Wayland-specific handling for platform surface readiness (#21382)

src/Avalonia.Base/Platform/RenderTargetProperties.cs

@@ -16,6 +16,13 @@ public readonly struct PlatformRenderTargetState
     /// </summary>
     public bool IsReady { get; init; }
     
+    /// <summary>
+    /// Indicates that the render target is currently not ready but will wake up the render loop
+    /// when it becomes ready (e.g. waiting for a compositor frame callback).
+    /// When true, the compositor should not keep polling for readiness.
+    /// </summary>
+    public bool WillWakeUpRenderLoopWhenReady { get; init; }
+    
     /// <summary>
     /// Indicates if the render target is no longer usable and needs to be recreated
     /// </summary>
@@ -31,6 +38,12 @@ public readonly struct PlatformRenderTargetState
     public static PlatformRenderTargetState Corrupted => new() { IsCorrupted = true, IsReady = true};
 
     public static PlatformRenderTargetState Disposed => new() { IsCorrupted = true};
+
+    public static PlatformRenderTargetState NotReadyWillWakeupRenderLoop => new PlatformRenderTargetState()
+    {
+        WillWakeUpRenderLoopWhenReady = true
+    };
+
 }
 
 [PrivateApi]

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositionTarget.cs

@@ -44,6 +44,12 @@ namespace Avalonia.Rendering.Composition.Server
         /// Returns true if the target is enabled and has pending work but its render target was not ready.
         /// </summary>
         internal bool IsWaitingForReadyRenderTarget { get; private set; }
+        
+        /// <summary>
+        /// Returns true if the target's render target is waiting for a render loop wakeup
+        /// (i.e. the platform will call Wakeup() when ready, no need to keep polling).
+        /// </summary>
+        internal bool IsWaitingForRenderLoopWakeup { get; private set; }
 
         public ServerCompositionTarget(ServerCompositor compositor, Func<IEnumerable<IPlatformRenderSurface>> surfaces)
             : base(compositor)
@@ -131,6 +137,7 @@ namespace Avalonia.Rendering.Composition.Server
         public void Render()
         {
             IsWaitingForReadyRenderTarget = false;
+            IsWaitingForRenderLoopWakeup = false;
             
             if (_disposed)
                 return;
@@ -181,6 +188,7 @@ namespace Avalonia.Rendering.Composition.Server
             if (!_renderTarget.PlatformRenderTargetState.IsReady)
             {
                 IsWaitingForReadyRenderTarget = IsEnabled;
+                IsWaitingForRenderLoopWakeup = IsEnabled && _renderTarget.PlatformRenderTargetState.WillWakeUpRenderLoopWhenReady;
                 return;
             }
 
@@ -310,5 +318,7 @@ namespace Avalonia.Rendering.Composition.Server
             if (_attachedVisuals.Remove(visual) && IsEnabled)
                 visual.Deactivate();
         }
+
+        public void RequestFullRedraw() => _redrawRequested = true;
     }
 }

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositor.UserApis.cs

@@ -83,4 +83,10 @@ internal partial class ServerCompositor
             }
         }
     }
+
+    public void InvalidateAllCompositionTargets()
+    {
+        foreach(var target in _activeTargets)
+            target.RequestFullRedraw();
+    }
 }

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositor.cs

@@ -281,8 +281,9 @@ namespace Avalonia.Rendering.Composition.Server
                 return true;
             
             // Request a tick if we had unready targets in the last tick, to check if they are ready next time
+            // But skip targets that are waiting for a render loop wakeup from the platform
             foreach (var target in _activeTargets)
-                if (target.IsWaitingForReadyRenderTarget)
+                if (target.IsWaitingForReadyRenderTarget && !target.IsWaitingForRenderLoopWakeup)
                     return true;
             
             // Otherwise there is no need to waste CPU cycles, tell the timer to pause