[Webkit-unassigned] [Bug 33520] Mapping from local to container coord space is O(N^2)

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=33520





--- Comment #14 from James Robinson <jamesr at chromium.org>  2010-02-01 18:35:32 PST ---
Yes, I've seen comments to that effect of doing all coordinate transforms via
RenderObjects throughout the code.  Is there a bug or a set of patches tracking
that code?  I think it would simplify things.

convertToLayerCoords() seems to be a slow spot in cases where the code is doing
a recursive walk from some 'root' through children.  What's needed for these is
a mechanism like LayoutState that maintained both:

- some 'root' for the current walk
- a transform from the current local coordinate space to that of the 'root'

I don't think there are many spots in the codebase that call
convertToLayerCoords() with different ancestorLayers willy-nilly, this seems to
be only done when recursing a subtree using a different 'root'.  If there are,
they will show up as hotspots pretty quickly.

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