Forward preview providing methods too

Author: sjchmiela

Source/IGListKit/IGListSectionController.h

@@ -132,6 +132,28 @@ NS_SWIFT_NAME(ListSectionController)
  */
 - (UIContextMenuConfiguration * _Nullable)contextMenuConfigurationForItemAtIndex:(NSInteger)index point:(CGPoint)point API_AVAILABLE(ios(13.0)) API_UNAVAILABLE(tvos);
 
+/**
+ Tells the section controller that the cell has requested a preview for context menu highlight.
+ 
+ @param configuration Context menu configuration.
+ 
+ @return An object that conforms to `UITargetedPreview`
+ 
+ @note The default implementation does nothing. **Calling super is not required.**
+ */
+- (UITargetedPreview * _Nullable)previewForHighlightingContextMenuWithConfiguration:(UIContextMenuConfiguration *)configuration API_AVAILABLE(ios(13.0)) API_UNAVAILABLE(tvos);
+
+/**
+ Tells the section controller that the cell has requested a preview for context menu dismiss.
+ 
+ @param configuration Context menu configuration.
+ 
+ @return An object that conforms to `UITargetedPreview`
+ 
+ @note The default implementation does nothing. **Calling super is not required.**
+ */
+- (UITargetedPreview * _Nullable)previewForDismissingContextMenuWithConfiguration:(UIContextMenuConfiguration *)configuration API_AVAILABLE(ios(13.0)) API_UNAVAILABLE(tvos);
+
 /**
  Identifies whether an object can be moved through interactive reordering.
 

Source/IGListKit/IGListSectionController.m

@@ -101,6 +101,14 @@ - (UIContextMenuConfiguration * _Nullable)contextMenuConfigurationForItemAtIndex
     return nil;
 }
 
+- (UITargetedPreview * _Nullable)previewForHighlightingContextMenuWithConfiguration:(UIContextMenuConfiguration *)configuration {
+    return nil;
+}
+
+- (UITargetedPreview * _Nullable)previewForDismissingContextMenuWithConfiguration:(UIContextMenuConfiguration *)configuration {
+    return nil;
+}
+
 - (BOOL)canMoveItemAtIndex:(NSInteger)index {
     return NO;
 }

Source/IGListKit/Internal/IGListAdapter+UICollectionView.m

@@ -18,6 +18,12 @@
 
 #import "IGListAdapterInternal.h"
 
+@interface IGListAdapter ()
+
+@property (nonatomic, strong) NSMapTable *configurationToSectionController;
+
+@end
+
 @implementation IGListAdapter (UICollectionView)
 
 #pragma mark - UICollectionViewDataSource
@@ -278,7 +284,35 @@ - (UIContextMenuConfiguration *)collectionView:(UICollectionView *)collectionVie
     }
 
     IGListSectionController * sectionController = [self sectionControllerForSection:indexPath.section];
-    return [sectionController contextMenuConfigurationForItemAtIndex:indexPath.item point:point];
+    
+    UIContextMenuConfiguration *configuration = [sectionController contextMenuConfigurationForItemAtIndex:indexPath.item point:point];
+    if (configuration) {
+        if (!self.configurationToSectionController) {
+            self.configurationToSectionController = [NSMapTable weakToWeakObjectsMapTable];
+        }
+        [self.configurationToSectionController setObject:configuration forKey:sectionController];
+    }
+    return nil;
+}
+
+- (UITargetedPreview *)collectionView:(UICollectionView *)collectionView previewForHighlightingContextMenuWithConfiguration:(UIContextMenuConfiguration *)configuration  API_AVAILABLE(ios(13.0)){
+    id<UICollectionViewDelegate> collectionViewDelegate = self.collectionViewDelegate;
+    if ([collectionViewDelegate respondsToSelector:@selector(collectionView:previewForHighlightingContextMenuWithConfiguration:)]) {
+        return [collectionViewDelegate collectionView:collectionView previewForHighlightingContextMenuWithConfiguration:configuration];
+    }
+    
+    IGListSectionController * sectionController = [self.configurationToSectionController objectForKey:configuration];
+    return [sectionController previewForHighlightingContextMenuWithConfiguration:configuration];
+}
+
+- (UITargetedPreview *)collectionView:(UICollectionView *)collectionView previewForDismissingContextMenuWithConfiguration:(UIContextMenuConfiguration *)configuration  API_AVAILABLE(ios(13.0)){
+    id<UICollectionViewDelegate> collectionViewDelegate = self.collectionViewDelegate;
+    if ([collectionViewDelegate respondsToSelector:@selector(collectionView:previewForDismissingContextMenuWithConfiguration:)]) {
+        return [collectionViewDelegate collectionView:collectionView previewForDismissingContextMenuWithConfiguration:configuration];
+    }
+    
+    IGListSectionController * sectionController = [self.configurationToSectionController objectForKey:configuration];
+    return [sectionController previewForDismissingContextMenuWithConfiguration:configuration];
 }
 #endif
 

Source/IGListKit/Internal/IGListAdapterProxy.m

@@ -34,6 +34,8 @@ static BOOL isInterceptedSelector(SEL sel) {
             sel == @selector(collectionView:didHighlightItemAtIndexPath:) ||
             sel == @selector(collectionView:didUnhighlightItemAtIndexPath:) ||
             sel == @selector(collectionView:contextMenuConfigurationForItemAtIndexPath:point:) ||
+            sel == @selector(collectionView:previewForHighlightingContextMenuWithConfiguration:) ||
+            sel == @selector(collectionView:previewForDismissingContextMenuWithConfiguration:) ||
             // UICollectionViewDelegateFlowLayout
             sel == @selector(collectionView:layout:sizeForItemAtIndexPath:) ||
             sel == @selector(collectionView:layout:insetForSectionAtIndex:) ||