(not so) harmless "Couldn't map window as subsurface" warning

[wmww]

When some popups appear (such as tooltips), the following warning is shown:

(gtk-layer-demo:143889): Gdk-WARNING **: 15:30:45.911: Couldn't map window 0x55e39f0aa030 as subsurface because its parent is not mapped.

I believe this to be a harmless GTK bug (there's a lot of questionable logic around custom surfaces). Considering it's not causing any other problems, it's not worth trying to fix at this time.

[wmww]

It doesn't seem to happen with my Ubuntu 20.04 system GTK. Might have been introduced in GTK v3.24.21

[w1ll-i-code]

I think this bug is what's causing an issue in the waybar project. Alexays/Waybar#859

[wmww]

Unlikely. It really is harmless (AFAIK)

[wb9688]

In my WIP port of PCManFM's desktop manager to Wayland using GTK Layer Shell, I'm getting (pcmanfm:14934): Gdk-WARNING **: 11:38:54.363: Couldn't map window 0x5555555b6ad0 as subsurface because its parent is not mapped. and I'm getting a normal window with SSD, while without GTK Layer Shell I'm not getting that warning and it's positioned correctly and doesn't have a SSD.

You could reproduce this by compiling it yourself (preferably in combination with my fork of LibFM), starting it with pcmanfm --desktop, focusing the desktop, pressing some key to start the "search". GTK Layer Shell could be disabled by uncommenting these lines, then it'll just show up as a normal window.

When I add a return TRUE; at https://gitlab.gnome.org/GNOME/gtk/-/blob/gtk-3-24/gdk/wayland/gdkwindow-wayland.c#L3038, it is positioned correctly though (but keyboard input doesn't work, maybe I just have to disable keyboard interactivity as long as search_window is visible?), so it seems like GTK just thinks GTK Layer Shell windows aren't mapped for some reason.

[wmww]

All right, so my assessment is this warning is usually harmless, but in some cases (such as yours) it's possible to create a subsurface that actually fails to map property. Can you point me to where in your pcmanfm fork the troublesome search box subsurface is created? I'll want to write an integration test with a minimal example of this behavior so once it's fixed it stays fixed.

[wb9688]

search_window is created around https://github.com/wb9688/pcmanfm/blob/gtk-layer-shell/src/desktop.c#L3823

However if I understand the GTK code I linked in my previous comment correctly, it thinks the parent (i.e. my full-screen GTK Layer Shell window) is not mapped. Like I said, if I change it so that it returns true even if the parent isn't mapped (for testing purposes, normally that wouldn't be a good idea of course), it's able to correctly map the search_window as a subsurface.

Thanks for looking into it!

[wmww]

With that code sample the issue was easy to reproduce, and with just one more gtk-priv call it's fixed. PR incoming.