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https://github.com/linebender/druid

A data-first Rust-native UI design toolkit.
https://github.com/linebender/druid

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A data-first Rust-native UI design toolkit.

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README 

        
![druid banner](https://raw.githubusercontent.com/linebender/druid/screenshots/images/small_banner.png)



## A data-first Rust-native UI toolkit.



[![crates.io](https://img.shields.io/crates/v/druid)](https://crates.io/crates/druid)

[![docs.rs](https://docs.rs/druid/badge.svg)](https://docs.rs/druid/)

[![license](https://img.shields.io/crates/l/druid)](https://github.com/linebender/druid/blob/master/LICENSE)

[![chat](https://img.shields.io/badge/zulip-join_chat-brightgreen.svg)](https://xi.zulipchat.com)



Druid was an experimental Rust-native UI toolkit. Its main goal was to offer a

polished user experience. There were many factors to this goal, including

performance, a rich palette of interactions (hence a widget library to support

them), and playing well with the native platform.

See the [goals section](#Goals) for more details.



We did periodic releases of Druid on crates.io. All changes were documented

in [the changelog](https://github.com/linebender/druid/blob/master/CHANGELOG.md).



For an overview of some key concepts, see the incomplete [Druid book].



## Project status



**UNMAINTAINED**



**The Druid project has been discontinued.**



New development effort moved on to [Xilem], which has a lot of fundamental changes to allow for

a wider variety of applications with better performance, but it also heavily inherits from Druid.

We see [Xilem] as the future of Druid.



Druid is reasonably usable for [some subset of applications](https://github.com/linebender/druid/issues/1360)

and has a significant testing history, which ensures some stability and correctness.

However, there will not be any new features or bug fixes coming to Druid. As such we don't recommend

using Druid for brand new applications. If you insist, then at least make sure your application

doesn't require a feature that Druid doesn't have, e.g. accessibility or 3D support.



## Contributions



As the Druid project has been discontinued, **we will not be accepting any more contributions**.



Please take a look at some of our other projects instead, especially the Druid successor [Xilem].



## Example



Here's a simple counter example app:



```rust

use druid::widget::{Button, Flex, Label};

use druid::{AppLauncher, LocalizedString, PlatformError, Widget, WidgetExt, WindowDesc};



fn main() -> Result<(), PlatformError> {

    let main_window = WindowDesc::new(ui_builder());

    let data = 0_u32;

    AppLauncher::with_window(main_window)

        .log_to_console()

        .launch(data)

}



fn ui_builder() -> impl Widget {

    // The label text will be computed dynamically based on the current locale and count

    let text =

        LocalizedString::new("hello-counter").with_arg("count", |data: &u32, _env| (*data).into());

    let label = Label::new(text).padding(5.0).center();

    let button = Button::new("increment")

        .on_click(|_ctx, data, _env| *data += 1)

        .padding(5.0);



    Flex::column().with_child(label).with_child(button)

}

```



Check out the [the examples folder] for a more comprehensive demonstration of

Druid's existing functionality and widgets. Check [druid_widget_nursery](https://github.com/linebender/druid-widget-nursery) for more widgets.



## Screenshots



[![calc.rs example](https://raw.githubusercontent.com/linebender/druid/screenshots/images/0.6.0/calc.png)](/druid/examples/calc.rs)

[![flex.rs example](https://raw.githubusercontent.com/linebender/druid/screenshots/images/0.6.0/flex.png)](/druid/examples/flex.rs)

[![custom_widget.rs example](https://raw.githubusercontent.com/linebender/druid/screenshots/images/0.6.0/custom_widget.png)](/druid/examples/custom_widget.rs)



## Using Druid



An explicit goal of Druid was to be easy to build.

Druid is available on [crates.io] and should work as a lone dependency

(it re-exports all the parts of `druid-shell`, `piet`, and `kurbo` that you'll need):



```toml

druid = "0.8.3"

```



### Platform notes



#### Linux



On Linux, Druid requires gtk+3; see [GTK installation page].

(On ubuntu-based distro, running `sudo apt-get install libgtk-3-dev` from the terminal will do the job.)



#### OpenBSD



On OpenBSD, Druid requires gtk+3;  install from packages:

```sh

pkg_add gtk+3

```



Alternatively, there is an X11 backend available, although it is currently

[missing quite a few features](https://github.com/linebender/druid/issues?q=is%3Aopen+is%3Aissue+label%3Ashell%2Fx11+label%3Amissing).

You can try it out with `--features=x11`.



## Goals



Druid's goal was to make it easy to write and deploy high quality desktop

applications with a smooth and polished user experience on all common

platforms. In order to achieve this we strived for a variety of things:



- Make it easy to build and package on all supported platforms.

- Implement abstractions to avoid platform specific quirks.

- Respect platform conventions and expectations.

- Handle display resolution and scaling reliably with little effort.

- Enable easy, yet powerful internationalization.

- Offer robust accessibility support.

- Produce small and fast binaries with low memory usage.

- Have a small dependency tree, a high quality code base and good organization.

- Focus on powerful, desktop-grade applications.

- Provide a flexible set of layouts and common widgets.

- Ease creation of custom components and application logic as needed.



### Non-Goals



In order to fulfill those goals, we couldn't support every use case. Luckily

the Rust community is working on a variety of different libraries with

different goals, so here are some of Druid's non-goals and possible

alternatives that can offer those capabilities:



- Use the platform-native widgets or mimic them. ([Relm], [Slint])

- Embed easily into custom render pipelines. ([Conrod])

- Adhere to a specific architectural style such as Elm. ([Iced], [Relm])

- Support rendering to HTML when targeting the web. ([Iced], [Moxie])



Druid was just one of many ongoing [Rust-native GUI experiments].



## Concepts



### druid-shell



The Druid toolkit uses `druid-shell` for a platform-abstracting application shell.

`druid-shell` is responsible for starting a native platform runloop, listening to

events, converting them into a platform-agnostic representation, and calling a

user-provided handler with them.



While `druid-shell` was being developed with the Druid toolkit in mind, it was

intended to be general enough that it could be reused by other projects

interested in experimenting with Rust GUI. The `druid-shell` crate includes a

couple of [non-`druid` examples].



### piet



Druid relies on the [Piet library] for drawing and text layout. Piet is a 2D graphics

abstraction with multiple backends: `piet-direct2d`, `piet-coregraphics`, `piet-cairo`,

`piet-web`, and `piet-svg` are currently available.

In terms of Druid platform support via Piet, macOS uses `piet-coregraphics`,

Linux/OpenBSD/FreeBSD use `piet-cairo`, Windows uses `piet-direct2d`, and web uses `piet-web`.



```rust

use druid::kurbo::{BezPath, Point, Rect};

use druid::piet::Color;



// Create an arbitrary bezier path

// (ctx.size() returns the size of the layout rect we're painting in)

let mut path = BezPath::new();

path.move_to(Point::ORIGIN);

path.quad_to(

    (80.0, 90.0),

    (ctx.size().width, ctx.size().height),

);

// Create a color

let stroke_color = Color::rgb8(0x00, 0x80, 0x00);

// Stroke the path with thickness 1.0

ctx.stroke(path, &stroke_color, 1.0);



// Rectangles: the path for practical people

let rect = Rect::from_origin_size((10., 10.), (100., 100.));

// Note the Color:rgba8 which includes an alpha channel (7F in this case)

let fill_color = Color::rgba8(0x00, 0x00, 0x00, 0x7F);

ctx.fill(rect, &fill_color);

```



### widgets



Widgets in Druid (text boxes, buttons, layout components, etc.) are objects

which implement the [Widget trait]. The trait is parametrized by a type (`T`)

for associated data. All trait methods (`event`, `lifecycle`, `update`, `paint`,

and `layout`) are provided with access to this data, and in the case of

`event` the reference is mutable, so that events can directly update the data.



Whenever the application data changes, the framework traverses the widget

hierarchy with an `update` method.



All the widget trait methods are provided with a corresponding context

([EventCtx], [LifeCycleCtx], [UpdateCtx], [LayoutCtx], [PaintCtx]). The widget can request

things and cause actions by calling methods on that context.



In addition, all trait methods are provided with an environment `Env`, which

includes the current theme parameters (colors, dimensions, etc.).



```rust

impl Widget for Button {

    fn event(&mut self, ctx: &mut EventCtx, event: &Event, data: &mut T, env: &Env) {

      ...

    }



    fn lifecycle(&mut self, ctx: &mut LifeCycleCtx, event: &LifeCycle, data: &T, env: &Env) {

      ...

    }



    fn update(&mut self, ctx: &mut UpdateCtx, old_data: &T, data: &T, env: &Env) {

      ...

    }



    fn layout(&mut self, ctx: &mut LayoutCtx, bc: &BoxConstraints, data: &T, env: &Env) -> Size {

      ...

    }



    fn paint(&mut self, ctx: &mut PaintCtx, data: &T, env: &Env) {

      ...

    }

}

```



Druid provides a number of [basic utility and layout widgets] and it's easy to

implement your own. You can also compose widgets into new widgets:



```rust

fn build_widget() -> impl Widget {

    let mut col = Flex::column();

    for i in 0..30 {

        let button = Button::new(format!("Button {}", i).padding(5.0);

        col.add_child(button);

    }

    Scroll::new(col)

}

```



### layout



Druid's layout protocol was strongly inspired by [Flutter's box layout model].

In Druid, widgets are passed a `BoxConstraint` that provides them a minimum and

maximum size for layout. Widgets are also responsible for computing appropriate

constraints for their children if applicable.



### data



Druid uses a [Data trait] to represent [value types]. These should be cheap to

compare and cheap to clone.



In general, you can use `derive` to generate a `Data` impl for your types.



```rust

#[derive(Clone, Data)]

struct AppState {

    which: bool,

    value: f64,

}

```



### lens



The [Lens datatype] gives access to a part of a larger data structure. Like

`Data`, this can be derived. Derived lenses are accessed as associated constants

with the same name as the field.



```rust

#[derive(Clone, Data, Lens)]

struct AppState {

    which: bool,

    value: f64,

}

```



To use the lens, wrap your widget with `LensWrap` (note the conversion of

CamelCase to snake_case):



```rust

LensWrap::new(WidgetThatExpectsf64::new(), AppState::value);

```



Alternatively, lenses for structs, tuples, and indexable containers can be

constructed on-demand with the `lens` macro:



```rust

LensWrap::new(WidgetThatExpectsf64::new(), lens!(AppState, value));

```



This is particularly useful when working with types defined in another crate.



## Authors



The main authors are Raph Levien and Colin Rofls, with much support from an

active and friendly community. See the AUTHORS file for more.



[Runebender]: https://github.com/linebender/runebender

[the examples folder]: /druid/examples

[Piet library]: https://github.com/linebender/piet

[custom_widget]: /druid/examples/custom_widget.rs

[basic utility and layout widgets]: /druid/src/widget

[Flutter's box layout model]: https://api.flutter.dev/flutter/rendering/BoxConstraints-class.html

[value types]: https://sinusoid.es/lager/model.html#id2

[GTK installation page]: https://www.gtk.org/docs/installations/linux/

[Rust-native GUI experiments]: https://areweguiyet.com

[CONTRIBUTING.md]: /CONTRIBUTING.md

[Zulip chat instance]: https://xi.zulipchat.com

[non-`druid` examples]: /druid-shell/examples/shello.rs

[crates.io]: https://crates.io/crates/druid

[EventCtx]: https://docs.rs/druid/0.8.3/druid/struct.EventCtx.html

[LifeCycleCtx]: https://docs.rs/druid/0.8.3/druid/struct.LifeCycleCtx.html

[LayoutCtx]: https://docs.rs/druid/0.8.3/druid/struct.LayoutCtx.html

[PaintCtx]: https://docs.rs/druid/0.8.3/druid/struct.PaintCtx.html

[UpdateCtx]: https://docs.rs/druid/0.8.3/druid/struct.UpdateCtx.html

[Widget trait]: https://docs.rs/druid/0.8.3/druid/trait.Widget.html

[Data trait]: https://docs.rs/druid/0.8.3/druid/trait.Data.html

[Lens datatype]: https://docs.rs/druid/0.8.3/druid/trait.Lens.html

[Druid book]: https://linebender.org/druid/

[Iced]: https://github.com/hecrj/iced

[Conrod]: https://github.com/PistonDevelopers/conrod

[Relm]: https://github.com/antoyo/relm

[Moxie]: https://github.com/anp/moxie

[Slint]: https://github.com/slint-ui/slint

[Xilem]: https://github.com/linebender/xilem