On first load, default to 80% of current screen size for main window

Using a fixed default window geometry wasn't working well anymore -
it made the default window size tiny on hidpi screens.

Author: nyalldawson

src/app/qgisapp.cpp

@@ -3787,9 +3787,13 @@ void QgisApp::restoreWindowState()
   }
 
   // restore window geometry
-  if ( !restoreGeometry( settings.value( QStringLiteral( "UI/geometry" ), QByteArray::fromRawData( reinterpret_cast< const char * >( defaultUIgeometry ), sizeof defaultUIgeometry ) ).toByteArray() ) )
+  if ( !restoreGeometry( settings.value( QStringLiteral( "UI/geometry" ) ).toByteArray() ) )
   {
     QgsDebugMsg( "restore of UI geometry failed" );
+    // default to 80% of screen size, at 10% from top left corner
+    resize( QDesktopWidget().availableGeometry( this ).size() * 0.8 );
+    QSize pos = QDesktopWidget().availableGeometry( this ).size() * 0.1;
+    move( pos.width(), pos.height() );
   }
 
 }