Re: [csswg-drafts] [css-page][css-env] Expose unprintable areas via CSS (#11395)

I don't think we should provide both `minimum` and `balanced`. True, Firefox and Chrome already support "minimum" margins in the print preview UI, and unless the unprintable insets are the same on all four sides, it's buggy, since we don't know what the printer is going to do regarding rotations. I don't think we want to expose this to the web. A related issue is the "scale: fit to printable area" option when printing PDFs (Chrome has this). See https://issues.chromium.org/u/1/issues/41495735#comment20 . My inglourious printer (used in that bug report) that had a solid half-inch unprintable inset at the bottom, and more reasonable insets along the other edges, is unfortunately no longer with us.

So I believe that leaves us with three options: do nothing, clamp to safe inset (the larger of the four), add to safe inset. The latter is especially useful when making room for page margin boxes (i.e. custom headers / footers / whatever).

Keyword value names could be: `none` (current behavior, initial value), `clamped`, `additive`.

It may be that we don't need both `additive` and `clamped`, though. `clamped` is essentially the same as `additive` and `margin:0`, isn't it? Otherwise, if we want both values, that's also a strong argument for allowing for specifying this per paper edge. Maybe one edge wants to clamp, and another edge wants to add? Maybe we want it per edge regardless, if someone wants safety at some edges, and no safety at some other edges? I have no idea who would want such a thing, though. Sounds weird, unless it's a one-pager.

Also, how should the `additive` value work with auto margins? I suppose it will just behave like `clamped` then.

```css
  @page {
    width: 200px;
    margin-left: auto;
  }
```

Hmm. So `additive` wouldn't always be additive then. If we land on only two options, maybe reasonable values would be `none` and `safe`. Property / descriptor name? `page-margin-inset`? `page-margin-safety`? And, if we must, make it a shorthand for `-top`, `-right`, `-bottom`, `-left`, `-block-start`, `-block-end`, `-inline-start`, `-inline-end` longhands.

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Received on Wednesday, 16 July 2025 08:22:24 UTC