diff --git a/rfcs/safe-printable-inset.md b/rfcs/safe-printable-inset.md new file mode 100644 index 0000000..bcba1f3 --- /dev/null +++ b/rfcs/safe-printable-inset.md @@ -0,0 +1,34 @@ +# RFC #233: Simulate safe printable inset + +## Summary + +We need a way of testing the [safe-printable-inset](https://github.com/w3c/csswg-drafts/pull/13190/files) property. + +## Details + +Most printers have a small region along each edge of the paper edges that's not +reliably printable, usually due to the printer's paper handling mechanism. +Authors can steer clear of such unprintable areas using the +`safe-printable-inset` property, which applies in `@page` and `@page` margin +contexts. + +There should be a way for print reftests to test this, by simulating unprintable +areas. + +One rather straight-forward solution would be a META value that sets the width +of the unprintable area on all four sides. For instance: + +`` + +where `inset-specifier` is a numeric value. The unit could be CSS pixels or +points. Using centimeters for anything here isn't a great idea, since they don't +convert nicely into CSS pixels (unlike inches). I suggest using CSS pixels. + +Why just one value for all four edges? Although many printers indeed don't +necessarily have a uniform unprintable area width along each of the four paper +edges (although many do), so that just providing one value for all is an +oversimplification of reality, printers may rotate the print output at their own +discretion. The user agent may therefore not be able to make assumptions about +which edge (long or short?) will be fed first into the printer, or what +orientation the sheet of paper has. Therefore using just one value (which should +represent the larger of the four) seems reasonable.