increase coalesce window when collection-view is not visible

Summary: In case the collection-view is not visible, lets try batching more updates together to minimize the amount of off-screen work we do.

Differential Revision: D60691861

fbshipit-source-id: 154164fcd370e016c12bace60269c946a153c284

Source/IGListDiffKit/IGListExperiments.h

@@ -50,6 +50,8 @@ typedef struct IGListAdaptiveCoalescingExperimentConfig {
     NSTimeInterval intervalIncrement;
     /// This is the maximum coalesce interval, so the slowest and update can wait.
     NSTimeInterval maxInterval;
+    /// Coalece using `maxInterval` if view is not visible according to `IGListViewVisibilityTracker`
+    BOOL useMaxIntervalWhenViewNotVisible;
 } IGListAdaptiveCoalescingExperimentConfig;
 
 /**

Source/IGListKit/IGListAdapterUpdater.m

@@ -60,7 +60,7 @@ - (void)_queueUpdateIfNeeded {
     }
 
     // Will call `-performUpdateWithCoalescer`
-    [self.coalescer queueUpdate];
+    [self.coalescer queueUpdateForView:self.transactionBuilder.collectionView];
 }
 
 - (void)performUpdateWithCoalescer:(IGListUpdateCoalescer *)coalescer {

Source/IGListKit/Internal/IGListUpdateCoalescer.h

@@ -5,7 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-#import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
 
 #if __has_include(<IGListDiffKit/IGListDiffKit.h>)
 #import <IGListDiffKit/IGListExperiments.h>
@@ -34,8 +34,12 @@ NS_SWIFT_NAME(ListUpdateCoalescer)
 
 @property (nonatomic, weak) id<IGListUpdateCoalescerDelegate> delegate;
 
-/// Start coalescing updates, which will eventually call `-performUpdateWithCoalescer`
-- (void)queueUpdate;
+/**
+ Start coalescing updates, which will eventually call `-performUpdateWithCoalescer`
+ 
+ @params view View used to track visibility (if enabled in config)
+ */
+- (void)queueUpdateForView:(nullable UIView *)view;
 
 @end
 

Source/IGListKit/Internal/IGListUpdateCoalescer.m

@@ -7,6 +7,8 @@
 
 #import "IGListUpdateCoalescer.h"
 
+#import "IGListViewVisibilityTracker.h"
+
 @implementation IGListUpdateCoalescer {
     BOOL _hasQueuedUpdate;
 
@@ -15,7 +17,7 @@ @implementation IGListUpdateCoalescer {
     NSTimeInterval _coalescenceInterval;
 }
 
-- (void)queueUpdate {
+- (void)queueUpdateForView:(nullable UIView *)view {
     if (_hasQueuedUpdate) {
         return;
     }
@@ -26,7 +28,7 @@ - (void)queueUpdate {
     // details on how coalescence is done.
 
     if (self.adaptiveCoalescingExperimentConfig.enabled) {
-        [self _adaptiveDispatchUpdate];
+        [self _adaptiveDispatchUpdateForView:view];
     } else {
         [self _regularDispatchUpdate];
     }
@@ -40,26 +42,41 @@ - (void)_regularDispatchUpdate {
     });
 }
 
-- (void)_adaptiveDispatchUpdate {
+static BOOL _isViewVisible(UIView *_Nullable view, IGListAdaptiveCoalescingExperimentConfig config) {
+    if (config.useMaxIntervalWhenViewNotVisible) {
+        IGListViewVisibilityTracker *const tracker = IGListViewVisibilityTrackerAttachedOnView((UIView *)view);
+        if (tracker && tracker.state == IGListViewVisibilityStateNotVisible) {
+            return NO;
+        }
+    }
+
+    return YES;
+}
+
+- (void)_adaptiveDispatchUpdateForView:(nullable UIView *)view {
     const IGListAdaptiveCoalescingExperimentConfig config = _adaptiveCoalescingExperimentConfig;
-
     const NSTimeInterval timeSinceLastUpdate = -[_lastUpdateStartDate timeIntervalSinceNow];
-    if (!_lastUpdateStartDate || timeSinceLastUpdate > _coalescenceInterval) {
-        // It's been long enough, so lets reset interval and perform update right away
-        _coalescenceInterval = config.minInterval;
-        [self _performUpdate];
-        return;
+    const BOOL isViewVisible = _isViewVisible(view, config);
+
+    if (isViewVisible) {
+        if (!_lastUpdateStartDate || timeSinceLastUpdate > _coalescenceInterval) {
+            // It's been long enough, so lets reset interval and perform update right away
+            _coalescenceInterval = config.minInterval;
+            [self _performUpdate];
+            return;
+        } else {
+            // If we keep hitting the delay, lets increase it.
+            _coalescenceInterval = MIN(_coalescenceInterval + config.intervalIncrement, config.maxInterval);
+        }
     }
-
-    // If we keep hitting the delay, lets increase it.
-    _coalescenceInterval = MIN(_coalescenceInterval + config.intervalIncrement, config.maxInterval);
-
+
     // Delay by the time remaining in the interval
-    const NSTimeInterval remainingTime = MAX(_coalescenceInterval - timeSinceLastUpdate, 0);
+    const NSTimeInterval remainingTime = isViewVisible ? (_coalescenceInterval - timeSinceLastUpdate) : config.maxInterval;
+    const NSTimeInterval remainingTimeCapped = MAX(remainingTime, 0);
 
     _hasQueuedUpdate = YES;
     __weak __typeof__(self) weakSelf = self;
-    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(remainingTime * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
+    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(remainingTimeCapped * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
         [weakSelf _performUpdate];
     });
 }

Source/IGListKit/Internal/IGListUpdateTransactionBuilder.h

@@ -92,6 +92,8 @@ Change the `UICollectionView` dataSource
 
 - (BOOL)hasChanges;
 
+- (nullable UICollectionView *)collectionView;
+
 @end
 
 NS_ASSUME_NONNULL_END

Source/IGListKit/Internal/IGListUpdateTransactionBuilder.m

@@ -188,4 +188,8 @@ - (BOOL)hasChanges {
     || self.sectionDataBlock != nil;
 }
 
+- (nullable UICollectionView *)collectionView {
+    return self.collectionViewBlock ? self.collectionViewBlock() : nil;
+}
+
 @end