[webkit-qt] Proposal for switching image decoders from Qt to WebCore

Dawit A adawit at kde.org
Fri Feb 10 08:54:11 PST 2012

On Fri, Feb 10, 2012 at 5:21 AM, Simon Hausmann
<simon.hausmann at nokia.com> wrote:
> Hi,
> I'd like to propose that we switch over to using the WebCore image decoders.
> Zoltan has spent some time comparing performance and memory usage between the
> ImageDecoderQt (and the qt plugins for image decoding) and the WebCore image
> decoders, in https://bugs.webkit.org/show_bug.cgi?id=71555
> My interpretation of the result is that performance and memory usage wise
> there's not much of a difference. However the WebCore image decoders have some
> advantages that are of a different nature:
>    1) They are an actively maintained piece of code. Unfortunately the Qt
> image decoder plugins are subject to less tender loving care. The WebCore
> decoders are used by pretty much all other ports, and from my totally biased
> point of view we have also found them working great for the N9 with the Qt
> based browser/webkit.
>    2) They support image downsampling, which is particularly nice for mobile
> devices with less memory than our gigabyte filled workstations.
>    3) The jpeg decoder supports progressive/interlaced jpegs, which is again
> an nice thing for image loading over slow connections.
> Therefore I'd like to re-open https://bugs.webkit.org/show_bug.cgi?id=32410 .
> Any opinions / objections / thoughts?

How about relying on the internal WebCore decoder for the formats it
supports and using Qt's image decoding facilities as a fall back ?
Otherwise, this is might negatively impact desktop environments. For
example, in KDE we have several qtimagedecoder plugins for formats not
supported by Qt out of the box. If you switch QtWebKit over to
WebCore's own image decoder, then the desktop browsers won't be able
to support image formats that are otherwise supported by other
application in the desktop environment.

As it stands, the changes in QtWebKit's WebKit2 API currently make it
impossible for KDE's wrapper classes to switch over to it. The last
thing I want to see is yet another item being added to that list.

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