On Wed, Sep 24, 2008 at 7:22 PM, Maciej Stachowiak <[EMAIL PROTECTED]> wrote: > Do you guys have cross-process rendering working on Mac yet, even as a > prototype? I am wondering if these statements about what is required to do > it have been tested or are just assumptions.
We have working proofs of concept for both rendering into a RAM bitmap and blitting that into a view within a single process and cross-process rendering using a shared memory CGBitmapContext. We also have validation of this approach from some other projects inside and outside of Google that have similarly high performance demands, so we're pretty confident that it's a workable approach, at least for now. > I ask because I suspect doing cross-process rendering efficiently on Mac is > nontrivial and I would be concerned that changes could be made that go in > the wrong direction, if there isn't a proof of concept done first. Cross-process rendering itself is a given--the only questions are details of the mechanism we use to get the bits onto the screen. There are several possible underlying mechanisms we could use with varying degrees of fragility. However, that seems orthogonal to the type of changes we're talking about here--all cross-process rendering approaches rely on an application that hosts views that are rendered in a different address space, and thus require some kind of proxy or delegate to do things that are done with direct method and function calls in WebKit. You can see some of this in the Chromium code base already, in classes like WebViewHost and RenderViewHost--those particular examples are outside of WebKit, of course, but since there's currently no well-defined abstraction layer between WebCore and WebKit, our choices appear to be to either add some feature flags to the current Mac rendering code or to do what we ended up doing for Windows, which is to duplicate its functionality--it just seems a shame to end up with two sets of CG + Cocoa rendering code. So, to boil it down a little further, a large part of the question becomes whether it's preferable to add build-time flexibility to save on code duplication, or to duplicate code to avoid complicating any single platform. There's no a priori right answer to that, of course. For Windows, since we didn't have the luxury of having a port of CG available, duplication was the clear way to go. On the Mac, it's less clear. Our first inclination is to alter some of the assumptions with build-time options, since there actually aren't too many places where it turns out we'd need to do that. Sorry for the long essay :-). --Amanda _______________________________________________ webkit-dev mailing list [email protected] http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
