Async texture loading

[nem0]

Hi, is there a way to make texture loading asynchronous? Right now RenderInterface::LoadTexture must load the texture before
the function returns, because it expects me to return dimensions. However I can't afford to synchronously load textures in the middle of frame, because that can cause stuttering.

[nem0]

I discussed this with some other programmers and what could work too is RmlUi telling us what textures are referenced in advance, so we preload them and don't even try to render ui before are textures all loaded.

[mikke89]

Yes, it's a good point. At least you don't want to load from disk in the middle of a frame. The way I do this is to load the GUI textures into memory during load-time. And then the textures are submitted to the GPU when requested by RmlUi during rendering. Seems to work fine for my use-cases.

For my case I have structured the documents and textures so it's quite easy to work out what is needed during which phases of the application. Could something like this work for you?

For more complex documents, or in general, I can see it being useful to know the textures in advance though. At what stage would you want to load the textures, just after loading the document?

[nem0]

Structuring documents and textures so it's easy to figure out what to load is possible, but it's not very user friendly in general case. The list getter would be much better option. Anything before render works, could be after first update.

[mikke89]

I agree it would be a nice option. Are you thinking of querying all textures that are visible, or all textures that are ever referenced? Globally or per-document?

[nem0]

All textures, not just visible would be probably better, since textures can become visible any time. Global is enough for me, but per-document can be useful too.

[mikke89]

Alright, it's helpful to know the requirements, thanks. I'll have a closer look at this at some point. It might be a bit tricky the way things are implemented right now, as each texture-using object decides when they want to load textures at their own merit, and there is no global way to get such a list until they do. Might have to do some restructuring.

[mikke89]

I made a stab at this, let me know how it works. It's only global, as adding per-document sources would require a lot more changes. I think I covered all the texture usages I could find, but let me know if there is anything that does not show up as it should.

[nem0]

Thanks, it seems to work.