Questions about ImGuiIO::DeltaTime ?

[tomazos]

Couple of quick imgui questions if you have time...

The first code comment on ImGuiIOs Configuration section says fill once. Is it not ok to modify the configuration between each frame? (example_null, at least, seems to set DisplaySize and DeltaTime prior to each NewFrame / Render. ?)

The code comment on ImGuiIO::DeltaTime states:

Time elapsed since last frame, in seconds.

Our engine has a mailbox mode where frames are continuously rendered and the most recent render is presented at vsync-time. In this mode, should I set DeltaTime to the time elapsed since last render or since last present? (ie What is DeltaTime used for?)

What should DeltaTime be set to for the first frame, since there is no last frame? Is zero okay? or is that going to break things?

Thanks

[ocornut]

That “fill once” comment is incorrect and will be changed now. All backends are submitting real wall clock time every time, its ok if it changes. DeltaTime=0.0 is accepted on the first frame to faciliate this. On subsequent frames it generally leads to an assert as it is considered a user mistake.

[tomazos]

Sure, thanks.