Chris Harrelson <chris...@chromium.org> writes:

> On Sun, Apr 16, 2023 at 11:45 PM Morten Stenshorne <msten...@chromium.org> 
> wrote:
>
>  Chris Harrelson <chris...@chromium.org> writes:
>
>  > On Fri, Apr 14, 2023 at 5:09 PM PhistucK <phist...@gmail.com> wrote:
>  >
>  >  Any alternatives? I thought there was a section in the intent templates 
> for that...
>  >
>  > One alternative for the use case mentioned in my earlier email is to
>  > apply a CSS transform instead. This will magnify the subtree visually
>  > but not cause a zoom-style layout change.
>
>  The fact that a CSS transform doesn't affect layout, whereas 'zoom'
>  does, means that we'll paginate (fragment) properly with 'zoom', but not
>  with transforms, since they are applied after fragmentation [1], causing
>  content to be sliced across fragmentainer boundaries, and the actual
>  page/column breaks (as far as layout is concerned) are shifted away from
>  the fragmentainer edges visually, and will appear in the middle of a
>  page/column, for instance.
>
>  [1] https://www.w3.org/TR/css-break-3/#transforms (never mind the
>  example there; it's not too relevant for this discussion, but I can
>  provide one if you want)
>
> Agreed that this is a difference. If a developer wants the result to
> flow through fragmentation, they'll have to use the second alternative
> I suggested.
>
> But in terms of web compat, I don't think this situation is anything
> to worry about (e.g. I didn't see any fragmentation when reviewing 25
> random sites linked to from chromestatus.com).

But as soon as someone prints any of those sites, there'll be
fragmentation.

That said, I couldn't find anything bad on those sites, either. I was
thinking that if it's actually okay to replace zoom with a scale
transform, we really need authors to make such elements monolithic
(because any break point inserted inside a transformed element will more
likely than not end up in the middle of some page, rather than at an
actual page boundary). So I changed the engine locally to treat zoom !=
1 as monolithic. But that didn't make any of sites that I tried look any
worse.

>  > Another alternative is for the developer to multiply the numbers in
>  > their CSS properties via calc + variables.
>
>  That alternative should always work, but more cumbersome for the
>  authors, I suppose?
>
> Yes, a bit more cumbersome, but interoperable across all browser engines.
>  
>  
>  >  On Sat, Apr 15, 2023 at 1:03 AM Chris Harrelson <chris...@chromium.org> 
> wrote:
>  >
>  >  Contact emails
>  >
>  >  chris...@chromium.org
>  >
>  >  Specification
>  >
>  >  https://developer.mozilla.org/en-US/docs/Web/CSS/zoom
>  >
>  >  Summary
>  >
>  >  Removes support for the non-standard "zoom" CSS property. This CSS 
> property causes computed lengths for an element to be multiplied by
>  >  the specified zoom factor. 
>  >
>  >  Blink component
>  >
>  >  Blink>CSS
>  >
>  >  TAG review
>  >
>  >  None
>  >
>  >  TAG review status
>  >
>  >  Not applicable
>  >
>  >  Risks
>  >
>  >  Interoperability and Compatibility
>  >
>  >  This feature is only available in Webkit and Blink-based browsers, and 
> has been present in Chrome since the beginning. Usage is a little above
>  >  0.5% of page loads: 
> https://chromestatus.com/metrics/feature/timeline/popularity/3578 However, 
> research shows that sites in HTTPArchive
>  >  triggering the feature mostly don't even seem to use it, and those that 
> do appear to always use it in a way that works fine without zoom applied
>  >  - worst case, just a very minor change to the size of a tiny number of UI 
> elements, but the UX is basically the same. See:
>  >  
> https://docs.google.com/document/d/1cmbXpjAcXAht2ufi7bNKy-rbVNveqaf0UzeYg_DIMNA/edit#
>  >
>  >  Gecko: Shipped/Shipping (Firefox never supported the feature.)
>  >
>  >  WebKit: No signal 
> (https://github.com/WebKit/standards-positions/issues/170)
>  >
>  >  Web developers: Some web developers like the feature, in particular for 
> the use case of zooming in content in a legible way with responsive
>  >  design. See comments regarding that in this issue; 
> https://github.com/w3c/csswg-drafts/issues/5623
>  >
>  >  Other signals: The CSSWG has decided to not specify this feature: 
> https://github.com/w3c/csswg-drafts/issues/5623
>  >
>  >  Ergonomics
>  >
>  >  See "other views" section.
>  >
>  >  Activation
>  >
>  >  N/A
>  >
>  >  Security
>  >
>  >  None
>  >
>  >  WebView application risks
>  >
>  >  Does this intent deprecate or change behavior of existing APIs, such that 
> it has potentially high risk for Android WebView-based applications?
>  >
>  >  Maybe. WebView-based apps might use this feature.
>  >
>  >  Debuggability
>  >
>  >  Sites should be able to see that zoom no longer applies to elements in 
> devtools, though there is no warning planned.
>  >
>  >  Will this feature be supported on all six Blink platforms (Windows, Mac, 
> Linux, Chrome OS, Android, and Android WebView)?
>  >
>  >  Yes
>  >
>  >  Is this feature fully tested by web-platform-tests?
>  >
>  >  No
>  >
>  >  Flag name
>  >
>  >  CSSZoom
>  >
>  >  Requires code in //chrome?
>  >
>  >  False
>  >
>  >  Sample links
>  >
>  >  https://output.jsbin.com/yimuwax
>  >
>  >  Estimated milestones
>  >
>  >   Shipping on desktop  114  
>  >   DevTrial on desktop  114  
>  >
>  >   Shipping on Android  114  
>  >   DevTrial on Android  114  
>  >
>  >   Shipping on WebView  114  
>  >
>  >  Anticipated spec changes
>  >
>  >  Open questions about a feature may be a source of future web compat or 
> interop issues. Please list open issues (e.g. links to known github
>  >  issues in the project for the feature specification) whose resolution may 
> introduce web compat/interop risk (e.g., changing to naming or
>  >  structure of the API in a non-backward-compatible way).
>  >
>  >  None
>  >
>  >  Link to entry on the Chrome Platform Status
>  >
>  >  https://chromestatus.com/feature/6535859207143424
>  >
>  >  Links to previous Intent discussions
>  >
>  >  This intent message was generated by Chrome Platform Status.
>  >
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>  
>
>  -- 
>  Morten Stenshorne, Software developer,
>  Blink/Layout, Google, Oslo, Norway
>
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>

-- 
Morten Stenshorne, Software developer,
Blink/Layout, Google, Oslo, Norway

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