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Fix comment textarea scroll issue in Firefox (#34438) #34446

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Merged
merged 1 commit into from
May 13, 2025
Merged

Fix comment textarea scroll issue in Firefox (#34438) #34446

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10 changes: 10 additions & 0 deletions web_src/js/utils/dom.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -168,6 +168,7 @@ export function autosize(textarea: HTMLTextAreaElement, {viewportMarginBottom =
function resizeToFit() {
if (isUserResized) return;
if (textarea.offsetWidth <= 0 && textarea.offsetHeight <= 0) return;
const previousMargin = textarea.style.marginBottom;

try {
const {top, bottom} = overflowOffset();
Expand All @@ -183,6 +184,9 @@ export function autosize(textarea: HTMLTextAreaElement, {viewportMarginBottom =
const curHeight = parseFloat(computedStyle.height);
const maxHeight = curHeight + bottom - adjustedViewportMarginBottom;

// In Firefox, setting auto height momentarily may cause the page to scroll up
// unexpectedly, prevent this by setting a temporary margin.
textarea.style.marginBottom = `${textarea.clientHeight}px`;
textarea.style.height = 'auto';
let newHeight = textarea.scrollHeight + borderAddOn;

Expand All @@ -203,6 +207,12 @@ export function autosize(textarea: HTMLTextAreaElement, {viewportMarginBottom =
textarea.style.height = `${newHeight}px`;
lastStyleHeight = textarea.style.height;
} finally {
// restore previous margin
if (previousMargin) {
textarea.style.marginBottom = previousMargin;
} else {
textarea.style.removeProperty('margin-bottom');
}
// ensure that the textarea is fully scrolled to the end, when the cursor
// is at the end during an input event
if (textarea.selectionStart === textarea.selectionEnd &&
Expand Down