web UI

VisionBuilder.UI.Blazor/Components/PreviewWindow.razor.cs

@@ -0,0 +1,94 @@
+using System.ComponentModel;
+using Microsoft.AspNetCore.Components;
+using OpenCvSharp;
+using VisionBuilder.UI.Blazor.Helpers;
+using VisionBuilder.UI.Common.ViewModel;
+
+namespace VisionBuilder.UI.Blazor.Components;
+
+public partial class PreviewWindow : ComponentBase, IDisposable
+{
+    [Parameter] public PreviewVM? ViewModel { get; set; }
+
+    private string _dataUri = string.Empty;
+    private bool _isError;
+    private DateTime _lastRenderTime = DateTime.MinValue;
+    private Timer? _pendingTimer;
+    private PreviewVM? _subscribedVm;
+
+    protected override void OnParametersSet()
+    {
+        if (_subscribedVm != ViewModel)
+        {
+            Unsubscribe();
+            Subscribe();
+        }
+    }
+
+    private void Subscribe()
+    {
+        _subscribedVm = ViewModel;
+        if (ViewModel != null)
+            ViewModel.PropertyChanged += OnPropertyChanged;
+    }
+
+    private void Unsubscribe()
+    {
+        if (_subscribedVm != null)
+            _subscribedVm.PropertyChanged -= OnPropertyChanged;
+        _subscribedVm = null;
+    }
+
+    private async void OnPropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (e.PropertyName != nameof(PreviewVM.ImagePreview) && e.PropertyName != nameof(PreviewVM.IsError))
+            return;
+
+        var now = DateTime.UtcNow;
+        var elapsed = (now - _lastRenderTime).TotalMilliseconds;
+
+        if (elapsed < 100)
+        {
+            // Schedule a render for when the throttle window expires,
+            // so we always show the latest frame.
+            _pendingTimer?.Dispose();
+            _pendingTimer = new Timer(_ => RenderLatest(), null,
+                (int)(100 - elapsed) + 1, Timeout.Infinite);
+            return;
+        }
+
+        await RenderCurrentFrame();
+    }
+
+    private async void RenderLatest()
+    {
+        _pendingTimer?.Dispose();
+        _pendingTimer = null;
+        await RenderCurrentFrame();
+    }
+
+    private async Task RenderCurrentFrame()
+    {
+        _lastRenderTime = DateTime.UtcNow;
+
+        var mat = ViewModel?.ImagePreview;
+        var isError = ViewModel?.IsError ?? false;
+
+        string dataUri = string.Empty;
+        if (mat != null && !mat.Empty())
+        {
+            dataUri = mat.ToBase64DataUri();
+        }
+
+        _dataUri = dataUri;
+        _isError = isError;
+
+        await InvokeAsync(StateHasChanged);
+    }
+
+    public void Dispose()
+    {
+        _pendingTimer?.Dispose();
+        Unsubscribe();
+    }
+}