xcb: Ignore disabling of outputs in the middle of the mode switch

X server may send RROutputChangeNotify event with null crtc and mode,
when it switches an output mode. Request RROutputInfo to distinguish
this case from the case when the output is explicitly disabled.

Change-Id: I4c2356ec71dbcc8013009ea8a6f46dd11f19d6bb
Task-number: QTBUG-44158
Task-number: QTBUG-46786
Task-number: QTBUG-46822
Reviewed-by: Daniel Vrátil <dvratil@redhat.com>
Reviewed-by: Gatis Paeglis <gatis.paeglis@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>

1 files changed, 13 insertions, 5 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index 08676152dc..29e1fd145d 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -265,11 +265,19 @@ void QXcbConnection::updateScreens(const xcb_randr_notify_event_t *event)
         } else if (screen) {
             // Screen has been disabled -> remove
             if (output.crtc == XCB_NONE && output.mode == XCB_NONE) {
-                qCDebug(lcQpaScreen) << "output" << screen->name() << "has been disabled";
-                m_screens.removeOne(screen);
-                foreach (QXcbScreen *otherScreen, m_screens)
-                    otherScreen->removeVirtualSibling((QPlatformScreen *) screen);
-                QXcbIntegration::instance()->destroyScreen(screen);
+                xcb_randr_get_output_info_cookie_t outputInfoCookie =
+                    xcb_randr_get_output_info(xcb_connection(), output.output, output.config_timestamp);
+                QScopedPointer<xcb_randr_get_output_info_reply_t, QScopedPointerPodDeleter> outputInfo(
+                    xcb_randr_get_output_info_reply(xcb_connection(), outputInfoCookie, NULL));
+                if (outputInfo->crtc == XCB_NONE) {
+                    qCDebug(lcQpaScreen) << "output" << screen->name() << "has been disabled";
+                    m_screens.removeOne(screen);
+                    foreach (QXcbScreen *otherScreen, m_screens)
+                        otherScreen->removeVirtualSibling((QPlatformScreen *) screen);
+                    QXcbIntegration::instance()->destroyScreen(screen);
+                } else {
+                    qCDebug(lcQpaScreen) << "output" << screen->name() << "has been temporarily disabled for the mode switch";
+                }
             } else {
                 // Just update existing screen
                 screen->updateGeometry(output.config_timestamp);