Improve WindowedContentDialog

Author: ghost1372

dev/DevWinUI.Controls/Controls/WindowedContentDialog/ContentDialogContent.cs

@@ -7,6 +7,7 @@ internal sealed partial class ContentDialogContent : ContentControl
     public ContentDialogContent() : base()
     {
         DefaultStyleKey = typeof(ContentDialogContent);
+        Unloaded += (o, e) => needsCustomMeasure = false;
     }
 
     private Button PrimaryButton;
@@ -21,6 +22,14 @@ public ContentDialogContent() : base()
     public Grid DialogSpace { get; private set; }
     public Grid CommandSpace { get; private set; }
 
+    /// <summary>
+    /// Whether customized measurement in MeasureOverride is needed.
+    /// <br/>
+    /// This variable is set to avoid redundant calculations.
+    /// <br/>
+    /// If the first measurement after Loaded is finished, there will be no need for customized measurement until Unloaded.
+    /// </summary>
+    private bool needsCustomMeasure;
     protected override void OnApplyTemplate()
     {
         base.OnApplyTemplate();
@@ -42,9 +51,11 @@ protected override void OnApplyTemplate()
     }
     protected override Size MeasureOverride(Size availableSize)
     {
-        if (IsLoaded)
+        if (needsCustomMeasure)
             return base.MeasureOverride(availableSize);
 
+        needsCustomMeasure = IsLoaded;
+
         int countButtons = 0;
         double buttonLongestWidth = 0.0;
         double buttonMaxWidth = (double)Application.Current.Resources["ContentDialogButtonMaxWidth"];

dev/DevWinUI.Controls/Controls/WindowedContentDialog/ContentDialogWindow.xaml.cs

@@ -110,13 +110,11 @@ public void SetParent(Window? parent, bool modal = true, bool center = true)
         _presenter.IsModal = parent is not null && modal;
     }
 
-    private ElementTheme _requestedTheme;
     public ElementTheme RequestedTheme
     {
-        get => content is not null ? content.RequestedTheme : _requestedTheme;
+        get => content.RequestedTheme;
         set
         {
-            _requestedTheme = value;
             content.RequestedTheme = value;
             AppWindow.TitleBar.PreferredTheme = value switch
             {

dev/DevWinUI.Controls/Controls/WindowedContentDialog/WindowedContentDialog.cs

@@ -215,13 +215,13 @@ private void DialogWindow_Closed(object sender, WindowEventArgs e)
 
     private void AttachPopupLifecycle(ContentDialogWindow dialogWindow, Popup popup)
     {
-        dialogWindow.Loaded -= DialogWindow_Loaded;
+        dialogWindow.Opened -= OnDialogWindowOpened;
         dialogWindow.Closed -= DialogWindow_ClosedPopup;
 
-        dialogWindow.Loaded += DialogWindow_Loaded;
+        dialogWindow.Opened += OnDialogWindowOpened;
         dialogWindow.Closed += DialogWindow_ClosedPopup;
 
-        void DialogWindow_Loaded(object sender, EventArgs e)
+        void OnDialogWindowOpened(object sender, EventArgs e)
         {
             popup.IsOpen = true;
             popup.Child.Opacity = 1.0;