1633936 - Add telemetry to determine how much content is clipped during printing

Status: NEW

(Core :: Printing: Output, task, P3)

Description

[Daniel Holbert [:dholbert]]

[filing based on a discussion with TYLin]

It seems like it'd be feasible to determine (either at reflow time or at paint time) how much content runs off the page and is clipped/lost, during printing.

As we work to improve printing, it seems like it'd be useful to measure this clipped area as a telemetry metric of some sort, so that we can hopefully watch for improvement as we land bug-fixes. Hopefully this could help validate that these bug-fixes are making a real difference for users.

We can spitball about the best way to report/represent this, but one possibility would be e.g. a histogram with a number of print operations that fall into different buckets, with each bucket representing some range of clipped area (measured in square CSS Pixels, perhaps).

e.g. results might be reported like:

clipped 0 square pixels: 5 print operations
clipped 100-1000 square pixels: 3 print operations
clipped 1000-10,000 square pixels: 1 print operation
clipped 10,000-100,000 square pixels: 0 print operations
clipped > 100,000 square pixels: 1 print operation

(where "print operation" is a particular print or print-preview instance.)

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Ideally we should compare against the content clipped without printing, right? Otherwise it feels a bit hard to measure / misleading.

E.g. if I have a big container with overflow: hidden, I am clipping a bunch of content, but maybe that's content that is meant to be hidden.