Crystal Webview

Crystal language bindings for zserge's Webview which is an excellent cross-platform single-header webview library for C/C++ using Gtk, Cocoa, or MSHTML/Edge, depending on the host OS.

Webview relys on default rendering engine of host Operating System, thus binaries generated with this Shard will be much more leaner as compared to Electron which bundles Chromium with each distribution.

This shard supports two-way bindings between Crystal and JavaScript. You can invoke JS code via Webview::Webview#eval and calling Crystal code from JS is done via WebView::Webview#bind (refer to Examples 3 & 4 for samples on how to invoke Crystal functions from JS).

Webview-supported platforms and the engines you can expect to render your application content are as follows:

Operating System	Browser Engine Used
macOS	Cocoa/WebKit
Linux	Gtk-webkit2
Windows	MSHTML or EdgeHTML

Pre-requisite

If you're planning on targeting Linux you must ensure that Webkit2gtk is already installed and available for discovery via the pkg-config command.

Installation

Add the dependency to your shard.yml:

dependencies:
  webview:
    github: naqvis/webview

Run shards install

Usage

Example 1: Loading URL

require "webview"

wv = Webview.window(640, 480, Webview::SizeHints::NONE, "Hello WebView", "http://crystal-lang.org")
wv.run
wv.destroy

Example 2: Loading HTML

require "webview"

html = <<-HTML
data:text/html,<!DOCTYPE html><html lang="en-US">
<head>
<title>Hello,World!</title>
</head>
<body>
<div class="container">
<header>
	<!-- Logo -->
   <h1>City Gallery</h1>
</header>
<nav>
  <ul>
    <li><a href="/London">London</a></li>
    <li><a href="/Paris">Paris</a></li>
    <li><a href="/Tokyo">Tokyo</a></li>
  </ul>
</nav>
<article>
  <h1>London</h1>
  <img src="pic_mountain.jpg" alt="Mountain View" style="width:304px;height:228px;">
  <p>London is the capital city of England. It is the most populous city in the  United Kingdom, with a metropolitan area of over 13 million inhabitants.</p>
  <p>Standing on the River Thames, London has been a major settlement for two millennia, its history going back to its founding by the Romans, who named it Londinium.</p>
</article>
<footer>Copyright &copy; W3Schools.com</footer>
</div>
</body>
</html>
HTML

wv = Webview.window(640, 480, Webview::SizeHints::NONE, "Hello WebView", html)
wv.run
wv.destroy

Example 3: Calling Crystal code from JavaScript

require "webview"

html = <<-HTML
data:text/html,<!doctype html>
<html>
  <body>hello</body>
  <script>
    window.onload = function() {
      document.body.innerText = "Javascript calling Crystal code";
      noop().then(function(res) {
        console.log('noop res', res);
        add(1, 2).then(function(res) {
          console.log('add res', res);
        });
      });
    };
  </script>
</html>
HTML

wv = Webview.window(640, 480, Webview::SizeHints::NONE, "Hello WebView", html, true)

wv.bind("noop", Webview::JSProc.new { |a|
  pp "Noop called with arguments: #{a}"
  JSON::Any.new("noop")
})

wv.bind("add", Webview::JSProc.new { |a|
  pp "add called with arguments: #{a}"
  ret = 0_i64
  a.each do |v|
    ret += v.as_i64
  end
  JSON::Any.new(ret)
})


wv.run
wv.destroy

Example 4: Calling Crystal code from JavaScript and executing JavaScript from Crystal

require "webview"

html = <<-HTML
<!DOCTYPE html><html lang="en-US">
<head>
<title>Hello,World!</title>
</head>
<body>
  <button onClick="add(document.body.children.length)">Add</button>
</body>
</html>
HTML


inject = <<-JS
  elem = document.createElement('div');  
  elem.innerHTML = "hello webview %s";
  document.body.appendChild(elem);
JS

wv = Webview.window(640, 480, Webview::SizeHints::NONE, "Hello WebView", "data:text/html,#{html}" , true)

wv.bind("add", Webview::JSProc.new { |n|
  wv.eval(sprintf(inject, n))
  JSON::Any.new(nil)
})

wv.run
wv.destroy

Example 5: Running your web app in another thread

Thread.new do
  get "/" do
    "hello from kemal"
  end
  Kemal.run
end

wv = Webview.window(640, 480, Webview::SizeHints::NONE, "WebView with local webapp!", "http://localhost:3000")
wv.run
wv.destroy

Contributing

Fork it (https://github.com/naqvis/webview/fork)
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create a new Pull Request

Contributors

Ali Naqvi - creator and maintainer

lancecarlson/webview