1242829 - Handle linecaps in bounds calculations for SVG circles and ellipses with dashed stroke

Status: NEW

(Core :: SVG, defect)

Description

[Tom Klein]

Attachment: dashed circle invalidation artifacts.html

This will be a followup to bug 1242147.

The bounds computation code currently assumes that the stroke of a circle or ellipse doesn't extend more than half a line-width, but that's not necessarily true (or rather won't be once 1242147 lands) if the stroke is dashed and stroke-linecap="square".

The too small computed bounds result in invalidation artifacts and a too small return from getBoundingClientRect() (see the attached testcase *with the patch from bug 1242147 applied*).

We'll need to consider SVG[Circle|Ellipse]Element::GetGeometryBounds and nsSVGUtils::PathExtentsToMaxStrokeExtents: 
https://dxr.mozilla.org/mozilla-central/rev/d6d81655dd9e146c300a64c0fcaeb04ca3300a19/layout/svg/nsSVGUtils.cpp#1231

Comment 1

[Liz Henry (:lizzard)]

Tracking as this looks like another regression from 42.

Comment 2

[Robert Longson [:longsonr]]

Its not a regression, it's always been like this. Do you still want to track it?

Comment 3

[Liz Henry (:lizzard)]

No, we try to track all known (recent) regressions. Thanks! I misunderstood the comments in the parent bug.