ADR-0040: Column editing as a GUI-only vertical cursor

• Status: Accepted
• Date: 2026-07-23
• Deciders: jka
• Decision: D40

Context

Notepad++'s column mode lets the user drag a vertical caret across several lines and type on all of them at once, or select a rectangle and overwrite it. rio's users asked for the same.

Decision

rio provides column editing, off by default and enabled by a setting.

• Gesture: Ctrl+Shift+drag. Notepad++ uses Alt+drag, but most Linux window managers take Alt+drag to move windows.
• Scope: bound in the windows editing mode only; the setting is greyed out in other modes.
• Mechanism: no core change. A column operation reads the affected line span, applies the per-line edit (padding short lines with spaces), and sends a single buffer.replace. A 40-line column edit is one undo step and one change event, the same technique used by Replace All and block indent.
• Rendering: a rectangular selection uses a tag in the selection colour; a zero-width column caret is drawn as thin blinking bars, one per line, with the native caret hidden while the column is active.

Consequences

• The core and the protocol learn nothing new.
• Columns are character columns, so a tab inside the band can look misaligned.
• Rectangular clipboard operations, keyboard-built columns and arbitrary multiple carets are out of scope; multiple carets would generalise the same single-replace approach.