Mozilla Firefox Extension Development

Course 2: Advanced

LittlebtcOSSF Workshop / MozTW Acitivity

The text of the slide is under CC-BY-SA-3.0.Most photos are under CC-BY-SA compatible license,while screenshots / logos are under Fair Use.Code is under MIT license.

Review

• Do you remember…?– XUL and controls?– Some JavaScript technique?– install.rdf and chrome.manifest?– Some XPCOM introduction?

Preference SystemMake options for your extension

Why preferences?

• Provide options to user– Which can be set in an option window– Or in the program operation

• Record user's choice

about:config

Available types

• String• Integer• Boolean: true / false

Default Preferences

• Can be included in the Extension Dir / XPI file• Will be loaded as default value of preferences• Place .js files in [ext-dir]/defaults/preferences/• Example of .js file content of default

preferences : pref("extensions.extensionname.preferencename", false);– Name: has a widely used naming convention– Value: Boolean / Integer / String

Take an example

• See defaults/preferences/ tutorial.js

pref("extensions.tutorial.option1", false);pref("extensions.tutorial.option2", "");pref("extensions.tutorial.option3", 32);pref("extensions.tutorial.default_editor", "");

See about:config

Preference System:<prefwindow>

• Way to make a "option window"• It is XUL, again• But it has a special system, in that system,

you don't need to write too much JavaScript/XPCOM to support changing preferences.

Set install.rdf, again

<em:optionsURL>chrome://tutorial/content/options.xul</em:optionsURL>

• This will point the "Options" button of your extension to the corresponding XUL pages:

<prefpane>

• Must be a child of <prefwindow>• Reprensent a pane (tab) in the prefwindow• Attributes: – label– image– onpaneload: a onload-like on this panel– src: Content can be external XUL

<prefpane id="paneGeneral" label="General" src="chrome://path/to/paneOverlay.xul"/>

<preferences> <preference>

• <preferences>: Container• <preference>: "Magic Attribute" to hold the

actual preference, attributes:– id– name: Corresponding preference name– type: bool/string/unichar/int/file

• In controls, use preference="id" to connect the magic!

Example: options.xul<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet href="chrome://global/skin/" type="text/css"?><?xml-stylesheet href="chrome://mozapps/content/preferences/preferences.css"?><?xml-stylesheet href="chrome://browser/skin/preferences/preferences.css"?>

<prefwindow xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <prefpane id="panel1" label="panel1"> <preferences> <preference name="extensions.tutorial.option1" id="extensions.tutorial.option1" type="bool" /> <preference name="extensions.tutorial.option2" id="extensions.tutorial.option2" type="unichar" /> </preferences> <checkbox id="option1" preference="extensions.tutorial.option1" label="Check me!" /> <hbox> <label value="Type Your Name:" accesskey="N" control="option2" /> <textbox id="option2" preference="extensions.tutorial.option2" /> </hbox> </prefpane> <prefpane id="panel2" label="panel2" src="chrome://tutorial/content/panel2.xul"/></prefwindow>

Example: panel2.xul<?xml version="1.0" encoding="UTF-8"?>

<overlay id="Pane2Overlay" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <prefpane id="panel2"> <preferences> <preference name="extensions.tutorial.option3" id="extensions.tutorial.option3"

type="int" /> </preferences> <hbox> <label value="Type a Integer:" accesskey="I" control="option3" /> <textbox id="option3" preference="extensions.tutorial.option3" type="number" /> </hbox> </prefpane></overlay>

Result

Part 2: Read/Write in XPCOM

• XPCOM: nsIPrefService / nsIPrefBranch• Changes Preferences in JavaScript• First step: Read branch// Get the root branchvar prefs = Components.classes["@mozilla.org/preferences-service;1"]

.getService(Components.interfaces.nsIPrefBranch);

// Get the "extensions.tutorial." branchvar prefs = Components.classes["@mozilla.org/preferences-service;1"]

.getService(Components.interfaces.nsIPrefService); prefs = prefs.getBranch("extensions.tutorial.");

Part 2: Read/Write in XPCOM

• Then, read/write• getBoolPref(), setBoolPref()• getCharPref(), setCharPref()– BEWARE: Not Unicode Compatible!

• getIntPref() and setIntPref()

Part 2: Read/Write in XPCOM

Examples to run in JavaScript Shell:// Get the "extensions.tutorial." branchvar prefs = Components.classes["@mozilla.org/preferences-service;1"]

.getService(Components.interfaces.nsIPrefService); prefs = prefs.getBranch("extensions.tutorial.");

// Get the value of option3 (a number)var option3 = prefs.getIntPref('option3');alert(option3);// Set the value of option1 (a boolean) to trueprefs.setBoolPref('option1', true);var option1 = prefs.getBoolPref('option1');alert(option1);

Part 2: Read/Write in XPCOM

• Read/Write Unicode Strings:(from https://developer.mozilla.org/en/Code_snippets/Preferences)// Example 1: getting Unicode valuevar option2 = prefs.getComplexValue("option2",

Components.interfaces.nsISupportsString).data;alert(option2);

// Example 2: setting Unicode valuevar str = Components.classes["@mozilla.org/supports-string;1"] .createInstance(Components.interfaces.nsISupportsString);str.data = "火狐 ";prefs.setComplexValue("option2", Components.interfaces.nsISupportsString, str);

When you should use XPCOM

• First run:– Make a default pref to detect first run

(Change it after first run processing is ended)

• Dialog to remember something:– Like "Exit Firefox":

File ProcessingAccess local fileshttps://developer.mozilla.org/en/Code_snippets/File_I%2f%2fO

The nsIFile / nsILocalFile• nsIFile: Cross-platform File I/O interface• nsILocalFile: extends nsIFile, can access local

filesystem• It is a "LOCATION INDICATOR"• What can nsILocalFile object do?– Check whether the file exists– Copy / Delete / Move files– Create files / folders– Work as a parameter to a lot of function

• Saving webpage into files, etc…

"Create" a nsILocalFile

• With a absolute path:var file = Components.classes["@mozilla.org/file/local;1"] .createInstance(Components.interfaces.nsILocalFile);file.initWithPath("C:\\");

• "Path" should be in a "native" waylike /home/littlebtc in Linux, C:\ in Windows

• file:// URI? Explained later

"Create" nsIFile pointing to special folders

• Get an object located to Profile Directory:// get profile directoryvar file = Components.classes["@mozilla.org/file/directory_service;1"] .getService(Components.interfaces.nsIProperties) .get("ProfD", Components.interfaces.nsIFile);

• You can replace the ProfD with:With… Where With… Where

CurProcD (Firefox) Installation Dir

Desk DesktopC:\Users\Littlebtc\Desktop

Home User's DirC:\Users\Littlebtc/home/littlebtc/

Progs "Programs" directory inWindows Start Menu

resource:app XULRunner App Directory

How to…

Assuming we have a nsIFile object file, how to• Get the native path representation of a nsIFile?

– file.path

• Know whether the path refers to a existed thing?– file.exists()

– Return true or false• Distinguish the path which this file object refers

to from a folder, a file, or a link, or others?– Use file.isFile() file.isFolder() file.isSymlink() file.isSpecial()

How to…

• Whether the path is readable/writable/executable/hidden?• Use file.isWritable() file.isReadable()

file.isExecutable() file.isHidden()

• Know the filesize (if it is a file)?– file.fileSize

• The file name without path?– file.leafName

• The parent of the path?– file.parent (It is a nsIFile object, and can be null!)

How to…

• "Open the file" by the OS?• file.launch();

• Do something like "Open containing folder" in download manager?• file.reveal();

• Both of them are not work on Unix-like!

How to…

• Delete the path?– file.remove();

– For folder, you can only remove empty folder

• Copy path?– file.copyTo(file2, 'newname');– file2 represents the parent path for the target item,

if it is null, it will be copied to the same parent of file• Move path?

– file.moveTo(file2, 'newname');

– file2 is the same as above– You can only move empty folder

How to…

• How to "run the file" if it is a executable?– file.launch(); (Not recommended)– Use nsIProcess:

https://developer.mozilla.org/En/Code_snippets/Running_applications

– nsIProcess cannot accept Unicode parameters on Windows…

How to…Assuming file is a nsIFile object refering to a folder path, how to:• Access a file in this directory?

– file.append('filename');Then file will be changed, will refer to this file, not the original folder!

• Access multiple files? Clone object, then append– var file1 = file.clone(); // Clone file object

file1.append('filename');

• How to create a subfolder?– file.append("DIR"); // Still, append first

if( !file.exists() || !file.isDirectory() ) { // if it doesn't exist, create file.create(Components.interfaces.nsIFile.DIRECTORY_TYPE, 0777);}

File contents read/write

• https://developer.mozilla.org/en/Code_snippets/File_I%2f%2fO

• A little complex, why? When it comes to the encoding, it will be complex

File Picker / <filefield>

• File Open / File Save / Select Folder Dialog• See

https://developer.mozilla.org/en/nsIFilePicker• <filefield> in the <prefwindow>, like Firefox

options (UNDOCUMENTED):http://www.xuldev.org/blog/?p=142

• We will have a small demo!

File I/O demo 1

• A run dialog like Windows, use undocumented <filefield>

run.xul<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet href="chrome://global/skin" type="text/css"?>

<dialog title="Run application" buttons="accept,cancel" ondialogaccept="runApp.go();"

xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"><script type="application/x-javascript" src="chrome://tutorial/content/run.js"/><hbox><label value="Select an file:" accesskey="F" /> <filefield id="file" /><button label="Browse..." oncommand="runApp.browse();" /></hbox><grid><columns> <column flex="1" /> <column flex="2" /></columns><rows> <row> <label value="File name:" /><label value="" id="file_name" /> </row><row> <label value="File size:" /><label value="" id="file_size" /> </row></rows></grid></dialog>

run.js (partial) browse: function() { // Initialize file picker var fp = Cc["@mozilla.org/filepicker;1"].createInstance(Ci.nsIFilePicker); fp.init(window, 'Select a file', Ci.nsIFilePicker.modeOpen);

// Set Filter: file types fp.appendFilter('Windows executable', '*.exe'); fp.appendFilter('All Files', '*.*');

// Show the dialog var result = fp.show(); if (result == Ci.nsIFilePicker.returnOK) { this.file = fp.file; // This should not be happened, but this is a demo :P if (!this.file.exists() || !this.file.isFile()) { return; } // Include it into filefield document.getElementById('file').file = this.file; // Load file infos document.getElementById('file_name').value = this.file.leafName; document.getElementById('file_size').value = this.file.fileSize + ' bytes'; }},

run.js (partial 2) go: function() { if (this.file && this.file.exists() &&

this.file.isFile()) { this.file.launch(); } }

URI Problem• In XPCOM, nsIURI is a common interface to represent

an URI (It can handle all types of URI)• nsIURI <-> String URL: Use nsIIOService

– var uri = Components.classes["@mozilla.org/network/io-service;1"].getService(Components.interfaces.nsIIOService).newURI('http://moztw.org/', null, null);

– uri.spec will contain the string representation of the URI• nsIURI <-> nsIFile

– var file_uri = Components.classes["@mozilla.org/network/io-service;1"] .getService(Components.interfaces.nsIIOService).newFileURI(file); // Assuming file is a nsIFIle

– var file = file_uri.QueryInterface(Components.interfaces.nsIFileURL).file;

When you will need nsIURI / nsIFile• Downloading files

https://developer.mozilla.org/en/Code_snippets/Downloading_Files (Basic)http://www.xuldev.org/blog/?p=163 (Advanced, by Gomita, a good intro to nsIWebBrowserPersist)

• Use Places API (Bookmarks, Tags, History)https://developer.mozilla.org/en/Places

• Progress listenershttps://developer.mozilla.org/en/Code_snippets/Progress_Listeners

• And much more…

TreeA somehow complex XUL structure

What is a tree?

• A complex item lists• An item may have some childs

Why is it so complex• There are A LOT OF way to implement• But none of them are NOT trivial • Some is easier but not so easy to be extended• Some is harder, but fully functional

The easiest: Content Tree• (Try XUL Editor!)• From https://developer.mozilla.org/En/XUL/Tree

<tree flex="1" rows="2"> <treecols> <treecol id="sender" label="Sender" flex="1"/> <treecol id="subject" label="Subject" flex="2"/> </treecols> <treechildren> <treeitem> <treerow> <treecell label="joe@somewhere.com"/> <treecell label="Top secret plans"/> </treerow> </treeitem> <treeitem> <treerow> <treecell label="mel@whereever.com"/> <treecell label="Let's do lunch"/> </treerow> </treeitem> </treechildren></tree>

The easiest: Content Tree

• <tree>: Sent a row number as rows attribute is recommended?

• <treecols>, <treecol>: Define the columns– Use flex to modify column width in <treecol>– Use id to build an identifier of the column

• <treeitem>, <treerow>: Represents a row• <treecell>: Represents a cell– Attribute: label

A tree with nested itemsFrom https://developer.mozilla.org/En/XUL/Tree

<tree id="myTree" flex="1" hidecolumnpicker="false" seltype="single" class="tree" rows="5"> <treecols id="myTree2-treeCols"> <treecol id="myTree2-treeCol0" primary="true" flex="2" label="Column A" persist="width" ordinal="1"/> <splitter class="tree-splitter" ordinal="2"/> <treecol id="myTree2-treeCol1" flex="1" label="Column B" persist="width" ordinal="3"/> </treecols> <treechildren> <treeitem> <treerow> <treecell label="1"/> <treecell label="a"/> </treerow> </treeitem> <!-- Make sure to set container="true" --> <treeitem container="true" open="true"> <treerow> <treecell label="2"/> <treecell label="b"/> </treerow> <treechildren> <treeitem> <treerow> <treecell label="2a"/> <treecell label="ba"/> </treerow> </treeitem> </treechildren> </treeitem> </treechildren></tree>

Wait, a lot of new thing…?

• <splitter>: Between columns, to make them resizable

• Nested items: <treechildren> under <treeitem>• hidecolumnpicker="false"– Whether to hide the column picker on the right– seltype="single": you can select only one item

or seltype="multiple" for multiple selection support• persist="attributename1 attributename2"– Make Firefox "remember" user's settings on specific

attribute

OK, now, what is wrong?

• Though we can multiply the tree with DOM, but it will the code will be somehow complex due to the bad XUL structure

• So DOM way is not a popular way if it comes to dynamic content trees

The most common: Custom TreeView

• Implements nsITreeView to create a tree• Set custom tree view into view property• It can be fully functional and dynamic

– …But somehow hard: poorly documented and buggy if having bad implementation

– You should check Firefox's code to understand – It takes me almost 20 hours to make <tree> on NicoFox works

and another 20 hours to fix bugs…• Are you ready? :Dhttps://developer.mozilla.org/en/XUL_Tutorial/

Custom_Tree_Viewshttp://www.xuldev.org/blog/?p=127 (Thank you again,

Gomita!)

Tree Selection / Box Object

• Tree Selection: Get currently selected itemshttps://developer.mozilla.org/en/XUL_Tutorial/Tree_Selection– A little like text selection we had mentioned at the

previous lecture (?)• Box Objects: Handle Tree's display

Needed, for example, if you need to know the which cell the cursor is athttps://developer.mozilla.org/en/XUL_Tutorial/Tree_Box_Objects

LUNCH TIME AGAIN!Take a break, there is a final boss: SQLite!

Storage: SQLiteGreat storage choice

What is SQLite?

• A lightweight relational database management system

• Its C/C++ library is very small (418KB in Firefox 3.5) and very easy-to-use

• Can use most of the SQL command• Resulting database is a single file• PUBLIC DOMAIN!(No any copyright restriction)• Used by a lot of software / framework

SQLite is in …

• Firefox, Safari, Google Chrome• Google Gears• Photoshop lightroom, Adobe AIR• Skype, McAfee, Songbird• PHP, Python…• iPhone, Symbian, Android…• Almost everywhere!!!!

Now, make a new database!

Now, make a new database!

• Find your profile dir and copy the path Orz

Now, make a new database!

• Close SQLite manager and restart:

Create a table

Table is ready!

Add a record

Simple way to display SQLite DB

• Use templatehttps://developer.mozilla.org/en/XUL/Template_Guide/SQLite_Templates

• Simple, but useful for our demo! :D• We will use the template technique and

<tree> in the following demo

students.xul

<tree flex="1"> <treecols> <treecol id="col-no" label="No" flex="1"/> <treecol id="col-name" label="Name" flex="1"/> <treecol id="col-score" label="Score" flex="1"/> </treecols> <treechildren datasources="profile:tutorial.sqlite" ref="*" querytype="storage"> <template> <query> SELECT * FROM students ORDER BY score DESC </query> <action> <treeitem uri="?"> <treerow> <treecell label="?no"/> <treecell label="?name"/> <treecell label="?score"/> </treerow> </treeitem> </action> </template> </treechildren></tree>

Explain

• <treechildren datasources="profile:tutorial.sqlite" ref="*" querytype="storage">

• Use SQLite database as a template datasources• <template>: <query> and <action>– <query>: SQL command

• SELECT * FROM students: Select all fields from students table• ORDER BY score DESC: Order by score field in descendant order

– <action>: Applied template• uri="?": (?)• Read score field from ?score

mozStorage API

• Mozilla's way to multiply SQLite database• So it is XPCOM again … • But it is not so difficult!

• I don't want to talk in detail, so go straight to examples!

Final Demo:"Add a record" function

A SQL preview

• INSERT INTO students (name, score) VALUES ("Littlebtc", 30)

• Insert a data into students table• Two fields: name and score• Their values: Littlebtc and 30

students.xul, again<hbox><label value="Student Name:" accesskey="N" control="new_name" /><textbox id="new_name" style="width: 8em;"/>

<label value="Score:" accesskey="S" control="new_score" /><textbox id="new_score" type="number" style="width: 4em;"

max="100" min="0"/>

<button label="Add" oncommand="students.add();"/></hbox>

student.js: student.add();/* use nsIPromptService to alert */ /*

https://developer.mozilla.org/en/Code_snippets/Dialogs_and_Prompts */

var prompts = Cc["@mozilla.org/embedcomp/prompt-service;1"] .getService(Ci.nsIPromptService);

/* Record user's choice */ var name = document.getElementById('new-name').value; var score = document.getElementById('new-score').value;

/* Required to enter a name */ if (!name) { prompts.alert(null, 'Error', 'Please Enter a Name.'); return; }

…continued try { // try-catch exception handling

/* We will see here later */ } catch(e) { // There may be some error in XPCOM, we can handle it prompts.alert(null, 'Error', 'Database/XPCOM Error:' + e); }

• XPCOM Will throw exception when error• So we need a good way to handle it• …Or it will be displayed in the error console

Connect to DB/* Find the tutorial.sqlite */var file = Components.classes["@mozilla.org/file/directory_service;1"] .getService(Components.interfaces.nsIProperties) .get("ProfD", Components.interfaces.nsIFile);

file.append("tutorial.sqlite");

/* Open database */var storageService = Cc["@mozilla.org/storage/service;1"] .getService(Ci.mozIStorageService);var db = storageService.openDatabase(file);

Execute a "statement"var sql = "INSERT INTO students (name, score) VALUES (?

1, ?2)";var statement = db.createStatement(sql);statement.bindUTF8StringParameter(0, name);statement.bindInt32Parameter(1, score);/* Execute the statement */statement.execute();/* Finallize */statement.finalize();

• "Statement" is a SQL command in mozStorage• Why we should use the "binding" way?

Prevent SQL injection, make database safe• https://developer.mozilla.org/en/

mozIStorageStatement#Binding_Functions

Finally…

• Don't forget to close your DB!

db.close();

After try{…} catch{…}

• We should update the tree and show a message

/* Update the tree */document.getElementById('students-treechildren').builder.rebuild();

/* Prompt the user */

prompts.alert(null, 'OK', 'Thank you!');

Working Example

How to do for you later

• Understand how to CRUD (Create, Read, Update, Delete) in SQLite– SQL commands: INSERT, SELECT, UPDATE, DELETE

• Remember: Always Binding, NEVER directly apply variables into SQL command strings– Google "SQL Injection" for details

• SQLite is simple but powerful – have fun!

This is the basic!• Actually, SQLite storage access with <tree> is

usually implemented in Custom Tree View way, both in Firefox and NicoFox

• That is another reason that I had spent 40 hours on a tree

• Edit / Remove may be a very hard work

THANK YOU!It is 5:34am, I had finished my slide

…….NOT YET!!!