docs: Improve docs of desktopCapturer

docs/api/desktop-capturer.md

@@ -1,11 +1,11 @@
-# desktop-capturer
+# desktopCapturer
 
-The `desktop-capturer` is a renderer module used to capture the content of
-screen and individual app windows.
+The `desktopCapturer` module can be used to get available sources that can be
+used to be captured with `getUserMedia`.
 
 ```javascript
 // In the renderer process.
-var desktopCapturer = require('desktop-capturer');
+var desktopCapturer = require('electron').desktopCapturer;
 
 desktopCapturer.getSources({types: ['window', 'screen']}, function(error, sources) {
   if (error) throw error;
@@ -44,35 +44,26 @@ The `desktopCapturer` module has the following methods:
 
 ### `desktopCapturer.getSources(options, callback)`
 
-`options` Object, properties:
-* `types` Array - An array of String that enums the types of desktop sources.
-  * `screen` String - Screen
-  * `window` String - Individual window
-* `thumbnailSize` Object (optional) - The suggested size that thumbnail should
-  be scaled.
-  * `width` Integer - The width of thumbnail. By default, it is 150px.
-  * `height` Integer - The height of thumbnail. By default, it is 150px.
+* `options` Object
+  * `types` Array - An array of String that lists the types of desktop sources
+    to be captured, available types are `screen` and `window`.
+  * `thumbnailSize` Object (optional) - The suggested size that thumbnail should
+    be scaled, it is `{width: 150, height: 150}` by default.
+* `callback` Function
 
-`callback` Function - `function(error, sources) {}`
-
-* `error` Error
-* `sources` Array - An array of Source
-
-Gets all desktop sources.
-
-**Note:** There is no garuantee that the size of `source.thumbnail` is always
-the same as the `thumnbailSize` in `options`. It also depends on the scale of
-the screen or window.
-
-## Source
-
-`Source` is an object represents a captured screen or individual window. It has
-following properties:
+Starts a request to get all desktop sources, `callback` will be called with
+`callback(error, sources)` when the request is completed.
 
+The `sources` is an array of `Source` objects, each `Source` represents a
+captured screen or individual window, and has following properties:
 * `id` String - The id of the captured window or screen used in
-  `navigator.webkitGetUserMedia`. The format looks like 'window:XX' or
-  'screen:XX' where XX is a random generated number.
-* `name` String - The descriped name of the capturing screen or window. If the
-  source is a screen, the name will be 'Entire Screen' or 'Screen <index>'; if
+  `navigator.webkitGetUserMedia`. The format looks like `window:XX` or
+  `screen:XX` where `XX` is a random generated number.
+* `name` String - The described name of the capturing screen or window. If the
+  source is a screen, the name will be `Entire Screen` or `Screen <index>`; if
   it is a window, the name will be the window's title.
 * `thumbnail` [NativeImage](NativeImage.md) - A thumbnail image.
+
+**Note:** There is no guarantee that the size of `source.thumbnail` is always
+the same as the `thumnbailSize` in `options`. It also depends on the scale of
+the screen or window.