Opening Dropdowns hang the UI when in a Screen Space - Camera Canvas

When in a canvas with a render mode of Screen Space - Camera, opening dropdowns will hang / block the entire UI.

Bug Report Filed: (Case 893585) Opening Dropdowns hang the UI when in a Screen Space - Camera Canvas

If you want to try it out, there's a description and an attached package

a. Open the DropDownTestScene
b. Inspect that the canvas is set to render mode Screen Space - Camera
c. Play the scene and open both dropdowns, one of them will always drop an empty list and will hang the UI until you stop play
d. Stop play, edit the canvas to render mode Screen Space - Overlay and play the scene again, you will see that the issue no longer exists and you can open both dropdowns with no issue and see fully populated lists
e. Stop play, edit the canvas back to Screen Space - Camera to see that the isssue comes back again.

3. Related Notes
a. This issue started with 5.6 b2, meaning 5.6 b1 and 5.5 and below all worked properly.
b. I have a hunch that it is related to ScrollRect which is created by unity code when the drop down opens. But I cannot see the source for the dropdown code. I have already filed a ScrollRect bug for a world space canvas and think it might be related. Here is some info on that bug
(Case 893559) ScrollRect putting NaN on Content transform in 5.6
https://forum.unity3d.com/threads/s...ransform-in-small-scaled-world-canvas.462190/

 

Hi Rational-MA, did you manage to fix the Dropdown issue?

Thanks

 

There's no fix for the scenaro. They accepted this bug as well. Help increase the votes!

https://issuetracker.unity3d.com/is...freezes-game-view-when-using-fixed-resolution