620941 - Canvas strokeText() becomes extremely slow with large lineWidth values

Status: RESOLVED WONTFIX

(Core :: Graphics, defect)

Description

[Jordan Osete]

User-Agent:       Mozilla/5.0 (X11; Linux i686; rv:2.0b7) Gecko/20100101 Firefox/4.0b7
Build Identifier: Mozilla/5.0 (X11; Linux i686; rv:2.0b7) Gecko/20100101 Firefox/4.0b7

When using large values for lineWidth, strokeText() becomes exponentially slow. See testcase for details.
This is useful when you want to add outlines to a text, for example.

Reproducible: Always

Comment 1

[Boris Zbarsky [:bzbarsky]]

Worsforme on Mac, so sounds like more path tesselator crap, right?

Comment 2

[Kevin Brosnan]

How slow are you talking about? On Fedora I get.
Spread radius: 1, time: 0.035 sec
Spread radius: 10, time: 0.041 sec
Spread radius: 30, time: 0.116 sec
Spread radius: 100, time: 0.658 sec

Comment 3

[Boris Zbarsky [:bzbarsky]]

Right.  And spending .7 seconds rendering three words is not really acceptable, right?  That's way out in "user-visible lag" territory.  Plus your numbers exactly show the nonlinear growth.

For comparison, on Mac where we don't use the cairo tesselator for this stuff, I get numbers like:

Spread radius: 1, time: 0.001 sec
Spread radius: 10, time: 0.008 sec
Spread radius: 30, time: 0.011 sec
Spread radius: 100, time: 0.033 sec

Comment 4

[Boris Zbarsky [:bzbarsky]]

Attachment: Testcase without the jquery gunk

Comment 5

[Joe Drew (not getting mail)]

It seems very unlikely that we're going to invest time in fixing this in Cairo; it will likely be fixed by switching to Skia or some other backend as part of the Azure project.

FWIW, this is plenty fast when using a D2D backend, even when using Cairo.