Pass original logical size to render targets (#21380)

* Pass original logical size to render targets

* Change FromSizeCeiling method to internal access

* api diff again?

api/Avalonia.nupkg.xml

@@ -19,6 +19,12 @@
     <Left>baseline/Avalonia/lib/net10.0/Avalonia.Base.dll</Left>
     <Right>current/Avalonia/lib/net10.0/Avalonia.Base.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Platform.IRenderTarget.RenderTargetSceneInfo.Deconstruct(Avalonia.PixelSize@,System.Double@)</Target>
+    <Left>baseline/Avalonia/lib/net10.0/Avalonia.Base.dll</Left>
+    <Right>current/Avalonia/lib/net10.0/Avalonia.Base.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0002</DiagnosticId>
     <Target>M:Avalonia.Input.PointerEventArgs.#ctor(Avalonia.Interactivity.RoutedEvent,System.Object,Avalonia.Input.IPointer,Avalonia.Visual,Avalonia.Point,System.UInt64,Avalonia.Input.PointerPointProperties,Avalonia.Input.KeyModifiers,System.Lazy{System.Collections.Generic.IReadOnlyList{Avalonia.Input.Raw.RawPointerPoint}})</Target>
@@ -37,4 +43,10 @@
     <Left>baseline/Avalonia/lib/net8.0/Avalonia.Base.dll</Left>
     <Right>current/Avalonia/lib/net8.0/Avalonia.Base.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Platform.IRenderTarget.RenderTargetSceneInfo.Deconstruct(Avalonia.PixelSize@,System.Double@)</Target>
+    <Left>baseline/Avalonia/lib/net8.0/Avalonia.Base.dll</Left>
+    <Right>current/Avalonia/lib/net8.0/Avalonia.Base.dll</Right>
+  </Suppression>
 </Suppressions>

src/Avalonia.Base/PixelSize.cs

@@ -203,6 +203,27 @@ namespace Avalonia
             (int)Math.Round(size.Width * scale),
             (int)Math.Round(size.Height * scale));
 
+        private const double FromSizeCeilingEpsilon = 1e-6;
+
+        /// <summary>
+        /// Converts logical size back to PixelSize and rounds it up with a small epsilon to avoid having
+        /// extra pixels when doing platform pixel size -> logical size -> pixel size conversions
+        /// </summary>
+        /// <param name="size">The logical size.</param>
+        /// <param name="scale">The scaling factor.</param>
+        /// <returns>The pixel size that contains the logical size at the given scale.</returns>
+        internal static PixelSize FromSizeCeiling(Size size, double scale) => new PixelSize(
+            CeilWithEpsilon(size.Width * scale),
+            CeilWithEpsilon(size.Height * scale));
+
+        private static int CeilWithEpsilon(double value)
+        {
+            var rounded = Math.Round(value);
+            if (Math.Abs(value - rounded) < FromSizeCeilingEpsilon)
+                return (int)rounded;
+            return (int)Math.Ceiling(value);
+        }
+
 
         /// <summary>
         /// Converts a <see cref="Size"/> to device pixels using the specified scaling factor.

src/Avalonia.Base/Platform/IRenderTarget.cs

@@ -32,6 +32,11 @@ namespace Avalonia.Platform
         /// </summary>
         PlatformRenderTargetState PlatformRenderTargetState => PlatformRenderTargetState.Ready;
         
-        public record struct RenderTargetSceneInfo(PixelSize Size, double Scaling);
+        public record struct RenderTargetSceneInfo(PixelSize Size, double Scaling, Size LogicalSize)
+        {
+            public RenderTargetSceneInfo(PixelSize size, double scaling) : this(size, scaling, size.ToSize(scaling))
+            {
+            }
+        }
     }
 }

src/Avalonia.Base/Rendering/Composition/CompositingRenderer.cs

@@ -173,7 +173,7 @@ internal class CompositingRenderer : IRendererWithCompositor, IHitTester
         _dirty.Clear();
         _recalculateChildren.Clear();
         
-        CompositionTarget.PixelSize = PixelSize.FromSizeRounded(_root.ClientSize, _root.RenderScaling);
+        CompositionTarget.Size = _root.ClientSize;
         CompositionTarget.Scaling = _root.RenderScaling;
         
         var commit = _compositor.RequestCompositionBatchCommitAsync();

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

@@ -109,7 +109,7 @@ internal class CompositionTargetOverlays
             targetContext.Transform = Matrix.CreateScale(_target.Scaling, _target.Scaling);
             
             using (var immediate = new ImmediateDrawingContext(targetContext, false))
-                DrawOverlays(immediate, hasLayer, _target.PixelSize.ToSize(_target.Scaling));
+                DrawOverlays(immediate, hasLayer, _target.Size);
         }
     }
 

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

@@ -39,6 +39,8 @@ namespace Avalonia.Rendering.Composition.Server
         public ICompositionTargetDebugEvents? DebugEvents { get; set; }
         public int RenderedVisuals { get; set; }
         public int VisitedVisuals { get; set; }
+
+        internal PixelSize PixelSize => Avalonia.PixelSize.FromSizeCeiling(Size, Scaling);
         
         /// <summary>
         /// Returns true if the target is enabled and has pending work but its render target was not ready.
@@ -197,7 +199,7 @@ namespace Avalonia.Rendering.Composition.Server
                             || !(_renderTarget.Properties.RetainsPreviousFrameContents
                                  && _renderTarget.Properties.IsSuitableForDirectRendering);
             
-            using (var renderTargetContext = _renderTarget.CreateDrawingContext(new(PixelSize, Scaling), out var properties))
+            using (var renderTargetContext = _renderTarget.CreateDrawingContext(new(PixelSize, Scaling, Size), out var properties))
             using (var renderTiming = Diagnostic.BeginCompositorRenderPass())
             {
                 var fullRedraw = false;

src/Avalonia.Base/composition-schema.xml

@@ -58,7 +58,7 @@
         <Property Name="DebugOverlays" Type="RendererDebugOverlays"/>
         <Property Name="LastLayoutPassTiming" Type="LayoutPassTiming" Internal="true"/>
         <Property Name="Scaling" Type="double"/>
-        <Property Name="PixelSize" Type="PixelSize" />
+        <Property Name="Size" Type="Size" />
     </Object>
     <KeyFrameAnimation Name="Scalar" Type="float"/>
     <KeyFrameAnimation Name="Double" Type="double"/>

tests/Avalonia.Base.UnitTests/PixelSizeTests.cs

@@ -74,4 +74,42 @@ public class PixelSizeTests
             null
         ];
     }
+
+    [Theory]
+    [InlineData(10, 1.0, 10)]
+    [InlineData(10, 1.25, 13)]
+    [InlineData(10, 1.5, 15)]
+    [InlineData(10, 1.75, 18)]
+    [InlineData(10, 2.0, 20)]
+    [InlineData(10, 1.125, 12)]
+    [InlineData(8, 1.5, 12)]
+    [InlineData(0, 1.5, 0)]
+    [InlineData(1, 2.5, 3)]
+    public void FromSizeCeiling_Computes_Expected_Pixels(int logical, double scale, int expected)
+    {
+        var pixel = PixelSize.FromSizeCeiling(new Size(logical, logical), scale);
+        Assert.Equal(expected, pixel.Width);
+        Assert.Equal(expected, pixel.Height);
+    }
+
+    [Theory]
+    [InlineData(1.5)]
+    [InlineData(2.0)]
+    [InlineData(3.0)]
+    public void FromSizeCeiling_Snaps_When_Within_Epsilon(double scale)
+    {
+        // Pick a logical size where logical * scale is an exact integer; perturbing it by a tiny
+        // amount in either direction must still produce that integer (no spurious +1 from ceiling).
+        const int logical = 10;
+        var exact = logical * scale;
+        var below = exact - 1e-9;
+        var above = exact + 1e-9;
+        var roundedBelow = below / scale;
+        var roundedAbove = above / scale;
+
+        var p1 = PixelSize.FromSizeCeiling(new Size(roundedBelow, roundedBelow), scale);
+        var p2 = PixelSize.FromSizeCeiling(new Size(roundedAbove, roundedAbove), scale);
+        Assert.Equal((int)exact, p1.Width);
+        Assert.Equal((int)exact, p2.Width);
+    }
 }

tests/Avalonia.Base.UnitTests/Rendering/CompositorLifetimeTests.cs

@@ -17,7 +17,7 @@ public class CompositorLifetimeTests : CompositorTestsBase
 
         var compositionTarget = ((CompositingRenderer)presentationSource.Renderer).CompositionTarget;
         Assert.True(compositionTarget.IsEnabled);
-        Assert.Equal(new PixelSize(200, 200), compositionTarget.PixelSize);
+        Assert.Equal(new Size(200, 200), compositionTarget.Size);
 
         // Stop rendering and invalidate a visual: this should not result in an update
         services.TopLevel.StopRendering();
@@ -25,12 +25,12 @@ public class CompositorLifetimeTests : CompositorTestsBase
         services.TopLevel.InvalidateVisual();
         services.RunJobs();
 
-        Assert.Equal(new PixelSize(200, 200), compositionTarget.PixelSize);
+        Assert.Equal(new Size(200, 200), compositionTarget.Size);
 
         // Check that restarting rendering re-queues the pending invalidation
         services.TopLevel.StartRendering();
         services.RunJobs();
 
-        Assert.Equal(new PixelSize(300, 300), compositionTarget.PixelSize);
+        Assert.Equal(new Size(300, 300), compositionTarget.Size);
     }
 }

tests/Avalonia.Benchmarks/Compositor/CompositionTargetUpdate.cs

@@ -55,7 +55,7 @@ public class CompositionTargetUpdateOnly : IDisposable
         _compositor = new Compositor(RenderLoop.FromTimer(new Timer()), null, true, new ManualScheduler(), true,
             Dispatcher.UIThread, null);
         _target = _compositor.CreateCompositionTarget(() => [new NullFramebuffer()]);
-        _target.PixelSize = new PixelSize(1000, 1000);
+        _target.Size = new Size(1000, 1000);
         _target.Scaling = 1;
         var root = _compositor.CreateContainerVisual();
         root.Size = new Vector(1000, 1000);