Created attachment 1844113 [details] gcc XDnDSource.c -o XDnDSource -lX11 && ./XDnDSource Description of problem: Unable to perform Drag and Drop using XDND protocol from Xlib application to application running on Wayland display server natively. How reproducible: always Steps to Reproduce: 1. compile attached file with "gcc XDnDSource.c -o XDnDSource -lX11 && ./XDnDSource". Attached file is a simple drag source client, written using XDND protocol. It has single mime-type to transfer: `text-plain`. 2. try to perform drag and drop starting from black area. 3. drop to gedit, firefox, etc. 4. <fail> Actual results: It fails to find any window having XdndAware property(except for apps running on XWayland), so it unable to perform drop action. Expected results: Performed drop. Additional info: The same example works for Ubuntu 21.04, Oracle Linux 8u5 on Wayland, but not on Fedora 35.
Hi Alexander, Thanks for the reproducer! Xwayland is just an Xserver, it doesn't play any active role in DnD nor copy/paste. The Wayland compositor itself plays the role of proxy between X11 and Wayland clients, therefore DnD or copy/paste issues usually find their root in either the client or the mutter, in the case of GNOME. Moving to mutter.
FWIW, I see a fairly consistent behaviour regardless on Wayland or X11 clients, the pointer turns to a question mark when hovering either Wayland or X11 windows (tried in Nautilus, gnome-terminal, for Wayland and also in X11 clients such as Google Chrome or geany running with GDK_BACKEND=x11). In all cases the logs show: process_motion_drag:339 0x1600007: Sending XdndPosition: (2543,397) XdndActionCopy main:413 1600007: XDnDStatus will accept: 0 action: None main:413 1600007: XDnDStatus will accept: 0 action: None find_aware_window:83 0x2B4: checking window for XdndAware find_aware_window:83 0x600583: checking window for XdndAware find_aware_window:83 0x1600007: checking window for XdndAware find_aware_window:106 0x1600007: XA_XdndAware found (that's a DnD onto gnome-terminal running on Wayland native, FWIW). And the drop fails in both cases (Wayland native or X11 client).
I can confirm the same works in mutter 40.6 (on el9) but not in mutter 41.1 (on F35).
Ran a bisection in git and filed the issue upstream
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