Annotator Design Overview
The annotator uses content scripts to build user interfaces, get user input, and examine the DOM of pages loaded by the user.
Meanwhile the main
module contains the application logic and mediates
interactions between the different SDK objects.
We could represent the basic interactions between the main
module and the
various content scripts like this:

User Interface
The annotator's main user interface consists of a widget and three panels.
- The widget is used to switch the annotator on and off, and to display a list of all the stored annotations.
- The annotation-editor panel enables the user to enter a new annotation.
- The annotation-list panel shows a list of all stored annotations.
- The annotation panel displays a single annotation.
Additionally, we use the notifications
module to notify the user when the
add-on's storage quota is full.
Working with the DOM
We'll use two page-mods to interact with the DOMs of pages that the user has opened.
-
The selector enables the user to choose an element to annotate. It identifies page elements which are eligible for annotation, highlights them on mouseover, and tells the main add-on code when the user clicks a highlighted element.
-
The matcher is responsible for finding annotated elements: it is initialized with the list of annotations and searches web pages for the elements they are associated with. It highlights any annotated elements that are found. When the user moves the mouse over an annotated element the matcher tells the main add-on code, which displays the annotation panel.
Working with Data
We'll use the simple-storage
module to store annotations.
Because we are recording potentially sensitive information, we want to prevent
the user creating annotations when in private browsing mode, so we'll use the
private-browsing
module for that.
Getting Started
Let's get started by creating a directory called "annotator". Navigate to it
and type cfx init
.
Next, we will implement the widget.