Membrane

Membrane is a platform agnostic clojure library for creating user interfaces.

Membrane provides three layers:

1. A UI framework, membrane.component, that provides state management for GUIs
2. A platform agnostic model for graphics and events
3. Multiple graphics backends that provide concrete implementations for #2

While these three layers are made to work together, they can also be mixed and matched with other implementations. For example, you could use your favorite UI framework and the other layers to reach another platform. Alternatively, you could provide your own ncurses graphics backend and leverage the ui framework and graphics model.

For membrane to run on a platform, the only requirements are

1. Drawing implementations for graphical primitives like rectangles, text, and images
2. An event loop that forwards events (eg. mouse clicks, key presses) to membrane and repaints

Supported platforms:

• Mac OSX
• Linux
• the web via WebGL

Experimental platforms

• Windows (see skija, swing, and javafx backends)
• Terminal (see example project)
• virtual dom
• java swing
• skija (see example project)
• javafx via cljfx (see example project)

Experimental UI framework integrations

• re-frame (see example project)
• fulcro (see example project)

Links

Tutorial
Docs
Examples
Distributing your desktop app
Targeting WebGL
Questions? Comments? Connect with us on clojurians slack in #membrane (join here) or discuss on twitter.

Rationale

Membrane was written because I wanted to build a desktop app with clojure, but I wanted all the cool functional features found in libraries targeting the browser, ie. react, reagent, re-frame, fulcro, etc.

Membrane does not build on top of any existing ui toolkits like Swing, JavaFX, HTML, UIKit, GTK, etc. These toolkits are fundamentally based on an object oriented model and have a deep impedance mismatch with idiomatic clojure code.

As much as possible, the development of the library was meant to follow clojure's principles

• Use the simplest construct that does the job
• Data first
• Pure functions that work with the data
• Side effects and process at the edges

By applying clojure's principles, several "extras" were obtained for free

• platform agnostic
• flexible
• great for tooling

For more info covering the design of membrane:
What is a User Interface?
Implementing a Functional UI Model
Reusable UI Components

Usage

Leiningen dependency:

[com.phronemophobic/membrane  "0.9.22-beta"]

deps.edn dependency:

com.phronemophobic/membrane {:mvn/version "0.9.22-beta"}

Examples

A Simple Example without the UI Framework

Screenshot:

(ns counter
  (:require [membrane.skia :as skia]
            [membrane.ui :as ui
             :refer [horizontal-layout
                     button
                     label
                     spacer
                     on]]))

(defonce counter-state (atom 0))

;; Display a "more!" button next to label showing num
;; clicking on "more!" will increment the counter
(defn counter [num]
  (horizontal-layout
   (on :mouse-down (fn [[mouse-x mouse-y]]
                     (swap! counter-state inc)
                     nil)
       (button "more!"))
   (spacer 5 0)
   (label num (ui/font nil 19))))

(comment
    ;; pop up a window that shows our counter
    (skia/run #(counter @counter-state)))

Simple Example using membrane.component UI Framework

Screenshot:

(ns counter
  (:require [membrane.skia :as skia]
            [membrane.ui :as ui
             :refer [horizontal-layout
                     vertical-layout
                     button
                     label
                     on]]
            [membrane.component :as component
             :refer [defui make-app defeffect]])
  (:gen-class))


;; Display a "more!" button next to label showing num
;; clicking on "more!" will dispatch a ::counter-increment effect
(defui counter [{:keys [num]}]
  (horizontal-layout
   (on :mouse-down (fn [[mouse-x mouse-y]]
                     [[::counter-increment $num]])
       (ui/button "more!"))
   (ui/label num)))

(defeffect ::counter-increment [$num]
  (dispatch! :update $num inc))

(comment
  ;; pop up a window showing our counter with
  ;; num initially set to 10
  (skia/run (make-app #'counter {:num 10})))

Here's an example of how you can use your counter component.

Screenshot:

;; Display an "Add Counter" button
;; on top of a stack of counters
;;
;; clicking on the "Add Counter" button will
;; add a new counter to the bottom of the stack
;; 
;; clicking on the counters' "more!" buttons will
;; update their respective numbers
(defui counter-counter [{:keys [nums]}]
  (apply
   vertical-layout
   (on :mouse-down (fn [[mx my]]
                     [[::add-counter $nums]])
       (ui/button "Add Counter"))
   (for [num nums]
     (counter {:num num}))))

(defeffect ::add-counter [$nums]
  (dispatch! :update $nums conj 0))

(comment
  ;; pop up a window showing our counter-counter
  ;; with nums initially set to [0 1 2]
  (skia/run (make-app #'counter-counter {:nums [0 1 2]})))

Fun Features

;; graphical elements are values
;; no need to attach elements to the dom to get layout info
(ui/bounds (vertical-layout
           (ui/label "hello")
           (ui/checkbox true)))
>> [30.79296875 27.0]


;; events are pure functions that return effects which are also values
(let [mpos [15 15]]
  (ui/mouse-down
   (ui/translate 10 10
                 (on :mouse-down (fn [[mx my]]
                                   ;;return a sequence of effects
                                   [[:say-hello]])
                     (ui/label "Hello")))
   mpos))
>> ([:say-hello])


;; horizontal and vertical centering!
(skia/run #(let [rect (ui/with-style :membrane.ui/style-stroke
                        (ui/rectangle 200 200))]
             [rect
              (ui/center (ui/label "hello") (ui/bounds rect))]) )


;; save graphical elem as an image
(let [todos [{:complete? false
              :description "first"}
             {:complete? false
              :description "second"}
             {:complete? true
              :description "third"}]]
  (skia/draw-to-image! "todoapp.png"
                       (todo-app {:todos todos :selected-filter :all})))

;; use spec to generate images of variations of your app
(doseq [[i todo-list] (map-indexed vector (gen/sample (s/gen ::todos)))]
  (skia/draw-to-image! (str "todo" i ".png")
                       (ui/vertical-layout
                        (ui/label (with-out-str
                                    (clojure.pprint/pprint todo-list)))
                        (ui/with-style :membrane.ui/style-stroke
                          (ui/path [0 0] [400 0]))
                        (todo-app {:todos todo-list :selected-filter :all}))))

Screenshots

More Info

That's it! For more in-depth info, check out the tutorial.

Tutorial
Docs
Examples
Distributing your desktop app
Targeting WebGL
Questions? Comments? Connect with us on clojurians slack in #membrane

License

Copyright 2021 Adrian Smith. Membrane is licensed under Apache License v2.0.