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fix: clamp cursor column during rendering to prevent display at invalid positions #1414

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Merged
savetheclocktower merged 1 commit into from
May 2, 2026
+12 −3
Merged

fix: clamp cursor column during rendering to prevent display at invalid positions #1414

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15 changes: 12 additions & 3 deletions src/text-editor-component.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1227,15 +1227,24 @@ module.exports = class TextEditorComponent {
let decorationToMeasure = this.decorationsToMeasure.cursors.get(marker);
if (!decorationToMeasure) {
const isLastCursor = model.getLastCursor().getMarker() === marker;
const screenPosition = reversed ? screenRange.start : screenRange.end;
const { row, column } = screenPosition;
const rawScreenPosition = reversed ? screenRange.start : screenRange.end;
const { row } = rawScreenPosition;
let { column } = rawScreenPosition;

if (row < this.getRenderedStartRow() || row >= this.getRenderedEndRow())
return;

// Clamp column to line length to prevent cursor rendering at invalid
// positions due to intermittent timing issues with display layer updates
const lineLength = model.lineLengthForScreenRow(row);
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@savetheclocktower savetheclocktower May 2, 2026

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You've moved the call to lineLengthForScreenRow earlier. This is fine.

The purpose of this comment is to make it clear for the record that:

  • requestHorizontalMeasurements does not do anything that could affect what is returned by model.lineLengthForScreenRow; it reads from the model but does not change it;
  • even if that weren't true, requestHorizontalMeasurements doesn't do any synchronous work; it just schedules work to be performed later.

Hence it's impossible that calling lineLengthForScreenRow earlier could result in a behavior change.

if (column > lineLength) {
column = lineLength;
}

const screenPosition = { row, column };
this.requestHorizontalMeasurement(row, column);
let columnWidth = 0;
if (model.lineLengthForScreenRow(row) > column) {
if (lineLength > column) {
columnWidth = 1;
this.requestHorizontalMeasurement(row, column + 1);
}
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