From f4f93fda159abf83937eece89ac574eff772a507 Mon Sep 17 00:00:00 2001
From: ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
Date: Mon, 10 Mar 2025 10:14:58 +0100
Subject: Fix handling of menu widnows taller than their screen

A problem was visible with the menubar test app and a 2-screen system where screens are one above the other.
When moving down the huge menu, it became positioned on the wrong screen.
---
 src/Fl_Menu.cxx          | 2 +-
 src/Fl_Window_Driver.cxx | 8 +++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/Fl_Menu.cxx b/src/Fl_Menu.cxx
index b85323ed2..500b20a5c 100644
--- a/src/Fl_Menu.cxx
+++ b/src/Fl_Menu.cxx
@@ -492,7 +492,7 @@ void menuwindow::autoscroll(int n) {
   int Y = y()+Fl::box_dx(box())+2+n*itemheight;
 
   int xx, ww;
-  Fl_Window_Driver::driver(this)->menu_window_area(xx, scr_y, ww, scr_h);
+  Fl_Window_Driver::driver(this)->menu_window_area(xx, scr_y, ww, scr_h, this->screen_num());
   if (n==0 && Y <= scr_y + itemheight) {
     Y = scr_y - Y + 10;
   } else if (Y <= scr_y + itemheight) {
diff --git a/src/Fl_Window_Driver.cxx b/src/Fl_Window_Driver.cxx
index f0fc76a89..ccf5f1a07 100644
--- a/src/Fl_Window_Driver.cxx
+++ b/src/Fl_Window_Driver.cxx
@@ -239,7 +239,13 @@ void Fl_Window_Driver::resize_after_scale_change(int ns, float old_f, float new_
 }
 
 void Fl_Window_Driver::reposition_menu_window(int x, int y) {
-  if (y != pWindow->y() || x != pWindow->x()) pWindow->Fl_Widget::position(x, y);
+  if (y != pWindow->y() || x != pWindow->x()) {
+    int ns = pWindow->screen_num();
+    pWindow->Fl_Widget::position(x, y);
+    Fl::check();
+    // the window move may erroneously change the window's screen number; reset it
+    if (pWindow->screen_num() != ns) screen_num(ns);
+  }
 }
 
 void Fl_Window_Driver::menu_window_area(int &X, int &Y, int &W, int &H, int nscreen) {
-- 
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