The current reworking of the TransformationMatrix class and friends
(https://bugs.webkit.org/show_bug.cgi?id=48031) got me thinking about the
future of this class. I've chit chatted about this with various people, but
nothing serious has been done yet.
As WebKit and "HTML5" get more 3D functionality (CSS Transforms now, WebGL
later) a 4x4 matrix class becomes more important. There has even been talk of
adding 3D transforms to SVG. Today, the workhorse 3D matrix class is
TransformationMatrix. This is used by SVGMatrix and CSSMatrix and internally in
several places. The above bug is making the functions in TransformationMatrix
more rational and that is a good first step. But we need to architect the most
efficient class hierarchy in this area as possible.
For instance, today you can use CSSMatrix in WebGL. But it has an inordinate
amount of overhead because the class is immutable. So every call that is made
must construct a new CSSMatrix. This not only adds call overhead, but in the GC
workload as well. I feel that making a mutable 4x4 matrix available is very
important. This could be done with a base Matrix class, available to
JavaScript, which would have mutable calls. Then SVGMatrix and CSSMatrix could
derive from this with their own APIs.
Internally, I think we should eventually restructure TransformationMatrix to
have mutable fast-path operations. Today, for instance, operator*= calls into
the operator* class, so there's always an extra matrix copy. That should be
changed and we should similarly have mutable versions of all the calls
(translate, rotate, etc.) on the fast path.
We should also restructure TransformationMatrix to allow for platform specific
versions of the calls. For instance, PLATFORM(CA) has access to CATransform3D,
which has accelerated versions of its API where possible. I'm sure QMatrix,
SkMatrix and others might also be able to be used for similar performance gains.
I've opened a couple of bugs for this:
https://bugs.webkit.org/show_bug.cgi?id=52488
https://bugs.webkit.org/show_bug.cgi?id=52490
Please feel free to comment here or there…
-----
~Chris
[email protected]
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