Crate walkers

Walkers, a map widget for Rust

Walkers is a slippy maps widget for egui, similar to very popular Leaflet, but written in Rust. It compiles to native applications as well as WASM. See the online demo here.

It supports OpenStreetMap, mapbox, and compatible tile servers.

Before deploying your application, please get yourself familiar with the OpenStreetMap usage policy, and consider donating the OpenStreetMap Foundation.

Quick start

Walkers has three main objects. Tiles downloads images from a tile map provider such as OpenStreetMap and stores them in a cache, MapMemory keeps track of the widget’s state and Map is the widget itself.

use walkers::{HttpTiles, Map, MapMemory, Position, sources::OpenStreetMap};
use egui::{Context, CentralPanel};
use eframe::{App, Frame};

struct MyApp {
    tiles: HttpTiles,
    map_memory: MapMemory,
}

impl MyApp {
    fn new(egui_ctx: Context) -> Self {
        Self {
            tiles: HttpTiles::new(OpenStreetMap, egui_ctx),
            map_memory: MapMemory::default(),
        }
    }
}

impl App for MyApp {
    fn update(&mut self, ctx: &Context, _frame: &mut Frame) {
        CentralPanel::default().show(ctx, |ui| {
            ui.add(Map::new(
                Some(&mut self.tiles),
                &mut self.map_memory,
                Position::from_lon_lat(17.03664, 51.09916)
            ));
        });
    }
}

You can see a more complete example here.

Running demos

Walkers suports numerous build options, such as Android and WASM. They all share a common library - demo, but require a different build workflow, not necessarily compatible with Cargo alone.

Native

To enable mapbox layers, you need to define MAPBOX_ACCESS_TOKEN environment variable before building. You can obtain one, by creating a mapbox account.

cd demo_native
cargo run

Web / WASM

cd demo_web
trunk serve --release

Android

You need to have Android SDK and cargo-ndk installed.

cd demo_android
make run-on-device

Modules

• extras
  Extra functionalities that can be used with the map.
• sources
  Some common HTTP tile sources. Make sure you follow terms of usage of the particular source.

Structs

• HeaderValue
  Represents an HTTP header field value.
• HttpOptions
  Controls how crate::HttpTiles use the HTTP protocol, such as caching.
• HttpTiles
  Downloads the tiles via HTTP. It must persist between frames.
• InvalidZoom
• Map
  The actual map widget. Instances are to be created on each frame, as all necessary state is stored in Tiles and MapMemory.
• MapMemory
  State of the map widget which must persist between frames.
• Position
  Geographical position with latitude and longitude.
• Projector
  Projects geographical position into pixels on the viewport, suitable for egui::Painter.
• Texture
• TextureWithUv
  Texture with UV coordinates.
• TileId
  Coordinates of the OSM-like tile.

Traits

• Plugin
  Plugins allow drawing custom shapes on the map. After implementing this trait for your type, you can add it to the map with Map::with_plugin
• Tiles

Functions

• screen_to_position
  Transforms screen pixels into a geographical position.