Allow the preview display position to be set to either the left or right side

QuickShelf/ContentView.swift

@@ -10,6 +10,10 @@ import QuickLook
 
 struct ContentView: View {
     @Environment(\.openSettings) private var openSettings
+    @AppStorage("preview.side")
+    private var sideRaw: String = PreviewSide.right.rawValue
+
+    private var side: PreviewSide { PreviewSide(rawValue: sideRaw) ?? .right }
 
     @State private var inputDir = ""
     @State private var items: [ShelfItem] = []
@@ -38,7 +42,7 @@ struct ContentView: View {
                         isSelected: selection.contains(item.url),
                         onPreview: { url in
                             if let anchor = NSApp.keyWindow {
-                                SlidePanelPreview.shared.show(url: url, beside: anchor,
+                                SlidePanelPreview.shared.show(url: url, beside: anchor, side: side,
                                                                size: NSSize(width: 380, height: 300))
                             }
                         }

QuickShelf/Views/Preview/SidePanelPreview.swift

@@ -17,14 +17,19 @@ final class SlidePanelPreview: NSObject {
     private weak var anchorWindow: NSWindow?
     private var closeEvent: Any?
 
-    func show(url: URL, beside anchor: NSWindow, size: NSSize = NSSize(width: 360, height: 300)) {
+    func show(
+        url: URL,
+        beside anchor: NSWindow,
+        side: PreviewSide,
+        size: NSSize = NSSize(width: 360, height: 300)
+    ) {
         anchorWindow = anchor
         let panel = self.panel == nil ? makePanel(size: size) : self.panel!
         if self.panel == nil { self.panel = panel }
 
         ensurePreviewViewAlive()
         previewView?.previewItem = url as NSURL
-        positionPanelBesideAnchor(panel: panel, anchor: anchor, size: size)
+        positionPanelBesideAnchor(panel: panel, anchor: anchor, side: side, size: size)
 
         // nonactivating
         panel.orderFrontRegardless()
@@ -73,11 +78,22 @@ final class SlidePanelPreview: NSObject {
         }
     }
 
-    private func positionPanelBesideAnchor(panel: NSPanel, anchor: NSWindow, size: NSSize) {
+    private func positionPanelBesideAnchor(panel: NSPanel, anchor: NSWindow, side: PreviewSide, size: NSSize) {
         let anchorFrame = anchor.frame
-        let origin = NSPoint(x: anchorFrame.maxX + 8,
+        let screen = anchor.screen ?? NSScreen.main
+        let visibleFrame = screen?.visibleFrame ?? .infinite
+
+        var origin = NSPoint(x: anchorFrame.maxX + 8,
                              y: anchorFrame.minY)
-        panel.setFrame(NSRect(origin: origin, size: size), display: true)
+        if side == .left {
+            var x = anchorFrame.minX - 8 - size.width
+            var y = anchorFrame.minY
+
+            y = max(min(y, visibleFrame.maxY - size.height), visibleFrame.minY)
+            if x < visibleFrame.minX { x = visibleFrame.minX }
+            origin = NSPoint(x: x, y: y)
+        }
+        panel.setFrame(NSRect(origin: origin, size: size), display: true, animate: true)
     }
 }
 

QuickShelf/Views/Settings/GeneralView.swift

@@ -9,14 +9,32 @@ import SwiftUI
 import KeyboardShortcuts
 import LaunchAtLogin
 
+enum PreviewSide: String, CaseIterable, Identifiable {
+    case left, right
+    var id: String { rawValue }
+}
+
 struct GeneralView: View {
+    @AppStorage("preview.side")
+    private var sideRaw: String = PreviewSide.right.rawValue
+
     var body: some View {
         VStack(alignment: .leading) {
             Text("General")
                 .font(.title)
                 .padding(.bottom, 18)
             LaunchAtLogin.Toggle()
-                .padding(.bottom, 18)
+                .padding(.bottom, 8)
+            Picker("Preview position", selection: Binding(
+                get: { PreviewSide(rawValue: sideRaw) ?? .right },
+                set: { sideRaw = $0.rawValue }
+            )) {
+                Text("Left").tag(PreviewSide.left)
+                Text("Right").tag(PreviewSide.right)
+            }
+            .pickerStyle(.menu)
+            .fixedSize()
+            .padding(.bottom, 18)
             Text("Shortcuts")
                 .font(.title)
                 .padding(.bottom, 18)