[macOS] Synchronize Metal drawable presentation (#21588)

* Add demo app

* [macOS] Present Metal drawable synchronously on main-thread resize frames

* write through the out-parameter

* Add ResizePattern to RenderDemo

* Remove MetalResizeDemo

native/Avalonia.Native/src/OSX/metal.mm

@@ -181,12 +181,13 @@ class AvnMetalRenderSession : public ComSingleObject<IAvnMetalRenderingSession,
     CAMetalLayer* _layer;
     AvnPixelSize _size;
     double _scaling;
+    bool _presentWithTransaction;
 public:
     FORWARD_IUNKNOWN()
 
-    AvnMetalRenderSession(AvnMetalDevice* device, CAMetalLayer* layer, id <CAMetalDrawable> drawable, const AvnPixelSize &size, double scaling)
+    AvnMetalRenderSession(AvnMetalDevice* device, CAMetalLayer* layer, id <CAMetalDrawable> drawable, const AvnPixelSize &size, double scaling, bool presentWithTransaction)
             : _drawable(drawable), _size(size), _scaling(scaling), _queue(device->queue),
-            _texture([drawable texture]) {
+            _texture([drawable texture]), _presentWithTransaction(presentWithTransaction) {
         _layer = layer;
     }
 
@@ -207,8 +208,19 @@ public:
     {
         START_ARP_CALL;
         auto buffer = [_queue commandBuffer];
-        [buffer presentDrawable: _drawable];
-        [buffer commit];
+        if(_presentWithTransaction)
+        {
+            [buffer commit];
+            [buffer waitUntilScheduled];
+            [_drawable present];
+            // Restore the default asynchronous presentation for the off-thread render loop.
+            _layer.presentsWithTransaction = NO;
+        }
+        else
+        {
+            [buffer presentDrawable: _drawable];
+            [buffer commit];
+        }
     }
 };
 
@@ -230,7 +242,8 @@ public:
 
     HRESULT BeginDrawing(IAvnMetalRenderingSession **ret) override {
         START_COM_ARP_CALL;
-        if([NSThread isMainThread])
+        bool onMainThread = [NSThread isMainThread];
+        if(onMainThread)
         {
             // Flush all existing rendering
             auto buffer = [_device->queue commandBuffer];
@@ -240,15 +253,21 @@ public:
             _scaling= PendingScaling;
             CGSize layerSize = {(CGFloat)_size.Width, (CGFloat)_size.Height};
 
+            [CATransaction begin];
+            [CATransaction setDisableActions:YES];
             [_layer setDrawableSize: layerSize];
+            _layer.presentsWithTransaction = YES;
+            [CATransaction commit];
         }
         auto drawable = [_layer nextDrawable];
         if(drawable == nil)
         {
-            ret = nil;
+            if(onMainThread)
+                _layer.presentsWithTransaction = NO;
+            *ret = nullptr;
             return E_FAIL;
         }
-        *ret = new AvnMetalRenderSession(_device, _layer, drawable, _size, _scaling);
+        *ret = new AvnMetalRenderSession(_device, _layer, drawable, _size, _scaling, onMainThread);
         return 0;
     }
 };

samples/RenderDemo/Controls/ResizePattern.cs

@@ -0,0 +1,73 @@
+using System;
+using System.Globalization;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Media;
+
+namespace RenderDemo.Controls
+{
+    public sealed class ResizePattern : Control
+    {
+        private static readonly IPen GridPen = new Pen(new SolidColorBrush(Color.FromRgb(60, 90, 130)), 1);
+        private static readonly IPen DiagonalPen = new Pen(new SolidColorBrush(Color.FromRgb(90, 90, 90)), 1);
+        private static readonly IPen CirclePen = new Pen(Brushes.OrangeRed, 4);
+        private static readonly IPen EdgePen = new Pen(Brushes.Lime, 6);
+        private static readonly IBrush Background = new SolidColorBrush(Color.FromRgb(16, 16, 24));
+        private static readonly IBrush TextBrush = Brushes.White;
+
+        private const double GridStep = 40;
+
+        static ResizePattern()
+        {
+            AffectsRender<ResizePattern>(BoundsProperty);
+        }
+
+        public override void Render(DrawingContext context)
+        {
+            var w = Bounds.Width;
+            var h = Bounds.Height;
+            if (w <= 0 || h <= 0)
+                return;
+
+            var rect = new Rect(0, 0, w, h);
+            context.FillRectangle(Background, rect);
+
+            // Grid -- uneven spacing on the far edges is the tell-tale of stretching.
+            for (double x = 0; x <= w; x += GridStep)
+                context.DrawLine(GridPen, new Point(x, 0), new Point(x, h));
+            for (double y = 0; y <= h; y += GridStep)
+                context.DrawLine(GridPen, new Point(0, y), new Point(w, y));
+
+            // Corner-to-corner diagonals -- they only meet exactly at the centre
+            // when the aspect ratio is correct.
+            context.DrawLine(DiagonalPen, new Point(0, 0), new Point(w, h));
+            context.DrawLine(DiagonalPen, new Point(w, 0), new Point(0, h));
+
+            // Edge frame -- a stretched drawable makes this peel away from the window edge.
+            context.DrawRectangle(null, EdgePen, rect.Deflate(3));
+
+            // Concentric perfect circles centred in the window.
+            var center = new Point(w / 2, h / 2);
+            var maxRadius = Math.Max(10, Math.Min(w, h) / 2 - 16);
+            for (var i = 1; i <= 3; i++)
+            {
+                var r = maxRadius * i / 3;
+                context.DrawEllipse(null, CirclePen, center, r, r);
+            }
+
+            // Centre crosshair.
+            context.DrawLine(CirclePen, new Point(center.X - 20, center.Y), new Point(center.X + 20, center.Y));
+            context.DrawLine(CirclePen, new Point(center.X, center.Y - 20), new Point(center.X, center.Y + 20));
+
+            // Live size read-out.
+            var text = new FormattedText(
+                string.Create(CultureInfo.InvariantCulture, $"{w:0} x {h:0} DIP"),
+                CultureInfo.InvariantCulture,
+                FlowDirection.LeftToRight,
+                Typeface.Default,
+                22,
+                TextBrush);
+            context.DrawText(text, new Point(12, 8));
+        }
+    }
+}

samples/RenderDemo/MainWindow.xaml

@@ -97,5 +97,8 @@
     <TabItem Header="3D Transformation">
       <pages:Transform3DPage />
     </TabItem>
+    <TabItem Header="Resize Pattern">
+      <pages:ResizePatternPage />
+    </TabItem>
   </controls:HamburgerMenu>
 </Window>

samples/RenderDemo/Pages/ResizePatternPage.xaml

@@ -0,0 +1,7 @@
+<UserControl
+  xmlns="https://github.com/avaloniaui"
+  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+  xmlns:controls="using:RenderDemo.Controls"
+  x:Class="RenderDemo.Pages.ResizePatternPage">
+  <controls:ResizePattern />
+</UserControl>

samples/RenderDemo/Pages/ResizePatternPage.xaml.cs

@@ -0,0 +1,18 @@
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+
+namespace RenderDemo.Pages
+{
+    public class ResizePatternPage : UserControl
+    {
+        public ResizePatternPage()
+        {
+            InitializeComponent();
+        }
+
+        private void InitializeComponent()
+        {
+            AvaloniaXamlLoader.Load(this);
+        }
+    }
+}