feat(linux): add graphical platform services

tests/AcDream.App.Tests/Rendering/LinuxMonotonicFramePacingWaiterTests.cs

@@ -0,0 +1,85 @@
+using System.Diagnostics;
+using AcDream.App.Rendering;
+
+namespace AcDream.App.Tests.Rendering;
+
+public sealed class LinuxMonotonicFramePacingWaiterTests
+{
+    [Theory]
+    [InlineData(1L, 1_000_000_000L, 1L)]
+    [InlineData(1L, 3L, 333_333_334L)]
+    [InlineData(15L, 1_000L, 15_000_000L)]
+    [InlineData(6_060L, 1_000_000L, 6_060_000L)]
+    public void TickConversionRoundsUpWithoutReturningZero(
+        long ticks,
+        long frequency,
+        long expected)
+    {
+        Assert.Equal(
+            expected,
+            LinuxMonotonicFramePacingWaiter
+                .ConvertTicksToNanoseconds(ticks, frequency));
+    }
+
+    [Fact]
+    public void PlatformFactorySelectsCurrentOperatingSystem()
+    {
+        IFramePacingWaiter waiter =
+            PlatformFramePacingWaiterFactory
+                .ForCurrentProcess()
+                .Create();
+
+        if (OperatingSystem.IsWindows())
+        {
+            Assert.IsType<WindowsHighResolutionFramePacingWaiter>(
+                waiter);
+            ((IDisposable)waiter).Dispose();
+            return;
+        }
+
+        if (OperatingSystem.IsLinux())
+        {
+            Assert.IsType<LinuxMonotonicFramePacingWaiter>(waiter);
+            ((IDisposable)waiter).Dispose();
+            return;
+        }
+
+        throw new PlatformNotSupportedException();
+    }
+
+    [Fact]
+    public void LinuxWaitBlocksUntilRequestedMonotonicDeadline()
+    {
+        if (!OperatingSystem.IsLinux())
+            return;
+
+        LinuxMonotonicFramePacingWaiter waiter =
+            LinuxMonotonicFramePacingWaiter.Create();
+        long start = Stopwatch.GetTimestamp();
+        waiter.Wait(
+            durationTicks: Stopwatch.Frequency / 200L,
+            clockFrequency: Stopwatch.Frequency);
+        TimeSpan elapsed = Stopwatch.GetElapsedTime(start);
+
+        Assert.True(
+            elapsed >= TimeSpan.FromMilliseconds(4),
+            $"Linux monotonic wait returned after {elapsed.TotalMilliseconds:F3} ms.");
+        Assert.True(
+            elapsed < TimeSpan.FromSeconds(1),
+            $"Linux monotonic wait stalled for {elapsed.TotalMilliseconds:F3} ms.");
+    }
+
+    [Fact]
+    public void LinuxWaiterRejectsUseAfterDisposal()
+    {
+        if (!OperatingSystem.IsLinux())
+            return;
+
+        LinuxMonotonicFramePacingWaiter waiter =
+            LinuxMonotonicFramePacingWaiter.Create();
+        waiter.Dispose();
+
+        Assert.Throws<ObjectDisposedException>(
+            () => waiter.Wait(1, Stopwatch.Frequency));
+    }
+}