[Webkit-unassigned] [Bug 117192] New: SVG nested use/symbol manipulaion is extremely slow

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=117192

           Summary: SVG nested use/symbol manipulaion is extremely slow
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: SVG
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: david at protonic.nl
                CC: zimmermann at kde.org


Created an attachment (id=203686)
 --> (https://bugs.webkit.org/attachment.cgi?id=203686&action=review)
SVG nested use/symbol benchmark test

When manipulating the SVG DOM in JavaScript of a SVG that uses nested use/symbol tags (up to 2 or 3 levels deep) execution gets extremely slow.
On chromium/chrome or rekonq executing the attached file takes at least 13 seconds or much more (depending on browser/version), while firefox does the same in 54 milliseconds on the same machine!!
Opening the attached file (svgbench.html) in different browsers produces the following results (total run time):

Firefox 21 (reference):     0.054 s
Chrome 14 (webkit 535.1):  13.650 s
Chrome 21 (webkit 537.1):  23.240 s
Chrome 27 (webkit 537.36): 26.250 s
Chrome 29 (webkit 537.36): 28.380 s
Rekonq 2.2.1 (KDE 4.10.2): 45.768 s

All the above tests where run on 32bit Ubuntu 13.04 on an Intel core-i7 class PC.
As can be seen, the performance differences with firefox are astronomical to say the least, and they are getting worse with every new version of webkit.

svgbench.html contains some JavaScript functions that are executed in a sequence, while logging the running time at the start and the end of each function in a <pre> tag below.

part0() creates 200 <symbol> tags with a <text> tag inside and appends them to the <defs> tag of the SVG.
part1() modifies the text content of each text tag.
part2() adds 200 more <symbol> tags, that each contain a <use> href to one of the previous <symbol> tags.
part3() again modifies the 200 <text> tags
part4() adds 200 <use> tags to the "mainsym" <symbol> href pointing to the symbols created in step 3. This makes all of the <text> tags become visible.
part5() again modifies the 200 <text> tags.

The first 4 functions execute very quickly all of the time. It's part4() and part5() that take huge amounts of time on webkit-based browsers.

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