Don't ask libwayland to set absurdly long window titles

It will cause libwayland to terminate the application.

Task-number: QTBUG-68715
Change-Id: I1d1830453da224bec8bf4c5d6ab087c0e05328a8
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

2 files changed, 23 insertions, 1 deletions

diff --git a/src/client/qwaylandwindow.cpp b/src/client/qwaylandwindow.cpp
index fdfd66688..5d658f675 100644
--- a/src/client/qwaylandwindow.cpp
+++ b/src/client/qwaylandwindow.cpp
@@ -287,7 +287,18 @@ void QWaylandWindow::setWindowTitle(const QString &title)
 {
     if (mShellSurface) {
         const QString separator = QString::fromUtf8(" \xe2\x80\x94 "); // unicode character U+2014, EM DASH
-        mShellSurface->setTitle(formatWindowTitle(title, separator));
+        const QString formatted = formatWindowTitle(title, separator);
+
+        const int libwaylandMaxBufferSize = 4096;
+        // Some parts of the buffer is used for metadata, so subtract 100 to be on the safe side
+        const int maxLength = libwaylandMaxBufferSize - 100;
+
+        auto truncated = QStringRef(&formatted).left(maxLength);
+        if (truncated.length() < formatted.length()) {
+            qCWarning(lcQpaWayland) << "Window titles longer than" << maxLength << "characters are not supported."
+                                    << "Truncating window title (from" << formatted.length() << "chars)";
+        }
+        mShellSurface->setTitle(truncated.toString());
     }
 
     if (mWindowDecoration && window()->isVisible())
diff --git a/tests/auto/client/client/tst_client.cpp b/tests/auto/client/client/tst_client.cpp
index a8e2d5e19..dcc0cb773 100644
--- a/tests/auto/client/client/tst_client.cpp
+++ b/tests/auto/client/client/tst_client.cpp
@@ -181,6 +181,7 @@ private slots:
     void hiddenTransientParent();
     void hiddenPopupParent();
     void glWindow();
+    void longWindowTitle();
 
 private:
     MockCompositor *compositor = nullptr;
@@ -582,6 +583,16 @@ void tst_WaylandClient::glWindow()
     QTRY_VERIFY(!compositor->surface());
 }
 
+void tst_WaylandClient::longWindowTitle()
+{
+    // See QTBUG-68715
+    QWindow window;
+    QString absurdlyLongTitle(10000, QLatin1Char('z'));
+    window.setTitle(absurdlyLongTitle);
+    window.show();
+    QTRY_VERIFY(compositor->surface());
+}
+
 int main(int argc, char **argv)
 {
     setenv("XDG_RUNTIME_DIR", ".", 1);