slint/docs/development.md

Slint development guide

The build instructions are in the building.md file. The testing instructions are in the testing.md file.

Repository structures

helper_crates

A set of crates that are somehow not strictly related to Slint, and that could be moved to their own repository and have their own version release at some point.

internal

internal contains code that isn't meant to be used directly by a user of Slint.

compiler

The main library for the compiler for .slint.

Nothing in there should depend on the runtime crates.

There is a test subdirectory that contains the syntax tests. These tests allow you to test the proper error conditions.

Runtime libraries

The library crates that are used at runtime.

• core is the main library. It's meant to be used for all front-ends. Ideally it should be kept as small as possible. corelib-macros contains some procedural macro used by core library.
• backends contains the different backend for the different platform, separated from core library. Currently there is just the gl backend
• interpreter is the library used by the more dynamic languages backend to compile and interpret .slint files. It links both against core library and the compiler lib

tools

• compiler is the tool to generate the target language (e.g. c++) from the .slint files for frontend that have a compilation step and generated code.
• viewer is a tool that allow to open and view a .slint file.

api

Here one can find the frontends for different languages.

tests

The integration test that are testing a bunch of .slint with different front-ends

See testing.md

examples

Some manual tests

Documentation

There are some documentations comments in the code. HTML documentation can be generated with something like

cargo doc --document-private-items --no-deps --open

Rust to C++ bindings

We use a rather complex mechanism to expose internal data structures implemented in Rust to C++, in a way that allows us to provide a nice C++ API.

As a starting point, we recommend reading the blog entry we published about this:

https://slint.dev/blog/expose-rust-library-to-other-languages.html

What this article omits are how we invoke cbindgen and what kind of tweaks we apply on various levels:

The C++ library consists of four components:

1. The slint-cpp cdylib created by cargo/rustc from api/cpp.
2. The public header files in api/cpp/include.
3. Internal header files generated by cbindgen, via cargo xtask cbindgen.
4. The CMake project to tie it all together by invoking corrosion to call cargo and invoking cbindgen.

cbindgen

The cbindgen xtask generates multiple header files for four different modules:

1. The types in the core library. This is the bulk of the generated code.
2. The entry points into the C++ library for creating backends, invoking the event loop, etc. - from api/cpp/lib.rs.
3. The types specific to the Qt backend used by the Qt style, such as NativeButton, etc.
4. The types used by the C++ interpreter API, written to slint_interpreter_internal.h.

Typically the input to cbindgen is within ffi sub-modules in the corresponding input crates to cbindgen. These ffi modules are gated with #[cfg(feature = "ffi")].