Heatmap PNG Download Missing Plot on macOS/iOS/iPadOS Safari and other iOS/iPadOS WebKit-based browsers

Something that I noticed while checking out 2.23.0, and with older versions of Plotly.js, is that saving the image of a heatmap using the built-in download plot as a PNG file does not include the heatmap image in Safari. Checking back with previous versions, including 2.20.0, the behavior exists there as well. It's included in the PNG download in Firefox and Chrome.

Since it seems to be an issue with WebKit, it would be a decent assumption that the issue would also appear on other iOS and iPadOS browsers that use WebKit as a rendering engine.

Screenshot: https://imgur.com/a/c4iCy9n
Live example (v2.20.0): https://graphs.wwdt.me/shows/monthly-aggregate-score-heatmap

Safariまたは別のiOS/iPadOS WebKitブラウザーを使って、リンクされたライブ例で欠落しているヒートマップを再現し、その後PNGのダウンロード結果をFirefoxまたはChromeと比較します。組み込みのdownload-plotエクスポートパスを追跡し、WebKitでヒートマップが欠落する理由を特定します。ダウンロードしたPNGにヒートマップが含まれ、他のブラウザーにリグレッションが発生しなければ完了です。