Hey Ion, A few things... - We didn't actually switch to floats for Layout, but with sub-pixel layout enabled, we use integers that represent 1/60th of a pixel instead of one (similar to Gecko). - The CSSOM defines those properties to be longs http://dev.w3.org/csswg/cssom-view/#extensions-to-the-htmlelement-interfaceso changing this would violate the spec and potentially lead to web-compat issues. - You can get floating-point-level precision values by using getClientBoundingRect(). - IE uses a flag that switches between ints and floats. I don't advocate this option (I think it adds complexity and doesn't solve a problem that can't be solved using getClientBoundingRect) but it at least avoids web compat issues. http://msdn.microsoft.com/en-us/library/ie/hh673543(v=vs.85).aspx
Hope that helps, -Levi On Mon, Jun 18, 2012 at 7:56 AM, Ion Rosca <[email protected]> wrote: > Hello,**** > > ** ** > > I have some questions regarding zooming and offsetWidth/Height/Top/Left*. > * > > Currently, Element.offset* properties return imprecise values when zooming > in/out. One of the bugs describing this problem would be Issue 104074: > offsetWidth of element is shrinking when zooming > in<http://code.google.com/p/chromium/issues/detail?id=104074>with a simple > test > case <http://jsfiddle.net/V4HQc/>. **** > > The product I’m working on also embeds WebKit and it would really need > more precision from Element.offset*. We’ve done some testing by making > offset*s to return floats and this approach appears to improve precision a > lot.**** > > ** ** > > I found in > archive<http://lists.webkit.org/pipermail/webkit-dev/2011-June.txt>an email > from > *Levi Weintraub <[email protected]>*, sent in June 2011, saying:**** > > *… Changing rendering (and hit testing) to use floats does not > necessarily mean* > > *that we need to expose floats through the dom api, however if we are to* > > *support sub-pixel layout (i.e. style=?left: 12.3px?) this would be > required.* > > *Specifically we?d need to change the offsetLeft/Top/Width/Height > properties* > > *to return floating point values > [2]<https://bugs.webkit.org/show_bug.cgi?id=54018> > .***** > > The meta bug 60318 <https://bugs.webkit.org/show_bug.cgi?id=60318> (*Switch > away from integers …)* Levi was working on is already fixed and the inner > bugs (addressing this problem) bug > 54018<https://bugs.webkit.org/show_bug.cgi?id=54018> > * (Make offset* return doubles instead of ints) *and* *bug > 39884<https://bugs.webkit.org/show_bug.cgi?id=39884> > * - Full Page Zoom: rounding errors with element metrics *are still > opened and theirs resolution is not clear.**** > > ** ** > > What’s your opinion on this subject? Were there some other discussions on > it I couldn’t find? Is there a chance for making offset properties > returning floats to be accepted? What are the implications of making this > change in terms of specifications?**** > > ** ** > > Thank you,**** > > Ion Rosca**** > > _______________________________________________ > webkit-dev mailing list > [email protected] > http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev > >
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