Understanding QQuickItem

[Creaperdown]

Hey, I need to display a pixmap to qml via a QQuickItem and after reading the documentation, I am still not entirely sure how it works.

From what I get, the key methods are geometryChange and updatePaintNode. updatePaintNode seems to be called (only?) when QQuickItem::update is called and it is the function that does the actual updating of the visual item, is that correct?

Also, when exactly is geometryChange called? Does this simply happen every time when an QQuickObject's size, position, ... changes?

Is the QQuickItem::update method ever called from Qt itself, or am I responsible to do this, in react to geometryChange being called?

Thanks in advance.

[aran]

Why not use Image paired with QQuickImageProvider? That way you can quite easily pass any pixmap to QML and have it displayed there.

[Creaperdown]

@aran It is a pixmap that is generated from a book page that is supposed to be scrolled, zoomed, etc. so it needs the flexibility and the extra properties as well as implicit widths and more.

[aran]

@Creaperdown Do you have access to the full pixmap? You could load it on the qml side and implement the scrolling (e.g., Flickable) and zooming (scale property) there. If that's no applicable to your use case, then I don't know, I have no experience with using QQuickItem directly unfortunately...

[jeremy_k]

QQuickImageProvider is likely the easier route to follow.

Image inherits Item, which instantiates QQuickItem. I don't believe that any of the properties in QQuickItem are final.

[JoeCFD]

@Creaperdown are you mixing qwidget and qml?

[Creaperdown]

@JoeCFD No

[Creaperdown]

@jeremy_k I am following an example of how Okular (the document viewer) is doing it, and they are using QQuickItem to generate and display items as well.