cocoa-cb: fix a Cocoa window position on init bug

on init an NSWindow can't be placed on a none Main screen NSScreen
outside the Main screen's frame bounds.

To fix this we just check if the target screen is different from the
main screen and if that is the case we check the actual position with
the expect one. if they are different we try to reposition the window
to the wanted position.

Fixes #6453

video/out/cocoa-cb/window.swift

@@ -107,6 +107,19 @@ class Window: NSWindow, NSWindowDelegate {
         self.init(contentRect: contentRect,
                   styleMask: [.titled, .closable, .miniaturizable, .resizable],
                   backing: .buffered, defer: false, screen: screen)
+
+        // workaround for an AppKit bug where the NSWindow can't be placed on a
+        // none Main screen NSScreen outside the Main screen's frame bounds
+        if screen != NSScreen.main() {
+            var absoluteWantedOrigin = contentRect.origin
+            absoluteWantedOrigin.x += screen!.frame.origin.x
+            absoluteWantedOrigin.y += screen!.frame.origin.y
+
+            if !NSEqualPoints(absoluteWantedOrigin, self.frame.origin) {
+                self.setFrameOrigin(absoluteWantedOrigin)
+            }
+        }
+
         cocoaCB = ccb
         title = cocoaCB.title
         minSize = NSMakeSize(160, 90)