Implementing Public Preview

This topic describes how to implement a public preview for the Smart Hub Preview feature. A public preview shows the same preview content to all users.

Related Info

Application API

Samples

Public preview content is defined by a remotely-hosted JSON file. You can configure the JSON file to expire and refresh at a specific time. The public preview generation process is shown in the following figure.

Figure 1. Public preview generation process

The URL of the remote JSON file is defined in the application's "config.xml" file.
The preview is generated and shown based on the JSON data.
The user clicks a preview tile.
The JSON action_data value corresponding to the selected tile is sent to the application.
The application parses the action_data value and shows the detail page.

Prerequisites

To enable your application to use the public preview functionality:

Define the remote JSON file URL in the "config.xml" file:

<tizen:metadata key='http://samsung.com/tv/metadata/use.preview' value='endpoint_URL=http://yourServer/JSONfile.json'></tizen:metadata>

Disable reloading the application main page when it receives an application control request. This allows your application, if it is already running, to receive the action_data information without reloading.
```
<tizen:app-control>
  <tizen:src name='index.html' reload='disable'></tizen:src>
  <tizen:operation name='http://samsung.com/appcontrol/operation/eden_resume'></tizen:operation> 
</tizen:app-control>
```
If you want the application to support 2015 TV models, set the required_version attribute to "2.3" and the development API version meta data attribute to "2.4" in the "config.xml" file:
```
<tizen:application ... required_version='2.3'></tizen:application>
<tizen:metadata key='http://samsung.com/tv/metadata/devel.api.version' value='2.4'></tizen:metadata> 
```

Configuring Public Preview Data

The preview content is defined in JSON format. The application can only use 1 preview content JSON file at a time.

The following table lists the structure and parameters for the preview content JSON data.

Parameter			Type	Mandatory	Description
`expires`			UNIX timestamp	false	For public preview only If specified, the time at which the preview content is updated. The time is at most 1 week into the future. By default, the preview content is updated every 10 minutes, whenever the TV is switched on, or the JSON file changes.
`expires_only`			Boolean	false	For public preview only If this value is "true", the preview content is updated only at the time specified by the `expires` parameter. The default value is "false". It is supported in 2018 TV models and newer.
`sections`			Array	true	Preview sections
	`title`		String	false	Section title
	`position`		Integer		Section position If specified, sections are shown in ascending position order.
	`title_display_mode`		String		The following three values are supported: `AlwaysOn` `HighlightedOnly` (default) Show the title while the tile is in focus. `AccessibilityOnly` Title is hidden when tile is in focus, Voice Guide is provided when the accessibility setting is set to ON. For more information, see the detailed description below the table.
	`subtitle_display_mode`		String		The following three values are supported: `AlwaysOn` `HighlightedOnly` (default) Show the subtitle while the tile is in focus. `AccessibilityOnly` Subtitle is hidden when tile is in focus. Voice Guide is provided when the accessibility setting is set to ON. For more information, see the detailed description below the table.
	`tiles`		Array	true	Tiles within the section
		`title`	String	false	Tile title
		`subtitle`		false	Tile subtitle
		`image_url`		true	Thumbnail image URL
		`image_ratio`			Thumbnail image aspect ratio: "16by9" "4by3" "1by1" (default) "2by3" The thumbnail height is fixed at 250 px on presentation.
		`action_data`			Data to send to the application when the tile is clicked
		`is_playable`			If "true", a "Play" icon is shown over the thumbnail image
		`display_from`	UNIX timestamp	false	Time to begin showing the tile
		`display_until`	UNIX timestamp		Time to stop showing the tile
		`position`	Integer		Section position If specified, sections are shown in an ascending order by the position value.

Table 1. Preview JSON parameters

For an example of a preview content JSON file, see sampleJSON.

The JSON parameters title_display_mode and subtitle_display_mode for displaying title and subtitle of tiles, respectively, support the following options:

AlwaysOn - If this option is enabled, the title or subtitle is always displayed when the preview is visible.
HighlightedOnly - This is the default option, which shows the title or subtitle when the tile is in focus.
AccessibilityOnly - If this option is enabled, the title or subtitle is not displayed. There is only a Voice Guide when the accessibility setting is set to ON and the preview tile is in focus.

ImportantVoice Guide (Text-to-Speech feature) is supported by all the three options detailed above, if the accessibility setting for Voice Guide is turned on by the user.
Please note that this behavior is an accessibility feature to assist users, and it should comply with the policies of the countries the application is released in.
If only the preview tile image is to be shown to user, and the title and subtitle are required to be hidden, add the title and subtitle values to the JSON file, and set the AccessibilityOnly value for both properties. This ensures that the title and subtitle will not be visible to user, but are read out loud when the tile is in focus.

When the preview system requests JSON data from your server, TV information is sent in the HTTP header. You can serve different preview content depending on TV information, such as the language, and application version.

The following table lists the HTTP header fields that contain TV information.

Field	Description
`ACCEPT-LANGUAGE`	TV language setting, such as 'en-US'
`X-SAMSUNG-APP-VERSION`	Application version
`X-SAMSUNG-COUNTRY-CODE`	TV Smarthub country setting, such as 'US' in ISO 3166-1 Alpha 2 Format

Table 2. HTTP header fields

Implementing Public Preview Deep Links

When a tile is clicked, its associated action_data value is converted to an ApplicationControlData object with the PAYLOAD key:

{
  "key": "PAYLOAD", 
  "value": ["{\"values\": \"{\\\"videoIdx\\\": 1}\"}"] 
}

For more information on ApplicationControlData objects, see the Application API.

To implement deep-linking:

To receive action_data information when the application is already running, add an event listener for the appcontrol event to the onload property:
```
window.addEventListener('appcontrol', deepLink); 
```

In the onload property, receive and parse the PAYLOAD key value, using the getCurrentApplication().getRequestedAppControl() method:

function deepLink() { 
  var requestedAppControl = tizen.application.getCurrentApplication().getRequestedAppControl(); 
  var appControlData;
  var actionData; 

  var videoIdx; 
  var pictureIdx; 

  if (requestedAppControl) {
    appControlData = requestedAppControl.appControl.data; 

    for (var i = 0; i < appControlData.length; i++) { 
      if (appControlData[i].key == 'PAYLOAD') { 
        actionData = JSON.parse(appControlData[i].value[0]).values; 

        if (JSON.parse(actionData).videoIdx) { 
          videoIdx = JSON.parse(actionData).videoIdx; 
          console.log(videoIdx); 
        } else if (JSON.parse(actionData).pictureIdx) { 
          pictureIdx = JSON.parse(actionData).pictureIdx; 
          console.log(pictureIdx); 
        } 
      } 
    } 
  } else { 
    console.log("no req app control"); 
  } 
}