Make ImageBitmap transferable #444
Conversation
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Regarding the content security model: the algorithm for transferring an ImageBitmap simply copies the value of the origin-clean flag. So no tainting happens when the ImageBitmap is tranferred to a cross-origin script. I am pretty sure this is the right thing to do, but I wanted to point this out because it is a bit tricky and I would like to make sure the security implications are considered by those who review this. |
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| <p>The following IDL block formalizes this:</p> | ||
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| <pre class="idl">typedef (<span>ArrayBuffer</span> or <span>CanvasProxy</span> or <span>MessagePort</span>) <dfn>Transferable</dfn>;</pre> | ||
| <pre class="idl">typedef (<span>ArrayBuffer</span> or <span>CanvasProxy</span> or | ||
| <span>MessagePort</span> or <span>ImageBitmap</span>) <dfn>Transferable</dfn>;</pre> |
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To match other multiline typedefs this should look more like
typedef (ArrayBuffer or
CanvasProxy or
MessagePort or
ImageBitmap) Transferable;
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While you are here if you could fix a mistake I made and correct <span>ArrayBuffer</span> to <span data-x="idl-ArrayBuffer">ArrayBuffer</span> that would be lovely <3.
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Reviewed, and looks good apart from editorial things. The newest build script (do a git pull in your html-build directory) gives better error output, which can help with some things. |
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New patch. |
| or <span>CanvasProxy</span> | ||
| or <span>MessagePort</span> | ||
| or <span>ImageBitmap</span>) <dfn>Transferable</dfn>; | ||
| </pre> |
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I think we try to avoid putting <pre> and </pre> on distinct lines. There's a bit of subtlety there display-wise.
ImageBitmap objects can already be sent using postMessage(), but this requires a duplication of the bitmap data in memory, which is inefficient and often unnecessary. This change is a pre-requisite for the OffscreenCanvas proposal, which relies on ImageBitmaps as an efficient means of transferring bitmap data to and from Workers. See: https://wiki.whatwg.org/wiki/OffscreenCanvas
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Committed as 334f9ed. Sorry for not linking the PR, I had the mistaken impression this was rebased. |
ImageBitmap objects can already be sent using postMessage(), but this
requires a duplication of the bitmap data in memory, which is
inefficient and often unnecessary. This change is a pre-requisite
for the OffscreenCanvas proposal, which relies on ImageBitmaps as
an efficient means of transferring bitmap data to and from Workers.
See: https://wiki.whatwg.org/wiki/OffscreenCanvas