Wayland: support basic Drag&Drop #2429

SludgePhD · 2022-08-12T23:56:04Z

Tested on all platforms changed
Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
Created or updated an example program if it would help users understand this functionality
Updated feature matrix, if new features were added or implemented

SludgePhD · 2022-08-13T15:37:41Z

I've also pushed a commit that emits all appropriate cursor events, which should address #1550 at least on Wayland. Other platforms don't do this yet, so let me know if I should leave it out.

(though one issue I noticed is that some compositors send DnD events when the cursor is slightly outside the window (eg. hovering over its shadow only on KDE), which results in out-of-bounds cursor coordinates being sent to the app)

kchibisov · 2022-08-14T18:14:19Z

Could you test that it doesn't blow up in alacritty for example or when using https://github.com/smithay/smithay-clipboard ? I think gnome doesn't allow to have drag and drop and clipboard by using multiple data device managers. IIRC it uses just the last one, and that's the reason I haven't implemented drag and drop inside winit, since winit should support clipboard, otherwise registering clipboard via external crates will disable drag and drop from inside the winit.

The work to bring clipboard is #2156 , but I don't have that much time to work on it right now unfortunately, but I hope to go back to it soon...

SludgePhD · 2022-08-14T23:13:17Z

I've tested with Alacritty on KDE Plasma, and both Drag&Drop and clipboard access work fine with this patch applied.

If GNOME doesn't support this properly, that does seem unfortunate, but this PR will at least make apps work on other compositors, and also make apps work everywhere that only need Drag&Drop and no clipboard access.

Do you happen to know if GNOME's behavior is correct here or does the Wayland specification require compositors to support multiple data device managers?

kchibisov · 2022-08-15T05:17:17Z

Would suggest to test GNOME, since it's a major compositor and we can't break it even when it's a GNOME bug.

SludgePhD · 2022-08-15T20:36:09Z

Alacritty built with this patch running in a nested GNOME session does not crash or break when dropping a file, but Drag&Drop doesn't do anything (so behavior matches winit master). Clipboard access still works fine.

Amusingly, Konsole in the same nested GNOME session does crash when dropping a file from a Dolphin window in the same session. Additionally, closing the nested GNOME shell window made it abort with several assertion failures, so it looks like winit is miles ahead of the typical Linux-on-the-desktop experience already... sadly

EDIT: also tested my drag&drop example app in the GNOME session and it works fine!

kchibisov · 2022-08-15T20:50:17Z

The thing is that it'll work, but if you create another device manager the privious one (in winit here) would stop working. I do want to have drag and drop in winit Wayland, but I'm not sure whether I'll have time to look into it, given I think that clipboard issue should be resolved first, so we can have both at the same time without collapsing.

SludgePhD · 2022-08-15T20:53:10Z

Yeah, I understand (unless Alacritty somehow does something differently?). As far as I can tell, this PR does not regress anything even if applications do use another data manager for accessing the clipboard. Drag&Drop simply won't work, just like it does now.

kchibisov · 2022-08-15T21:14:12Z

I know what alacritty does and I know why the feature wasn't in winit, since I remember the GNOME bug given that it's quite easy to repro it. Besides that it's fair to assume that we can have drag and drop that way for now.

kchibisov

See the clipboard PR I've linked to you before on how to handle pipe reading with calloop. It could also give an idea how to integrate dnd given that it has data device as well.

src/platform_impl/linux/wayland/seat/dnd/handlers.rs

src/platform_impl/linux/wayland/seat/dnd/mod.rs

kchibisov · 2022-08-15T21:19:51Z

src/platform_impl/linux/wayland/seat/dnd/handlers.rs

+            }
+        }
+        DndEvent::Motion { x, y, .. } => {
+            if let Some(window_id) = inner.window_id {


I'm not sure why it generates that event, could you elaborate?

kchibisov · 2022-08-15T21:20:31Z

src/platform_impl/linux/wayland/seat/dnd/handlers.rs

+                    .event_sink
+                    .push_window_event(WindowEvent::HoveredFileCancelled, window_id);
+                winit_state.event_sink.push_window_event(
+                    WindowEvent::CursorLeft {


Also not sure how it's related, I'm pretty sure wl_pointer will send the right events anyway?

That doesn't seem to happen at least on KDE and GNOME. Only when no file is being dragged over.

kchibisov · 2022-08-15T21:21:05Z

src/platform_impl/linux/wayland/seat/dnd/handlers.rs

+                    winit_state.event_sink.push_window_event(
+                        WindowEvent::CursorEntered {
+                            device_id: crate::event::DeviceId(
+                                crate::platform_impl::DeviceId::Wayland(DeviceId),
+                            ),
+                        },
+                        window_id,
+                    );
+                    winit_state.event_sink.push_window_event(
+                        WindowEvent::CursorMoved {
+                            device_id: crate::event::DeviceId(


src/platform_impl/linux/wayland/event_loop/state.rs

SludgePhD · 2022-08-19T00:38:17Z

Addressed your comments

kchibisov

Unfortunatelly this doesn't work for me on sway and I think the reason is that serial we pass in accept is zero.

The issue with sway that there's no drop event. The mime types do match, etc.

Given that it's likely broken due to sctk bug I can't merge it, unless there's a way to make it work with e.g. thunar + alacritty on sway without patching gtk. Other applications do work here, but they pass normal serial.

kchibisov · 2022-08-23T20:16:15Z

src/platform_impl/linux/wayland/seat/dnd/handlers.rs

+            let window_id = make_wid(&surface);
+            inner.window_id = Some(window_id);
+            offer.accept(Some(MIME_TYPE.into()));
+            let _ = parse_offer(&inner.loop_handle, offer, move |paths, winit_state| {


None of these is needed.

The callback emits the HoveredFile event though?

Hm, yeah. Sure. I'm not sure why anyone would need it. but ok.

SludgePhD · 2022-08-23T22:07:55Z

sway appears to (correctly) send CRLF-delimited URI lists, while GNOME and KDE only use \n as a delimiter. I've pushed a fix for that, which makes things work correctly on sway for me.

kchibisov · 2022-08-23T22:09:32Z

sway appears to (correctly) send CRLF-delimited URI lists, while GNOME and KDE only use \n as a delimiter. I've pushed a fix for that, which makes things work correctly on sway for me.

My problem that I don't see done event at all. It's not like something is crlf or anything. Also sway has nothing to do with crlf, that's what applications set. Could you try sway master branch?

SludgePhD · 2022-08-23T22:16:33Z

Huh, right, that must be thunar's doing then. I'll check if I can repro with sway master.

SludgePhD · 2022-08-23T22:33:59Z

Sorry for the confusion, it reproduces even with the release of sway that I was using, the \r issue just distracted me a bit.

I've patched sctk to pass the correct serial to the compositor but it still does not work (Smithay/client-toolkit@bef07ea). The sway debug log is also not very helpful, it only contains this when I try to drag&drop:

00:00:59.201 [wlr] [types/data_device/wlr_data_source.c:189] Offering additional MIME type after wl_data_device.set_selection
00:00:59.201 [wlr] [types/data_device/wlr_data_source.c:196] Ignoring duplicate MIME type offer text/uri-list
00:00:59.201 [wlr] [types/data_device/wlr_data_source.c:189] Offering additional MIME type after wl_data_device.set_selection

SludgePhD · 2022-08-23T22:36:22Z

Sway also appears to send multiple hover enter events in sequence, which end up in the application as multiple HoveredFile events without any intervening HoveredFileCancelled or DroppedFile. I think this might be a sway or wlroots bug?

kchibisov · 2022-08-23T22:42:35Z

But it works for me with any other application, so it's confusing.

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SludgePhD requested a review from kchibisov as a code owner August 12, 2022 23:56

SludgePhD force-pushed the drag-n-deez branch from 0b8f3af to b7e4286 Compare August 13, 2022 15:36

maroider added the DS - wayland label Aug 14, 2022

SludgePhD force-pushed the drag-n-deez branch from b7e4286 to 9ee3ce7 Compare August 15, 2022 20:37

kchibisov requested changes Aug 15, 2022

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SludgePhD added 7 commits August 19, 2022 02:37

Wayland: support basic Drag&Drop

9092ade

Update markdown files

e0b6a93

Address clippy lints

611c82d

Use make_wid to simplify code

cd489be

Also emit all appropriate cursor events

3ab24c6

Read the pipe without blocking

ad9468e

Follow style

13b3605

SludgePhD force-pushed the drag-n-deez branch from 8a1af5d to 13b3605 Compare August 19, 2022 00:38

Address clippy lint

1b54682

kchibisov requested changes Aug 23, 2022

View reviewed changes

Fix parsing of CRLF-delimited lines

cde68dd

TheNumerus added a commit to TheNumerus/black-hole that referenced this pull request Dec 5, 2022

removed wayland support due to rust-windowing/winit#2429, drag&drop s…

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Wayland: support basic Drag&Drop #2429

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