File 0009-wayland-Implement-EplImplFuncs-QueryBufferAge.patch of Package libnvidia-egl-wayland2

From 40d205187661699d96d2e27ece56af9bf61295aa Mon Sep 17 00:00:00 2001
From: Kyle Brenneman <kbrenneman@nvidia.com>
Date: Tue, 14 Oct 2025 17:00:07 -0600
Subject: [PATCH 09/18] wayland: Implement EplImplFuncs::QueryBufferAge.

Add a buffer_age field to WlPresentBuffer, and add a new
eplWlSwapChainUpdateBufferAge function to increment the ages of the
buffers in a swapchain.

Add an EplImplFuncs::QueryBufferAge implementation that returns the age
of the current back buffer.
---
 src/wayland/wayland-platform.c  |  1 +
 src/wayland/wayland-platform.h  |  2 ++
 src/wayland/wayland-surface.c   | 15 +++++++++++++++
 src/wayland/wayland-swapchain.c | 24 ++++++++++++++++++++++++
 src/wayland/wayland-swapchain.h | 19 +++++++++++++++++++
 5 files changed, 61 insertions(+)

diff --git a/src/wayland/wayland-platform.c b/src/wayland/wayland-platform.c
index aad82af..a4b7c2b 100644
--- a/src/wayland/wayland-platform.c
+++ b/src/wayland/wayland-platform.c
@@ -60,6 +60,7 @@ static const EplImplFuncs WL_IMPL_FUNCS =
     .SwapBuffers = eplWlSwapBuffers,
     .WaitGL = eplWlWaitGL,
     .SwapInterval = eplWlSwapInterval,
+    .QueryBufferAge = eplWlQueryBufferAge,
 };
 
 static EGLBoolean LoadProcHelper(EplPlatformData *plat, void *handle, void **ptr, const char *name)
diff --git a/src/wayland/wayland-platform.h b/src/wayland/wayland-platform.h
index 5f89c42..c85b656 100644
--- a/src/wayland/wayland-platform.h
+++ b/src/wayland/wayland-platform.h
@@ -140,4 +140,6 @@ EGLBoolean eplWlSwapInterval(EplDisplay *pdpy, EplSurface *psurf, EGLint interva
 
 EGLBoolean eplWlWaitGL(EplDisplay *pdpy, EplSurface *psurf);
 
+EGLint eplWlQueryBufferAge(EplDisplay *pdpy, EplSurface *psurf);
+
 #endif // WAYLAND_PLATFORM_H
diff --git a/src/wayland/wayland-surface.c b/src/wayland/wayland-surface.c
index 762e076..1c12de2 100644
--- a/src/wayland/wayland-surface.c
+++ b/src/wayland/wayland-surface.c
@@ -1518,6 +1518,9 @@ EGLBoolean eplWlSwapBuffers(EplPlatformData *plat, EplDisplay *pdpy,
 
         psurf->priv->current.swapchain->current_back = next_back;
         psurf->priv->current.swapchain->render_buffer = next_back->buffer;
+
+        eplWlSwapChainUpdateBufferAge(inst, psurf->priv->current.swapchain, present_buf);
+
     }
 
     // Note that for PRIME, since we don't have a front buffer at all, so we
@@ -1586,3 +1589,15 @@ EGLBoolean eplWlWaitGL(EplDisplay *pdpy, EplSurface *psurf)
 
     return ret;
 }
+
+EGLint eplWlQueryBufferAge(EplDisplay *pdpy, EplSurface *psurf)
+{
+    if (psurf->priv->current.swapchain->prime)
+    {
+        return 0;
+    }
+    else
+    {
+        return psurf->priv->current.swapchain->current_back->buffer_age;
+    }
+}
diff --git a/src/wayland/wayland-swapchain.c b/src/wayland/wayland-swapchain.c
index 9afb0db..58eacd5 100644
--- a/src/wayland/wayland-swapchain.c
+++ b/src/wayland/wayland-swapchain.c
@@ -797,3 +797,27 @@ WlPresentBuffer *eplWlSwapChainFindFreePresentBuffer(WlDisplayInstance *inst,
         }
     }
 }
+
+void eplWlSwapChainUpdateBufferAge(WlDisplayInstance *inst, WlSwapChain *swapchain,
+        WlPresentBuffer *presented_buffer)
+{
+    WlPresentBuffer *buf = NULL;
+
+    if (swapchain->prime)
+    {
+        return;
+    }
+
+    glvnd_list_for_each_entry(buf, &swapchain->present_buffers, entry)
+    {
+        if (buf != presented_buffer)
+        {
+            if (buf->buffer_age != 0)
+            {
+                buf->buffer_age++;
+            }
+        }
+    }
+
+    presented_buffer->buffer_age = 1;
+}
diff --git a/src/wayland/wayland-swapchain.h b/src/wayland/wayland-swapchain.h
index 145a805..5358bc3 100644
--- a/src/wayland/wayland-swapchain.h
+++ b/src/wayland/wayland-swapchain.h
@@ -72,6 +72,15 @@ typedef struct
      */
     WlBufferStatus status;
 
+    /**
+     * The value of the EGL_BUFFER_AGE_KHR attribute when this is the current
+     * back buffer.
+     *
+     * Note that with PRIME, this will never be the current back buffer, so it
+     * will always be zero.
+     */
+    EGLint buffer_age;
+
     /**
      * The wl_buffer object for this buffer.
      */
@@ -200,4 +209,14 @@ WlPresentBuffer *eplWlSwapChainCreatePresentBuffer(WlDisplayInstance *inst,
 WlPresentBuffer *eplWlSwapChainFindFreePresentBuffer(WlDisplayInstance *inst,
         WlSwapChain *swapchain);
 
+/**
+ * Updates the buffer age counters for each buffer.
+ *
+ * \param inst The WlDisplayInstance for the display
+ * \param swapchain The swapchain to update
+ * \param presented_buffer The buffer that we just presented.
+ */
+void eplWlSwapChainUpdateBufferAge(WlDisplayInstance *inst, WlSwapChain *swapchain,
+        WlPresentBuffer *presented_buffer);
+
 #endif // WAYLAND_SWAPCHAIN_H
-- 
2.51.0