[webkit-dev] Point within WebKit API to extract Bitmaps

[Konstantin Tokarev]

09.09.2016, 17:46, "Mark Gilbert" <webkit at gallery.co.uk>:
> Hi Folks
>
> We have code which extracts RGB+A bitmaps from WebKit pages in real time. Currently we do this via an OSX WebKit View in a window and by requesting the bitmap through the OSX View mechanism (not directly from WebKit). It works well and we get clean RGB+A in real time from the WebKit structure (usually..)
>
> However, we are finding that this approach does not always give us the *performance* that we need, particularly where we have things like deep opacity changes (eg fading things on and off). We have to disable some of the 3d acceleration stuff in the WebKit view to ensure we continue to see changes on the CPU side (otherwise the change happens on the GPU and we only see the completed transition at the CPU side)
>
> I have seen other systems which are more deeply knitted into the guts of WebKit which have better performance and I wondered if any WebKit experts here could tell me where in the API of webkit I should look to pull out bitmaps repeatedly (eg 25 FPS)
>
> I am reasonably familiar with the overall components of WebKit, but the render layer / context arrangement is fairly complicated to unpick, I understand that QT has a call something like:
> QWebElement::render(QPainter*, QRect const&) (in QtWebKit)
>
> and this may be doing approximately what I want, but I dont want to use QT

For what reason?

>, so I need to understand which WebKit calls this QWebElement::render is digging into.

Basically, it calls FrameView::paintContents(), for more details look at the code of QWebElement::render():

https://github.com/annulen/webkit/blob/qtwebkit-stable/Source/WebKit/qt/Api/qwebelement.cpp#L1467

>
> Any ideas ?
>
> Thanks
>
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-- 
Regards,
Konstantin