Introduce firstDescendant for faster descendants enumeration (#113)

Author: cyanzhong

MarkEditMac/Modules/Sources/AppKitControls/BackgroundTheming.swift

@@ -14,7 +14,7 @@ public extension BackgroundTheming {
     layerBackgroundColor = color
     needsDisplay = true
 
-    enumerateChildren { (button: NonBezelButton) in
+    enumerateDescendants { (button: NonBezelButton) in
       button.layerBackgroundColor = color
       button.needsDisplay = true
     }

MarkEditMac/Modules/Sources/AppKitExtensions/UI/NSView+Extension.swift

@@ -57,7 +57,7 @@ public extension NSView {
     }
   }
 
-  /// Check if the view itself or its children is the first responder in a window.
+  /// Check if the view itself or one of its descendants is the first responder in a window.
   func isFirstResponder(in window: NSWindow?) -> Bool {
     (window?.firstResponder as? NSView)?.belongs(to: self) ?? false
   }
@@ -79,14 +79,30 @@ public extension NSView {
     animated ? animator() : self
   }
 
-  /// Enumerate all children, recursively, self first.
-  func enumerateChildren<T: NSView>(where: ((T) -> Bool)? = nil, handler: (T) -> Void) {
+  /// Enumerate all descendants, recursively, self first.
+  func enumerateDescendants<T: NSView>(where: ((T) -> Bool)? = nil, handler: (T) -> Void) {
     if let view = self as? T, `where`?(view) ?? true {
       handler(view)
     }
 
     subviews.forEach {
-      $0.enumerateChildren(where: `where`, handler: handler)
+      $0.enumerateDescendants(where: `where`, handler: handler)
     }
   }
+
+  /// Returns the first descendant that matches a predicate, self is included.
+  func firstDescendant<T: NSView>(where: ((T) -> Bool)? = nil) -> T? {
+    var stack = [self]
+    while !stack.isEmpty {
+      let node = stack.removeLast()
+      if let view = node as? T, `where`?(view) ?? true {
+        return view
+      }
+
+      // Depth-first search
+      stack.append(contentsOf: node.subviews)
+    }
+
+    return nil
+  }
 }

MarkEditMac/Modules/Sources/AppKitExtensions/UI/NSWindow+Extension.swift

@@ -12,25 +12,13 @@ public extension NSWindow {
   }
 
   var toolbarEffectView: NSVisualEffectView? {
-    guard let rootView else {
-      assertionFailure("Missing rootView from window to proceed")
-      return nil
+    let result = rootView?.firstDescendant { (effectView: NSVisualEffectView) in
+      // What we want is an NSVisualEffectView child of an NSTitlebarView
+      effectView.superview?.className.hasPrefix("NSTitlebar") == true
     }
 
-    var stack = [rootView]
-    while !stack.isEmpty {
-      let node = stack.removeLast()
-      if node is NSVisualEffectView && node.superview?.className.hasPrefix("NSTitlebar") == true {
-        // What we want is an NSVisualEffectView child of an NSTitlebarView
-        return node as? NSVisualEffectView
-      }
-
-      // Depth-first search
-      stack.append(contentsOf: node.subviews)
-    }
-
-    assertionFailure("Failed to find NSVisualEffectView in toolbar")
-    return nil
+    assert(result != nil, "Failed to find NSVisualEffectView in toolbar")
+    return result
   }
 
   /// Change the frame size, treat the top-left corner as the anchor point.
@@ -66,18 +54,9 @@ public extension NSWindow {
   ///
   /// There's no public API to programmatically show the menu assigned to an NSToolbarItem.
   func popUpButton(with menuIdentifier: NSUserInterfaceItemIdentifier) -> NSPopUpButton? {
-    guard let view = contentView?.superview else {
-      return nil
+    contentView?.superview?.firstDescendant { (button: NSPopUpButton) in
+      button.menu?.identifier == menuIdentifier
     }
-
-    var result: NSPopUpButton?
-    view.enumerateChildren { (button: NSPopUpButton) in
-      if button.menu?.identifier == menuIdentifier {
-        result = button
-      }
-    }
-
-    return result
   }
 }