xcb: fix missing initialization of m_cursor

Regression introduced in 9a4c98e55659b32db984612e6247ac193812a502:

m_cursor is not initialized and never set when monitorInfo is not
available in QXcbScreen::setMonitor. This seems to happen when running
in VNC, e.g. on a Raspberry Pi.

This usually results in crashing the application pretty soon.

Using a unique_ptr solves both the initialization and a possible leak
when setMonitor is called multiple times.

[ChangeLog][Linux/XCB] Fixed crash when no monitorInfo is available (e.g. VNC).

Fixes: QTBUG-104443
Pick-to: 6.3 6.4
Change-Id: If13493c177121a1994b5d00dfbd64f1da694df2e
Reviewed-by: Liang Qi <liang.qi@qt.io>

2 files changed, 6 insertions, 7 deletions

diff --git a/src/plugins/platforms/xcb/qxcbscreen.cpp b/src/plugins/platforms/xcb/qxcbscreen.cpp
index bb33f393ec..36c5cd0d78 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.cpp
+++ b/src/plugins/platforms/xcb/qxcbscreen.cpp
@@ -499,6 +499,7 @@ QXcbScreen::QXcbScreen(QXcbConnection *connection, QXcbVirtualDesktop *virtualDe
     , m_crtc(output ? output->crtc : XCB_NONE)
     , m_outputName(getOutputName(output))
     , m_outputSizeMillimeters(output ? QSize(output->mm_width, output->mm_height) : QSize())
+    , m_cursor(std::make_unique<QXcbCursor>(connection, this))
 {
     if (connection->isAtLeastXRandR12()) {
         xcb_randr_select_input(xcb_connection(), screen()->root, true);
@@ -519,8 +520,6 @@ QXcbScreen::QXcbScreen(QXcbConnection *connection, QXcbVirtualDesktop *virtualDe
     if (m_sizeMillimeters.isEmpty())
         m_sizeMillimeters = virtualDesktop->physicalSize();
 
-    m_cursor = new QXcbCursor(connection, this);
-
     updateColorSpaceAndEdid();
 }
 
@@ -585,6 +584,7 @@ QXcbScreen::QXcbScreen(QXcbConnection *connection, QXcbVirtualDesktop *virtualDe
     : QXcbObject(connection)
     , m_virtualDesktop(virtualDesktop)
     , m_monitor(monitorInfo)
+    , m_cursor(std::make_unique<QXcbCursor>(connection, this))
 {
     setMonitor(monitorInfo, timestamp);
 }
@@ -683,8 +683,6 @@ void QXcbScreen::setMonitor(xcb_randr_monitor_info_t *monitorInfo, xcb_timestamp
     else
         m_primary = false;
 
-    m_cursor = new QXcbCursor(connection(), this);
-
     updateColorSpaceAndEdid();
 }
 
@@ -702,7 +700,6 @@ QString QXcbScreen::defaultName()
 
 QXcbScreen::~QXcbScreen()
 {
-    delete m_cursor;
 }
 
 QString QXcbScreen::getOutputName(xcb_randr_get_output_info_reply_t *outputInfo)
@@ -869,7 +866,7 @@ QDpi QXcbScreen::logicalDpi() const
 
 QPlatformCursor *QXcbScreen::cursor() const
 {
-    return m_cursor;
+    return m_cursor.get();
 }
 
 void QXcbScreen::setOutput(xcb_randr_output_t outputId,
diff --git a/src/plugins/platforms/xcb/qxcbscreen.h b/src/plugins/platforms/xcb/qxcbscreen.h
index 12c13ef80e..5a844f944a 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.h
+++ b/src/plugins/platforms/xcb/qxcbscreen.h
@@ -18,6 +18,8 @@
 
 #include <QtGui/private/qedidparser_p.h>
 
+#include <memory>
+
 QT_BEGIN_NAMESPACE
 
 class QXcbConnection;
@@ -212,7 +214,7 @@ private:
     QRect m_availableGeometry;
     QColorSpace m_colorSpace;
     Qt::ScreenOrientation m_orientation = Qt::PrimaryOrientation;
-    QXcbCursor *m_cursor;
+    std::unique_ptr<QXcbCursor> m_cursor;
     qreal m_refreshRate = 60.0;
     QEdidParser m_edid;