Bring specifc item into view (VirtualScrollView)

[vivi-rad]

Hi,

I'm using the VirtualScrollView and have implemented the following behavior. I can select an item in a list. I can move the selection with arrow key up and arrow key down. What I want now is that the selected item is always visible when I move the selection. I have seen for custom scroll behavior I can use ScrollController. But I'm not sure how I can read the the y position of the selected item to check if is currently visible or not. Any ideas?

[marc2332]

But I'm not sure how I can read the the y position of the selected item to check if is currently visible or not.

You can calculate the y of an item by simply multiplying its index * <item_size> and then making it negative, example:

• item index is 58
• item size is 35
• item y is then: -(58 x 35) = -2610

if you scroll to the -2160 you should be able to see the item on top, for this you will need to use a scroll controller

hope it helps!

[vivi-rad]

Hi thank you the response.

The thing to get y of an item is clear, what is missing for me is to read the current y scroll offset. To calculate the current y value of an item if the content is scrolled.

[marc2332]

I just added a x and y getters to the scroll controller, that should let you easily get the current scroll position :D

[vivi-rad]

Awesome thank you :-)

[vivi-rad]

That was fast ;-)

By the way this is what I am working on.

It's an application launcher for Linux. It is already usable.

[marc2332]

That looks cool!

[vivi-rad]

Thank you :-)

[vivi-rad]

@marc2332 one other question. How to get the actual height of the VirtualScrollView I need it to check if item_y + item_height > scroll_view_height.

[marc2332]

mmm, I think something like -(<item-size> * <item-len>) should be it

[vivi-rad]

What I need is the visible height of the VirtualScrollView I need to check if I scroll if the item is partial of full outside of the visible area.

[vivi-rad]

@marc2332 maybe something like use_node for a child node?

[marc2332]

Ah yes, you can wrap the virtual scroll view inside a rect and use use_node in the rect, the virtual scroll view will expand to the rect size, so it should be fine