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>

4 files changed, 34 insertions, 8 deletions

diff --git a/src/plugins/shellintegration/xdg-shell-v6/qwaylandxdgshellv6.cpp b/src/plugins/shellintegration/xdg-shell-v6/qwaylandxdgshellv6.cpp
index 447e8fb6a..3d3af6929 100644
--- a/src/plugins/shellintegration/xdg-shell-v6/qwaylandxdgshellv6.cpp
+++ b/src/plugins/shellintegration/xdg-shell-v6/qwaylandxdgshellv6.cpp
@@ -258,9 +258,14 @@ void QWaylandXdgSurfaceV6::setAppId(const QString &appId)
         m_toplevel->set_app_id(appId);
 }
 
+bool QWaylandXdgSurfaceV6::isExposed() const
+{
+    return m_configured || m_pendingConfigureSerial;
+}
+
 bool QWaylandXdgSurfaceV6::handleExpose(const QRegion &region)
 {
-    if (!m_configured && !region.isEmpty()) {
+    if (!isExposed() && !region.isEmpty()) {
         m_exposeRegion = region;
         return true;
     }
@@ -333,10 +338,18 @@ void QWaylandXdgSurfaceV6::setPopup(QWaylandWindow *parent, QWaylandInputDevice
 
 void QWaylandXdgSurfaceV6::zxdg_surface_v6_configure(uint32_t serial)
 {
-    m_window->applyConfigureWhenPossible();
     m_pendingConfigureSerial = serial;
+    if (!m_configured) {
+        // We have to do the initial applyConfigure() immediately, since that is the expose.
+        applyConfigure();
+    } else {
+        // Later configures are probably resizes, so we have to queue them up for a time when we
+        // are not painting to the window.
+        m_window->applyConfigureWhenPossible();
+    }
+
     if (!m_exposeRegion.isEmpty()) {
-        QWindowSystemInterface::handleExposeEvent(m_window->window(), m_exposeRegion);
+        m_window->handleExpose(m_exposeRegion);
         m_exposeRegion = QRegion();
     }
 }
diff --git a/src/plugins/shellintegration/xdg-shell-v6/qwaylandxdgshellv6_p.h b/src/plugins/shellintegration/xdg-shell-v6/qwaylandxdgshellv6_p.h
index 38b711f88..874dba014 100644
--- a/src/plugins/shellintegration/xdg-shell-v6/qwaylandxdgshellv6_p.h
+++ b/src/plugins/shellintegration/xdg-shell-v6/qwaylandxdgshellv6_p.h
@@ -85,7 +85,7 @@ public:
     void setTitle(const QString &title) override;
     void setAppId(const QString &appId) override;
 
-    bool isExposed() const override { return m_configured; }
+    bool isExposed() const override;
     bool handleExpose(const QRegion &) override;
     bool handlesActiveState() const { return m_toplevel; }
     void applyConfigure() override;
diff --git a/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp b/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp
index 0756e4d02..c723192c8 100644
--- a/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp
+++ b/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp
@@ -292,9 +292,14 @@ void QWaylandXdgSurface::setWindowFlags(Qt::WindowFlags flags)
         m_toplevel->requestWindowFlags(flags);
 }
 
+bool QWaylandXdgSurface::isExposed() const
+{
+    return m_configured || m_pendingConfigureSerial;
+}
+
 bool QWaylandXdgSurface::handleExpose(const QRegion &region)
 {
-    if (!m_configured && !region.isEmpty()) {
+    if (!isExposed() && !region.isEmpty()) {
         m_exposeRegion = region;
         return true;
     }
@@ -367,10 +372,18 @@ void QWaylandXdgSurface::setPopup(QWaylandWindow *parent, QWaylandInputDevice *d
 
 void QWaylandXdgSurface::xdg_surface_configure(uint32_t serial)
 {
-    m_window->applyConfigureWhenPossible();
     m_pendingConfigureSerial = serial;
+    if (!m_configured) {
+        // We have to do the initial applyConfigure() immediately, since that is the expose.
+        applyConfigure();
+    } else {
+        // Later configures are probably resizes, so we have to queue them up for a time when we
+        // are not painting to the window.
+        m_window->applyConfigureWhenPossible();
+    }
+
     if (!m_exposeRegion.isEmpty()) {
-        QWindowSystemInterface::handleExposeEvent(m_window->window(), m_exposeRegion);
+        m_window->handleExpose(m_exposeRegion);
         m_exposeRegion = QRegion();
     }
 }
diff --git a/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell_p.h b/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell_p.h
index 45d7d4b0e..5e97a34b3 100644
--- a/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell_p.h
+++ b/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell_p.h
@@ -89,7 +89,7 @@ public:
     void setAppId(const QString &appId) override;
     void setWindowFlags(Qt::WindowFlags flags) override;
 
-    bool isExposed() const override { return m_configured; }
+    bool isExposed() const override;
     bool handleExpose(const QRegion &) override;
     bool handlesActiveState() const { return m_toplevel; }
     void applyConfigure() override;