# TextView (JavaScript)

Taryn Fox
jewelfox@fursona.net 2012
A multiline text editor
Anders Jonsson
anders.jonsson@norsjovallen.se 2018

# TextView

A TextView is really (or at least usually) a nested set of three objects.

At the bottom there is a TextBuffer. This holds the text itself.

In the middle there is the TextView, which is a widget that lets you see and edit the text in the buffer. It automatically resizes itself depending on how much text there is.

Since the automatic resizing can make a TextView unwieldy, you normally place it inside of a ScrolledWindow. Despite the name, it's not an actual window in terms of having a title bar and an X button; it's a widget you put on the application you're making, which acts like a window onto a more manageable chunk of a TextView. If the text in the buffer is too big to fit, scrollbars will appear.

If you want to change what text is displayed in the TextView, you act on the TextBuffer, since it's what actually holds the text. The same goes for if you want to see what text someone typed in. This sample application lets you talk to a (make-believe) penguin, and checks the TextBuffer to see if you typed the word "fish" anywhere in it.

Real-life penguin populations are declining fast, because climate change is melting the ice that they live on and killing the fish that they eat. If you'd like to play a (somewhat silly) GNOME game based on this premise, take a look at Pingus.

# Libraries to import

#!/usr/bin/gjs

const Gtk = imports.gi.Gtk; const Lang = imports.lang;

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.

# Creating the application window

const TextViewExample = new Lang.Class ({ Name: 'TextView Example',

// Create the application itself _init: function () { this.application = new Gtk.Application ({ application_id: 'org.example.jstextview' });

// Connect 'activate' and 'startup' signals to the callback functions this.application.connect('activate', Lang.bind(this, this._onActivate)); this.application.connect('startup', Lang.bind(this, this._onStartup)); },

// Callback function for 'activate' signal presents windows when active _onActivate: function () { this._window.present (); },

// Callback function for 'startup' signal builds the UI _onStartup: function () { this._buildUI (); },

All the code for this sample goes in the TextViewExample class. The above code creates a Gtk.Application for our widgets and window to go in.

// Build the application's UI _buildUI: function () {

// Create the application window this._window = new Gtk.ApplicationWindow ({ application: this.application, window_position: Gtk.WindowPosition.CENTER, title: "Talk to a Penguin", default_height: 400, default_width: 440, border_width: 20 });

The _buildUI function is where we put all the code to create the application's user interface. The first step is creating a new Gtk.ApplicationWindow to put all our widgets into.

# Creating the TextView

// Create a label for the penguin to talk to you this._penguin = new Gtk.Label ({ height_request: 180, width_request: 400, label: "Squaaaak?", wrap: true });

Our first step in this example is to create the Label that the penguin will use to talk to you. We set the text in it to wrap by setting its wrap property to true, but we'll use a different method on the TextView itself that allows for more fine-grained control.

// Create a textview for you to talk to the penguin this.buffer = new Gtk.TextBuffer(); this._textView = new Gtk.TextView ({ buffer: this.buffer, editable: true, wrap_mode: Gtk.WrapMode.WORD });

Our first step is to create a TextBuffer to put the words into. After that we create the TextView, and tell it to use the TextBuffer we created as its buffer. We also set it to be editable, since we want to be able to type new things in.

The wrap_mode property lets you select from four different WrapModes. Gtk.WrapMode.CHAR, for instance, starts wrapping around in the middle of a word if you keep typing when it gets to the edge. Most people are probably used to Gtk.WrapMode.WORD, which will automatically put the word you're typing on the next line if it gets to be too long.

// Create a "scrolled window" to put your textview in so it will scroll this._scrolled = new Gtk.ScrolledWindow ({ hscrollbar_policy: Gtk.PolicyType.AUTOMATIC, vscrollbar_policy: Gtk.PolicyType.AUTOMATIC, shadow_type: Gtk.ShadowType.ETCHED_IN, height_request: 180, width_request: 400, });

// Put the textview into the scrolled window this._scrolled.add_with_viewport (this._textView);

Here we create a ScrolledWindow, and set it to automatically scroll if it gets to be too big horizontally or vertically. We also give it a nice-looking ETCHED_IN border. After that, we put our TextView inside, and tell the ScrolledWindow to give us a viewport onto it.

# Creating the rest of the user interface

// Create a grid to organize them in this._grid = new Gtk.Grid ({ halign: Gtk.Align.CENTER, valign: Gtk.Align.CENTER });

// Put the label and textview in the grid one on top of the other this._grid.attach (this._penguin, 0, 0, 1, 1); this._grid.attach (this._scrolled, 0, 1, 1, 1);

The first Grid we create only has the Label and the ScrolledWindow inside it.

// Create a button to send your message to the penguin this._send = new Gtk.Button ({ halign: Gtk.Align.END, margin_top: 20, label: "Send" }); this._send.connect ('clicked', Lang.bind (this, this._chat));

// Create a grid that will have the other grid on top and the button on bottom this._mainGrid = new Gtk.Grid ({ halign: Gtk.Align.CENTER, valign: Gtk.Align.CENTER });

// Add the other grid and the button to the main grid this._mainGrid.attach (this._grid, 0, 0, 1, 1); this._mainGrid.attach (this._send, 0, 1, 1, 1);

We create a Button to send your message to the penguin, and a new Grid that has the other one on top and the Button on the bottom. The Button has a margin on top, so that it isn't squished up against the ScrolledWindow.

// Attach the main grid to the window this._window.add (this._mainGrid);

// Show the window and all child widgets this._window.show_all(); },

Finally, we attach the main Grid to the window, then we tell the window and everything inside it to become visible when the application is run.

# Function which handles the penguin's response

_chat: function () {

// Create a random number to determine what the penguin says this.number = Math.floor ((Math.random() * 3) + 1);

// Did you actually say anything? if (this.buffer.text) {

// Did you mention fish? if (this.buffer.text.match (/fish/gi)) {

// Have the penguin squaak about fish if (this.number == 1) this._penguin.set_label ("FISH!");

else if (this.number == 2) this._penguin.set_label ("Fish fish fish fish. Fish!");

else this._penguin.set_label ("Fish? Fish fish fish. Fish fish. FISH!");

}

// I guess you didn't mention fish else {

// Have the penguin talk about penguinny stuff if (this.number == 1) this._penguin.set_label ("SQUAAK!");

else if (this.number == 2) this._penguin.set_label ("Ork ork ork ork squaak. Squaak squaak! *waves flippers*");

else this._penguin.set_label ("Ork ork ork ork ork?");

}

}

// Clear the buffer this.buffer.text = "";

// Give focus back to the textview so you don't have to click it again this._textView.has_focus = true;

}

});

Here we use some basic JavaScript functions to have the penguins say something random. Penguins like fish, though, so if you mention fish we want the penguin to respond to that. To do that, we use the JavaScript String object's match method on this.buffer.text, which returns the contents of our TextBuffer.

Since we want to clear out the TextBuffer after each time you click Send, we set this.buffer.text to contain an empty string afterwards. Then we return focus to our TextView, so that you can keep typing without having to click on it beforehand.

// Kör programmet let app = new TextViewExample (); app.application.run (ARGV);

Finally, we create a new instance of the finished TextViewExample class, and set the application running.

# Complete code sample

#!/usr/bin/gjs

imports.gi.versions.Gtk = '3.0'; const Gtk = imports.gi.Gtk;

class TextViewExample {

// Create the application itself constructor() { this.application = new Gtk.Application({ application_id: 'org.example.jstextview' });

// Connect 'activate' and 'startup' signals to the callback functions this.application.connect('activate', this._onActivate.bind(this)); this.application.connect('startup', this._onStartup.bind(this)); }

// Callback function for 'activate' signal presents windows when active _onActivate() { this._window.present(); }

// Callback function for 'startup' signal builds the UI _onStartup() { this._buildUI(); }

// Build the application's UI _buildUI() {

// Create the application window this._window = new Gtk.ApplicationWindow ({ application: this.application, window_position: Gtk.WindowPosition.CENTER, title: "Talk to a Penguin", default_height: 400, default_width: 440, border_width: 20 });

// Create a label for the penguin to talk to you this._penguin = new Gtk.Label ({ height_request: 180, width_request: 400, label: "Squaaaak?", wrap: true });

// Create a textview for you to talk to the penguin this.buffer = new Gtk.TextBuffer(); this._textView = new Gtk.TextView ({ buffer: this.buffer, editable: true, wrap_mode: Gtk.WrapMode.WORD });

// Create a "scrolled window" to put your textview in so it will scroll this._scrolled = new Gtk.ScrolledWindow ({ hscrollbar_policy: Gtk.PolicyType.AUTOMATIC, vscrollbar_policy: Gtk.PolicyType.AUTOMATIC, shadow_type: Gtk.ShadowType.ETCHED_IN, height_request: 180, width_request: 400, });

// Put the textview into the scrolled window this._scrolled.add_with_viewport (this._textView);

// Create a grid to organize them in this._grid = new Gtk.Grid ({ halign: Gtk.Align.CENTER, valign: Gtk.Align.CENTER });

// Put the label and textview in the grid one on top of the other this._grid.attach (this._penguin, 0, 0, 1, 1); this._grid.attach (this._scrolled, 0, 1, 1, 1);

// Create a button to send your message to the penguin this._send = new Gtk.Button ({ halign: Gtk.Align.END, margin_top: 20, label: "Send" }); this._send.connect ('clicked', this._chat.bind(this));

// Create a grid that will have the other grid on top and the button on bottom this._mainGrid = new Gtk.Grid ({ halign: Gtk.Align.CENTER, valign: Gtk.Align.CENTER });

// Add the other grid and the button to the main grid this._mainGrid.attach (this._grid, 0, 0, 1, 1); this._mainGrid.attach (this._send, 0, 1, 1, 1);

// Attach the main grid to the window this._window.add (this._mainGrid);

// Show the window and all child widgets this._window.show_all(); }

_chat() {

// Create a random number to determine what the penguin says this.number = Math.floor ((Math.random() * 3) + 1);

// Did you actually say anything? if (this.buffer.text) {

// Did you mention fish? if (this.buffer.text.match (/fish/gi)) {

// Have the penguin squaak about fish if (this.number == 1) this._penguin.set_label ("FISH!");

else if (this.number == 2) this._penguin.set_label ("Fish fish fish fish. Fish!");

else this._penguin.set_label ("Fish? Fish fish fish. Fish fish. FISH!");

}

// I guess you didn't mention fish else {

// Have the penguin talk about penguinny stuff if (this.number == 1) this._penguin.set_label ("SQUAAK!");

else if (this.number == 2) this._penguin.set_label ("Ork ork ork ork squaak. Squaak squaak! *waves flippers*");

else this._penguin.set_label ("Ork ork ork ork ork?");

}

}

// Clear the buffer this.buffer.text = "";

// Give focus back to the textview so you don't have to click it again this._textView.has_focus = true; } };

// Run the application let app = new TextViewExample (); app.application.run (ARGV);

# In-depth documentation

Gtk.Application

Gtk.ApplicationWindow

Gtk.Button

Gtk.Grid

Gtk.Label

Gtk.RadioButton

Gtk.ScrolledWindow

Gtk.TextBuffer

Gtk.TextView