From fb19f9b3f31404b91a9b80a78d8bcadcfdb116e3 Mon Sep 17 00:00:00 2001
From: Tsanie Lily <tsorgy@gmail.com>
Date: Sun, 17 May 2020 11:51:51 +0800
Subject: [PATCH] optimize: keep filter opened while scrolling

---
 Pixiview/Illust/IllustCollectionPage.cs |  2 +-
 Pixiview/Illust/RankingPage.xaml.cs     | 19 ++++++++++++++++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/Pixiview/Illust/IllustCollectionPage.cs b/Pixiview/Illust/IllustCollectionPage.cs
index f90ef0a..81b2a8a 100644
--- a/Pixiview/Illust/IllustCollectionPage.cs
+++ b/Pixiview/Illust/IllustCollectionPage.cs
@@ -614,7 +614,7 @@ namespace Pixiview.Illust
         private double lastRefreshY = double.MinValue;
         private double offset;
 
-        protected bool ScrollingDown(double y)
+        protected bool IsScrollingDown(double y)
         {
             return y > lastScrollY;
         }
diff --git a/Pixiview/Illust/RankingPage.xaml.cs b/Pixiview/Illust/RankingPage.xaml.cs
index 6ab2307..4268f96 100644
--- a/Pixiview/Illust/RankingPage.xaml.cs
+++ b/Pixiview/Illust/RankingPage.xaml.cs
@@ -86,6 +86,7 @@ namespace Pixiview.Illust
         private bool previousEnabled;
         private bool dateEnabled;
         private bool nextEnabled;
+        private ScrollDirection scrollDirection = ScrollDirection.Stop;
 
         private bool isFilterVisible;
         private string lastQueryKey;
@@ -229,6 +230,11 @@ namespace Pixiview.Illust
             if (flag)
             {
                 isFilterVisible = true;
+                if (scrollDirection == ScrollDirection.Down)
+                {
+                    // stop the scrolling
+                    await scrollView.ScrollToAsync(0, scrollView.ScrollY, false);
+                }
                 await Task.WhenAll(
                     labelCaret.RotateTo(180, easing: Easing.CubicOut),
                     gridFilter.TranslateTo(0, 0, easing: Easing.CubicOut),
@@ -324,14 +330,25 @@ namespace Pixiview.Illust
         private void ScrollView_Scrolled(object sender, ScrolledEventArgs e)
         {
             var y = e.ScrollY;
-            if (ScrollingDown(y))
+            if (IsScrollingDown(y))
             {
+                if (scrollDirection != ScrollDirection.Down)
+                {
+                    scrollDirection = ScrollDirection.Down;
+                }
                 // down
                 if (isFilterVisible)
                 {
                     ToggleFilterPanel(false);
                 }
             }
+            else
+            {
+                if (scrollDirection != ScrollDirection.Up)
+                {
+                    scrollDirection = ScrollDirection.Up;
+                }
+            }
             OnScrolled(y);
         }