[webkit-qt] progressive rendering in a QML browser

Andras Becsi abecsi at webkit.org
Mon Mar 25 04:14:18 PDT 2013


On 25 March 2013 11:28, Olivier Tilloy <olivier at tilloy.net> wrote:

> Hi all,
> I have been observing that the rendering of web pages in a QML browser
> seems to happen in one go at the very end of the loading process, as
> opposed to other webkit browsers (such as chromium).
> In my tests, I deleted the cache and I intentionally slowed down the
> network interface to better observe when rendering starts to happen.
> I’ve mostly experimented with http://nytimes.com, which is a rather heavy
> page. I’m running those tests on an x86 desktop machine, but the same
> results are observed on mobile hardware (armhf).
> With the QML MiniBrowser compiled from webkit trunk against QtWebKit 5.0,
> nothing is rendered until the page is fully loaded (i.e. the webview
> remains completely blank until the progress bar reaches completion).
Just quickly ran a test with MiniBrowser on my desktop and for me with a
clean cache even heavy pages like nytimes.com start to render when the
progress bar is at about 50% completion. Although this probably varies
depending on network and HW speed.

This is comparably similar behaviour as you would experience with Safari on

> With chromium (25.0.1364.160-0ubuntu0.12.10.**1), rendering is clearly
> progressive, with elements of the page being displayed before loading is
> complete (and of course, some re-layout happening).
With Chromium the perceived page load / rendering speed is much faster
because the browser uses a variety of speculative optimization techniques
to speed up page loading. Among others these are resource pre-fetching and
page pre-rendering, which are implemented in the browser [1] and depend on
mouse-hover and usage heuristics.

> Is this a known issue/feature? Are there some build options that I can
> experiment with to tweak this?

As far as I know we have only access to DNS-prefetching with WebKit2
QtWebKit, which is enabled by default.

> Thanks!
>  Olivier

[1] http://www.igvita.com/posa/high-performance-networking-in-google-chrome/
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