Event when a widget is "in view"?

Development Programming & Scripting C++
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1

I am looking for a delegate to process when a UWidget “enters the view” and leaves it, example:

  1. When it becomes visible.
  2. When it enters visible screen space by widget position or by scrolling to it.
  3. On Construct, when step 1. and 2. apply.

I have been scanning the widget code, slate and the viewport but I just can’t find it. I want this for a performance optimizer I am writing. Optimally the UWidget itself must bind to such delegate to process itself.

The challenge here is that:

  1. Only the UUserWidget implements a delegate for change in visibility, but it isn’t executed when added / removed / or in / out of view by geometry.
  2. Construct / WidgetRebuilt executes for the entire widget tree at once, not when the widgets actually become visible by some form of navigation.

This leaves me with hundreds of widgets I could technically optimize away at any given time.

2

Bump

3

do you trying OnVisibilityChanged

4

Yes thanks for the suggestion. This event only executes on the UserWidget when you set its visibility variable. It does not reflect the actual visibility on the screen.

5

There is no such event for this, widgets will not tick unless painted, but that’s up to the parent to decide whether to paint or not.

1 Like
6

This sounds right, I’ll have to research if I can use the Paint method on the UWidget or a parent to implement something similar then

7

Yikes, OnPaint runs like tick even when a widget has been added but not rendered yet.

8

Since this “tick” is running anyhow, it seems I can write a custom implementation on OnPaint.

9

No idea if this gonna help, but I had similar issue (using pure C++) and my widget class inherited from UUserWidget. There is a method called NativeConstruct it you are navigating by CreateWidget<…> it can be overrided . Or use OnNativeVisibilityChanged event when you are dealing with visibility variable.

10

Construct runs when a widget is added or removed from a parent or viewport. OnVisibilityChanged does not reflect the actual state of the widget being visible. It might be visible but inside a list that is scrolled down to the bottom, making it invisible to the user. It might be translated off screen etc,.