[Webkit-unassigned] [Bug 29156] New: [Qt] Fix scrolling implementation on QWebGraphicsItem

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=29156

           Summary: [Qt] Fix scrolling implementation on QWebGraphicsItem
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: All
            Status: NEW
          Keywords: Qt
          Severity: Normal
          Priority: P2
         Component: WebKit Qt
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: tonikitoo at gmail.com
                CC: hausmann at webkit.org, ariya.hidayat at trolltech.com,
                    kenneth.christiansen at openbossa.org


from comment https://bugs.webkit.org/show_bug.cgi?id=28862#c22 ariya said:

<quoted>

> +void QWebGraphicsItemPrivate::_q_doScroll(int dx, int dy, const QRect& rectToScroll)
> +{
> +    q->scroll(qreal(dx), qreal(dy), QRectF(rectToScroll));
> +}

I found out that this does not really work if I subclass QWebGraphicsItem.
An example: I have my customized QWebGraphicsItem that clips the painting so
that the corners are rounded. When this function is invoked, say scrolling
vertically, the whole painted item is scrolled, meaning the bottom rounded
corners are also scrolled. The correct thing of course that the _contents_ of
the web page is scrolled, not merely the item.
The real fix would be to call update, instead of scroll. I understand that this
is optimization issue, but I'd rather have a correctly painted item than a fast
but garbage one.

</quoted>


and kenneth's:

<quote>
According to Alexis, you are supposed to reimplement

QPainterPath QGraphicsItem::shape () const   [virtual]

to not return a rectangular shape anymore, but the shape of the item with
clipping. This is also used for events (the clipped area should be able to
receive events), collision detection, and the QGraphicsScene::items() function.

If thsi doesn't work, it can be considered a graphics view bug, I suspect.
</quote>

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