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99 lines
4.6 KiB
Plaintext
99 lines
4.6 KiB
Plaintext
/*! \page splash How To Enable Splash Screen For The Application
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\section splashsec Enabling splash screen
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Applauncherd supports showing a splash screen if there is mcompositor
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(the MeeGo window manager) running.
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The splash screen is not shown by default. If an application wants it
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to be shown, it must pass --splash, and optionally --splash-landscape
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arguments to the invoker.
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System default splash images can be obtained by giving \c default or
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\c default-landscape in place of image file names.
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For instance,
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\verbatim
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/usr/bin/invoker --splash=/usr/share/application_name/splash.jpg --splash-landscape=/usr/share/application_name/splash-l.jpg --type=m /usr/bin/application_name
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\endverbatim
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shows the splash screen with splash.jpg as its content when the device
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is in the portrait orientation. Otherwise splash-l.jpg is shown. If
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only --splash is given, that image is shown in both orientations.
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Invoker passes the splash request to the booster. The booster sends
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the splash request to the window manager by setting a window property
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to window manager's window.
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If the filenames do not include absolute paths, the window manager
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looks for the files from a default location.
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The file should be in a format recognized by QPixmap, preferably JPEG
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as it is fast to load. The size of the image should not be larger than
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the screen. If it is smaller, it will be stretched.
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\subsection splashndbus Splash and D-Bus interaction
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Some care needs to be taken if the application is to be invoked via
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D-Bus as well as from the application grid. The single instance
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behavior provided by \c MApplication falls under this category as
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well, so you may be using D-Bus even if there is no D-Bus related code
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in your application.
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If splash is not used, the \c Exec line in the application's \c
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.desktop file may contain the invoker command line for starting the
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application. One of the first things that D-Bus enabled applications
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do is to register a service with the session D-Bus, which fails if
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another instance of the application is already running. In this case,
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an \c MApplication based application by default first calls the \c
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launch() D-Bus method of the existing application instance and then
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exits. The end result is that the existing instance is brought to the
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foreground and there is just one instance of the application running.
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Things change when the \c --splash option is used in an invoker command
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in the \c Exec line of the \c .desktop file. When the application is
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started from the grid and there is already an instance of the
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application running, the following sequence of events takes place:
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\li The path to the splash image and the pid of the new application
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instance are passed to the compositor.
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\li The application's \c main() is called and the application starts to execute
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\li The compositor shows the splash image and starts to wait for the
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application with the specified pid to map a window.
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\li The freshly started application attempts to register the D-Bus service,
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fails, calls the \c launch() D-Bus method of the existing instance, and exits.
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\li The window of the already running application instance is mapped.
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\li The compositor ignores this window, because it has a different pid
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from the one specified in the splash request.
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\li The compositor finally gives up waiting for the specified pid to
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map a window, and fades away the splash screen, revealing the
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application window.
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It would be nice if the invoker/applauncherd could skip requesting the
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splash screen in case another instance of the application is running.
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Unfortunately this would require knowing \a in \a advance whether the
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application is going to execute the code that attempts D-Bus registration.
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This reduces to the Halting Problem, so if invoker/applauncherd could
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achieve it, much of theoretical computer science would disappear in
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a puff of smoke.
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\subsection splashndbusdeploy Deployment with splash and D-Bus on Harmattan
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In order to avoid the problems with D-Bus and splash screen, the
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following setup can be used.
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\li The application's \c .service file contains an \c Exec line with
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an invoker command with \c --splash parameter. This way the splash
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screen is shown if the application is not running and D-Bus decides
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to start it. Subsequent invocations via D-Bus do not show the splash
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while the application is running.
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\li The application's \c .desktop file contains a \c X-Maemo-Service line
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that specifies the application's D-Bus service. When this line is present,
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the home screen calls the \c launch() method of the specified D-Bus service
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to start the application, and consequently the splash screen is shown as
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appropriate.
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*/
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