[Webkit-unassigned] [Bug 28045] New: Unable to correctly paint the page if widget is not displayed

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Thu Aug 6 05:26:32 PDT 2009


           Summary: Unable to correctly paint the page if widget is not
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: WebKit Gtk
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: luka.napotnik at gmail.com


I have two WebKit sourcetrees. One that shows a simple Gtk+ window and
displays the page. Besides that the page gets painted onto a cairo
source which I save to a PNG image. The image correctly shows the

The other source tree is the same as the first but now I don't show
the Gtk+ window. Again I paint the page to a cairo surface and save it
to a PNG image. But the problem is that the page now doesn't have
layout nor any styles even when I called layoutIfNeeded() just before
paint(). I paint the page using:

 if (m_frame->contentRenderer()) {
     m_frame->view()->paint(&ctx, pageRect);

The output only shows unstyled text and even javascript sources. I
think there' s some condition that if the view is not visible then
some methods are not called. I browsed the loader/ sources a bit but
don't have a clue what could it be. Any ideas?

Here's a detailed description of my work:

I've been working on an offscreen hack for webkit for a while now.
While I managed to paint the pages on a cairo surface using the clutter
offscreen functions in WebKit rev. 38000, the code is now old and I
would like to migrate to the latest revisions.

The problem is that my patches don't work anymore.

My current patch works like this: the WebCore functions
RenderView::layout() and FrameView::layoutTimerFired() emit an
"update-request" event to the Gtk+ WebKitWebView widget which I added
and then forces the whole render tree to layout and calls
paintContents() to get the page on the cairo surface. This worked well
but still got some unnecessary "update-request" calls.

But with the latest code I suspect some methods are not called and I
get an unformatted (no style, no layout) image on the cairo surface. And
this is useless because the pages aren't rendered correctly.

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