From 745b303fbda983c35357c33aca19d67b72437021 Mon Sep 17 00:00:00 2001
From: ZhuchkaTriplesix <mrlololoshka94@gmail.com>
Date: Sun, 11 Oct 2026 09:02:55 +0300
Subject: [PATCH] perf(ui): eliminate per-frame ImageFilter.blur sigma
 animation in showAppDialog backdrop

---
 lib/shared/widgets/app_dialog.dart | 6 +++---
 test/shared/app_dialog_test.dart   | 8 ++++----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/lib/shared/widgets/app_dialog.dart b/lib/shared/widgets/app_dialog.dart
index bfb9e357..0dffda0d 100644
--- a/lib/shared/widgets/app_dialog.dart
+++ b/lib/shared/widgets/app_dialog.dart
@@ -132,8 +132,8 @@ class _BlurredDialogScaffoldState extends State<_BlurredDialogScaffold> {
 
 /// Frosted, dimmed dialog backdrop at [progress] (0 = none, 1 = full).
 ///
-/// Both blur sigma and tint alpha scale with [progress], so the frost fades in
-/// and out without pop-in and without an enclosing `Opacity`.
+/// Uses constant blur sigma (8) whenever visible and fades the background
+/// tint alpha, eliminating per-frame Gaussian blur shader re-rasterization (#1341).
 class _DialogBackdrop extends StatelessWidget {
   const _DialogBackdrop({required this.progress});
 
@@ -151,7 +151,7 @@ class _DialogBackdrop extends StatelessWidget {
     if (t <= 0) return const SizedBox.expand();
     return ClipRect(
       child: BackdropFilter(
-        filter: ImageFilter.blur(sigmaX: sigma * t, sigmaY: sigma * t),
+        filter: ImageFilter.blur(sigmaX: sigma, sigmaY: sigma),
         child: ColoredBox(
           color: const Color(0xFF000000).withValues(alpha: tintAlpha * t),
         ),
diff --git a/test/shared/app_dialog_test.dart b/test/shared/app_dialog_test.dart
index 938e62a7..576e01fd 100644
--- a/test/shared/app_dialog_test.dart
+++ b/test/shared/app_dialog_test.dart
@@ -143,7 +143,7 @@ void main() {
       return box.color;
     }
 
-    testWidgets('blur and tint scale in during enter; no Opacity wraps the filter',
+    testWidgets('constant blur with tint scaling during enter; no Opacity wraps the filter (#1341)',
         (tester) async {
       final ctx = await pumpHost(tester);
 
@@ -155,7 +155,7 @@ void main() {
       await tester.pump(const Duration(milliseconds: 40));
 
       final filter = tester.widget<BackdropFilter>(find.byType(BackdropFilter));
-      expect(filter.filter, isNot(fullFilter), reason: 'sigma is still ramping');
+      expect(filter.filter, fullFilter, reason: 'sigma is constant to avoid per-frame blur re-rasterization');
       expect(tintOf(tester).a, greaterThan(0));
       expect(tintOf(tester).a, lessThan(fullTint.a));
 
@@ -190,7 +190,7 @@ void main() {
       );
     });
 
-    testWidgets('blur and tint fade out again on dismiss', (tester) async {
+    testWidgets('tint fades out on dismiss while blur remains constant until route pops (#1341)', (tester) async {
       final ctx = await pumpHost(tester);
 
       final future = showAppDialog<void>(
@@ -204,7 +204,7 @@ void main() {
       await tester.pump(const Duration(milliseconds: 40));
 
       final filter = tester.widget<BackdropFilter>(find.byType(BackdropFilter));
-      expect(filter.filter, isNot(fullFilter));
+      expect(filter.filter, fullFilter);
       expect(tintOf(tester).a, lessThan(fullTint.a));
 
       await tester.pumpAndSettle();