fix: app icons could sometimes be at the wrong size

src/api-wrappers/HelperExtensions.swift

@@ -195,12 +195,8 @@ extension DispatchQoS {
 
 extension NSImageView {
     func setSize(_ size: NSSize) {
+        image?.size = size
         frame.size = size
-        // TODO: NSImageView does some internal magic, and ends up with constraints. We need to add our own to force its size
-        // We can't update .image.size because we share the image between multiple NSImageViews
-        // I wish there was a better way to only set the frame.size
-        addOrUpdateConstraint(widthAnchor, size.width)
-        addOrUpdateConstraint(heightAnchor, size.height)
     }
 }
 
@@ -214,6 +210,12 @@ extension NSTextField {
 }
 
 extension NSImage {
+    /// if an image can be used in different contexts (e.g. multiple NSTextViews), it's safer to copy it
+    /// see https://www.noodlesoft.com/blog/2011/04/15/the-proper-care-and-feeding-of-nsimage/
+    func copyToSeparateContexts() -> NSImage {
+        return copy() as! NSImage
+    }
+
     // NSImage(named) caches/reuses NSImage objects; we force separate instances of images by using copy()
     static func initCopy(_ name: String) -> NSImage {
         return NSImage(named: name)!.copy() as! NSImage

src/logic/Window.swift

@@ -104,10 +104,9 @@ class Window {
             if let index = (Windows.list.firstIndex { $0.cgWindowId == cgWindowId }) {
                 let view = ThumbnailsView.recycledViews[index]
                 if !view.thumbnail.isHidden {
-                    view.thumbnail.image = thumbnail
+                    view.thumbnail.image = thumbnail?.copyToSeparateContexts()
                     let thumbnailSize = ThumbnailView.thumbnailSize(thumbnail, false)
-                    view.thumbnail.image?.size = thumbnailSize
-                    view.thumbnail.frame.size = thumbnailSize
+                    view.thumbnail.setSize(thumbnailSize)
                 }
             }
         }

src/ui/main-window/PreviewPanel.swift

@@ -29,7 +29,7 @@ class PreviewPanel: NSPanel {
 
     func show(_ id: CGWindowID, _ preview: NSImage, _ position: CGPoint, _ size: CGSize) {
         if id != currentId {
-            previewView.image = preview
+            previewView.image = preview.copyToSeparateContexts()
             previewView.image!.size = size
             var frame = NSRect(origin: position, size: size)
             // Flip Y coordinate from Quartz (0,0 at bottom-left) to Cocoa coordinates (0,0 at top-left)

src/ui/main-window/ThumbnailView.swift

@@ -299,19 +299,14 @@ class ThumbnailView: FlippedView {
     }
 
     private func updateThumbnail(_ element: Window) {
-        // we need to reset the original size, otherwise it may be too small and not get resized
-        // this can happen when switching from one screen to another for example
-        if let screenshot = element.thumbnail, let thumbnailFullSize = element.thumbnailFullSize {
-            screenshot.size = thumbnailFullSize
-        }
         if !thumbnail.isHidden && thumbnail != element.thumbnail {
             if let screenshot = element.thumbnail {
-                thumbnail.image = screenshot
-            } else if let appIconFallback = element.icon {
+                thumbnail.image = screenshot.copyToSeparateContexts()
+            } else {
+                thumbnail.image = element.icon?.copyToSeparateContexts()
                 // if no thumbnail, show appIcon instead
                 // .icon is always 32x32 by default. We scale it so it can be "thumbnail-ed" down
-                appIconFallback.size = NSSize(width: 1024, height: 1024)
-                thumbnail.image = appIconFallback
+                thumbnail.setSize(NSSize(width: 1024, height: 1024))
             }
             // for Accessibility > "speak items under the pointer"
             thumbnail.setAccessibilityLabel(element.title)
@@ -321,7 +316,7 @@ class ThumbnailView: FlippedView {
     private func updateAppIcon(_ element: Window, _ title: String) -> Bool {
         let appIconChanged = appIcon.image != element.icon
         if appIconChanged {
-            appIcon.image = element.icon
+            appIcon.image = element.icon?.copyToSeparateContexts()
             appIcon.setAccessibilityLabel(title)
         }
         return appIconChanged
@@ -362,7 +357,7 @@ class ThumbnailView: FlippedView {
             setAccessibilityHelp(getAccessibilityHelp(element.application.runningApplication.localizedName, element.dockLabel))
         }
         if element.isWindowlessApp && windowlessIcon.image != element.icon {
-            windowlessIcon.image = element.icon
+            windowlessIcon.image = element.icon?.copyToSeparateContexts()
         }
         windowControlIcons.forEach { $0.window_ = element }
         showOrHideWindowControls(false)