: collapse_selection + keep_primary_selection
+            const c = modal.selectionCursor(text, rs[got.pri]);
+            return setRange(t, text, 0, .{ .anchor = c, .head = c }, false);
+        }
+        // helix: the first survivor that OVERLAPS the old primary, else the last
+        const pf = @min(rs[got.pri].anchor, rs[got.pri].head);
+        const pt = @max(rs[got.pri].anchor, rs[got.pri].head);
+        var pri = m - 1;
+        for (out[0..m], 0..) |r, i| {
+            const f = @min(r.anchor, r.head);
+            const to = @max(r.anchor, r.head);
+            if (f == pf or (to > pf and pt > f)) {
+                pri = i;
+                break;
+            }
+        }
+        return setRanges(t, text, out[0..m], &.{}, pri, expl);
+    }
+    const below = kind == .copy_below;
+    var out: [max_selections]modal.Selection = undefined;
+    var m: usize = 0;
+    var pri: usize = 0;
+    const nlines = modal.cursorLineCount(text);
+    for (rs[0..n], 0..) |r, ri| {
+        const is_pri = ri == got.pri;
+        // head-exclusive: back the leading end off onto its own cell
+        const hp = modal.positionAt(text, if (r.anchor < r.head) modal.prevGrapheme(text, r.head) else r.head);
+        const ap = modal.positionAt(text, if (r.anchor < r.head) r.anchor else modal.prevGrapheme(text, r.anchor));
+        const height = @max(hp.row, ap.row) - @min(hp.row, ap.row) + 1;
+        if (m >= max_selections) break;
+        if (is_pri) pri = m;
+        out[m] = r;
+        m += 1;
+        var made: usize = 0;
+        var k: usize = 0;
+        while (made < cnt and m < max_selections) : (k += 1) {
+            const d = (k + 1) * height;
+            const arow = if (below) ap.row + d else ap.row -| d;
+            const hrow = if (below) hp.row + d else hp.row -| d;
+            if (arow >= nlines or hrow >= nlines) break;
+            const a2 = modal.offsetAt(text, .{ .row = arow, .col = ap.col });
+            const h2 = modal.offsetAt(text, .{ .row = hrow, .col = hp.col });
+            // a line too short to reach the column is skipped, not clamped
+            if (modal.positionAt(text, a2).col == ap.col and modal.positionAt(text, h2).col == hp.col) {
+                if (is_pri) pri = m;
+                out[m] = modal.moveSelectionCursor(text, .{ .anchor = a2, .head = a2 }, h2, true);
+                m += 1;
+                made += 1;
+            }
+            if (arow == 0 and hrow == 0) break;
+        }
+    }
+    setRanges(t, text, out[0..m], &.{}, pri, expl);
+}
+
+/// a range's start CELL (document order key) — the smaller of its two ends
+pub fn selStart(s: SelRange) struct { row: i32, col: i32 } {
+    if (s.arow < s.row or (s.arow == s.row and s.acol < s.col)) return .{ .row = s.arow, .col = s.acol };
+    return .{ .row = s.row, .col = s.col };
+}
+
+pub fn maxLine(text: []const u8) usize {
+    const nl = modal.cursorLineCount(text);
+    return if (text.len == 0 or text[text.len - 1] == '\n') nl -| 2 else nl - 1;
+}
+
+/// point-target motion: collapse there (extend in select mode)
+pub fn pointMove(t: *Text, text: []const u8, range: modal.Selection, target: usize) void {
+    setRange(t, text, 0, modal.moveSelectionCursor(text, range, target, t.select), false);
+}
+
+/// word motions select their traversed span (extend mode: head only)
+pub fn wordMove(t: *Text, text: []const u8, range: modal.Selection, cnt: usize, target: modal.WordTarget) void {
+    const wr = modal.moveWord(text, range, cnt, target);
+    const res = if (t.select) modal.moveSelectionCursor(text, range, modal.selectionCursor(text, wr), true) else wr;
+    setRange(t, text, 0, res, false);
+}
+
+/// f/t/F/T: anchor at the old cursor cell, head on the hit (not found: no move)
+pub fn findMove(t: *Text, text: []const u8, range: modal.Selection, ch: u21, fwd: bool, till: bool, cnt: usize) void {
+    const cur = modal.selectionCursor(text, range);
+    const target = modal.findTarget(text, cur, ch, fwd, till, cnt) orelse return;
+    const res = if (t.select)
+        modal.moveSelectionCursor(text, range, target, true)
+    else
+        modal.moveSelectionCursor(text, .{ .anchor = cur, .head = cur }, target, true);
+    setRange(t, text, 0, res, false);
+}
+
+/// j/k and friends: sticky goal column, clamped onto short lines' newline
+pub fn verticalMove(t: *Text, text: []const u8, range: modal.Selection, down: bool, cnt: usize) void {
+    const cur = modal.selectionCursor(text, range);
+    const pos = File.textPosition(t, text, cur);
+    const goal: usize = if (t.sticky_col >= 0)
+        @intCast(t.sticky_col)
+    else
+        File.rawDisplayCol(File.textLine(t, text, pos.row), pos.col);
+    const last_row = File.textLineCount(t, text) - 1;
+    const nline = if (down) @min(pos.row + @max(1, cnt), last_row) else pos.row -| @max(1, cnt);
+    const target_col = File.rawAtDisplay(File.textLine(t, text, nline), goal);
+    const target = File.textOffset(t, text, .{ .row = nline, .col = target_col });
+    // extend mode never walks onto the empty trailing line (helix)
+    if (t.select and target == text.len and text.len > 0 and text[text.len - 1] == '\n') return;
+    setRange(t, text, 0, modal.moveSelectionCursor(text, range, target, t.select), false);
+    t.sticky_col = @intCast(goal);
+}
+
+pub fn visualMove(
+    t: *Text,
+    text: []const u8,
+    range: modal.Selection,
+    down: bool,
+    cnt: usize,
+    width: usize,
+) void {
+    const cur = modal.selectionCursor(text, range);
+    const pos = File.textPosition(t, text, cur);
+    const last_row = File.textLineCount(t, text) - 1;
+    var row = pos.row;
+    var line = modal.lineSlice(text, row);
+    var vrow = File.visualRow(line, pos.col, width);
+    const goal: usize = if (t.sticky_col >= 0)
+        @intCast(t.sticky_col)
+    else
+        File.rawDisplayCol(line[vrow.start..vrow.end], pos.col -| vrow.start);
+    var steps = @max(1, cnt);
+    while (steps > 0) : (steps -= 1) {
+        if (down) {
+            if (vrow.end < line.len) {
+                vrow = File.visualRow(line, vrow.end, width);
+                continue;
+            }
+            if (row == last_row) break;
+            row += 1;
+            line = modal.lineSlice(text, row);
+            vrow = File.visualRow(line, 0, width);
+        } else {
+            if (vrow.start > 0) {
+                vrow = File.visualRow(line, vrow.start - 1, width);
+                continue;
+            }
+            if (row == 0) break;
+            row -= 1;
+            line = modal.lineSlice(text, row);
+            vrow = File.visualRow(line, line.len, width);
+        }
+    }
+    // The newline slot is a real cursor position, but the first byte of the
+    // NEXT visual row is not: landing there would read as two rows moved.
+    var target_col = vrow.start + File.rawAtDisplay(line[vrow.start..vrow.end], goal);
+    if (vrow.end < line.len and target_col >= vrow.end)
+        target_col = modal.graphemeStart(line, vrow.end - 1);
+    const target = File.textOffset(t, text, .{ .row = row, .col = target_col });
+    // extend mode never walks onto the empty trailing line (helix)
+    if (t.select and target == text.len and text.len > 0 and text[text.len - 1] == '\n') return;
+    setRange(t, text, 0, modal.moveSelectionCursor(text, range, target, t.select), false);
+    t.sticky_col = @intCast(goal);
+}
+
+/// Ctrl-d/u: scroll half a page AND move the cursor by the same rows
+pub fn halfPageMove(t: *Text, text: []const u8, range: modal.Selection, down: bool) void {
+    const half: i32 = @max(1, @divTrunc(@as(i32, t.pane().rows), 2));
+    t.pane().scrollBy(if (down) half else -half);
+    verticalMove(t, text, range, down, @intCast(half));
+}
+
+/// helix `scroll` without cursor sync (Ctrl-f/b, PgUp/PgDn, zj/zk): shift
+/// the view, then snap a fallen-out cursor to the near scrolloff edge, col 0
+pub fn scrollViewMove(t: *Text, text: []const u8, range: modal.Selection, delta: i32) void {
+    const margin: i32 = @min(config.scroll_off, @divTrunc(@as(i32, t.pane().rows) - 1, 2));
+    t.pane().scrollBy(delta);
+    const top = t.pane().scroll();
+    const last_row: i32 = @intCast(File.textLineCount(t, text) - 1);
+    const cur = modal.selectionCursor(text, range);
+    if (delta > 0) {
+        const snap: i32 = @max(0, @min(top + margin, last_row));
+        const head = File.textLineStart(t, text, @intCast(snap));
+        if (head <= cur) return;
+        const anchor = if (t.select) range.anchor else head;
+        setRange(t, text, 0, .{ .anchor = anchor, .head = head }, false);
+    } else {
+        const snap: i32 = @max(0, @min(top + @as(i32, t.pane().rows) - margin - 1, last_row));
+        const head = File.textLineStart(t, text, @intCast(snap));
+        if (head >= cur) return;
+        const anchor = if (t.select) range.anchor else head;
+        setRange(t, text, 0, .{ .anchor = anchor, .head = head }, false);
+    }
+}
+
+/// gt/gc/gb: view-relative rows, col 0, scrolloff clamped (helix goto_window)
+pub fn gotoWindow(t: *Text, text: []const u8, range: modal.Selection, which: enum { top, center, bottom }, cnt: usize) void {
+    const margin: i32 = @min(config.scroll_off, @divTrunc(@as(i32, t.pane().rows) - 1, 2));
+    const top = t.pane().scroll();
+    const last_row: i32 = @intCast(File.textLineCount(t, text) - 1);
+    const last_vis: i32 = @min(@as(i32, t.pane().rows) - 1, last_row - top);
+    const n: i32 = @intCast(cnt - 1);
+    var vline: i32 = switch (which) {
+        .top => top + margin + n,
+        .center => top + @divTrunc(last_vis, 2),
+        .bottom => top + last_vis - (margin + n),
+    };
+    vline = @max(vline, top + margin);
+    vline = @min(vline, top + last_vis - margin);
+    const row: i32 = std.math.clamp(vline, 0, last_row);
+    pointMove(t, text, range, File.textLineStart(t, text, @intCast(row)));
+}
+
+/// helix Range::line_range — the inclusive line span a range covers
+pub fn rangeLineSpan(text: []const u8, r: modal.Selection) struct { start: usize, end: usize } {
+    const from = @min(r.anchor, r.head);
+    const to = @max(r.anchor, r.head);
+    const to_adj = if (from == to) to else @max(modal.prevGrapheme(text, to), from);
+    return .{ .start = modal.lineAtOffset(text, from), .end = modal.lineAtOffset(text, to_adj) };
+}
+
+fn lineStartOrEof(text: []const u8, line: usize) usize {
+    if (line >= modal.cursorLineCount(text)) return text.len;
+    return modal.lineStartOffset(text, line);
+}
+
+/// helix `x` extend_line_below: full lines incl. the newline, cursor ON
+/// the last one's '\n'; an already-line-bounded selection grows downward
+pub fn lineSelect(t: *Text, text: []const u8, range: modal.Selection, cnt: usize) void {
+    const span = rangeLineSpan(text, range);
+    const start = modal.lineStartOffset(text, span.start);
+    const end = lineStartOrEof(text, span.end + 1);
+    const full = @min(range.anchor, range.head) == start and @max(range.anchor, range.head) == end;
+    const head = lineStartOrEof(text, span.end + cnt + @intFromBool(full));
+    setRange(t, text, 0, .{ .anchor = start, .head = head }, true);
+}
+
+/// helix `X` extend_to_line_bounds (direction kept)
+pub fn lineBoundsSelect(t: *Text, text: []const u8, range: modal.Selection) void {
+    const span = rangeLineSpan(text, range);
+    const start = modal.lineStartOffset(text, span.start);
+    const end = lineStartOrEof(text, span.end + 1);
+    const r: modal.Selection = if (range.head < range.anchor)
+        .{ .anchor = end, .head = start }
+    else
+        .{ .anchor = start, .head = end };
+    setRange(t, text, 0, r, true);
+}
+
+/// helix `Alt-x` shrink_to_line_bounds (single-line selections untouched)
+pub fn shrinkSelToLineBounds(t: *Text, text: []const u8, range: modal.Selection) void {
+    const span = rangeLineSpan(text, range);
+    if (span.start == span.end) return;
+    const from = @min(range.anchor, range.head);
+    const to = @max(range.anchor, range.head);
+    var start = modal.lineStartOffset(text, span.start);
+    var end = lineStartOrEof(text, span.end + 1);
+    if (start != from) start = lineStartOrEof(text, span.start + 1);
+    if (end != to) end = modal.lineStartOffset(text, span.end);
+    const expl = (t.vsel.active and t.vsel.explicit) or t.msel.active;
+    const r: modal.Selection = if (range.head < range.anchor)
+        .{ .anchor = end, .head = start }
+    else
+        .{ .anchor = start, .head = end };
+    setRange(t, text, 0, r, expl);
+}
+
+/// pull the cursor back inside `text` after a rewrite; `row0` is the
+/// absolute surface row of its first line (0 for a file)
+pub fn clampCursor(t: *Text, text: []const u8, row0: i32) void {
+    const n = modal.lineCount(text);
+    const row: usize = @min(@as(usize, @intCast(@max(0, t.cur_row - row0))), if (n == 0) 0 else n - 1);
+    const llen = modal.lineSlice(text, row).len;
+    t.cur_row = @as(i32, @intCast(row)) + row0;
+    t.cur_col = @intCast(@min(@as(usize, @intCast(@max(0, t.cur_col))), llen));
+    t.cur_pinned = true;
+    t.vsel.active = false;
+    t.msel.active = false;
+    t.pane().ensureCursorVisible();
+}