From f4ffe2a2439928992c3f44085e81686d4f911417 Mon Sep 17 00:00:00 2001
From: Friedemann Kleint <Friedemann.Kleint@digia.com>
Date: Thu, 27 Feb 2014 12:28:48 +0100
Subject: [PATCH] Enable menuless dialogs on Windows.

Handle the flags combination Qt::Dialog && !Qt::WindowSystemMenuHint
such that it results in exStyle = WS_EX_DLGMODALFRAME and style =
WS_POPUP | WS_BORDER | WS_SYSMENU and a window class without icon.

Do not set !Qt::WindowSystemMenuHint in QWidgetPrivate::adjustFlags()
for dialogs on Windows.

[ChangeLog][QtWidgets][QDialog][Windows] Dialogs can now be menuless.

Task-number: QTBUG-2027

Change-Id: Ieb86985e8a5291d826c103fe478ecde43971f08e
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
---
 src/plugins/platforms/windows/qwindowscontext.cpp | 10 +++++++++-
 src/plugins/platforms/windows/qwindowswindow.cpp  |  6 ++++++
 src/widgets/kernel/qwidget.cpp                    |  6 +++++-
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index f67fb9bc19..c35af3623a 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -412,9 +412,17 @@ QString QWindowsContext::registerWindowClass(const QWindow *w, bool isGL)
         && (type == Qt::Popup || w->property("_q_windowsDropShadow").toBool())) {
         style |= CS_DROPSHADOW;
     }
-    if (type == Qt::Tool || type == Qt::ToolTip || type == Qt::Popup) {
+    switch (type) {
+    case Qt::Tool:
+    case Qt::ToolTip:
+    case Qt::Popup:
         style |= CS_SAVEBITS; // Save/restore background
         icon = false;
+        break;
+    case Qt::Dialog:
+        if (!(flags & Qt::WindowSystemMenuHint))
+            icon = false; // QTBUG-2027, dialogs without system menu.
+        break;
     }
     // Create a unique name for the flag combination
     QString cname = QStringLiteral("Qt5QWindow");
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index d77f587b92..223ac9ac2d 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -110,6 +110,8 @@ static QByteArray debugWinExStyle(DWORD exStyle)
         rc += " WS_EX_CONTEXTHELP";
     if (exStyle & WS_EX_LAYERED)
         rc += " WS_EX_LAYERED";
+    if (exStyle & WS_EX_DLGMODALFRAME)
+        rc += " WS_EX_DLGMODALFRAME";
     return rc;
 }
 
@@ -513,6 +515,10 @@ void WindowCreationData::fromWindow(const QWindow *w, const Qt::WindowFlags flag
                 }
                 if (flags & Qt::WindowSystemMenuHint)
                     style |= WS_SYSMENU;
+                else if (dialog) {
+                    style |= WS_SYSMENU | WS_BORDER; // QTBUG-2027, dialogs without system menu.
+                    exStyle |= WS_EX_DLGMODALFRAME;
+                }
                 if (flags & Qt::WindowMinimizeButtonHint)
                     style |= WS_MINIMIZEBOX;
                 if (shouldShowMaximizeButton(w, flags))
diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index ba8147c4a6..c52e0d47ce 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -1064,7 +1064,11 @@ void QWidgetPrivate::adjustFlags(Qt::WindowFlags &flags, QWidget *w)
         // interpret WindowSystemMenuHint as a close button and we can't change that behavior
         // we can't just add this in.
 #ifndef Q_WS_MAC
-        if (flags & (Qt::WindowMinMaxButtonsHint | Qt::WindowCloseButtonHint | Qt::WindowContextHelpButtonHint)) {
+        if ((flags & (Qt::WindowMinMaxButtonsHint | Qt::WindowCloseButtonHint | Qt::WindowContextHelpButtonHint))
+#  ifdef Q_OS_WIN
+            && type != Qt::Dialog // QTBUG-2027, allow for menu-less dialogs.
+#  endif
+           ) {
             flags |= Qt::WindowSystemMenuHint;
 #else
         if (flags & (Qt::WindowMinMaxButtonsHint | Qt::WindowCloseButtonHint