311936 - Clipping causing serious performance problems

Status: RESOLVED FIXED

(Core :: SVG, defect)

Description

[tor]

If the clip path is larger than the target surface, cairo ends up creating a
clip surface big enough to contain the clip trapezoids.  When the pan&zoom apis
are being used, this can cause very serious performance problems.

Comment 1

[tor]

Attachment: bound clip surface to target surface

Comment 2

[Jonathan Watt [:jwatt]]

marking critical and adding hang keyword

Comment 3

[Carl Worth]

I've reviewed this patch, and it seems an obviously correct performance fix.

I've tested it with cairo's test suite as well as with a cairo-using svg2png on
the W3C SVG suite, and in both cases found no differences in the output result.
The patch can only affect performance in a positive way, and can do so
dramatically, as you have noted.

Will you please commit this (with an appropriate ChangeLog entry) to both cairo
HEAD and cairo BRANCH_1_0.

Thanks,

-Carl

Comment 4

[tor]

Comment on attachment 199086 [details] [diff] [review]
bound clip surface to target surface

Setting review flag based on comment 3 by Carl Worth (cairo author), as he
doesn't have permission to change the flags.

Checked into cairo cvs trunk and branch.

Requesting 1.8rc1 approval as this is a denial of service problem
that content developers can stumble into accidentally.	Cartography
is an example of a userbase whose document structures are prone to
experience this.  Patch has been reviewed by the author of cairo,
and is merged upstream.  Risk is very small.

Comment 5

[tor]

Checked in on branch.