Fix blur theme backdrop, corners, margin issues & simplify AutoDropShadow

Flow.Launcher.Core/Resource/Theme.cs

@@ -554,6 +554,11 @@ public void RemoveDropShadowEffectFromCurrentTheme()
             ThemeHelper.CopyStyle(windowBorderStyle, newWindowBorderStyle);
 
             // Copy Setters, excluding the Effect setter and updating the Margin setter
+            // Only adjust margin if there's actually a shadow effect to remove,
+            // preventing it from shrinking on repeated calls.
+            bool hasEffect = windowBorderStyle.Setters.OfType<Setter>()
+                .Any(s => s.Property == UIElement.EffectProperty);
+
             foreach (var setterBase in windowBorderStyle.Setters)
             {
                 if (setterBase is Setter setter)
@@ -562,7 +567,7 @@ public void RemoveDropShadowEffectFromCurrentTheme()
                     if (setter.Property == UIElement.EffectProperty) continue;
 
                     // Update Margin by subtracting the extra margin we added for the shadow
-                    if (setter.Property == FrameworkElement.MarginProperty)
+                    if (hasEffect && setter.Property == FrameworkElement.MarginProperty)
                     {
                         var currentMargin = (Thickness)setter.Value;
                         var newMargin = new Thickness(
@@ -635,20 +640,8 @@ await Application.Current.Dispatcher.InvokeAsync(() =>
                 // Get the actual backdrop type and drop shadow effect settings
                 var (backdropType, useDropShadowEffect) = GetActualValue();
 
-                // Remove OS minimizing/maximizing animation
-                // Methods.SetWindowAttribute(new WindowInteropHelper(mainWindow).Handle, DWMWINDOWATTRIBUTE.DWMWA_TRANSITIONS_FORCEDISABLED, 3);
-
-                // The timing of adding the shadow effect should vary depending on whether the theme is transparent.
-                if (BlurEnabled)
-                {
-                    AutoDropShadow(useDropShadowEffect);
-                }
                 SetBlurForWindow(_settings.Theme, backdropType);
-
-                if (!BlurEnabled)
-                {
-                    AutoDropShadow(useDropShadowEffect);
-                }
+                AutoDropShadow(useDropShadowEffect);
             }, DispatcherPriority.Render);
         }
 
@@ -725,39 +718,42 @@ private void SetBlurForWindow(string theme, BackdropTypes backdropType)
                 // Apply the blur effect
                 Win32Helper.DWMSetBackdropForWindow(mainWindow, backdropType);
                 ColorizeWindow(theme, backdropType);
+
+                // DWM renders rounded corners for backdrop windows
+                SetWindowCornerPreference("Round");
+
+                // Clear any stale directly-set WindowBorderStyle that might shadow
+                // the merged dictionary entry we just modified above.
+                if (Application.Current.Resources.Contains("WindowBorderStyle"))
+                    Application.Current.Resources.Remove("WindowBorderStyle");
+
+                // For blur themes the resize border defaults to the system thickness.
+                SetResizeBoarderThickness(null);
             }
             else
             {
                 // Apply default style when Blur is disabled
                 Win32Helper.DWMSetBackdropForWindow(mainWindow, BackdropTypes.None);
                 ColorizeWindow(theme, backdropType);
+
+                // Non-blur themes use the default window corner preference
+                SetWindowCornerPreference("Default");
             }
 
             UpdateResourceDictionary(dict);
         }
 
         private void AutoDropShadow(bool useDropShadowEffect)
         {
+            if (BlurEnabled)
+                return; // Blur themes have no drop shadow effect
+
             if (useDropShadowEffect)
             {
-                if (BlurEnabled && Win32Helper.IsBackdropSupported())
-                {
-                    // For themes with blur enabled, the window border is rendered by the system,
-                    // so we set corner preference to round and remove drop shadow effect to avoid rendering issues.
-                    SetWindowCornerPreference("Round");
-                    RemoveDropShadowEffectFromCurrentTheme();
-                }
-                else
-                {
-                    // For themes without blur, we set corner preference to default and add drop shadow effect.
-                    SetWindowCornerPreference("Default");
-                    AddDropShadowEffectToCurrentTheme();
-                }
+                AddDropShadowEffectToCurrentTheme();
             }
             else
             {
-                // When drop shadow effect is disabled, we set corner preference to default and remove drop shadow effect.
-                SetWindowCornerPreference("Default");
                 RemoveDropShadowEffectFromCurrentTheme();
             }
         }

Flow.Launcher.Infrastructure/NativeMethods.txt

@@ -14,6 +14,7 @@ VIRTUAL_KEY
 EnumWindows
 
 DwmSetWindowAttribute
+DwmExtendFrameIntoClientArea
 DWM_SYSTEMBACKDROP_TYPE
 DWM_WINDOW_CORNER_PREFERENCE
 

Flow.Launcher.Infrastructure/Win32Helper.cs

@@ -21,6 +21,7 @@
 using Windows.Win32.Graphics.Dwm;
 using Windows.Win32.System.Power;
 using Windows.Win32.System.Threading;
+using Windows.Win32.UI.Controls;
 using Windows.Win32.UI.Input.KeyboardAndMouse;
 using Windows.Win32.UI.Shell.Common;
 using Windows.Win32.UI.WindowsAndMessaging;
@@ -61,6 +62,14 @@ public static unsafe bool DWMSetBackdropForWindow(Window window, BackdropTypes b
                 _ => DWM_SYSTEMBACKDROP_TYPE.DWMSBT_AUTO
             };
 
+            // The backdrop renders in the non-client frame area. WindowStyle=None
+            // removes that area, so we extend it across the entire client area.
+            // This is harmless when backdrop is None or blur not enabled
+            // as DWM has nothing to render in the extended area.
+            // https://learn.microsoft.com/en-us/windows/win32/api/dwmapi/nf-dwmapi-dwmextendframeintoclientarea
+            var margins = new MARGINS { cxLeftWidth = -1, cxRightWidth = -1, cyTopHeight = -1, cyBottomHeight = -1 };
+            PInvoke.DwmExtendFrameIntoClientArea(GetWindowHandle(window), in margins);
+
             return PInvoke.DwmSetWindowAttribute(
                 GetWindowHandle(window),
                 DWMWINDOWATTRIBUTE.DWMWA_SYSTEMBACKDROP_TYPE,