ADR 0123: A range that ends where a line begins

Status

Accepted

Context

Reported after ADR 0122 fixed where the linewise cursor sits: pressing V highlighted the line correctly, and left a thin vertical mark under it — narrower than a character, on the row below, looking like a selection that was not one.

Decision

highlightRange() walks lineForOffset(start) to lineForOffset(end) inclusive. The end is exclusive, so a range finishing exactly at a line's first byte still counted that line as its last.

For such a line the computed span is empty — rangeStartCol and rangeEndCol are both zero — and the fill was guarded by std::max(1, rectWidth), which turned nothing into one pixel of full line height at the left edge of the text.

A linewise selection ends at the start of the following line every time, so it produced this on every use of V.

The fix is to skip a line the range does not reach into, rather than to drop the max(1, ...), which is still wanted for a real span narrower than a pixel.

Consequences

Measured rather than eyeballed, by diffing the frame with V pressed against the same frame without it: the row below the selection had exactly one column changed at x=25 before, and none after.

The bug predates ADR 0122 — a linewise range has always ended at the next line's start. It only became visible once the cursor stopped sitting on that line, because the caret was drawn over the same pixels and hid it.

The + m_charWidth / 2 on lines before the last one still marks the selected newline, which is the deliberate cue that a linewise selection takes the line break with it.