[dash] home screen misses icons for applications that are not installed

same behaviour with rhythmbox if banshee is not installed .

seeing the same on the armel images which come without email client (we ship the desktop-webmail package instead which only installs a mime type but no mailer icons) and with rhythmbox (due to mono issues on arm) by default.

either the icons need to get default fallbacks (i.e. if a mime type and app assignment through this exists but no icon is available) or simply be hidden if the relevant app is not available.

this is what I get when I open dash:

unity-2d-places: [DEBUG] Server supports the Composite extension (ver 0.4)
unity-2d-places: [WARNING] QWidget::setMinimumSize: (/LauncherContextualMenu) Negative sizes (57,-1) are not possible
unity-2d-places: [WARNING] QWidget::setMinimumSize: (/LauncherContextualMenu) Negative sizes (57,-1) are not possible
unity-2d-places: [WARNING] QWidget::setMinimumSize: (/LauncherContextualMenu) Negative sizes (57,-1) are not possible
unity-2d-places: [CRITICAL] Wnck: wnck_set_client_type got called multiple times.
unity-2d-places: [WARNING] file:///usr/share/unity-2d/places/Home.qml:62:9: QML Text: Binding loop detected for property "width"
unity-2d-places: [WARNING] QPainter::begin: Paint device returned engine == 0, type: 2
unity-2d-places: [WARNING] QPainter::setBackgroundMode: Painter not active
unity-2d-places: [WARNING] QPainter::setBackground: Painter not active
unity-2d-places: [WARNING] QPainter::setPen: Painter not active
unity-2d-places: [CRITICAL] Gtk: IA__gtk_icon_info_load_icon: assertion `icon_info != NULL' failed
unity-2d-places: [WARNING] QWidget::setMinimumSize: (/LauncherContextualMenu) Negative sizes (57,-1) are not possible
unity-2d-places: [WARNING] QWidget::setMinimumSize: (/LauncherContextualMenu) Negative sizes (57,-1) are not possible
unity-2d-places: [WARNING] QWidget::setMinimumSize: (/LauncherContextualMenu) Negative sizes (57,-1) are not possible
unity-2d-places: [WARNING] QWidget::setMinimumSize: (/LauncherContextualMenu) Negative sizes (57,-1) are not possible
unity-2d-places: [WARNING] file:///usr/share/unity-2d/places/HomeButton.qml:36:9: QML QDeclarativeImage_QML_29: Failed to get image from provider: image://icons/
unity-2d-places: [WARNING] file:///usr/share/unity-2d/places/HomeButton.qml:36:9: QML QDeclarativeImage_QML_29: Failed to get image from provider: image://icons/
unity-2d-places: [WARNING] file:///usr/share/unity-2d/places/HomeButton.qml:36:9: QML QDeclarativeImage_QML_29: Failed to get image from provider: image://icons/

Related to bug #730623 and bug #708479

we should not display an icon if no app exists

@bfiller: thats fine but what do you do for apps that exist but dont have a .desktop file or icon they ship ? i.e. desktop-webmail only sets a mime type that makes the system default to a webmail app for all mail relates bits.

and we still support rhythmbox. even though its not shipped by default anywhere it should enable the icon for "listen to music" if it is installed.

@Oliver: the implementation I wrote (see linked branch) will pick up the default applications as defined by gnome-default-applications-properties. So if rhythmbox is installed and defined as the default music player, it will be listed in the home screen of the dash.

Note that the current implementation has some shortcomings as pointed out by Aurélien in his review, essentially the same shortcomings as unity itself.

This bug was fixed in the package unity-2d - 3.8.2-0ubuntu1

---------------
unity-2d (3.8.2-0ubuntu1) natty; urgency=low

  [ Oliver Grawert ]
  * New upstream bugfix release
   - (LP: #632526) Dash elipsizes file and application names too soon, making them
     unreadable
   - (LP: #669926) [launcher] Web favorites support
   - (LP: #708479) Dash view should use "Prefferred Applications" icons where
     appropriate
   - (LP: #718686) [dash] Group of results sometimes badly positioned
   - (LP: #727483) unity-2d-panel crashed with SIGSEGV in g_return_if_fail_warning()
   - (LP: #731449) [launcher] Dragging a tile at the top of the launcher while
     autoscrolling makes autoscroll wrong afterwards
   - (LP: #736097) [dash] home screen misses icons for applications that are not
     installed
   - (LP: #744999) [launcher] launchers are truncated when too many items to fit
     onscreen
   - (LP: #745077) [spread] clicking launcher with open windows not working correctly
     across workspaces
   - (LP: #745237) [dash] search field default string not translated
   - (LP: #746693) [launcher] .places messages not i18nized
   - (LP: #747836) [dash] Banshee no longer works from the dash home page in 3.8.2
   - (LP: #750753) [dash] showing/hiding places causing graphical corruption
   - (LP: #670608) [dash] Home screen customization should be easy
   - (LP: #683084) Global menu doesn't work well with more than one screen
   - (LP: #714646) [launcher] icons jagged edges during animation
   - (LP: #717744) [panel] inactive menus are clickable
   - (LP: #729002) First four items in Dash begin "Find" "Find" "Find" "Find"
   - (LP: #745758) [spread] super+s should toggle the workspace switcher
   - (LP: #751284) [launcher] Escaping of title broken with webfavorites
   - (LP: #751325) [panel] circle of friends button icon needs to be updated to match
     Unity's
   - (LP: #697816) [launcher] if an urgent window is available then the spread should
     not be activated
   - (LP: #729478) [launcher] Clicking middle mouse button should launch another
     instance of application
   - (LP: #750244) [launcher] Newly installed lenses don’t appear
   - (LP: #752948) Home's "Shortcuts" not i18n/l10n

  [ Aurélien Gâteau ]
  * Include .mo files in unity-2d package (LP: #751425)
 -- Oliver Grawert <email address hidden> Fri, 08 Apr 2011 16:03:10 +0200