lv_bevy_ecs

Safe Rust bindings to the LVGL library using bevy_ecs.

What is an ECS?

ECS stands for Entity Component System. You can think of it as a database with rows (entities), columns (components) and jobs (systems).

You have to move LVGL objects into this database, so that they don't go out of scope and get deallocated. Bevy's Observers will mirror these database operations to LVGL's world.

Usage

It is highly recommended to read Chapter 14 of the Unofficial Bevy Cheat Book before using this library.

1. Create a project with cargo new or esp-generate, then

   cargo add lv_bevy_ecs
   

2. This package depends on lightvgl-sys to generate the raw unsafe bindings. It needs an environment variable called DEP_LV_CONFIG_PATH that specifies the path to the folder containing lv_conf.h file.

   It is recommended to put it into .cargo/config.toml

[env]
DEP_LV_CONFIG_PATH = { relative = true, value = "." }

3. You have to obtain a World instance with LvglWorld::new();. This is a global variable, it can be stored in lazy_static! or passed around in an Arc<Mutex<>> if needed elsewhere than in main().

lazy_static! {
    static ref WORLD: Mutex<World> = Mutex::new(LvglWorld::new());
}

5. Last thing is a Schedule instance with LvglSchedule::new(). Then call it in every loop cycle

let schedule = LvglSchedule::new();
// ...
loop {
    // ...
    schedule.run(&mut world);
    lv_timer_handler();
}

Check the respective module documentations and the examples for further usage.

Running the demo

sudo apt install libsdl2-dev

git clone git@github.com:SakiiCode/lv_bevy_ecs.git
cd lv_bevy_ecs
cargo run --example basic

Building for embedded

This package has been tested with ESP32 only.

You need three more env variables in config.toml and the PATH applied from ~/export-esp.sh

LIBCLANG_PATH="..."
CROSS_COMPILE="xtensa-esp32-elf"
BINDGEN_EXTRA_CLANG_ARGS="--sysroot ..."

LIBCLANG_PATH can be found in ~/export-esp.sh

BINDGEN_EXTRA_CLANG_ARGS sysroot can be found with xtensa-esp32-elf-ld --print-sysroot

LVGL Global Allocator

A global allocator for Rust leveraging the LVGL memory allocator is provided, but not enabled by default. Can be enabled by the feature lvgl-alloc. This will make all dynamic memory to be allocated by LVGL internal memory manager.

Partitions

It can happen that the project does not fit in the default main partition. To fix that you need to generate a partitions.csv with

cargo espflash partition-table -o partitions.csv --to-csv target/xtensa-esp32-espidf/release/partition-table.bin

and increase the factory partition size.

Then add this to espflash.toml:

[idf]
partition_table = "partitions.csv"

Upload speed

To increase upload speed set baudrate = 460800 in espflash.toml

Features

• Displays
• Widgets
• Events
• Styles
• Input devices
• Animations
• Timers
• Async calls
• Subjects
• Auto-generated enums
• Copy C docs to rustdoc
• #![no_std] compatibility
• File system
• Custom fonts
• Snapshots
• Some widget functions
• Layouts
• XML UI

Compatibility table

Contributing

Feel free to open issues for features you find important and missing. I am not completely satisfied with the API, so open to API improvement ideas as well.

Troubleshooting

#[ctor]/#[dtor] is not supported on the current target

You are probably on RISC-V. Please help your architecture get upstreamed into rust-ctor. Until then set default-features = false and manually call lv_init(); in the main function.

Thanks

This project heavily builds upon the work in the the original lv_binding_rust repo.