[Webkit-unassigned] [Bug 142238] Extremely low performance layer compositing with Google Maps API v3

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=142238

--- Comment #6 from Nick Dolezal <nick at safecast.org> ---
Re #5: Made a request but you may need to follow-up. (I'm just some random person on the internets)


Erratum to #3: All instances of "Chrome 8" should be "Safari 8".


Two more things to add if I may; I tested other major web map APIs, and finally managed to test Chrome properly without translateZ(0).


Scope: Other Map APIs

I briefly tested every other major tiled web map API I could think of offhand.  OpenLayers 1/2/3/Cs, Leaflet (MapBox), Bing Maps, and ArcGIS.  Either these issues didn't apply (OL; giant canvas element) or more commonly, an analog of translateZ(0) was already getting set for both Chrome and Safari (Leaflet, Bing Maps).

To be clear, the same core "layer smushing -> low tile FPS" issue is present.  But because the workarounds normally prevent that, Safari 8 was merely the first to get a the-real-dark-souls-starts-here experience for any length of time.

As the test below shows, Chrome also suffers when the useragent string stops matching.  Potential risk exists for both browsers.


Test: Chrome: No translateZ(0):

Chrome's layering performance was isolated from the effects of translateZ(0) with a useragent override extension[1] which was set to Firefox's UA string.


Results: Performance:

Significant decrease in performance, though not as much as Safari under the same conditions.  This was mostly a result of minimum framerate changes.

Holding down left mouse and rapidly spinning the map in small-radius circles with Chrome's UA set to Firefox measured 30 FPS consistently.  With Chrome's default UA it measured 55 FPS.


Conclusion:

This test provides further evidence both Chrome and Safari display suboptimal Gmaps API v3 tiled map performance without translateZ(0px), and that this has a more significant impact upon Safari than Chrome.

Chromium issue 356734 [2] states "we don't create big squashing layers on maps".  Unfortunately, internal layer squashing heuristics alone were unable to provide expected performance in this test.


[1]: https://chrome.google.com/webstore/detail/user-agent-switcher/ffhkkpnppgnfaobgihpdblnhmmbodake
[2]: https://code.google.com/p/chromium/issues/detail?id=356734

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