1<?xml version='1.0' encoding='UTF-8'?> 2<page xmlns="http://projectmallard.org/1.0/" 3 xmlns:its="http://www.w3.org/2005/11/its" 4 xmlns:xi="http://www.w3.org/2001/XInclude" 5 type="guide" style="task" 6 id="switch.js"> 7 <info> 8 <title type="text">Switch (JavaScript)</title> 9 <link type="guide" xref="beginner.js#buttons"/> 10 <revision version="0.1" date="2012-06-18" status="draft"/> 11 12 <credit type="author copyright"> 13 <name>Taryn Fox</name> 14 <email its:translate="no">jewelfox@fursona.net</email> 15 <years>2012</years> 16 </credit> 17 18 <desc>A sliding switch that can be flipped on and off</desc> 19 </info> 20 21 <title>Switch</title> 22 <media type="image" mime="image/png" src="media/switchanimals.png"/> 23 <p>A Switch has two positions, on and off. This example shows how you can use multiple switches together to control which <link xref="image.js">Image</link> is shown in the window. The pictures used in this example <link href="https://live.gnome.org/TarynFox?action=AttachFile&do=get&target=Animal+Photos.zip">can be downloaded here</link>.</p> 24 <note><p>The window will contain a "broken image" icon instead of a picture if picture files named <file>redfox.png</file>, <file>muteswan.png</file>, <file>fruitbat.png</file>, and <file>gentoopenguin.png</file> aren't in the same directory. You can change the code and the pictures around as you like, but the Creative Commons-licensed photos used in this example were taken from the following sources and cropped to 640x425:</p> 25 <list> 26 <item><p><link href="http://en.wikipedia.org/wiki/File:Fuzzy_Freddy.jpg">Red fox photo</link> by Rob Lee, licensed <link href="http://creativecommons.org/licenses/by/2.0/deed.en">CC-By</link></p></item> 27 <item><p><link href="http://en.wikipedia.org/wiki/File:Pygoscelis_papua_-Nagasaki_Penguin_Aquarium_-swimming_underwater-8a.jpg">Gentoo penguin photo</link> by Ken Funakoshi, licensed <link href="http://creativecommons.org/licenses/by-sa/2.0/deed.en">CC-By-SA</link></p></item> 28 <item><p><link href="http://www.flickr.com/photos/shekgraham/127431519/in/photostream/">Fruit bat photo</link> by Shek Graham, licensed <link href="http://creativecommons.org/licenses/by/2.0/deed.en">CC-By</link></p></item> 29 <item><p><link href="http://commons.wikimedia.org/wiki/File:Mute_Swan-Mindaugas_Urbonas.jpg">Mute swan photo</link> by Mindaugas Urbonas, licensed <link href="http://creativecommons.org/licenses/by-sa/2.5/deed.en">CC-By-SA</link></p></item> 30 </list> 31 <p>Photo credits and licensing information are shown in the application's <link xref="aboutdialog.js">AboutDialog</link>. Always remember to credit the original artist when using <link href="http://creativecommons.org">Creative Commons-licensed works!</link></p></note> 32 <links type="section" /> 33 34 <section id="imports"> 35 <title>Libraries to import</title> 36 <code mime="application/javascript"><![CDATA[ 37#!/usr/bin/gjs 38 39const Gio = imports.gi.Gio; 40const Gtk = imports.gi.Gtk; 41const Lang = imports.lang; 42]]></code> 43 <p>These are the libraries we need to import for this application to run. Remember that the line which tells GNOME that we're using Gjs always needs to go at the start.</p> 44 </section> 45 46 <section id="applicationwindow"> 47 <title>Creating the application window</title> 48 <code mime="application/javascript"><![CDATA[ 49const SwitchExample = new Lang.Class({ 50 Name: 'Switch Example', 51 52 // Create the application itself 53 _init: function() { 54 this.application = new Gtk.Application({ 55 application_id: 'org.example.jsswitch', 56 flags: Gio.ApplicationFlags.FLAGS_NONE 57 }); 58 59 // Connect 'activate' and 'startup' signals to the callback functions 60 this.application.connect('activate', Lang.bind(this, this._onActivate)); 61 this.application.connect('startup', Lang.bind(this, this._onStartup)); 62 }, 63 64 // Callback function for 'activate' signal presents window when active 65 _onActivate: function() { 66 this._window.present(); 67 }, 68 69 // Callback function for 'startup' signal creates the menu and builds the UI 70 _onStartup: function() { 71 this._initMenus(); 72 this._buildUI (); 73 }, 74]]></code> 75 <p>All the code for this sample goes in the SwitchExample class. The above code creates a <link href="http://www.roojs.com/seed/gir-1.2-gtk-3.0/gjs/Gtk.Application.html">Gtk.Application</link> for our widgets and window to go in.</p> 76 <note><p>Before we call _buildUI to create the window and the widgets inside it, we need to call _initMenus, which tells GNOME to create the menu. We can put the actual code for _initMenus after the code for _buildUI, since it doesn't matter what order we put them in so long as _initMenus is called first in _onStartup.</p></note> 77 <code mime="application/javascript"><![CDATA[ 78 // Build the application's UI 79 _buildUI: function() { 80 81 // Create the application window 82 this._window = new Gtk.ApplicationWindow({ 83 application: this.application, 84 window_position: Gtk.WindowPosition.CENTER, 85 border_width: 20, 86 title: "Animal Creator"}); 87]]></code> 88 <p>The _buildUI function is where we put all the code to create the application's user interface. The first step is creating a new <link xref="GtkApplicationWindow.js">Gtk.ApplicationWindow</link> to put all our widgets into.</p> 89 </section> 90 91 <section id="button"> 92 <title>Creating the switches</title> 93 <code mime="application/javascript"><![CDATA[ 94 // Create the image widget and set its default picture 95 this._image = new Gtk.Image ({file: "redfox.png"}); 96]]></code> 97 98 <p>We first create the <link xref="image.js">Image</link> that the switches will control. Remember that a file named <file>redfox.png</file> needs to be in the same directory as this application.</p> 99 100 <code mime="application/javascript"><![CDATA[ 101 // Create a label for the first switch 102 this._flyLabel = new Gtk.Label ({ 103 label: "Make it fly", 104 margin_right: 30}); 105 106 // Create the first switch and set its default position 107 this._flySwitch = new Gtk.Switch ({active: false}); 108 this._flySwitch.connect ('notify::active', Lang.bind (this, this._switchFlip)); 109 110 // Create a label for the second switch 111 this._birdLabel = new Gtk.Label ({ 112 label: "Make it a bird", 113 margin_right: 30}); 114 115 // Create the second switch 116 this._birdSwitch = new Gtk.Switch ({active: false}); 117 this._birdSwitch.connect ('notify::active', Lang.bind (this, this._switchFlip)); 118]]></code> 119 120 <p>We use a <link xref="label.js">Label</link> to mark each Switch, and give them a bit of a margin on the right so that they aren't crammed right next to the Switches. After that we create the Switches, and set them to be switched off by default.</p> 121 <p>The signal a switch sends out when it's flipped on or off is called notify::active. After we create each switch, we connect its notify::active signal to a function called _switchFlip. If you have multiple switches that each do something different, you might want to connect them to different functions, but here they're both used for the same thing: To control what picture's displayed by _image.</p> 122 123 <code mime="application/javascript"><![CDATA[ 124 // Create a grid for the labels and switches beneath the picture 125 this._UIGrid = new Gtk.Grid ({ 126 halign: Gtk.Align.CENTER, 127 valign: Gtk.Align.CENTER, 128 margin_top: 20}); 129 130 // Attach the labels and switches to that grid 131 this._UIGrid.attach (this._flyLabel, 0, 0, 1, 1); 132 this._UIGrid.attach (this._flySwitch, 1, 0, 1, 1); 133 this._UIGrid.attach (this._birdLabel, 0, 1, 1, 1); 134 this._UIGrid.attach (this._birdSwitch, 1, 1, 1, 1); 135 136 // Create a master grid to put both the UI and the picture into 137 this._mainGrid = new Gtk.Grid ({ 138 halign: Gtk.Align.CENTER, 139 valign: Gtk.Align.CENTER }); 140 141 // Attach the picture and the UI grid to the master grid 142 this._mainGrid.attach (this._image, 0, 0, 1, 1); 143 this._mainGrid.attach (this._UIGrid, 0, 1, 1, 1); 144]]></code> 145 <p>We create a <link xref="grid.js">Grid</link> for the Labels and Switches first, so that we can organize them in a 2x2 layout with a margin between it and the Image. Then we put that Grid into a larger 2x1 Grid that has the Image on top, and the Grid with the Labels and Switches on the bottom.</p> 146 <code mime="application/javascript"><![CDATA[ 147 // Add the master grid to the window 148 this._window.add (this._mainGrid); 149 150 // Show the window and all child widgets 151 this._window.show_all(); 152 }, 153]]></code> 154 <p>Finally, we add the larger Grid to the window, then tell the window to show itself and all the widgets inside of it.</p> 155 </section> 156 157 <section id="switch-handler"> 158 <title>Function which handles the switches being flipped</title> 159 160 <code mime="application/javascript"><![CDATA[ 161 _switchFlip: function() { 162 163 // Change the picture depending on which switches are flipped 164 if (this._flySwitch.get_active()) { 165 166 if (this._birdSwitch.get_active()) this._image.set_from_file ("muteswan.png"); 167 168 else this._image.set_from_file ("fruitbat.png"); 169 } 170 171 else { 172 173 if (this._birdSwitch.get_active()) this._image.set_from_file ("gentoopenguin.png"); 174 175 else this._image.set_from_file ("redfox.png"); 176 177 } 178 179 }, 180]]></code> 181 <p>Each time a Switch is flipped, this function checks to see which of the two Switches are active afterwards, using the Switches' built-in get_active() function. It then changes the Image accordingly. You can change the filenames around as you like, so long as you have pictures to go with them.</p> 182</section> 183 184<section id="about"> 185 <title>Creating the AboutDialog</title> 186 <code mime="application/javascript"><![CDATA[ 187 _initMenus: function() { 188 189 // Build the application's menu so we can have an "About" button 190 let menu = new Gio.Menu(); 191 menu.append("About", 'app.about'); 192 menu.append("Quit",'app.quit'); 193 this.application.set_app_menu(menu); 194 195 // Bind the "About" button to the _showAbout() function 196 let aboutAction = new Gio.SimpleAction ({ name: 'about' }); 197 aboutAction.connect('activate', Lang.bind(this, 198 function() { 199 this._showAbout(); 200 })); 201 this.application.add_action(aboutAction); 202 203 // Bind the "Quit" button to the function that closes the window 204 let quitAction = new Gio.SimpleAction ({ name: 'quit' }); 205 quitAction.connect('activate', Lang.bind(this, 206 function() { 207 this._window.destroy(); 208 })); 209 this.application.add_action(quitAction); 210 }, 211]]></code> 212 <p>The first step is building the <link xref="gmenu.js">GMenu</link> that the "About" button goes into. This is the menu that appears when you click the application's name in the upper-left corner of the screen, next to the Activities menu. Our menu only has two options in it: About, and Quit.</p> 213 214 <code mime="application/javascript"><![CDATA[ 215 _showAbout: function () { 216 217 // String arrays of the names of the people involved in the project 218 var artists = ['Rob Lee http://en.wikipedia.org/wiki/File:Fuzzy_Freddy.jpg', 'Ken Funakoshi http://en.wikipedia.org/wiki/File:Pygoscelis_papua_-Nagasaki_Penguin_Aquarium_-swimming_underwater-8a.jpg', 'Shek Graham http://www.flickr.com/photos/shekgraham/127431519/in/photostream/', 'Mindaugas Urbonas http://commons.wikimedia.org/wiki/File:Mute_Swan-Mindaugas_Urbonas.jpg']; 219 var authors = ["GNOME Documentation Team"]; 220 var documenters = ["GNOME Documentation Team"]; 221 222 // Create the About dialog 223 let aboutDialog = new Gtk.AboutDialog({ 224 title: "AboutDialog Example", 225 program_name: "Animal Creator", 226 copyright: "Copyright \xa9 2012 GNOME Documentation Team\n\nRed fox photo licensed CC-By by Rob Lee\nGentoo penguin photo licensed CC-By-SA by Ken Funakoshi\nFruit bat photo licensed CC-By by Shek Graham\nMute swan photo licensed CC-By-SA by Mindaugas Urbonas\nLinks to the originals are available under Credits.\n\nHave you hugged a penguin today?", 227 artists: artists, 228 authors: authors, 229 documenters: documenters, 230 website: "http://developer.gnome.org", 231 website_label: "GNOME Developer Website" }); 232 233 // Attach the About dialog to the window 234 aboutDialog.modal = true; 235 aboutDialog.transient_for = this._window; 236 237 // Show the About dialog 238 aboutDialog.show(); 239 240 // Connect the Close button to the destroy signal for the dialog 241 aboutDialog.connect('response', function() { 242 aboutDialog.destroy(); 243 }); 244 } 245 246}); 247]]></code> 248 <p>An <link xref="aboutdialog.js">AboutDialog</link> has a lot of different things you can set, to credit everyone who worked on the application and leave a note to whomever reads it. In this case, the copyright section contains our note and credits the original photographers, while the artists section shows you a list of the photographers with links to the original photos when you click the Credits button. The web URLs put after their names in the array turn their names into clickable links in the Credits section.</p> 249 250 <code mime="application/javascript"><![CDATA[ 251// Run the application 252let app = new SwitchExample (); 253app.application.run (ARGV); 254]]></code> 255 <p>Finally, we create a new instance of the finished SwitchExample class, and set the application running.</p> 256 </section> 257 258 <section id="complete"> 259 <title>Complete code sample</title> 260<code mime="application/javascript" style="numbered"><xi:include href="samples/switch.js" parse="text"><xi:fallback/></xi:include></code> 261 </section> 262 263 <section id="in-depth"> 264 <title>In-depth documentation</title> 265<list> 266 <item><p><link href="http://developer.gnome.org/gio/unstable/GMenu.html">GMenu</link></p></item> 267 <item><p><link href="http://developer.gnome.org/gio/stable/GSimpleAction.html">GSimpleAction</link></p></item> 268 <item><p><link href="http://www.roojs.com/seed/gir-1.2-gtk-3.0/gjs/Gtk.Application.html">Gtk.Application</link></p></item> 269 <item><p><link href="http://developer.gnome.org/gtk3/stable/GtkApplicationWindow.html">Gtk.ApplicationWindow</link></p></item> 270 <item><p><link href="http://www.roojs.org/seed/gir-1.2-gtk-3.0/gjs/Gtk.Grid.html">Gtk.Grid</link></p></item> 271 <item><p><link href="http://www.roojs.org/seed/gir-1.2-gtk-3.0/gjs/Gtk.Image.html">Gtk.Image</link></p></item> 272 <item><p><link href="http://www.roojs.org/seed/gir-1.2-gtk-3.0/gjs/Gtk.Label.html">Gtk.Label</link></p></item> 273 <item><p><link href="http://www.roojs.org/seed/gir-1.2-gtk-3.0/gjs/Gtk.Switch.html">Gtk.Switch</link></p></item> 274</list> 275 </section> 276</page> 277
