Hello Michael,
The scrolling performance is indeed hindered by creating new delegates as the path moves. This has been verified by using the Loader since there is a notable pause at the time when switching between heavy and light components (the switching logic is actually more complex than the example given). I'm not sure how much painting/rendering affects the performance, but if I use the heavy component, I would need to clip the bounding rectangle (which further decreases performance according to the documentation). I was hoping to take a snapshot once and then save to disk (at least for now). Ideally, I would have liked to generate the images on the fly, but I accept that this may prove to be more difficult. Thanks for your help. Regards, Jevon ________________________________ From: michael.bras...@nokia.com [mailto:michael.bras...@nokia.com] Sent: 18 November 2010 04:21 To: BECKLES Jevon RD-ILAB-LON Cc: qt-qml@trolltech.com Subject: Re: [Qt-qml] QML Component Snapshot / Cover-Flow (PathView)implementation suggestions Hi, Have you verified that the slowdown is primarily from painting (and not, for example, from instantiating new delegates as the path moves)? Were you hoping to generate the images on the fly, every time, or were you planning to e.g. take a snapshot once and then save to disk? There's no built-in QML-based way to take snapshots -- you'd need a custom C++ component to do something like this (it does seem to be a frequent request; has anyone else made a component for this already?). Regards, Michael On 18/11/2010, at 12:39 AM, ext jevon.beck...@orange-ftgroup.com wrote: Hello, I'm trying to make a Cover Flow using a PathView. Ideally, the delegate is a heavy/complex user-defined component (intended for user interaction) but this affects the scrolling performance (scrolling is not directly done by user interaction with PathView). Only the current-index delegate is available for user interaction at any given time. As a work around, I've replaced the delegate with a Loader to load the heavy component only when I'm not scrolling (see code snippet below). I want to take a snapshot of my complex component and save it as an image (or Pixmap or other light resource) to use for my light component. Is there an easy way to do this? If not, is there an easy way or another way to improve the performance of the PathView scrolling? PathView{ property variant dataModel: myModel property bool readyToScroll: false id: coverFlow width: 360 height: 540 pathItemCount: 3 preferredHighlightBegin: 0.5 preferredHighlightEnd: 0.5 interactive: false path: Path { id: myPath // path definition } model: dataModel delegate: Loader{ id: delLoader width: coverFlow.width height: coverFlow.height sourceComponent: (readyToScroll) ? lightComponent : heavyComponent } Component{ id: heavyComponent Rectangle { // heavy component definition } } Component{ id: lightComponent Image{ source: // snapshot image of heavy component } } } Regards, Jevon <ATT00001..txt>
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