302294 - (longlines) [meta] Bugs in rendering of long text strings (e.g. thousands of characters)

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Jesse Ruderman]

There are many bugs that occur when Firefox tries to render a large amount of
text (e.g. thousands of characters). Common themes are severe slowdowns, system
freezes, overlapping text, and invisible text.  Some of these issues might
impact security -- overlapping or invisible text could lead to spoofing or at
least users having less information than they should, and system freezes are
considered a security issue even though they're really the fault of the
operating system.

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

There's a workaround for many of these in the Xft font code, but not other font
backends.  Probably we should just do something in nsTextFrame -- perhaps even
just creating a maximum text frame size (say, 512 characters, which is I think
what Xft uses) and using next-in-flow linkage for text frames within the same
line.  While it might be nice to want the Gfx API to be pure, it's probably a
lot easier to restrict it and require layout to put things in chunks.  We should
be careful not to separate grapheme clusters between chunks -- i.e., be careful
of both surrogates (representing characters outside of Unicode Plane 0) and
combining characters (which are a bit harder).

Comment 2

[Philip Withnall (unavailable)]

*** Bug 326229 has been marked as a duplicate of this bug. ***

Comment 3

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

I'm working on something along the lines of comment #1. But I don't want to change how textframes break, that's rather risky. Instead I'm defining some wrapper functions around the nsIRenderingContext functions that break the text up into chunks of limited size.

Comment 4

[Jesse Ruderman]

Bug 338251 has a patch that fixes most of these issues.

Comment 5

[Jesse Ruderman]

The patch in bug 338251 has been checked in.  Bug 237085 has a patch that fixes some more issues.

Comment 6

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

Someone want to retest these bugs on trunk? Most of them should be fixed now.

Comment 7

[Benoit Girard (:BenWa)]

I've been going through the tracked bug here and I can't reproduce any of these issues. Closing this tracking bug.