Strange values of contentY property of ListView

FOXLISIN

Hi to all! I have noticed a strange behaviour of contentY property of ListView.

And i watch for contentY property like this:

onContentYChanged: {
    console.log( "---> " + contentY )
}

1: i have a list with C++ model with 15 elements
http://s33.postimg.org/8tcx86xbz/image.png

contentY at the top of list view is 0 (as expected)

2: scroll this list view to bottom
http://s33.postimg.org/f5x62oj7j/image.png

contentY at this position is 220 (as expected)

3: click "prepend" button (i prepend 8 items to model) and scroll to top:
http://s33.postimg.org/c47avh3y7/image.png

And now contentY at the top of ListView is -400! But it should be 0?

Is it qml bug or my misunderstanding?

Hi @FOXLISIN!

Is it qml bug or my misunderstanding?

It's the latter. To cite the docs (Flickable QML Type):

originX : real

These properties hold the origin of the content. This value always refers to the top-left position of the content regardless of layout direction.
This is usually (0,0), however ListView and GridView may have an arbitrary origin due to delegate size variation, or item insertion/removal outside the visible region.

So you need to include originX, originY, contentHeight and contentWidth in your calculations.

FOXLISIN

@Wieland Thank you friend! It really helped me!