From 321109c1beb6e7720838e23f28a2d3a64ba9869e Mon Sep 17 00:00:00 2001
From: ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
Date: Mon, 3 Feb 2025 11:57:04 +0100
Subject: [PATCH] macOS: fix transition from single-screen fullscreen to "All
 Screens" fullscreen

---
 src/Fl_cocoa.mm | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Fl_cocoa.mm b/src/Fl_cocoa.mm
index 6e38757b7..bafcfd83a 100644
--- a/src/Fl_cocoa.mm
+++ b/src/Fl_cocoa.mm
@@ -3162,7 +3162,10 @@ void Fl_Window::fullscreen_x() {
   } else if (fl_mac_os_version >= 100600) {
 #  if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
     if (fl_mac_os_version >= 100700 && (i->xid.styleMask & NSWindowStyleMaskFullScreen)) {
+      // from single-screen fullscreen to "All Screens" fullscreen, with border
+      i->xid.collectionBehavior &= ~NSWindowCollectionBehaviorFullScreenNone; // just transiently
       [i->xid toggleFullScreen:nil];
+      i->xid.collectionBehavior |= NSWindowCollectionBehaviorFullScreenNone;
       if (no_fullscreen_w == 0) {
         no_fullscreen_x = x();
         no_fullscreen_y = y();