Constant editor stutter / freezes when moving over UI elements

Development Pipeline & Plugins
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1

I’m having constant editor stutters when I move the mouse cursor over most editor UI elements.

This is especially the case for Blueprint nodes, the top bar and items in drop down menus.

This makes the editor barely usable.

  • The issue doesn’t happen at my work PC, only at my home PC
  • I have a Radeon RX 7900 XTX with the newest driver
  • I re-installed the driver
  • This issue started to happen (again) a few weeks ago: At one time in the past I had the exact same issue. I can’t remember what caused it or how I fixed it
  • I have a HDR monitor, but had to disable HDR because of Unreal Engine: The entire monitor would just flicker randomly from time to time. Having it enabled doesn’t change anything
  • The DPI options in the editor settings also don’t change anything
  • The issue doesn’t happen in UE 5.4.2
2

Hi,

Does this still occur if you disable tooltips? You can test this via Slate.EnableTooltips 0 to see if tooltip generation is a problem (it’s a separate SWindow, so maybe that’s a factor).

Either way, I think an Insights trace would be a good first step to see what might be causing the hitch. Are you able to grab a trace of an editor session and point out some spots where the hitching occurs?

Best,

Cody

3

Were you able to check if it reproduces with tooltips disabled? I’d also recommend disabling any variable refresh rate features you have on, since that could be a factor here.

Looking at the trace again, it’s slow in pretty much every part of the Slate tick, but the info here is pretty limited so it’s tough to say for sure. You could also disable “Use Less CPU when in Background” in your editor settings, it shouldn’t impact anything while the editor has focus but it’s worth ruling out in case something is going wrong with the editor throttling.

4

Hej,

I’m going to test the tooltips on Monday.

There is a trace log attached to my first post: “UE4_27”. I should have named it better.

5

Ah sorry, I totally missed that! If we’re looking at the big blob of expensive frames starting around 1900, I see some slowdown on QueryCursor. We had some issues in the past with mice that had extremely high polling rates, any chance that applies here? Basically, message processing is tied to the game thread, so we’d get a massive number of mouse events within one frame and would have to process all of them before moving on. We’ve fixed this in newer engine versions, but it’s likely still an issue in 4.27. You could test that out by trying a different mouse, if that’s the issue here then I could send along a CL to cherrypick, though I’m not sure how risky it will be to integrate.

Best,

Cody

6

Hej,

I have a Logitech Pro Wireless and was running it at polling rate 1000 Hz.

At work I have a different mouse, but it has the same polling rate. There I don’t have this issue.