[Qtwebengine] QtWebEngine on embedded linux (broadcom mips with OpenES 2.0) displays black rectangles

Mon Oct 20 11:47:03 CEST 2014

Hello Pawel,

On Fri, Oct 17, 2014 at 09:38:50AM +0200, pszlendak at dcclabs.tv wrote:
> Hi Guys,
> 
> First of all, great work of integrating chromium into Qt. This is huge and we are looking forward to using it on our platform.
> As far as using is concerned... we have just compiled the most recent Qt 5.4 sources (including QtWebEngine) and sadly it does not work out-of-the-box.
> 
> The websites render with black rectangles in place of images/divs. For example the following HTML:
> <html>
>      <head></head>
>      <body style="background-color: blue;">
>          <div style="background-color: green; width: 10px; height: 100px"></div>
>      </body>
> </html>
> 
> renders with blue background body (this is ok) and black rectangle in place of the div (not ok). This happens on all the websites.
> 
> Any tips on the possible cause of this behavior? Or where we can start debugging?
> 
> Our QPA backend is EGLFS with OpenES 2.0.

Since the div is probably not a compositing layer, this might have more
to do with Skia than with Qt or OpenGL.

We haven't tried very hard to get QtWebEngine or Chromium running on MIPS
yet, if this is related to Skia you might have to dig a bit to find the cause.

Personally I would start digging around ResourceProvider::TransferResource
since this is where the texture ID is handed out to Qt through a mailbox,
but the problem is probably very far from there. A RasterWorkerPool
seems to be the one doing the previous step, and I assume that you could
dump the produced tile pixels to a png on disk to see if already at this
point your div is produced with the wrong color.

It seems like they already ship the Chrome WebView on MIPS for Android, it
might be worth looking at the configuration that they use there and try to
match it as much as possible too.

Cheers,
Jocelyn