Remove some no-longer-needed #available checks.

Mac/MainWindow/Detail/DetailWebView.swift

@@ -73,27 +73,25 @@ final class DetailWebView: WKWebView {
 		
 		This code adjusts the height of the window by -1pt/+1pt,
 		which puts the webview back in the correct place.
-		*/
-		if #available(macOS 11, *) {
-			guard var frame = window?.frame else {
-				return
-			}
-
-			guard !inBigSurOffsetFix else {
-				return
-			}
-			
-			inBigSurOffsetFix = true
-			
-			defer {
-				inBigSurOffsetFix = false
-			}
-
-			frame.size = NSSize(width: window!.frame.width, height: window!.frame.height - 1)
-			window!.setFrame(frame, display: false)
-			frame.size = NSSize(width: window!.frame.width, height: window!.frame.height + 1)
-			window!.setFrame(frame, display: false)
+		 */
+		guard var frame = window?.frame else {
+			return
 		}
+
+		guard !inBigSurOffsetFix else {
+			return
+		}
+
+		inBigSurOffsetFix = true
+
+		defer {
+			inBigSurOffsetFix = false
+		}
+
+		frame.size = NSSize(width: window!.frame.width, height: window!.frame.height - 1)
+		window!.setFrame(frame, display: false)
+		frame.size = NSSize(width: window!.frame.width, height: window!.frame.height + 1)
+		window!.setFrame(frame, display: false)
 	}
 }
 

Mac/MainWindow/Detail/DetailWebViewController.swift

@@ -119,19 +119,6 @@ final class DetailWebViewController: NSViewController {
 
 		view = webView
 
-		// Use the safe area layout guides if they are available.
-		if #available(OSX 11.0, *) {
-			// These constraints have been removed as they were unsatisfiable after removing NSBox.
-		} else {
-			let constraints = [
-				webView.topAnchor.constraint(equalTo: view.topAnchor),
-				webView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
-				webView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
-				webView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
-			]
-			NSLayoutConstraint.activate(constraints)
-		}
-
 		// Hide the web view until the first reload (navigation) is complete (plus some delay) to avoid the awful white flash that happens on the initial display in dark mode.
 		// See bug #901.
 		webView.isHidden = true
@@ -343,10 +330,8 @@ private extension DetailWebViewController {
 	}
 
 	func fetchScrollInfo(_ completion: @escaping (ScrollInfo?) -> Void) {
-		var javascriptString = "var x = {contentHeight: document.body.scrollHeight, offsetY: document.body.scrollTop}; x"
-		if #available(macOS 10.15, *) {
-			javascriptString = "var x = {contentHeight: document.body.scrollHeight, offsetY: window.pageYOffset}; x"
-		}
+		
+		let javascriptString = "var x = {contentHeight: document.body.scrollHeight, offsetY: window.pageYOffset}; x"
 
 		webView.evaluateJavaScript(javascriptString) { (info, error) in
 			guard let info = info as? [String: Any] else {

Mac/MainWindow/Sidebar/Cell/SidebarCellAppearance.swift

@@ -23,11 +23,7 @@ struct SidebarCellAppearance: Equatable {
 			textFieldFontSize = 11
 		case .large:
 			imageSize = CGSize(width: 22, height: 22)
-			if #available(macOS 11.0, *) {
-				textFieldFontSize = 15
-			} else {
-				textFieldFontSize = 13
-			}
+			textFieldFontSize = 15
 		default:
 			imageSize = CGSize(width: 19, height: 19)
 			textFieldFontSize = 13

Mac/MainWindow/Timeline/Cell/TimelineCellAppearance.swift

@@ -56,11 +56,7 @@ struct TimelineCellAppearance: Equatable {
 
 		self.showIcon = showIcon
 		
-		if #available(macOS 11.0, *) {
-			cellPadding = NSEdgeInsets(top: 8.0, left: 4.0, bottom: 10.0, right: 4.0)
-		} else {
-			cellPadding = NSEdgeInsets(top: 8.0, left: 18.0, bottom: 10.0, right: 18.0)
-		}
+		cellPadding = NSEdgeInsets(top: 8.0, left: 4.0, bottom: 10.0, right: 4.0)
 
 		let margin = self.cellPadding.left + self.unreadCircleDimension + self.unreadCircleMarginRight
 		self.boxLeftMargin = margin

Mac/MainWindow/Timeline/TimelineTableRowView.swift

@@ -53,27 +53,21 @@ class TimelineTableRowView : NSTableRowView {
 	}
 	
 	private func addSeparatorView() {
+
 		guard let cellView = cellView, separator == nil else { return }
+
 		separator = NSView()
 		separator!.translatesAutoresizingMaskIntoConstraints = false
 		separator!.wantsLayer = true
 		separator!.layer?.backgroundColor = AppAssets.timelineSeparatorColor.cgColor
+
 		addSubview(separator!)
-		if #available(macOS 11.0, *) {
-			NSLayoutConstraint.activate([
-				separator!.leadingAnchor.constraint(equalTo: cellView.leadingAnchor, constant: 20),
-				separator!.trailingAnchor.constraint(equalTo: cellView.trailingAnchor, constant: -4),
-				separator!.heightAnchor.constraint(equalToConstant: 1),
-				separator!.bottomAnchor.constraint(equalTo: bottomAnchor, constant: 0)
-			])
-		} else {
-			NSLayoutConstraint.activate([
-				separator!.leadingAnchor.constraint(equalTo: cellView.leadingAnchor, constant: 34),
-				separator!.trailingAnchor.constraint(equalTo: cellView.trailingAnchor, constant: -28),
-				separator!.heightAnchor.constraint(equalToConstant: 1),
-				separator!.bottomAnchor.constraint(equalTo: bottomAnchor, constant: 0)
-			])
-		}
+		
+		NSLayoutConstraint.activate([
+			separator!.leadingAnchor.constraint(equalTo: cellView.leadingAnchor, constant: 20),
+			separator!.trailingAnchor.constraint(equalTo: cellView.trailingAnchor, constant: -4),
+			separator!.heightAnchor.constraint(equalToConstant: 1),
+			separator!.bottomAnchor.constraint(equalTo: bottomAnchor, constant: 0)
+		])
 	}
-	
 }

Mac/MainWindow/Timeline/TimelineViewController.swift

@@ -207,10 +207,7 @@ final class TimelineViewController: NSViewController, UndoableCommandRunner, Unr
 		tableView.doubleAction = #selector(openArticleInBrowser(_:))
 		tableView.setDraggingSourceOperationMask(.copy, forLocal: false)
 		tableView.keyboardDelegate = keyboardDelegate
-		
-		if #available(macOS 11.0, *) {
-			tableView.style = .inset
-		}
+		tableView.style = .inset
 		
 		if !didRegisterForNotifications {
 			NotificationCenter.default.addObserver(self, selector: #selector(statusesDidChange(_:)), name: .StatusesDidChange, object: nil)