Web source: CSS reset per document + (0,0) anchor — kill box-vs-content padding

Services/WebView2Manager.cs

@@ -15,6 +15,20 @@ namespace ytLive.Services;
 
 public sealed class WebView2Manager : IDisposable
 {
+    // Eliminates the wrapper padding/whitespace between the box and the page:
+    // clears UA margins/paddings, forces html/body to fill the viewport and
+    // anchors content at (0,0) so the rendered frame matches the widget's size.
+    private const string CssResetInjection =
+        "(function(){" +
+        "var s=document.createElement('style');" +
+        "s.textContent='html,body{margin:0!important;padding:0!important;" +
+        "width:100%!important;height:100%!important;overflow:hidden!important;" +
+        "background:transparent!important}';" +
+        "(document.head||document.documentElement).appendChild(s);" +
+        "if(document.documentElement)document.documentElement.style.background='transparent';" +
+        "if(document.body)document.body.style.background='transparent';" +
+        "})();";
+
     private readonly Panel _hostPanel;
     private readonly Dispatcher _dispatcher;
     private readonly Dictionary<string, WebSourceSession> _sessions = new();
@@ -108,18 +122,11 @@ public sealed class WebView2Manager : IDisposable
 
             var cws = session.Control.CoreWebView2!;
 
-            cws.NavigationStarting += (_, e) =>
-            {
-                _ = cws.ExecuteScriptAsync(
-                    "document.documentElement.style.background='transparent';" +
-                    "document.body.style.background='transparent';");
-            };
+            await cws.AddScriptToExecuteOnDocumentCreatedAsync(CssResetInjection);
 
             cws.NavigationCompleted += (_, _) =>
             {
-                _ = cws.ExecuteScriptAsync(
-                    "document.documentElement.style.background='transparent';" +
-                    "document.body.style.background='transparent';");
+                _ = cws.ExecuteScriptAsync(CssResetInjection);
                 _ = CaptureFrame(source.Id);
             };