[webkit-qt] Pinch zoom for QWebView?

[Kenneth Rohde Christiansen]

A site can use javascript to scroll, like window.scrollBy() etc...
also the user can click on an anchor link <a href="#hest">.

Cheers
Kenneth

On Mon, Jan 10, 2011 at 5:51 PM, Harri Pasanen <grego at mpaja.com> wrote:
> Saturday, January 08, 2011 05:35 pm
> Kenneth Rohde Christiansen writes:
>> Let me repost as I was subscribed with another address:
>>
>> Hi there,
>>
>> To get the right result you will need to scale the contents and not
>> zoom it, as zooming is not the same as just applying a scale. Scaling
>> the QPainter would do. On the other hand, you cannot ensure a really
>> smooth pinch animation as you repaint the whole time without being
>> able to ensure how long that repaint will take. What you really should
>> do is to use the QGraphicsWebView as it supports a tiled backing
>> store. Then you can pinch the following way:
>>
>> 1) freeze the backing store
>> 2) apply a scale to the QGraphicsWebView (this will scale the frozen
>> tiles (pixmaps))
>> 3) unfreeze the backing store (it will now repaint and become crisp)
>>
>> It would be nice if you could add such support to our demo/test
>> browser QtTestBrowser found in our webkit repository.
>>
>> Just to make it clear, with the QGraphicsWebView you do not need to
>> change the QPainter directly. A QGraphicsWebView is a QGraphicsWidget
>> and it has a ::setScale() method, which you can use.
>>
>> I forgot to mention one more thing:
>>
>> 1) You need to enable resizesToContents if you are going to scale the
>> QGraphicsWebView, which means that you need to implement your own
>> panning as well. ie have a QGraphicsItem serve as a view to your
>> QGraphicsWebView. Every time, the viewport is (re)sized, or a
>> pinch/panning animation has ended, you will need to call
>> setActualVisibleContentsRect(). Do not do this during animations for
>> performance reasons.
>>
>> QtTestBrowser shows how to use resizesToContents with tiling etc, but
>> it still lacks the setActualVisibleContentsRect() code, which is
>> needed:
>>
>> 1) for not ending up in infinit tiling creation (it needs an initial
>> size; the (re)sizing)
>> 2) for programmatic scrolling to work, anchor links (it needs the new
>> visible rect after each pinch, panning ended)
>>
>
> I'm not quite sure what you mean with "for programmatic scrolling to work,
> anchor links"...
>
> What do you mean by "anchor links"
>
> Anyway, thanks for the advice.   If I have the time I'll delve into this a bit
> deeper, no promises yet...  If I get it to work I'm happy to contribute it to
> QtTestBrowser.
>
> Harri
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-- 
Kenneth Rohde Christiansen
Senior Engineer
Application and Service Frameworks, Nokia Danmark A/S
Phone  +45 4093 0598 / E-mail kenneth.christiansen at gmail.com

http://codeposts.blogspot.com ﹆﹆﹆