Alternative dark theme search bar

Rather than our custom class, we can get pretty far using existing UISearchBar
styling, and then apply the final tweak, the search bar text field background
color by traversing the view.

This fixes a couple issues:

1. There was a small wavering in height of the custom search bar
2. When your table header view is a UISearchBar you get nice scroll "snapping"
   when showing/hiding the search bar.

SignalMessaging/Views/OWSSearchBar.m

@@ -56,17 +56,21 @@ NS_ASSUME_NONNULL_BEGIN
 {
     OWSAssertIsOnMainThread();
 
-    self.searchBarStyle = UISearchBarStyleMinimal;
-    self.backgroundColor = Theme.searchBarBackgroundColor;
     self.barTintColor = Theme.backgroundColor;
     self.barStyle = Theme.barStyle;
-    self.searchBarStyle = Theme.searchBarStyle;
+
+    // Hide searchBar border.
+    // Alternatively we could hide the border by using `UISearchBarStyleMinimal`, but that causes an issue when toggling
+    // from light -> dark -> light theme wherein the textField background color appears darker than it should
+    // (regardless of our re-setting textfield.backgroundColor below).
+    self.backgroundImage = [UIImage new];
 
     [self traverseViewHierarchyWithVisitor:^(UIView *view) {
         if ([view isKindOfClass:[UITextField class]]) {
             UITextField *textField = (UITextField *)view;
-            textField.keyboardAppearance
-                = (Theme.isDarkThemeEnabled ? UIKeyboardAppearanceDark : UIKeyboardAppearanceDefault);
+            textField.backgroundColor = Theme.searchFieldBackgroundColor;
+            textField.textColor = Theme.primaryColor;
+            textField.keyboardAppearance = Theme.keyboardAppearance;
         }
     }];
 }

SignalMessaging/categories/Theme.h

@@ -47,8 +47,7 @@ extern NSString *const ThemeDidChangeNotification;
 #pragma mark -
 
 @property (class, readonly, nonatomic) UIBarStyle barStyle;
-@property (class, readonly, nonatomic) UISearchBarStyle searchBarStyle;
-@property (class, readonly, nonatomic) UIColor *searchBarBackgroundColor;
+@property (class, readonly, nonatomic) UIColor *searchFieldBackgroundColor;
 @property (class, readonly, nonatomic) UIBlurEffect *barBlurEffect;
 @property (class, readonly, nonatomic) UIKeyboardAppearance keyboardAppearance;
 

SignalMessaging/categories/Theme.m

@@ -143,29 +143,16 @@ NSString *const ThemeKeyThemeEnabled = @"ThemeKeyThemeEnabled";
     return Theme.isDarkThemeEnabled ? UIKeyboardAppearanceDark : UIKeyboardAppearanceDefault;
 }
 
-#pragma mark -
+#pragma mark - Search Bar
 
 + (UIBarStyle)barStyle
 {
-    if (Theme.isDarkThemeEnabled) {
-        return UIBarStyleDefault;
-    } else {
-        return UIBarStyleDefault;
-    }
-}
-
-+ (UISearchBarStyle)searchBarStyle
-{
-    if (Theme.isDarkThemeEnabled) {
-        return UISearchBarStyleProminent;
-    } else {
-        return UISearchBarStyleMinimal;
-    }
+    return Theme.isDarkThemeEnabled ? UIBarStyleBlack : UIBarStyleDefault;
 }
 
-+ (UIColor *)searchBarBackgroundColor
++ (UIColor *)searchFieldBackgroundColor
 {
-    return Theme.backgroundColor;
+    return Theme.isDarkThemeEnabled ? Theme.offBackgroundColor : UIColor.ows_light10Color;
 }
 
 #pragma mark -