Avoid document.write in Chrome with iframe linker #9836
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Does this mean it is still required in Firefox? Also, is there any way to test rather than looking for a string in user agent? The unfinished linked patch for example is waiting on detecting the presence of currentScript before trying to use it. |
That's what I meant, sorry for not being clear.
I don't know. Not even sure if the behaviors in Firefox, IE and Safari that we're trying to avoid here can be tested in the same way. |
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The biggest issue I see with excluding the doc.open/write/close is for the compatibility mode potentially being different in the iframe as it is in the parent document. In chrome, if there's no doctype, it will use BackCompat mode and not CSS1Compat (that you get with the I've been investigating other options, such as using the iframe srcdoc attribute, etc, but they seem to be asynchronous. I was able to use |
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@jhickman thanks for checking this. Do you think the compatibility mode matters for the hidden iframe? Since that frame does not render any HTML, only serves as "sandbox" for loading JS, it might not be an issue. |
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@zbynek - you may be right; but it would need to be determined if that's the case. I don't imagine the iframe being used as any kind of 'staging' area for HTML content. Will have to trace uses of the 'getInstallLocatioDoc()' call. |
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AFAICT, all the uses of |
I think the main reason is to make sure the document is accessible immediately in all browsers - if you skip |
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@zbynek - you may be right. I've been looking into this and can't really find any firm information on it. In a release or two when GWT cuts out IE11 entirely, then we may not even need that bit of code at all and just allow the browser to choose the compatMode of the newly constructed iframe. Although, we don't necessarily have to avoid using document.write in chrome altogether; maybe just with extensions and other environments (embedded) that have restricted API access. I would almost suggest a separate linker specifically for browser extensions? |
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Since |
This PR avoids
document.writein Chrome browser. It cannot be simply removed for all browsers for reasons mentioned in the code comment (I verified it's still valid in Firefox, didn't check Safari or IE).Motivation
Same as #9814 --
document.writeis considered bad for perfomance (flagged by Lighthouse performance audits) and completely forbidden in some contexts (chrome extensions, packaged chrome apps).Testing
This is part of GeoGebra codebase for a few months (via geogebra/geogebra@ac5c880) and we didn't notice any problems.