Auto-dismiss search keyboard; "cancel search" button.

Signal/src/ViewControllers/HomeView/ConversationSearchViewController.swift

@@ -4,9 +4,17 @@
 
 import Foundation
 
+@objc
+protocol ConversationSearchViewDelegate: class {
+    func conversationSearchViewWillBeginDragging()
+}
+
 @objc
 class ConversationSearchViewController: UITableViewController {
 
+    @objc
+    public weak var delegate: ConversationSearchViewDelegate?
+
     @objc
     public var searchText = "" {
         didSet {
@@ -300,6 +308,12 @@ class ConversationSearchViewController: UITableViewController {
         // TODO: more performant way to do this?
         self.tableView.reloadData()
     }
+
+    // MARK: - UIScrollViewDelegate
+
+    override func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
+        delegate?.conversationSearchViewWillBeginDragging()
+    }
 }
 
 class EmptySearchResultCell: UITableViewCell {

Signal/src/ViewControllers/HomeView/HomeViewController.m

@@ -45,7 +45,8 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
 @interface HomeViewController () <UITableViewDelegate,
     UITableViewDataSource,
     UIViewControllerPreviewingDelegate,
-    UISearchBarDelegate>
+    UISearchBarDelegate,
+    ConversationSearchViewDelegate>
 
 @property (nonatomic) UITableView *tableView;
 @property (nonatomic) UILabel *emptyBoxLabel;
@@ -378,6 +379,7 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
     self.tableView.tableHeaderView = self.searchBar;
 
     ConversationSearchViewController *searchResultsController = [ConversationSearchViewController new];
+    searchResultsController.delegate = self;
     self.searchResultsController = searchResultsController;
     [self addChildViewController:searchResultsController];
     [self.view addSubview:searchResultsController.view];
@@ -938,16 +940,22 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
     [self.tableView setContentOffset:CGPointZero animated:NO];
 
     [self updateSearchResultsVisibility];
+
+    [self ensureSearchBarCancelButton];
 }
 
 - (void)searchBarTextDidEndEditing:(UISearchBar *)searchBar
 {
     [self updateSearchResultsVisibility];
+
+    [self ensureSearchBarCancelButton];
 }
 
 - (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
 {
     [self updateSearchResultsVisibility];
+
+    [self ensureSearchBarCancelButton];
 }
 
 - (void)searchBarSearchButtonClicked:(UISearchBar *)searchBar
@@ -959,7 +967,17 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
 {
     self.searchBar.text = nil;
 
+    [self.searchBar resignFirstResponder];
+    OWSAssert(!self.searchBar.isFirstResponder);
+
     [self updateSearchResultsVisibility];
+
+    [self ensureSearchBarCancelButton];
+}
+
+- (void)ensureSearchBarCancelButton
+{
+    self.searchBar.showsCancelButton = (self.searchBar.isFirstResponder || self.searchBar.text.length > 0);
 }
 
 - (void)updateSearchResultsVisibility
@@ -979,6 +997,22 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
     }
 }
 
+#pragma mark - UIScrollViewDelegate
+
+- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
+{
+    [self.searchBar resignFirstResponder];
+    OWSAssert(!self.searchBar.isFirstResponder);
+}
+
+#pragma mark - ConversationSearchViewDelegate
+
+- (void)conversationSearchViewWillBeginDragging
+{
+    [self.searchBar resignFirstResponder];
+    OWSAssert(!self.searchBar.isFirstResponder);
+}
+
 #pragma mark - HomeFeedTableViewCellDelegate
 
 - (void)tableViewCellTappedDelete:(NSIndexPath *)indexPath