868050 - Sometimes only the top-left sub-rectangle of a page draws on load

Status: RESOLVED INVALID

(Core :: Graphics, defect)

Description

[Chris Lord [:cwiiis]]

Sometimes when a page loads, it only draws a sub-rectangle in the top-left.

STR:

1. Open browser
2. Navigate to developer.mozilla.org

We had a similar thing in the Android browser, which was caused by us not setting the display-port early enough in the page load sequence. Perhaps this is a similar issue?

Not absolutely vital as scrolling will correct the issue (unless it happens on a page that can't scroll and doesn't otherwise update?), but looks kinda bad.

Verified the bug exists on v1.0.1 and v1-train.

Comment 1

[Ben Francis [:benfrancis]]

If I load that web page, I see the top rectangle appear first, then the rest of the page appears. Is that not what you see?

This bug should probably live in Core somewhere btw.

Comment 2

[Chris Lord [:cwiiis]]

Whether the bug manifests I think depends on if the page takes more than one draw to fully render - I was seeing it consistently on that page, but it probably depends on connection, page, device, etc.

If it's the same cause as the similar bug we had on Android, it's the browser's responsibility to set the display-port at the right time (and there are already hooks in Core to allow this).

Comment 3

[Ben Francis [:benfrancis]]

(In reply to Chris Lord [:cwiiis] from comment #2) 
> If it's the same cause as the similar bug we had on Android, it's the
> browser's responsibility to set the display-port at the right time (and
> there are already hooks in Core to allow this).

What do you mean by set the display port at the right time? How would you do this via the Browser API?

Comment 4

[Chris Lord [:cwiiis]]

(In reply to Ben Francis [:benfrancis] from comment #3)
> (In reply to Chris Lord [:cwiiis] from comment #2) 
> > If it's the same cause as the similar bug we had on Android, it's the
> > browser's responsibility to set the display-port at the right time (and
> > there are already hooks in Core to allow this).
> 
> What do you mean by set the display port at the right time? How would you do
> this via the Browser API?

I don't know about the browser api, but the way a larger area than the screen is rendered is by setting a 'display port' which is description of the area you want to be rendered (and isn't dependent on viewport size). If you don't set the display-port, Gecko will render the size of the scroll frame, and if you're zoomed out, you'll end up seeing what you see here.

When I say 'browser', I guess in this situation, I mean the code that implements the browser api.

Comment 5

[Ben Francis [:benfrancis]]

Moving to Graphics for further diagnosis, I'm seeing this fairly regularly.

Comment 6

[Gregory Pappas [:gregp]]

Closing old B2G bugs