From 9bc58dc024e20a6d82916c6d0007e08790dca020 Mon Sep 17 00:00:00 2001
From: Adlai Holler <adlai@pinterest.com>
Date: Mon, 5 Dec 2016 15:00:39 -0800
Subject: [PATCH] When not visible, only batch fetch to fill visible area

---
 AsyncDisplayKit/ASCollectionView.mm         |  6 +++++
 AsyncDisplayKit/ASTableView.mm              |  6 +++++
 AsyncDisplayKit/Private/ASBatchFetching.h   |  4 ++-
 AsyncDisplayKit/Private/ASBatchFetching.m   | 15 ++++++++---
 AsyncDisplayKitTests/ASBatchFetchingTests.m | 28 ++++++++++-----------
 5 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/AsyncDisplayKit/ASCollectionView.mm b/AsyncDisplayKit/ASCollectionView.mm
index 5d31f49a4c..642a9fb825 100644
--- a/AsyncDisplayKit/ASCollectionView.mm
+++ b/AsyncDisplayKit/ASCollectionView.mm
@@ -1708,6 +1708,12 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
     [_rangeController setNeedsUpdate];
     [_rangeController updateIfNeeded];
   }
+
+  // When we aren't visible, we will only fetch up to the visible area. Now that we are visible,
+  // we will fetch visible area + leading screens, so we need to check.
+  if (visible) {
+    [self _checkForBatchFetching];
+  }
 }
 
 #pragma mark ASCALayerExtendedDelegate
diff --git a/AsyncDisplayKit/ASTableView.mm b/AsyncDisplayKit/ASTableView.mm
index 1f0ec1d5c2..44da18d057 100644
--- a/AsyncDisplayKit/ASTableView.mm
+++ b/AsyncDisplayKit/ASTableView.mm
@@ -1725,6 +1725,12 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
     [_rangeController setNeedsUpdate];
     [_rangeController updateIfNeeded];
   }
+
+  // When we aren't visible, we will only fetch up to the visible area. Now that we are visible,
+  // we will fetch visible area + leading screens, so we need to check.
+  if (visible) {
+    [self _checkForBatchFetching];
+  }
 }
 
 @end
diff --git a/AsyncDisplayKit/Private/ASBatchFetching.h b/AsyncDisplayKit/Private/ASBatchFetching.h
index a09fb898d3..7effc6bcb7 100644
--- a/AsyncDisplayKit/Private/ASBatchFetching.h
+++ b/AsyncDisplayKit/Private/ASBatchFetching.h
@@ -45,6 +45,7 @@ BOOL ASDisplayShouldFetchBatchForScrollView(UIScrollView<ASBatchFetchingScrollVi
  @param contentSize The content size of the scrollview.
  @param targetOffset The offset that the scrollview will scroll to.
  @param leadingScreens How many screens in the remaining distance will trigger batch fetching.
+ @param visible Whether the view is visible or not.
  @return Whether or not the current state should proceed with batch fetching.
  @discussion This method is broken into a category for unit testing purposes and should be used with the ASTableView and
  * ASCollectionView batch fetching API.
@@ -55,6 +56,7 @@ extern BOOL ASDisplayShouldFetchBatchForContext(ASBatchContext *context,
                                                 CGRect bounds,
                                                 CGSize contentSize,
                                                 CGPoint targetOffset,
-                                                CGFloat leadingScreens);
+                                                CGFloat leadingScreens,
+                                                BOOL visible);
 
 ASDISPLAYNODE_EXTERN_C_END
diff --git a/AsyncDisplayKit/Private/ASBatchFetching.m b/AsyncDisplayKit/Private/ASBatchFetching.m
index 539a8a1f90..52b6ecd54a 100644
--- a/AsyncDisplayKit/Private/ASBatchFetching.m
+++ b/AsyncDisplayKit/Private/ASBatchFetching.m
@@ -22,7 +22,8 @@ BOOL ASDisplayShouldFetchBatchForScrollView(UIScrollView<ASBatchFetchingScrollVi
   CGRect bounds = scrollView.bounds;
   CGSize contentSize = scrollView.contentSize;
   CGFloat leadingScreens = scrollView.leadingScreensForBatching;
-  return ASDisplayShouldFetchBatchForContext(context, scrollDirection, scrollableDirections, bounds, contentSize, contentOffset, leadingScreens);
+  BOOL visible = (scrollView.window != nil);
+  return ASDisplayShouldFetchBatchForContext(context, scrollDirection, scrollableDirections, bounds, contentSize, contentOffset, leadingScreens, visible);
 }
 
 BOOL ASDisplayShouldFetchBatchForContext(ASBatchContext *context,
@@ -31,7 +32,8 @@ BOOL ASDisplayShouldFetchBatchForContext(ASBatchContext *context,
                                          CGRect bounds,
                                          CGSize contentSize,
                                          CGPoint targetOffset,
-                                         CGFloat leadingScreens)
+                                         CGFloat leadingScreens,
+                                         BOOL visible)
 {
   // Do not allow fetching if a batch is already in-flight and hasn't been completed or cancelled
   if ([context isFetching]) {
@@ -55,12 +57,17 @@ BOOL ASDisplayShouldFetchBatchForContext(ASBatchContext *context,
     contentLength = contentSize.width;
   }
 
-  // target offset will always be 0 if the content size is smaller than the viewport
-  BOOL hasSmallContent = offset == 0.0 && contentLength < viewLength;
+  BOOL hasSmallContent = contentLength < viewLength;
   if (hasSmallContent) {
     return YES;
   }
 
+  // If we are not visible, but we do have enough content to fill visible area,
+  // don't batch fetch.
+  if (visible == NO) {
+    return NO;
+  }
+
   // If they are scrolling toward the head of content, don't batch fetch.
   BOOL isScrollingTowardHead = (ASScrollDirectionContainsUp(scrollDirection) || ASScrollDirectionContainsLeft(scrollDirection));
   if (isScrollingTowardHead) {
diff --git a/AsyncDisplayKitTests/ASBatchFetchingTests.m b/AsyncDisplayKitTests/ASBatchFetchingTests.m
index 3a5804ead7..9d30479330 100644
--- a/AsyncDisplayKitTests/ASBatchFetchingTests.m
+++ b/AsyncDisplayKitTests/ASBatchFetchingTests.m
@@ -30,26 +30,26 @@
 
 - (void)testBatchNullState {
   ASBatchContext *context = [[ASBatchContext alloc] init];
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, CGRectZero, CGSizeZero, CGPointZero, 0.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, CGRectZero, CGSizeZero, CGPointZero, 0.0, YES);
   XCTAssert(shouldFetch == NO, @"Should not fetch in the null state");
 }
 
 - (void)testBatchAlreadyFetching {
   ASBatchContext *context = [[ASBatchContext alloc] init];
   [context beginBatchFetching];
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0, YES);
   XCTAssert(shouldFetch == NO, @"Should not fetch when context is already fetching");
 }
 
 - (void)testUnsupportedScrollDirections {
   ASBatchContext *context = [[ASBatchContext alloc] init];
-  BOOL fetchRight = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionRight, ASScrollDirectionHorizontalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0);
+  BOOL fetchRight = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionRight, ASScrollDirectionHorizontalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0, YES);
   XCTAssert(fetchRight == YES, @"Should fetch for scrolling right");
-  BOOL fetchDown = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0);
+  BOOL fetchDown = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0, YES);
   XCTAssert(fetchDown == YES, @"Should fetch for scrolling down");
-  BOOL fetchUp = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionUp, ASScrollDirectionVerticalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0);
+  BOOL fetchUp = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionUp, ASScrollDirectionVerticalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0, YES);
   XCTAssert(fetchUp == NO, @"Should not fetch for scrolling up");
-  BOOL fetchLeft = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionLeft, ASScrollDirectionHorizontalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0);
+  BOOL fetchLeft = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionLeft, ASScrollDirectionHorizontalDirections, PASSING_RECT, PASSING_SIZE, PASSING_POINT, 1.0, YES);
   XCTAssert(fetchLeft == NO, @"Should not fetch for scrolling left");
 }
 
@@ -57,7 +57,7 @@
   CGFloat screen = 1.0;
   ASBatchContext *context = [[ASBatchContext alloc] init];
   // scroll to 1-screen top offset, height is 1 screen, so bottom is 1 screen away from end of content
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, VERTICAL_RECT(screen), VERTICAL_SIZE(screen * 3.0), VERTICAL_OFFSET(screen * 1.0), 1.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, VERTICAL_RECT(screen), VERTICAL_SIZE(screen * 3.0), VERTICAL_OFFSET(screen * 1.0), 1.0, YES);
   XCTAssert(shouldFetch == YES, @"Fetch should begin when vertically scrolling to exactly 1 leading screen away");
 }
 
@@ -65,7 +65,7 @@
   CGFloat screen = 1.0;
   ASBatchContext *context = [[ASBatchContext alloc] init];
   // 3 screens of content, scroll only 1/2 of one screen
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, VERTICAL_RECT(screen), VERTICAL_SIZE(screen * 3.0), VERTICAL_OFFSET(screen * 0.5), 1.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, VERTICAL_RECT(screen), VERTICAL_SIZE(screen * 3.0), VERTICAL_OFFSET(screen * 0.5), 1.0, YES);
   XCTAssert(shouldFetch == NO, @"Fetch should not begin when vertically scrolling less than the leading distance away");
 }
 
@@ -73,7 +73,7 @@
   CGFloat screen = 1.0;
   ASBatchContext *context = [[ASBatchContext alloc] init];
   // 3 screens of content, top offset to 3-screens, height 1 screen, so its 1 screen past the leading
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, VERTICAL_RECT(screen), VERTICAL_SIZE(screen * 3.0), VERTICAL_OFFSET(screen * 3.0), 1.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, VERTICAL_RECT(screen), VERTICAL_SIZE(screen * 3.0), VERTICAL_OFFSET(screen * 3.0), 1.0, YES);
   XCTAssert(shouldFetch == YES, @"Fetch should begin when vertically scrolling past the content size");
 }
 
@@ -81,7 +81,7 @@
   CGFloat screen = 1.0;
   ASBatchContext *context = [[ASBatchContext alloc] init];
   // scroll to 1-screen left offset, width is 1 screen, so right is 1 screen away from end of content
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionRight, ASScrollDirectionVerticalDirections, HORIZONTAL_RECT(screen), HORIZONTAL_SIZE(screen * 3.0), HORIZONTAL_OFFSET(screen * 1.0), 1.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionRight, ASScrollDirectionVerticalDirections, HORIZONTAL_RECT(screen), HORIZONTAL_SIZE(screen * 3.0), HORIZONTAL_OFFSET(screen * 1.0), 1.0, YES);
   XCTAssert(shouldFetch == YES, @"Fetch should begin when horizontally scrolling to exactly 1 leading screen away");
 }
 
@@ -89,7 +89,7 @@
   CGFloat screen = 1.0;
   ASBatchContext *context = [[ASBatchContext alloc] init];
   // 3 screens of content, scroll only 1/2 of one screen
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionLeft, ASScrollDirectionHorizontalDirections, HORIZONTAL_RECT(screen), HORIZONTAL_SIZE(screen * 3.0), HORIZONTAL_OFFSET(screen * 0.5), 1.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionLeft, ASScrollDirectionHorizontalDirections, HORIZONTAL_RECT(screen), HORIZONTAL_SIZE(screen * 3.0), HORIZONTAL_OFFSET(screen * 0.5), 1.0, YES);
   XCTAssert(shouldFetch == NO, @"Fetch should not begin when horizontally scrolling less than the leading distance away");
 }
 
@@ -97,7 +97,7 @@
   CGFloat screen = 1.0;
   ASBatchContext *context = [[ASBatchContext alloc] init];
   // 3 screens of content, left offset to 3-screens, width 1 screen, so its 1 screen past the leading
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionHorizontalDirections, HORIZONTAL_RECT(screen), HORIZONTAL_SIZE(screen * 3.0), HORIZONTAL_OFFSET(screen * 3.0), 1.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionHorizontalDirections, HORIZONTAL_RECT(screen), HORIZONTAL_SIZE(screen * 3.0), HORIZONTAL_OFFSET(screen * 3.0), 1.0, YES);
   XCTAssert(shouldFetch == YES, @"Fetch should begin when vertically scrolling past the content size");
 }
 
@@ -105,7 +105,7 @@
   CGFloat screen = 1.0;
   ASBatchContext *context = [[ASBatchContext alloc] init];
   // when the content size is < screen size, the target offset will always be 0
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, VERTICAL_RECT(screen), VERTICAL_SIZE(screen * 0.5), VERTICAL_OFFSET(0.0), 1.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionDown, ASScrollDirectionVerticalDirections, VERTICAL_RECT(screen), VERTICAL_SIZE(screen * 0.5), VERTICAL_OFFSET(0.0), 1.0, YES);
   XCTAssert(shouldFetch == YES, @"Fetch should begin when the target is 0 and the content size is smaller than the scree");
 }
 
@@ -113,7 +113,7 @@
   CGFloat screen = 1.0;
   ASBatchContext *context = [[ASBatchContext alloc] init];
   // when the content size is < screen size, the target offset will always be 0
-  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionRight, ASScrollDirectionHorizontalDirections, HORIZONTAL_RECT(screen), HORIZONTAL_SIZE(screen * 0.5), HORIZONTAL_OFFSET(0.0), 1.0);
+  BOOL shouldFetch = ASDisplayShouldFetchBatchForContext(context, ASScrollDirectionRight, ASScrollDirectionHorizontalDirections, HORIZONTAL_RECT(screen), HORIZONTAL_SIZE(screen * 0.5), HORIZONTAL_OFFSET(0.0), 1.0, YES);
   XCTAssert(shouldFetch == YES, @"Fetch should begin when the target is 0 and the content size is smaller than the scree");
 }