1958839 - Remove support for 'discard' element

Status: NEW

(Core :: SVG, task)

Description

[Daniel Holbert [:dholbert]]

We recently landed a patch to add experimental support for the SVG <discard> element, partly on the hypothesis that doing so might prompt Chromium engineers to add back their historical implementation of that element (if their removal was largely due to lack-of-support-in-other-browsers and if adding it back was not to much trouble).

However, since then:
(1) we ran across a bug in our experimental implementation; this bug indicated that there's some added complexity in making our implementation robust, and it prompted us to disable the feature (in bug 1954608).
(2) we ran across https://github.com/w3c/svgwg/issues/717#issue-470289163 where Chromium implementors requested to remove the feature from the spec when they un-shipped the feature -- they expressed additional reasons that they opted to remove the feature beyond lack-of-support-in-other-browsers, and they seem disinclined to add the feature back, given that the cost/benefit is not particularly favorable. (They note that the complexity & perf cost was nontrivial, and usage of the feature was ~zero, and it doesn't add much in the way of utility aside from the potential for SVG authors to reduce memory usage in long-running unscripted SVG animations.)
(3) @zcorpan closed the loop on the issue referenced in (2), removing the feature from the SVG spec.

Given the above (particularly (2)), it appears that the the benefits of this feature are not worth the maintenance burden & increased attack-surface cost of having this feature. Let's remove our implementation.

Comment 1

[Hamish Willee]

Added dev-doc-needed. MDN will need some cleanup if this happens.