1 files changed, 16 insertions, 5 deletions
diff --git a/src/modal.zig b/src/modal.zig
index 742dbc6f..cdc49142 100644
--- a/src/modal.zig
+++ b/src/modal.zig
@@ -438,7 +438,7 @@ pub fn lineStartOffset(content: []const u8, row: usize) usize {
     var off: usize = 0;
     var r: usize = 0;
     while (r < row) : (r += 1) {
-        const nl = std.mem.indexOfPos(u8, content, off, "\n") orelse return content.len;
+        const nl = std.mem.indexOfScalarPos(u8, content, off, '\n') orelse return content.len;
         off = nl + 1;
     }
     return off;
@@ -775,15 +775,24 @@ pub fn hxLineEndIdx(text: []const u8, line: usize) usize {
 
 /// gap offset -> (row, col) cell
 pub fn hxPos(text: []const u8, off: usize) Cursor {
-    const row = hxLineOf(text, off);
-    return .{ .row = row, .col = @min(off, text.len) - lineStartOffset(text, row) };
+    const o = @min(off, text.len);
+    // The line start is the byte after the last '\n' BEFORE off, which is the
+    // same number lineStartOffset(text, row) walks the whole prefix to reach —
+    // one backward scan of a single line instead of a second pass over
+    // everything above the cursor. On a multi-MB buffer that second pass was
+    // most of what a keystroke cost.
+    const s = if (std.mem.lastIndexOfScalar(u8, text[0..o], '\n')) |nl| nl + 1 else 0;
+    return .{ .row = hxLineOf(text, off), .col = o - s };
 }
 
 /// (row, col) -> clamped gap offset; col == line length lands ON the '\n'
 pub fn hxOff(text: []const u8, c: Cursor) usize {
     const row = @min(c.row, hxLineCount(text) - 1);
     const s = lineStartOffset(text, row);
-    return @min(s + c.col, hxLineEndIdx(text, row));
+    // hxLineEndIdx(text, row) inlined: it starts by walking to `row` again,
+    // and we are already standing there
+    const e = std.mem.indexOfScalarPos(u8, text, s, '\n') orelse text.len;
+    return @min(s + c.col, e);
 }
 
 pub const WordTarget = enum {
@@ -979,7 +988,9 @@ pub fn hxVertTarget(text: []const u8, pos: usize, down: bool, count: usize, goal
     const line = hxLineOf(text, pos);
     const nline = if (down) @min(line + @max(1, count), nlines - 1) else line -| @max(1, count);
     const s = lineStartOffset(text, nline);
-    return @min(s + goal_col, hxLineEndIdx(text, nline));
+    // hxLineEndIdx(text, nline) without its second walk to nline (see hxOff)
+    const e = std.mem.indexOfScalarPos(u8, text, s, '\n') orelse text.len;
+    return @min(s + goal_col, e);
 }
 
 /// f/F/t/T target cell. helix find_char: the exclusive (till) search starts