From 88a0246a46c30e08e9730d16cf8739773447d058 Mon Sep 17 00:00:00 2001
From: Johan Klokkhammer Helsing <johan.helsing@qt.io>
Date: Mon, 24 Sep 2018 13:04:51 +0200
Subject: 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>
---
 src/client/qwaylandshmbackingstore.cpp |  3 +--
 src/client/qwaylandwindow.cpp          | 22 ++++++++++++++++++++++
 src/client/qwaylandwindow_p.h          |  4 ++++
 3 files changed, 27 insertions(+), 2 deletions(-)

(limited to 'src/client')

diff --git a/src/client/qwaylandshmbackingstore.cpp b/src/client/qwaylandshmbackingstore.cpp
index ecb03c0d6..3fe2ce80c 100644
--- a/src/client/qwaylandshmbackingstore.cpp
+++ b/src/client/qwaylandshmbackingstore.cpp
@@ -234,8 +234,7 @@ void QWaylandShmBackingStore::flush(QWindow *window, const QRegion &region, cons
     mFrontBuffer = mBackBuffer;
 
     QMargins margins = windowDecorationMargins();
-
-    waylandWindow()->commit(mFrontBuffer, region.translated(margins.left(), margins.top()));
+    waylandWindow()->safeCommit(mFrontBuffer, region.translated(margins.left(), margins.top()));
 }
 
 void QWaylandShmBackingStore::resize(const QSize &size, const QRegion &)
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;
diff --git a/src/client/qwaylandwindow_p.h b/src/client/qwaylandwindow_p.h
index d11ed871b..ad24b7358 100644
--- a/src/client/qwaylandwindow_p.h
+++ b/src/client/qwaylandwindow_p.h
@@ -116,6 +116,8 @@ public:
     using QtWayland::wl_surface::damage;
     void damage(const QRect &rect);
 
+    void safeCommit(QWaylandBuffer *buffer, const QRegion &damage);
+    void handleExpose(const QRegion &region);
     void commit(QWaylandBuffer *buffer, const QRegion &damage);
 
     void waitForFrameSync();
@@ -231,6 +233,8 @@ protected:
     Qt::WindowStates mLastReportedWindowStates = Qt::WindowNoState;
 
     QWaylandShmBackingStore *mBackingStore = nullptr;
+    QWaylandBuffer *mQueuedBuffer = nullptr;
+    QRegion mQueuedBufferDamage;
 
 private slots:
     void handleScreenRemoved(QScreen *qScreen);
-- 
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