Making an arrow that points toward target

Unity Engine
,
1

I’m trying to make a runtime tooltip, and I need to have an arrow UI element that points toward parent object. Something like this:

It needs to be dynamic because tooltip can be located at the edge of the screen and have to be clamped to bounds, making static pointer look wrong.

Issue is… I can calculate the position, but I can’t find a place where I update the position.

  1. If I update VisualElement’s position using 60 FPS schedule timer - it does update, but it’s always 1 frame behind and looks quite weird
  2. If I try to update on GeometryChangedEvent - it stops updating alltogether for some reason. It won’t move even if I start a schedule from the event.
  3. I also tried to draw this part with generateVisualContent, but it’s not redrawn when tooltip moves or resizes. How do I even make it trigger update whenever parent or target changes then?
2

You need to mark the visual dirty for a repaint as required: https://docs.unity3d.com/ScriptReference/UIElements.VisualElement.MarkDirtyRepaint.html , which will call generateVisualContent again. Currently I just do it every frame in a current project that draws borders around interactable objects.

3

Well, yes. Calling it does update it, but I’m not sure from where to call it. A 60 fps schedule? I feel like it may still have a delay. If only I could catch GeometryChangeEvent for the whole hierarchy instead of only current object…

4

In my situation I had a monobehaviour managing this high-lighting system, so I just repaint it every frame in Update(). I haven’t noticed any delay; it seems to remain spot on.

5

Using Mono is a bit tricky because those objects keep getting created and destroyed internally. It may be not very pretty to track their creation/destruction so I can call their MarkDirty method. Maybe I should make a manipulator that will try to subscribe to all parent objects’ GeometryChangedEvents - this should do it… probably…

6

You could use the visual element’s scheduler: Unity - Scripting API: IVisualElementScheduler

7

Tried using
schedule.Execute(MarkDirtyRepaint).Every(1)
It kinda works, but it seems to be a tiny bit behind the transition animation. And performance will be not super good with the amount of repaints it does.
Ugh… I guess I’ll try looking into GeometryChange event some more.

8

After messing with it some more, it seems like using schedule can’t be avoided? At least there are no events that are called on each tick.
Here, I tried making a manipulator that calls a method when anything down the hierarchy changes. Should be more effective than calling update every tick. Though, it’s not tested very well yet.

9930972–1437087–HierarchyChangedManipulator.cs (3.96 KB)