backend/winit: Add DMA-BUF support (#3327)

* backend/winit: DMA-BUF setup for Nvidia support

Creates a dmabuf global in the same manner as the tty backend. This
fixes applications failing to launch on Nvidia when using the winit
backend.

This code is adapted from Smithay's Anvil compositor.
See smithay/anvil/src/winit.rs

* fixes

---------

Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

src/backend/winit.rs

@@ -4,8 +4,10 @@ use std::mem;
 use std::rc::Rc;
 use std::sync::{Arc, Mutex};
 
+use anyhow::Context as _;
 use niri_config::{Config, OutputName};
 use smithay::backend::allocator::dmabuf::Dmabuf;
+use smithay::backend::egl::EGLDevice;
 use smithay::backend::renderer::damage::OutputDamageTracker;
 use smithay::backend::renderer::gles::GlesRenderer;
 use smithay::backend::renderer::{DebugFlags, ImportDma, ImportEgl, Renderer};
@@ -16,6 +18,7 @@ use smithay::reexports::wayland_protocols::wp::presentation_time::server::wp_pre
 use smithay::reexports::winit::dpi::LogicalSize;
 use smithay::reexports::winit::platform::wayland::WindowAttributesExtWayland;
 use smithay::reexports::winit::window::Window;
+use smithay::wayland::dmabuf::{DmabufFeedbackBuilder, DmabufGlobal};
 use smithay::wayland::presentation::Refresh;
 
 use super::{IpcOutputMap, OutputId, RenderResult};
@@ -29,6 +32,7 @@ pub struct Winit {
     output: Output,
     backend: WinitGraphicsBackend<GlesRenderer>,
     damage_tracker: OutputDamageTracker,
+    dmabuf_global: Option<DmabufGlobal>,
     ipc_outputs: Arc<Mutex<IpcOutputMap>>,
 }
 
@@ -137,6 +141,7 @@ impl Winit {
             output,
             backend,
             damage_tracker,
+            dmabuf_global: None,
             ipc_outputs,
         })
     }
@@ -164,9 +169,44 @@ impl Winit {
 
         niri.update_shaders();
 
+        self.create_dmabuf_global(niri);
+
         niri.add_output(self.output.clone(), None, false);
     }
 
+    pub fn create_dmabuf_global(&mut self, niri: &mut Niri) {
+        let renderer = self.backend.renderer();
+
+        let default_feedback = || {
+            let display = renderer.egl_context().display();
+            let device =
+                EGLDevice::device_for_display(display).context("error getting EGL device")?;
+            let node = device
+                .try_get_render_node()
+                .context("error getting EGL device render node")?
+                .context("failed to query EGL device render node")?;
+
+            let primary_formats = renderer.dmabuf_formats();
+            DmabufFeedbackBuilder::new(node.dev_id(), primary_formats)
+                .build()
+                .context("error building dmabuf feedback")
+        };
+
+        // Fallback to dmabuf v3 if we failed to build feedback.
+        let dmabuf_global = match default_feedback() {
+            Ok(feedback) => niri
+                .dmabuf_state
+                .create_global_with_default_feedback::<State>(&niri.display_handle, &feedback),
+            Err(err) => {
+                debug!("failed building default dmabuf feedback, falling back to v3: {err:?}");
+                let primary_formats = renderer.dmabuf_formats();
+                niri.dmabuf_state
+                    .create_global::<State>(&niri.display_handle, primary_formats)
+            }
+        };
+        assert!(self.dmabuf_global.replace(dmabuf_global).is_none());
+    }
+
     pub fn seat_name(&self) -> String {
         "winit".to_owned()
     }