Client: Don't attach buffers to unexposed windows

QBackingStore::flush is sometimes called with an unxeposed window, in that
case, don't attach the buffer to the wl_surface immediately, as that causes
protocol errors with xdg_shell.

Flushed buffers are instead stored until we get the first configure event.

[ChangeLog][QPA plugin][xdg-shell] Fixed a bug where buffers were sometimes
attached and committed before the first configure event, causing protocol
errors.

Fixes: QTBUG-71345
Change-Id: If9409d97bd25f6b13940c56141920a664c349c8e
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
Reviewed-by: David Edmundson <davidedmundson@kde.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/client/qwaylandwindow.cpp b/src/client/qwaylandwindow.cpp
index 52bee6ae3..1801c2a4b 100644
--- a/src/client/qwaylandwindow.cpp
+++ b/src/client/qwaylandwindow.cpp
@@ -248,6 +248,7 @@ void QWaylandWindow::reset(bool sendDestroyEvent)
     }
 
     mMask = QRegion();
+    mQueuedBuffer = nullptr;
 }
 
 QWaylandWindow *QWaylandWindow::fromWlSurface(::wl_surface *surface)
@@ -566,8 +567,29 @@ void QWaylandWindow::damage(const QRect &rect)
     damage(rect.x(), rect.y(), rect.width(), rect.height());
 }
 
+void QWaylandWindow::safeCommit(QWaylandBuffer *buffer, const QRegion &damage)
+{
+    if (isExposed()) {
+        commit(buffer, damage);
+    } else {
+        mQueuedBuffer = buffer;
+        mQueuedBufferDamage = damage;
+    }
+}
+
+void QWaylandWindow::handleExpose(const QRegion &region)
+{
+    QWindowSystemInterface::handleExposeEvent(window(), region);
+    if (mQueuedBuffer) {
+        commit(mQueuedBuffer, mQueuedBufferDamage);
+        mQueuedBuffer = nullptr;
+        mQueuedBufferDamage = QRegion();
+    }
+}
+
 void QWaylandWindow::commit(QWaylandBuffer *buffer, const QRegion &damage)
 {
+    Q_ASSERT(isExposed());
     if (buffer->committed()) {
         qCDebug(lcWaylandBackingstore) << "Buffer already committed, ignoring.";
         return;