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chrome_settings.md

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What is chrome://settings?

Chrome (version 10 and above) uses WebUI settings by default for all platforms. Access it via the wrench menu ("Preferences" on Mac and Linux; "Options" on Windows and ChromeOS), or by typing chrome://settings into the address bar.

One advantage of chrome://settings over platform-native dialogs is that it is shared by all platforms; therefore, it is easier to add new options UI and to keep all platforms in sync.

Note that at the time of this writing, DOMUI is being renamed to WebUI. The two terms will be used interchangeably herein.

Moving parts

String resources

Strings live in chrome/app/generated_resources.grd. There are several rules governing the format of strings:

  • the casing of button text depends on the platform. If your string will be displayed on a button, you need to add it twice, in sentence case and title case. Follow examples inside <if expr="pp_ifdef('use_titlecase')"> blocks. Do this even if your string is a single word because it may not be a single word in another locale.
  • strings that are associated with form controls (buttons, checkboxes, dropdowns, etc.) should NOT have trailing punctuation. Standalone strings, such as sectional descriptive text, should have trailing punctuation.
  • strings may be different between Google Chrome and chromium. If they differ only in product name, put them in generated_resources.grd and use product name placeholders; if they differ more substantially, use chromium_strings.grd and google_chrome_strings.grd.

WebUI Handlers

The C++ WebUI handler classes for chrome://settings live in chrome/browser/ui/webui/options/. These objects both handle messages from and dispatch messages to the page. Each handler is a logical grouping of related functionality. Hence ContentSettingsHandler is both the delegate and controller of the content settings subpage.

A handler sends a message to the page via dom_ui_->CallJavascriptFunction() and registers for messages from the page via dom_ui_->RegisterMessageCallback().

HTML/CSS/JS

The HTML, CSS, and JS resources live in chrome/browser/resources/options. They are compiled into one resource at compile time by grit, via <link>, <src> and <include> tags in options.html. There is no need to add new files to any .gyp file.

Some things that are good to know:

  • JS objects are bound to HTML nodes via decorate(). * Javascript calls into C++ via chrome.send. * Some automatic preference handling is provided in preferences.js and pref_ui.js. * Strings defined in a WebUI handler are available via localStrings.getString() and friends.

Example: adding a simple pref

Suppose you want to add a pref controlled by a checkbox.

1. Getting UI approval

Ask one of the UI leads where your option belongs. First point of contact should be Alex Ainslie .

2. Adding Strings

Add the string to chrome/app/generated_resources.grd near related strings. No trailing punctuation; sentence case.

3. Changing WebUI Handler

For simple prefs, the UI is kept in sync with the value automagically (see CoreOptionsHandler). Find the handler most closely relevant to your pref. The only action we need take here is to make the page aware of the new string. Locate the method in the handler called GetLocalizedStrings and look at its body for examples of SetString usage. The first parameter is the javascript name for the string.

4. HTML/CSS/JS

An example of the form a checkbox should take in html:

<label class="checkbox">
  <input id="clear-cookies-on-exit"
       pref="profile.clear_site_data_on_exit" type="checkbox">
  <span i18n-content="clearCookiesOnExit"></span>
</label>

Of note:

  • the checkbox class allows us to style all checkboxes the same via CSS
  • the class and ID are in dash-form * the i18n-content value is in camelCase
  • the pref attribute matches that which is defined in chrome/common/pref_names.cc and allows the prefs framework to automatically keep it in sync with the value in C++
  • the i18n-content value matches the string we defined in the WebUI handler. The textContent of the span will automatically be set to the associated text.

In this example, no additional JS or CSS are needed.