gnome-shell-extensions drag and drop

Question

While trying to add D&D support to a gnome-shell-extension that I'm writing I ran into a bit of trouble. I can create drop targets to any open window, but that's all I've managed to pull off.

I can't differentiate between the windows. I tried to use global.get_stage().get_actor_at_pos(Clutter.PickMode.ALL, x, y).get_parent().get_parent().get_meta_window().get_wm_class(), but half the time it gives me the wrong window and every now and again it just returns null. Also I'm not sure how to drop the information into the target.

All I'm trying to do is drop a file URI into a browser window or the file into a file manager.

Is it even possible in gnome-shell-extensions and how would I pull it off? Any advice would be welcome!

Answer 1

Here is the current available shell code about DND between windows: https://github.com/GNOME/gnome-shell/blob/master/js/ui/xdndHandler.js You can do practically nothing with it.

In Mutter, there are more than one procedure to handled a drag and drop in a window, because there are one implementation for X11-windows and another implementation for Wayland-windows.

To be honest, i don't know if there are a way on Wayland and how will be.

I can tell you that in gnome-shell (Mutter to be specific) there are not a fully implementation of this ability on X11. Most you can know, it's if a drag and drop occurs from a window to the shell and the position of the dragged actor, but the shell dosen't provide any api to create an internal drag and drop from the shell to a particular window.

The shell drag and drop that you can fully used, it's only an internal (just the shell) drag and drop from and to the shell (only for clutter actors) and not an external one between different windows.

In X11, the drag and drop process occurs between windows only. One window provide the dragged object and the information that it's associate to that object. The another window (could be the same) will accept the drop of the object, taking on account the information that the first window provide.

As there are not way in the shell to be possible setting the requiered information to the target-window and like your GUI is inside a big top window (The window that represent the shell global stage: https://github.com/GNOME/mutter/blob/6c18bae83cd27a7397a1ed0c1c0c81b282f1b44e/src/compositor/meta-dnd.c#L152) and like you don't have access to this big internal window, finally you can not do anything to interact directly with other windows.

Here (https://github.com/swayfreeda/blender-2.77a/tree/5969d704f44952ea8cbecba2ba4150fb4a48e6de/extern/xdnd) you can find a fully implementation of drag and drop on X11, you will need to modify the code to be adapted to the Mutter workflow and then add this code to Mutter. After that you will have support, but you will need to create the corresponding procedured to then invoked the functionalities, provide information and recive usefull events from the shell to the window, to be possible finally control it in gjs, but it will be only for X11, not for Wayland. I suppose you will need to do something similar if you want support on Wayland.

Good loock.