Add Quick Look preview for directories

.gitignore

@@ -5,3 +5,5 @@ xcuserdata/
 # `go build` output
 HTMLConverter/htmlconverter*.a
 HTMLConverter/htmlconverter*.h
+
+.idea

Glance.xcodeproj/project.pbxproj

@@ -110,6 +110,7 @@
 		7EB36482244B03CC00D7F96F /* markdown-main.css in Resources */ = {isa = PBXBuildFile; fileRef = 7EB3643D244B03CC00D7F96F /* markdown-main.css */; };
 		7EB36488244B65D900D7F96F /* String.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7EB36487244B65D900D7F96F /* String.swift */; };
 		7EB3648A244B665700D7F96F /* ZIPPreview.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7EB36489244B665700D7F96F /* ZIPPreview.swift */; };
+		A1B2C3D4E5F6789000112234 /* DirectoryPreview.swift in Sources */ = {isa = PBXBuildFile; fileRef = A1B2C3D4E5F6789000112233 /* DirectoryPreview.swift */; };
 		7EB7491924228549007265A4 /* JupyterPreview.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7EB7491824228549007265A4 /* JupyterPreview.swift */; };
 		7ECC8CF2240CB4CC000D6970 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7ECC8CF1240CB4CC000D6970 /* AppDelegate.swift */; };
 		7ECC8CF4240CB4CC000D6970 /* ViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7ECC8CF3240CB4CC000D6970 /* ViewController.swift */; };
@@ -269,6 +270,7 @@
 		7EB3643D244B03CC00D7F96F /* markdown-main.css */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.css; path = "markdown-main.css"; sourceTree = "<group>"; };
 		7EB36487244B65D900D7F96F /* String.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = String.swift; sourceTree = "<group>"; };
 		7EB36489244B665700D7F96F /* ZIPPreview.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ZIPPreview.swift; sourceTree = "<group>"; };
+		A1B2C3D4E5F6789000112233 /* DirectoryPreview.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DirectoryPreview.swift; sourceTree = "<group>"; };
 		7EB7491824228549007265A4 /* JupyterPreview.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = JupyterPreview.swift; sourceTree = "<group>"; };
 		7ECC8CEE240CB4CC000D6970 /* Glance.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = Glance.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		7ECC8CF1240CB4CC000D6970 /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
@@ -360,6 +362,7 @@
 				7E1DC529240E6FDE00D0A061 /* CodePreview.swift */,
 				7EB7491824228549007265A4 /* JupyterPreview.swift */,
 				7E1DC520240E6D8000D0A061 /* MarkdownPreview.swift */,
+				A1B2C3D4E5F6789000112233 /* DirectoryPreview.swift */,
 				7E7A9DAC244F24B900276E51 /* TARPreview.swift */,
 				7E413F7F2418DD6200CFBB1D /* TSVPreview.swift */,
 				7EB36489244B665700D7F96F /* ZIPPreview.swift */,
@@ -871,6 +874,7 @@
 				7E9F0D7E24168870007F1008 /* Script.swift in Sources */,
 				7EB3648A244B665700D7F96F /* ZIPPreview.swift in Sources */,
 				103654F42F726241006F2538 /* SevenZipPreview.swift in Sources */,
+				A1B2C3D4E5F6789000112234 /* DirectoryPreview.swift in Sources */,
 				7E9F0D7D24168870007F1008 /* Stylesheet.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

QLPlugin/Info.plist

@@ -36,6 +36,9 @@
 					- public.xml (.xml)
 				-->
 
+				<!-- Directory -->
+				<string>public.folder</string>
+
 				<!-- Archive -->
 				<string>org.7-zip.7-zip-archive</string> <!-- .7z -->
 				<string>com.sun.java-archive</string> <!-- .jar (Java) -->

QLPlugin/MainVC.swift

@@ -105,7 +105,10 @@ class MainVC: NSViewController, QLPreviewingController {
 	/// Generates a preview of the selected file and adds the corresponding child view controller.
 	private func previewFile(file: File) throws {
 		// Initialize `PreviewVC` for the file type
-		if let previewInitializerType = PreviewVCFactory.getPreviewInitializer(fileURL: file.url) {
+		if let previewInitializerType = PreviewVCFactory.getPreviewInitializer(
+			fileURL: file.url,
+			isDirectory: file.isDirectory
+		) {
 			// Generate file preview
 			let previewInitializer = previewInitializerType.init()
 			let previewVC = try previewInitializer.createPreviewVC(file: file)

QLPlugin/Views/PreviewVCFactory.swift

@@ -3,7 +3,10 @@ import Foundation
 /// Returns a `PreviewVC` subclass that can be used to generate a preview of the provided file.
 /// May return `nil` if the file is not supported.
 class PreviewVCFactory {
-	static func getPreviewInitializer(fileURL: URL) -> Preview.Type? {
+	static func getPreviewInitializer(fileURL: URL, isDirectory: Bool = false) -> Preview.Type? {
+		if isDirectory {
+			return DirectoryPreview.self
+		}
 		switch fileURL.pathExtension.lowercased() {
 			case "gz":
 				// `gzip` is only supported for tarballs

QLPlugin/Views/PreviewVCs/OutlinePreviewVC.swift

@@ -3,25 +3,38 @@ import Cocoa
 class OutlinePreviewVC: NSViewController, PreviewVC {
 	@objc dynamic var rootNodes: [FileTreeNode]
 	private let labelText: String?
+	private let expandAll: Bool
 
 	@objc dynamic var customSortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
 
 	@IBOutlet private var treeController: NSTreeController!
 	@IBOutlet private var outlineView: NSOutlineView!
 	@IBOutlet private var label: NSTextField!
 
-	required convenience init(rootNodes: [FileTreeNode], labelText: String?) {
-		self.init(nibName: nil, bundle: nil, rootNodes: rootNodes, labelText: labelText)
+	required convenience init(
+		rootNodes: [FileTreeNode],
+		labelText: String?,
+		expandAll: Bool = false
+	) {
+		self.init(
+			nibName: nil,
+			bundle: nil,
+			rootNodes: rootNodes,
+			labelText: labelText,
+			expandAll: expandAll
+		)
 	}
 
 	init(
 		nibName nibNameOrNil: NSNib.Name?,
 		bundle nibBundleOrNil: Bundle?,
 		rootNodes: [FileTreeNode],
-		labelText: String?
+		labelText: String?,
+		expandAll: Bool = false
 	) {
 		self.rootNodes = rootNodes
 		self.labelText = labelText
+		self.expandAll = expandAll
 		super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
 
 		// Register required value transformers
@@ -38,7 +51,11 @@ class OutlinePreviewVC: NSViewController, PreviewVC {
 	override func viewDidLoad() {
 		super.viewDidLoad()
 		setUpView()
-		expandSingleRootItem()
+		if expandAll {
+			expandAllItems()
+		} else {
+			expandSingleRootItem()
+		}
 	}
 
 	private func setUpView() {
@@ -58,6 +75,11 @@ class OutlinePreviewVC: NSViewController, PreviewVC {
 			outlineView.expandItem(root.children?.first!)
 		}
 	}
+
+	/// Expands all items in the outline view.
+	private func expandAllItems() {
+		outlineView.expandItem(nil, expandChildren: true)
+	}
 }
 
 /// `ValueTransformer` which formats the provided date.
@@ -72,9 +94,13 @@ class DateTransformer: ValueTransformer {
 		dateFormatter.doesRelativeDateFormatting = true
 	}
 
-	override class func transformedValueClass() -> AnyClass { NSString.self }
+	override class func transformedValueClass() -> AnyClass {
+		NSString.self
+	}
 
-	override class func allowsReverseTransformation() -> Bool { false }
+	override class func allowsReverseTransformation() -> Bool {
+		false
+	}
 
 	override func transformedValue(_ value: Any?) -> Any? {
 		guard let date = value as? Date else {
@@ -97,9 +123,13 @@ class IconTransformer: ValueTransformer {
 		contentsOfFile: "/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/GenericDocumentIcon.icns"
 	)
 
-	override class func transformedValueClass() -> AnyClass { NSImage.self }
+	override class func transformedValueClass() -> AnyClass {
+		NSImage.self
+	}
 
-	override class func allowsReverseTransformation() -> Bool { false }
+	override class func allowsReverseTransformation() -> Bool {
+		false
+	}
 
 	override func transformedValue(_ value: Any?) -> Any? {
 		guard let isDirectoryNumber = value as? NSNumber else {
@@ -116,9 +146,13 @@ class SizeTransformer: ValueTransformer {
 	let byteCountFormatter = ByteCountFormatter()
 	let fallbackValue = "--"
 
-	override class func transformedValueClass() -> AnyClass { NSString.self }
+	override class func transformedValueClass() -> AnyClass {
+		NSString.self
+	}
 
-	override class func allowsReverseTransformation() -> Bool { false }
+	override class func allowsReverseTransformation() -> Bool {
+		false
+	}
 
 	override func transformedValue(_ value: Any?) -> Any? {
 		guard let size = value as? NSNumber else {

QLPlugin/Views/Previews/DirectoryPreview.swift

@@ -0,0 +1,129 @@
+import Foundation
+import os.log
+
+class DirectoryPreview: Preview {
+	let fileManager = FileManager.default
+
+	/// Max number of items to include in the tree to avoid performance issues.
+	let maxItems = 500
+	/// Max recursion depth.
+	let maxDepth = 5
+
+	required init() {}
+
+	/// Directories inside temporary extraction paths (e.g. from ZIP browsing in Finder)
+	/// should not be previewed by our plugin.
+	private func isTemporaryPath(_ path: String) -> Bool {
+		path.hasPrefix("/private/var/folders/")
+			|| path.hasPrefix("/var/folders/")
+			|| path.hasPrefix("/tmp/")
+			|| path.hasPrefix("/private/tmp/")
+	}
+
+	func createPreviewVC(file: File) throws -> PreviewVC {
+		if isTemporaryPath(file.path) {
+			throw PreviewError.fileSizeError(path: file.path)
+		}
+
+		let fileTree = FileTree()
+		var itemCount = 0
+		scanDirectory(
+			url: file.url,
+			fileTree: fileTree,
+			basePath: file.url.path,
+			depth: 0,
+			itemCount: &itemCount
+		)
+
+		let childrenCount = countItems(nodes: fileTree.root.childrenList)
+		let labelText = "\(childrenCount) items"
+
+		return OutlinePreviewVC(
+			rootNodes: fileTree.root.childrenList,
+			labelText: labelText,
+			expandAll: true
+		)
+	}
+
+	private func scanDirectory(
+		url: URL,
+		fileTree: FileTree,
+		basePath: String,
+		depth: Int,
+		itemCount: inout Int
+	) {
+		guard depth < maxDepth, itemCount < maxItems else {
+			return
+		}
+
+		let contents: [URL]
+		do {
+			contents = try fileManager.contentsOfDirectory(
+				at: url,
+				includingPropertiesForKeys: [
+					.isDirectoryKey,
+					.fileSizeKey,
+					.contentModificationDateKey,
+				],
+				options: [.skipsHiddenFiles]
+			)
+		} catch {
+			os_log(
+				"Could not read directory %{public}s: %{public}s",
+				log: Log.general,
+				type: .error,
+				url.path,
+				error.localizedDescription
+			)
+			return
+		}
+
+		for itemURL in contents {
+			guard itemCount < maxItems else {
+				return
+			}
+
+			let resourceValues = try? itemURL.resourceValues(forKeys: [
+				.isDirectoryKey,
+				.fileSizeKey,
+				.contentModificationDateKey,
+			])
+			let isDir = resourceValues?.isDirectory ?? false
+			let size = resourceValues?.fileSize ?? 0
+			let dateModified = resourceValues?.contentModificationDate
+
+			// Build relative path from the base directory
+			let relativePath = String(itemURL.path.dropFirst(basePath.count + 1))
+
+			do {
+				try fileTree.addNode(
+					path: relativePath,
+					isDirectory: isDir,
+					size: size,
+					dateModified: dateModified
+				)
+				itemCount += 1
+			} catch {
+				os_log("%{public}s", log: Log.parse, type: .error, error.localizedDescription)
+			}
+
+			if isDir {
+				scanDirectory(
+					url: itemURL,
+					fileTree: fileTree,
+					basePath: basePath,
+					depth: depth + 1,
+					itemCount: &itemCount
+				)
+			}
+		}
+	}
+
+	private func countItems(nodes: [FileTreeNode]) -> Int {
+		var count = nodes.count
+		for node in nodes where node.isDirectory {
+			count += countItems(nodes: node.childrenList)
+		}
+		return count
+	}
+}

README.md

@@ -46,6 +46,8 @@ Alternatively, you can install Glance directly. The installation is slightly com
 
   <p><img src="./AppStore/Assets/Screenshots/ScreenshotTSV.png" alt="" width="600"></p>
 
+- **Directory**: folders are previewed as a tree view showing their contents (files, subfolders, sizes and dates)
+
 ## FAQ
 
 **There are existing Quick Look apps for some of the supported file types. Why create another one?**