From 3c85e2e8899d1253430783a618d7584d985bd614 Mon Sep 17 00:00:00 2001
From: Fabian Vogt <fabian@ritter-vogt.de>
Date: Tue, 21 Feb 2023 16:03:51 +0100
Subject: [PATCH] Use the QScreen of the QWindow as default output

If the Window::setDesiredOutput API was not called for the QWindow, use
QWindow::screen(). This allows assigning QWindows to specific screens using
the plain Qt API.

Passing nullptr to Window::setDesiredOutput explicitly results in nil as
desired output for the layer, which lets the compositor select a screen.
---
 src/interfaces/window.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/interfaces/window.cpp b/src/interfaces/window.cpp
index 477b74e..7aa39f4 100644
--- a/src/interfaces/window.cpp
+++ b/src/interfaces/window.cpp
@@ -8,6 +8,7 @@
 #include <layershellqt_logging.h>
 
 #include <QPointer>
+#include <optional>
 
 using namespace LayerShellQt;
 
@@ -26,7 +27,7 @@ public:
     Window::KeyboardInteractivity keyboardInteractivity = Window::KeyboardInteractivityExclusive;
     Window::Layer layer = Window::LayerTop;
     QMargins margins;
-    QPointer<QScreen> desiredOutput;
+    std::optional<QPointer<QScreen>> desiredOutput;
 };
 
 static QMap<QWindow *, Window *> s_map;
@@ -103,7 +104,12 @@ Window::Layer Window::layer() const
 
 QScreen *Window::desiredOutput() const
 {
-    return d->desiredOutput;
+    // Don't use .value_or here to avoid a temporary QPointer
+    if (d->desiredOutput.has_value()) {
+        return d->desiredOutput.value();
+    }
+
+    return d->parentWindow->screen();
 }
 
 void Window::setDesiredOutput(QScreen *output)
-- 
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