From 96ef605f4b91d15713bc358094603521745ffde8 Mon Sep 17 00:00:00 2001
From: Joachim Henze <Joachim.Henze@reactos.org>
Date: Fri, 11 Oct 2019 23:21:39 +0200
Subject: [PATCH] [WIN32SS] Fix regression CORE-16393

Symptom "cmd did not hide the taskbar anymore when switching to fullscreen"

It regressed by SVN r75407 == git
09ab5ea7ed2ab0e709ed2e8f8f9f6c3711b2ac7f

VBox LGTM https://reactos.org/testman/compare.php?ids=69295,69297
 KVM LGTM https://reactos.org/testman/compare.php?ids=69296,69298

Many thanks to the patches author James Tabor.
---
 win32ss/user/ntuser/display.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/win32ss/user/ntuser/display.c b/win32ss/user/ntuser/display.c
index 20bbdfceacb..3f2b99cc229 100644
--- a/win32ss/user/ntuser/display.c
+++ b/win32ss/user/ntuser/display.c
@@ -783,6 +783,13 @@ UserChangeDisplaySettings(
         }
     }
 
+    /* Check if DEVMODE matches the current mode */
+    if (pdm == ppdev->pdmwDev && !(flags & CDS_RESET))
+    {
+        ERR("DEVMODE matches, nothing to do\n");
+        goto leave;
+    }
+
     /* Shall we apply the settings? */
     if (!(flags & CDS_NORESET))
     {
@@ -926,6 +933,11 @@ NtUserChangeDisplaySettings(
         return DISP_CHANGE_BADFLAGS;
     }
 
+    if ((dwflags & CDS_RESET) && (dwflags & CDS_NORESET))
+    {
+        return DISP_CHANGE_BADFLAGS;
+    }
+
     /* Copy the device name */
     if (pustrDevice)
     {
-- 
2.17.1