WebVR: add metric for sites using preserveDrawingBuffer=true |
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Issue descriptionSummary: add a new metric to track usage of the permitted-but-not-recommended preserveDrawingBuffer=true drawing mode in WebVR. The WebVR 1.1 spec allows sites to use the preserveDrawingBuffer=true canvas option, this forces the browser to preserve the old buffer content from frame to frame to support incrementally rendering new content on top. This conflicts with planned optimizations such as directly drawing WebVR frames into a per-frame buffer, and would require using a slower render path or adding an extra copy. Sites are unlikely to be using this option, but we should check to confirm that this is the case, and consider doing developer outreach. The upcoming WebXR no longer offers an equivalent option.
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Jan 4 2018
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Jan 11 2018
(offline discussion) Given the very short remaining lifetime of 1.1, and the absence of preserveDrawingBuffer in WebXR, there isn't much point in collecting this data, though it might be a good idea to reach out to developers who might be using it via DevRel
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Jan 18 2018
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Jan 18 2018
Given that this usage will be removed in the WebXR Device API gathering this information does seem less than useful. Closing.
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Jan 22 2018
Capturing some notes here from separate discussions for context. This will affect a planned polyfill to emulate WebVR 1.1 on top of WebXR. Since WebXR doesn't support a preserveDrawingBuffer=true mode, the polyfill should detect that and generate an appropriate diagnostic. The current working assumption is that it's unlikely that sites actually depend on the preserve semantics for rendering, so it should continue to work. A separate issue that was discussed is that developers sometimes use preserveDrawingBuffer=true to take screenshots without affecting rendering. According to bajones@: If preserveDrawingBuffer is false certain methods for reading back the image (like toDataURL) have the same effect as compositing the canvas with the page, which causes it to clear. See also https://github.com/immersive-web/webxr/issues/310 which discusses options for capturing screen content.
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Feb 7 2018
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Jul 4
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Comment 1 by ddorwin@chromium.org
, Dec 15 2017