HomeScreen GUI Application / HomeScreen Service Guide

Revision: 0.1
Advanced Driver Information Technology

Table of content

Target reader of this document

Application developer whose software uses HomeScreen.


HomeScreen is built with a GUI application created with Qt(referred as HomeScreenGUI), and a service running on afb-daemon (referred as HomeScreenBinder). HomeScreen can start/switch applications run in AGL, also displays information such as onscreen messages.

You can find these projects in AGL gerrit.

Also HomeScreenGUI is using libwindowmanager.

Getting Start

Supported environment

Item Description
AGL version Grumpy Guppy
Hardware Renesas R-Car Starter Kit Pro(M3)


Download recipe

$ mkdir WORK
$ cd WORK
$ repo init -u
$ repo sync

Then you can find the following recipes.

  • meta-agl-demo/recipes-demo-hmi/homescreen

  • meta-agl-devel/meta-hmi-framework/recipes-demo-hmi/launcher

  • meta-agl-demo/recipes-demo-hmi/agl-service-homescreen

  • meta-agl-demo/recipes-demo-hmi/libhomescreen

  • meta-agl-devel/meta-hmi-framework/recipes-demo-hmi/qlibhomescreen


$ source meta-agl/scripts/ -m m3ulcb agl-demo agl-devel agl-appfw-smack agl-hmi-framework
$ bitbake agl-demo-platform


To use HomeScreen API, an application shall paste the following configuration definition into “config.xml” of application.

<feature name="urn:AGL:widget:required-api">
	<param name="homescreen" value="ws" />
    <param name="windowmanager" value="ws" />

How to call HomeScreen APIs from your Application?

HomeScreen provides a library which is called “libhomescreen”. This library treats “json format” as API calling. For example, if an application wants to call “showWIndow()” API, the you should implement as below.

At first the application should create the instance of libhomescreen.

LibHomeScreen* libhs;
libhs = new LibHomeScreen();
libhs->init(port, token);

The port and token is provided by Application Framework

Execute the “showWindow()” function.

libhs->showWindow("application_id", "display_area");

Regarding the detail of showWindow() API, please refer this section. The first parameter is the appid of application which want to display,liked “dashboard”. And the second parameter corresponds to display_area which defined by windowmanager,usually “normal”, so in this case “showWindow” the two parameters are proper string.

See also our Sample code.

Supported usecase

  1. HomeScreenGUI sending showWindow event to applications
    • Applications using libhomescreen to subscribe the showWindow event, HomeScreenGUI will send showWindow event to applications.
  2. Display OnScreen messages(deprecated)
    • Applications sending OnScreen messages to homescreen-service, and OnScreenAPP will get these message and display.
  3. Get OnSreen Reply event(deprecated)
    • When OnScreen messages is displaying, OnScreenAPP will send a reply event to applications.
  4. Display OnScreen by showWindow
    • When application who want to show OnScreen,it can call “showWindow”,then OnScreenApp will display request OnScreen.
  5. Hide OnScreen by hideWindow
    • When application who want to hide OnScreen which is displaying,it can call “hideWindow”,then OnScreenApp will hide OnScreen.
  6. Send OnScreen Reply by replyShowWindow
    • When user touch the button of OnScreen, OnScreenApp can call “relplyShowWindow” to send reply information back to application.
  7. Show Notification on HomeScreenGUI
    • When application who want to display a notification,it can call “showNotification”,then HomeScreenGUI will display the notification contents on the screen top area.
  8. Show Information on HomeScreenGUI
    • When application who want to display a information,it can call “showInformation”,then HomeScreenGUI will display the information contents on the screen bottom area.

Software Architecture

The architecture of HomeScreen is shown below. HomeScreen is the service designed to be used by multiple applications. Therefore HomeScreen framework consists on two binder layers. Please refer the following figure. The upper binder is for application side security context for applications. The lower binder is for servide side security context. Usually application side binder has some business logic for each application, so the number of binders depend on the number of applications which use HomeScreen. On the other hand, regarding lower binder there is only one module in the system. This binder receives all messages from multiple applications (in detail, it comes from upper layer binder).

The communication protocols between libhomescreen and upper binder, upper binder and lower binder, lower binder (homescreen-binding) are WebSocket.


API reference

“libhomescreen” and “agl-service-homescreen” provides several kinds of APIs.

HomeScreen Specific API


Initialize Sequence


Tap Shortcut Sequence


ShowWindow Sequence


On Screen Message / Reply Sequence


ShowOnScreen Sequence


ShowNotification Sequence


ShowInformation Sequence


Sample code

You can find sample implementation of HomeScreen as below.

  • libhomescreen/sample/simple-egl

  • libhomescreen/sample/template


Now OnScreenApp is developing,approximately it will finished at GG.

Next Plan




title Application initialization phase

entity App
entity HomeScreenBinder
entity HomeScreenGUI

App->HomeScreenBinder: init(port, token)
App->HomeScreenBinder: set_event_handler()

note over HomeScreenBinder
    setup event handler the App wishes to receive
end note

title Application Callback Event TapShortcut phase
entity App
entity HomeScreenBinder
entity HomeScreenGUI
App->HomeScreenBinder: set_event_handler()

note over App
end note

HomeScreenGUI->HomeScreenBinder: tapShortcut(application_id)
HomeScreenBinder->App: event_handler(application_id)

title Application callback event showWindow phase

actor user
entity "homescreen-service" as hss
entity launcher
entity App
entity windowmanager as wm

user-->launcher: tap app's icon
launcher->hss: showWindow()
note over hss,App
{"application_id":"tapped application id", "parameter":{"area":"display area", ...}}
end note
hss->App: push showWindow event
App->wm: activateWindow("application_name","display area")
wm-->App: push syncDraw event
App->App: display

title Application Callback Event On Screen Message / Reply phase
entity App
entity HomeScreenBinder
entity HomeScreenGUI

HomeScreenGUI->HomeScreenBinder: set_event_handler()

note over HomeScreenGUI
end note

App->HomeScreenBinder: set_event_handler()

note over App
end note

App->HomeScreenBinder: onScreenMessage(display_message)
HomeScreenBinder->HomeScreenGUI: event_handler(display_message)
HomeScreenGUI->HomeScreenBinder: onScreenReply(reply_message)
HomeScreenBinder->App: event_handler(reply_message)

title show/hide onscreen phase

actor user
entity "homescreen-service" as hss
entity App
entity onscreenapp
entity windowmanager as wm

== show onscreen ==
user->App: the operation request onscreen
App->hss: showWindow()
note over App,hss
"parameter":{"area":"display area", "file":"qml file path", 
"data":{"the datas to onscreen qml"}}}
end note

hss->onscreenapp: push showWindow event
note over hss,onscreenapp
"parameter":{"area":"display area", "file":"qml file path", 
"data":{"the datas to onscreen qml"},
<font color=red >"replyto":"caller application id"
end note

onscreenapp->onscreenapp: get and save parameters
onscreenapp->wm: activateWindow("onscreeapp", "display area")
alt can show
wm-->onscreenapp: push syncDraw event
onscreenapp->wm: endDraw("onscreeapp")
onscreenapp->onscreenapp: load and display qml file
else can't show
note over onscreenapp,wm
do nothing
end note

== hide onscreen ==

user->onscreenapp: tap onscreen's button
onscreenapp->hss: replyShowWindow()
note over onscreenapp,hss
{"application_id":"the application id who called onscreenapp", 
"parameter": {"buttonName": "VOLUME_UP", "buttonPressMode": "shortPress", "buttonPressState": "release"}}
end note
hss->App: push replyShowWindow event
App->App: call reply function
App->hss: hideWindow("onscreenapp")
hss->onscreenapp: push hideWindow event
note over hss,onscreenapp
{"application_id":"request hideWindow application id"}
end note
onscreenapp->wm: deactivateWindow("onscreenapp");
onscreenapp->onscreenapp: hide window


title show notification on HomeScreen top area

entity "homescreen-service" as hss
entity homescreen
entity App

App->hss: showNotification()
note over App,hss
{"icon":"display icon", "text":"display text"}
end note
hss-> homescreen: push showNotification event
note over hss,homescreen
{"application_id":"request application id", 
"parameter":{"icon":"display icon", "text":"display text"}}
end note

homescreen->homescreen: display notification message 3s


title show information on HomeScreen bottom area

entity "homescreen-service" as hss
entity homescreen
entity App

App->hss: showInformation()
note over hss
{"info":"display information"}
end note
hss-> homescreen: push showInformation event

homescreen->homescreen: display information message 3s