Make things work with really dark backgrounds

This fixes issue #1549

macos/Sources/Features/Terminal/TerminalWindow.swift

@@ -80,18 +80,6 @@ class TerminalWindow: NSWindow {
 
 		_ = bindings
 
-        // By hiding the visual effect view, we allow the window's (or titlebar's in this case)
-        // background color to show through. If we were to set `titlebarAppearsTransparent` to true
-        // the selected tab would look fine, but the unselected ones and new tab button backgrounds
-        // would be an opaque color. When the titlebar isn't transparent, however, the system applies
-        // a compositing effect to the unselected tab backgrounds, which makes them blend with the
-        // titlebar's/window's background.
-        if let titlebarContainer = contentView?.superview?.subviews.first(where: {
-            $0.className == "NSTitlebarContainerView"
-        }), let effectView = titlebarContainer.descendants(withClassName: "NSVisualEffectView").first {
-            effectView.isHidden = true
-        }
-
         // Create the tab accessory view that houses the key-equivalent label and optional un-zoom button
         let stackView = NSStackView(views: [keyEquivalentLabel, resetZoomTabButton])
         stackView.setHuggingPriority(.defaultHigh, for: .horizontal)
@@ -131,25 +119,81 @@ class TerminalWindow: NSWindow {
         resetZoomToolbarButton.contentTintColor = .tertiaryLabelColor
     }
 
+	override func layoutIfNeeded() {
+		super.layoutIfNeeded()
+
+		guard titlebarTabs else { return }
+
+		// We need to be aggressive with this, and it has to be done as well in `update`,
+		// otherwise things can get out of sync and flickering can occur.
+		updateTabsForVeryDarkBackgrounds()
+	}
+
+	// We only need to set this once, but need to do it after the window has been created in order
+	// to determine if the theme is using a very dark background, in which case we don't want to
+	// remove the effect view if the default tab bar is being used since the effect created in
+	// `updateTabsForVeryDarkBackgrounds`.
+	private var effectViewIsHidden = false
+
     override func update() {
         super.update()
 
-        updateResetZoomTitlebarButtonVisibility()
-
 		titlebarSeparatorStyle = tabbedWindows != nil && !titlebarTabs ? .line : .none
 
+		if !effectViewIsHidden {
+			// By hiding the visual effect view, we allow the window's (or titlebar's in this case)
+			// background color to show through. If we were to set `titlebarAppearsTransparent` to true
+			// the selected tab would look fine, but the unselected ones and new tab button backgrounds
+			// would be an opaque color. When the titlebar isn't transparent, however, the system applies
+			// a compositing effect to the unselected tab backgrounds, which makes them blend with the
+			// titlebar's/window's background.
+			if let titlebarContainer = contentView?.superview?.subviews.first(where: {
+				$0.className == "NSTitlebarContainerView"
+			}), let effectView = titlebarContainer.descendants(withClassName: "NSVisualEffectView").first {
+				effectView.isHidden = titlebarTabs || !titlebarTabs && !hasVeryDarkBackground
+			}
+
+			effectViewIsHidden = true
+		}
+
+		if titlebarTabs {
+			updateTabsForVeryDarkBackgrounds()
 			// This is called when we open, close, switch, and reorder tabs, at which point we determine if the
 			// first tab in the tab bar is selected. If it is, we make the `windowButtonsBackdrop` color the same
 			// as that of the active tab (i.e. the titlebar's background color), otherwise we make it the same
 			// color as the background of unselected tabs.
-        if let index = windowController?.window?.tabbedWindows?.firstIndex(of: self), titlebarTabs {
+			if let index = windowController?.window?.tabbedWindows?.firstIndex(of: self) {
 				windowButtonsBackdrop?.isHighlighted = index == 0
 			}
+		}
+
+        updateNewTabButtonOpacity()
+		updateNewTabButtonImage()
+		updateResetZoomTitlebarButtonVisibility()
+    }
+
+    // MARK: -
+
+    private var newTabButtonImageLayer: VibrantLayer? = nil
+
+    // Since we are coloring the new tab button's image, it doesn't respond to the
+    // window's key status changes in terms of becoming less prominent visually,
+    // so we need to do it manually.
+    private func updateNewTabButtonOpacity() {
+        guard let titlebarContainer = contentView?.superview?.subviews.first(where: {
+            $0.className == "NSTitlebarContainerView"
+        }) else { return }
+        guard let newTabButton: NSButton = titlebarContainer.firstDescendant(withClassName: "NSTabBarNewTabButton") as? NSButton else { return }
+        guard let newTabButtonImageView: NSImageView = newTabButton.subviews.first(where: {
+            $0 as? NSImageView != nil
+        }) as? NSImageView else { return }
+
+        newTabButtonImageView.alphaValue = isKeyWindow ? 1 : 0.5
+    }
 
 	// Color the new tab button's image to match the color of the tab title/keyboard shortcut labels,
 	// just as it does in the stock tab bar.
-        updateNewTabButtonOpacity()
+	private func updateNewTabButtonImage() {
-
 		guard let titlebarContainer = contentView?.superview?.subviews.first(where: {
 			$0.className == "NSTitlebarContainerView"
 		}) else { return }
@@ -186,23 +230,28 @@ class TerminalWindow: NSWindow {
 		newTabButtonImageView.frame = newTabButton.bounds
 	}
 
-    // MARK: -
+	var hasVeryDarkBackground: Bool {
+		backgroundColor.luminance < 0.05
+	}
 
-    private var newTabButtonImageLayer: VibrantLayer? = nil
+	lazy var backgroundColorWithOpacity: NSColor = backgroundColor.withAlphaComponent(titlebarOpacity)
+
+	private func updateTabsForVeryDarkBackgrounds() {
+		guard hasVeryDarkBackground else { return }
 
-    // Since we are coloring the new tab button's image, it doesn't respond to the
-    // window's key status changes in terms of becoming less prominent visually,
-    // so we need to do it manually.
-    private func updateNewTabButtonOpacity() {
 		guard let titlebarContainer = contentView?.superview?.subviews.first(where: {
 			$0.className == "NSTitlebarContainerView"
 		}) else { return }
-        guard let newTabButton: NSButton = titlebarContainer.firstDescendant(withClassName: "NSTabBarNewTabButton") as? NSButton else { return }
-        guard let newTabButtonImageView: NSImageView = newTabButton.subviews.first(where: {
-            $0 as? NSImageView != nil
-        }) as? NSImageView else { return }
 
-        newTabButtonImageView.alphaValue = isKeyWindow ? 1 : 0.5
+		if let tabGroup = tabGroup, tabGroup.isTabBarVisible {
+			guard let activeTabBackgroundView = titlebarContainer.firstDescendant(withClassName: "NSTabButton")?.superview?.subviews.last?.firstDescendant(withID: "_backgroundView")
+			else { return }
+
+			activeTabBackgroundView.layer?.backgroundColor = backgroundColorWithOpacity.cgColor
+			titlebarContainer.layer?.backgroundColor = backgroundColorWithOpacity.highlight(withLevel: 0.14)?.cgColor
+		} else {
+			titlebarContainer.layer?.backgroundColor = backgroundColorWithOpacity.cgColor
+		}
 	}
 
     private func updateResetZoomTitlebarButtonVisibility() {
@@ -407,9 +456,7 @@ class TerminalWindow: NSWindow {
             return
         }
         
-        let backdropColor = backgroundColor.withAlphaComponent(titlebarOpacity).usingColorSpace(colorSpace!)!.cgColor
+        let view = WindowButtonsBackdropView(window: self)
-
-        let view = WindowButtonsBackdropView(backgroundColor: backdropColor)
         view.identifier = NSUserInterfaceItemIdentifier("_windowButtonsBackdrop")
         titlebarView.addSubview(view)
         
@@ -491,8 +538,9 @@ fileprivate class WindowDragView: NSView {
 
 // A view that matches the color of selected and unselected tabs in the adjacent tab bar.
 fileprivate class WindowButtonsBackdropView: NSView {
-    private let overlayLayer = VibrantLayer()
+	private let terminalWindow: TerminalWindow
 	private let isLightTheme: Bool
+    private let overlayLayer = VibrantLayer()
 
     var isHighlighted: Bool = true {
         didSet {
@@ -500,8 +548,14 @@ fileprivate class WindowButtonsBackdropView: NSView {
                 overlayLayer.isHidden = isHighlighted
                 layer?.backgroundColor = .clear
             } else {
+				let systemOverlayColor = NSColor(cgColor: CGColor(genericGrayGamma2_2Gray: 0.0, alpha: 0.45))!
+				let titlebarBackgroundColor = terminalWindow.backgroundColorWithOpacity.blended(withFraction: 1, of: systemOverlayColor)
+
+				let highlightedColor = terminalWindow.hasVeryDarkBackground ? terminalWindow.backgroundColor : .clear
+				let backgroundColor = terminalWindow.hasVeryDarkBackground ? titlebarBackgroundColor : systemOverlayColor
+
                 overlayLayer.isHidden = true
-                layer?.backgroundColor = isHighlighted ? .clear : CGColor(genericGrayGamma2_2Gray: 0.0, alpha: 0.45)
+				layer?.backgroundColor = isHighlighted ? highlightedColor?.cgColor : backgroundColor?.cgColor
             }
         }
     }
@@ -510,8 +564,9 @@ fileprivate class WindowButtonsBackdropView: NSView {
         fatalError("init(coder:) has not been implemented")
     }
 
-    init(backgroundColor: CGColor) {
+    init(window: TerminalWindow) {
-        self.isLightTheme = NSColor(cgColor: backgroundColor)!.isLightColor
+		self.terminalWindow = window
+		self.isLightTheme = window.backgroundColor.isLightColor
 
         super.init(frame: .zero)
 

macos/Sources/Helpers/NSView+Extension.swift

@@ -28,4 +28,17 @@ extension NSView {
 
         return result
     }
+
+	/// Recursively finds and returns the first descendant view that has the given identifier.
+	func firstDescendant(withID id: String) -> NSView? {
+		for subview in subviews {
+			if subview.identifier == NSUserInterfaceItemIdentifier(id) {
+				return subview
+			} else if let found = subview.firstDescendant(withID: id) {
+				return found
+			}
+		}
+
+		return nil
+	}
 }