830479 - Page down scrolls too far on pages with multiple fixed headers

Status: RESOLVED FIXED

(Core :: Layout, defect)

Description

[Jesse Ruderman]

Attachment: testcase (reduced from Pocket article view)

Bug 780345 fixed the case where a page has a single fixed-position header element.  But if a page has two fixed-position header elements, the lower one seems to be ignored.

I noticed this when using the Pocket web app to read a saved article.

Comment 1

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Hmm, GetScrollPortSizeExcludingHeadersAndFooters tries to handle that case.

I can't prioritize this. Feel like scratching your own itch, Jesse? Should be easy :-).

Comment 2

[Timothy Nikkel (:tnikkel)]

GetScrollPortSizeExcludingHeadersAndFooters finds the lowest bottom of all elements that have their top at 0. The example has one element at 0, and a second element at 4px down, so the second element isn't considered.

We could sort the fixed pos elements by top and then consider elements whose top is above the current headerBottom (instead of considering one's whose top is 0). Similarly for footers.

Comment 3

[Robert O'Callahan (:roc) (email my personal email if necessary)]

That sounds reasonable.

Comment 4

[Timothy Nikkel (:tnikkel)]

Attachment: patch

Comment 5

[Timothy Nikkel (:tnikkel)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/0c10e026f7f3

Comment 6

[Timothy Nikkel (:tnikkel)]

to fix fatal signed/unsigned comparison warning
https://hg.mozilla.org/integration/mozilla-inbound/rev/4f3625b862a7

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/0c10e026f7f3
https://hg.mozilla.org/mozilla-central/rev/4f3625b862a7