Merge lp:~kaihengfeng/unity-greeter/fix-hidpi-trasition-wallpaper into lp:unity-greeter

[Kai-Heng Feng]

Explicitly set scale and geometry for Cairo.XlibSurface. (LP: #1557893)

[Robert Ancell (robert-ancell)]

The code change makes sense to me, I just don't have any high DPI hardware to confirm.

review: Approve

[Sebastien Bacher (seb128)]

Looks like an improvement to me, I don't have hidpi hardware either but I force some scaling by replacing the binary by a wrapper setting GDK_SCALE and calling the greeter and there was graphical corruption before which seems solved by those change, great work!
(I still see a greeter bg -> empty screen -> wrongly scaled/tiled bg -> session bg sequence, but that tiled bg seems more a session/nautilus issue, I think the unity-greeter issue is resolved)

[Robert Ancell (robert-ancell)]

Thanks Kai-Heng!

=== modified file 'src/unity-greeter.vala'
--- src/unity-greeter.vala	2015-10-26 22:42:32 +0000
+++ src/unity-greeter.vala	2016-03-16 06:55:13 +0000
@@ -183,11 +183,16 @@
 
     public bool start_session (string? session, Background bg)
     {
+        /* Explicitly set the right scale before closing window */
+        var screen = Gdk.Screen.get_default ();
+        var scale = screen.get_monitor_scale_factor (screen.get_number ());
+        background_surface.set_device_scale (scale, scale);
+
         /* Paint our background onto the root window before we close our own window */
         var c = new Cairo.Context (background_surface);
         bg.draw_full (c, Background.DrawFlags.NONE);
         c = null;
-        refresh_background (Gdk.Screen.get_default (), background_surface);
+        refresh_background (screen, background_surface);
 
         if (test_mode)
         {
@@ -387,18 +392,19 @@
         var visual = screen.get_system_visual ();
 
         unowned X.Display display = (screen.get_display () as Gdk.X11.Display).get_xdisplay ();
+        unowned X.Screen xscreen = (screen as Gdk.X11.Screen).get_xscreen ();
 
         var pixmap = X.CreatePixmap (display,
                                      (screen.get_root_window () as Gdk.X11.Window).get_xid (),
-                                     screen.get_width (),
-                                     screen.get_height (),
+                                     xscreen.width_of_screen (),
+                                     xscreen.height_of_screen (),
                                      visual.get_depth ());
 
         /* Convert into a Cairo surface */
         var surface = new Cairo.XlibSurface (display,
                                              pixmap,
                                              (visual as Gdk.X11.Visual).get_xvisual (),
-                                             screen.get_width (), screen.get_height ());
+                                             xscreen.width_of_screen (), xscreen.height_of_screen ());
 
         return surface;
     }