From a4f2729608b183572e7d41fb536c34d128ac87c3 Mon Sep 17 00:00:00 2001
From: Victor Brekenfeld <me@drakulix.de>
Date: Tue, 23 Nov 2021 17:28:48 +0100
Subject: [PATCH] gbm: expose buffer age

---
 CHANGELOG.md                   | 1 +
 anvil/src/udev.rs              | 4 ++--
 src/backend/drm/surface/gbm.rs | 7 ++++---
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e3b1538..728bdbf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@
 - Remove `InputBackend::dispatch_new_events`, turning `InputBackend` into a definition of backend event types. Future input backends should be a `calloop::EventSource`.
 - Remove `InputBackend::EventError` associated type as it is unneeded since `dispatch_new_events` was removed.
 - `Swapchain` does not have a generic Userdata-parameter anymore, but utilizes `UserDataMap` instead
+- `GbmBufferedSurface::next_buffer` now additionally returns the age of the buffer
 
 ### Additions
 
diff --git a/anvil/src/udev.rs b/anvil/src/udev.rs
index fbec837..957a419 100644
--- a/anvil/src/udev.rs
+++ b/anvil/src/udev.rs
@@ -738,7 +738,7 @@ fn render_surface(
         return Ok(());
     };
 
-    let dmabuf = surface.surface.next_buffer()?;
+    let (dmabuf, _age) = surface.surface.next_buffer()?;
     renderer.bind(dmabuf)?;
 
     // and draw to our buffer
@@ -867,7 +867,7 @@ fn schedule_initial_render<Data: 'static>(
 }
 
 fn initial_render(surface: &mut RenderSurface, renderer: &mut Gles2Renderer) -> Result<(), SwapBuffersError> {
-    let dmabuf = surface.next_buffer()?;
+    let (dmabuf, _age) = surface.next_buffer()?;
     renderer.bind(dmabuf)?;
     // Does not matter if we render an empty frame
     renderer
diff --git a/src/backend/drm/surface/gbm.rs b/src/backend/drm/surface/gbm.rs
index b6b8be2..3bc5be0 100644
--- a/src/backend/drm/surface/gbm.rs
+++ b/src/backend/drm/surface/gbm.rs
@@ -167,11 +167,11 @@ where
         }
     }
 
-    /// Retrieves the next buffer to be rendered into.
+    /// Retrieves the next buffer to be rendered into and it's age.
     ///
     /// *Note*: This function can be called multiple times and
     /// will return the same buffer until it is queued (see [`GbmBufferedSurface::queue_buffer`]).
-    pub fn next_buffer(&mut self) -> Result<Dmabuf, Error> {
+    pub fn next_buffer(&mut self) -> Result<(Dmabuf, u8), Error> {
         if self.next_fb.is_none() {
             let slot = self.swapchain.acquire()?.ok_or(Error::NoFreeSlotsError)?;
 
@@ -189,7 +189,7 @@ where
         }
 
         let slot = self.next_fb.as_ref().unwrap();
-        Ok(slot.userdata().get::<Dmabuf>().unwrap().clone())
+        Ok((slot.userdata().get::<Dmabuf>().unwrap().clone(), slot.age()))
     }
 
     /// Queues the current buffer for rendering.
@@ -213,6 +213,7 @@ where
     pub fn frame_submitted(&mut self) -> Result<(), Error> {
         if let Some(mut pending) = self.pending_fb.take() {
             std::mem::swap(&mut pending, &mut self.current_fb);
+            self.swapchain.submitted(pending);
             if self.queued_fb.is_some() {
                 self.submit()?;
             }