Lock screen wallpaper does not respect monitor index

NixOS unstable, xfce4-screensaver git 89618254, gtk3 3.24.41, glib 2.78.4.

Let's say monitors are 0-indexed.

I have 2 monitors and when trying to unlock on the monitor 1 I found it shows wallpaper used by the monitor 0, I would expect wallpaper used by monitor 1 to be shown instead. I honestly do believe this is supported since 49c3db8c, looking at the prefix = g_strconcat("/backdrop/screen0/monitor", monitor_name, "/workspace0", NULL); line.

My settings:

$ xfconf-query -c xfce4-desktop -p /backdrop/screen0/monitoreDP-1/workspace0/last-image # monitor 0
/var/lib/wallpaper/bobby285271/current.jpg
$ xfconf-query -c xfce4-desktop -p /backdrop/screen0/monitorDP-2/workspace0/last-image # monitor 1
/nix/store/rgpv71rr27kvixlpj92v6xnx6l7m6l30-xfdesktop-4.18.1/share/backgrounds/xfce/xfce-shapes.svg

I tried looking at things, after adding & printing some debug messages I think here are the observations I saw so far (ordered by the time it happened to me), here I am unlocking from monitor 1:

• In src/xfce4-screensaver-dialog.c, a --monitor= arg is accecpted, from my testing the value passed here is correct (the global monitor_index is set to 1).
• In popup_dialog_idle, a new gs_lock_plug is created here.
  • In src/gs-lock-plug.c, gs_lock_plug_add_login_window is triggered, it calls redraw_background, which calls get_draw_dimensions.
  • In get_draw_dimensions, it gets the monitor, using plug->priv->monitor_index. Here it looks like plug->priv->monitor_index is still 0
  • Now xfce_bg_load_from_preferences fetches the wallpaper from my above settings via xfce_bg_get_property_prefix, and we got the wallpaper used by monitor 0.
  • gs_lock_plug_add_login_window finishes.
• g_object_set(widget, "monitor-index", monitor_index, NULL); happens.
  • In gs_lock_plug_set_monitor_index, plug->priv->monitor_index is now set to 1.

To verify the part I went ahead and change the line to monitor = gdk_display_get_monitor (display, 1);, and as expected it is now always showing wallpapers used by monitor 1 now. I guess the problem here is that we are setting the monitor index property too late?

(Anyway thanks for reading this issue!)

changed the description

added 5. Lock Screen label

marked this issue as related to #68 (closed)

I guess the problem here is that we are setting the monitor index property too late?

Yes, or rather we call gs_lock_plug_add_login_window too early, in _init. Thanks for the investigations, I'll look into it, it'll probably solve #68 (closed) too.

changed milestone to %4.18.4

assigned to @Tamaranch

closed with commit b51ce343

Thanks for the commit! It does fix the original problem, though now I find the background loaded slower than before (both in a VM and on my laptop), is that a side-effect of using g_idle_add here?

Here is a recording for this, I see the background "white" before the actual background comes out

It looks like this at the very first:

Yes, probably. It's not too serious, but it should be fixable with a little refactoring that I wanted to avoid, out of laziness :) I'll see about that later.

@bobby285271 could you give this patch a try and tell me if it's better for you?

0001-lock-plug-Draw-background-in-constructed.patch

Yes, it's much better!

Thanks for testing!

mentioned in commit b896ec0b