Add Rust UI and layouts

[jpochyla]

PoC

[mmilata]

This is shaping up nicely!

I'm wondering how we can use different component (and layout) directories when compiling for T1 and for TT. Can we just wrap two versions of module in e.g. #[cfg(feature = "model_1")] or does this need to be handled by build.rs?

I'm a bit tempted to start implementing the T1 components since we don't have all of them in python yet. Then we could do it like this?

• implement T1 components in rust, keep TT components in python, both layouts in python
• swap TT components for rust versions
• eventually rewrite layout functions to rust

We'll probably still need a python layer of layouts to handle ButtonRequests/other async stuff.

Is there anything missing that would be needed to implement e.g. confirm_action layout using the rust ui?

[jpochyla]

This is shaping up nicely!

<3

I'm wondering how we can use different component (and layout) directories when compiling for T1 and for TT. Can we just wrap two versions of module in e.g. #[cfg(feature = "model_1")] or does this need to be handled by build.rs?

It doesn't need any changes in the build script. In case you want to export same (or very compatible) interface, but use different impl under each feature (or a platform), see here for an example, it's a rather common Rust pattern. If you just want to conditionally include a module, under it's usual path, #[cfg(feature = "model_1")] is enough.

I'm a bit tempted to start implementing the T1 components since we don't have all of them in python yet. Then we could do it like this?

* implement T1 components in rust, keep TT components in python, both layouts in python

* swap TT components for rust versions

* eventually rewrite layout functions to rust

We'll probably still need a python layer of layouts to handle ButtonRequests/other async stuff.

Is there anything missing that would be needed to implement e.g. confirm_action layout using the rust ui?

I don't think anything substantial is missing. Although I haven't done any work re. T1 components, they should be much simpler than the TT counterparts, so we can try.

[mmilata]

Looking good, I appreciate moving the components under model_tt, gonna make the T1 work easier. The diff is large but there are lots of formatting/import changes. I haven't done super in-depth review of the TT components since our customers currently won't see them, though the code generally looks good.

From my point of view two things are missing, which I can add if @jpochyla is working on something else:

• additional feature flag (ui?) that would allow us not to build the ui module for production builds, but still allow us to use the code in CI, for T1, and for TT experiments,
• adding support for LayoutObj to matejcik's memory analyzer so that layouts are not reported as unused memory.

Also not sure about the fuzz crate, if I understand correctly it's not used in normal builds so we can keep it in this PR even though it's not really related?

[mmilata]

I've implemented the changes suggested above. They are probably not straightforward enough so I won't push them directly, feel free to cherry pick them if they make sense:

• 062e921 adds ui feature flag that is only enabled on T1 or when NEW_UI=1 variable is set when invoking SCons
• 65657b7 extends the memory analyzer to recognize rust layouts, this is very basic since it reports no children (e.g. pointers to strings held in embedded struct Buffers)

[matejcik]

looks mostly good.

we will probably want to squash all of this except maybe rustfmt/clippy changes, if it will be easy to separate them out.