Commit 6689abaf authored by Vlad Zahorodnii's avatar Vlad Zahorodnii
Browse files

[Shell Corona] Work around popup dismissal bug on Wayland

A popup needs to grab the keyboard and the pointer in order to dismiss
itself when another window is clicked. It works perfectly on X11.

On Wayland though, the compositor is responsible for dismissing popups
if some surface of another application has been clicked. Note that I
said "of another application." If user clicks some surface of the same
application, the compositor won't dismiss the popup.

If the application uses only QtWidgets, then the popup will be closed
as expected in both cases. But if the application uses both Qt Quick and
Qt Widgets, e.g. plasmashell, then the popup won't be dismissed if a
QQuickItem has been clicked.

It is a Qt bug, but for the time being, this change introduces an event
filter that monitors Qt::MouseButtonPress events and when needed closes
the active popup widget. This is a workaround.

CCBUG: 379635
parent 333e8ef5
......@@ -2033,6 +2033,99 @@ void ShellCorona::insertContainment(const QString &activity, int screenNum, Plas
* @internal
* The DismissPopupEventFilter class monitors mouse button press events and
* when needed dismisses the active popup widget.
* plasmashell uses both QtQuick and QtWidgets under a single roof, QtQuick is
* used for most of things, while QtWidgets is used for things such as context
* menus, etc.
* If user clicks outside a popup window, it's expected that the popup window
* will be closed. On X11, it's achieved by establishing both a keyboard grab
* and a pointer grab. But on Wayland, you can't grab keyboard or pointer. If
* user clicks a surface of another app, the compositor will dismiss the popup
* surface. However, if user clicks some surface of the same application, the
* popup surface won't be dismissed, it's up to the application to decide
* whether the popup must be closed. In 99% cases, it must.
* Qt has some code that dismisses the active popup widget if another window
* of the same app has been clicked. But, that code works only if the
* application uses solely Qt widgets. See QTBUG-83972. For plasma it doesn't
* work, because as we said previously, it uses both Qt Quick and Qt Widgets.
* Ideally, this bug needs to be fixed upstream, but given that it'll involve
* major changes in Qt, the chances of it being fixed any time soon are slim.
* In order to work around the popup dismissal bug, we install an event filter
* that monitors Qt::MouseButtonPress events. If it happens that user has
* clicked outside an active popup widget, that popup will be closed. This
* event filter is not needed on X11!
class DismissPopupEventFilter : public QObject
explicit DismissPopupEventFilter(QObject *parent = nullptr);
bool eventFilter(QObject *watched, QEvent *event) override;
bool m_filterMouseEvents = false;
DismissPopupEventFilter::DismissPopupEventFilter(QObject *parent)
: QObject(parent)
bool DismissPopupEventFilter::eventFilter(QObject *watched, QEvent *event)
if (event->type() == QEvent::MouseButtonPress) {
if (m_filterMouseEvents) {
// Eat events until all mouse buttons are released.
return true;
QWidget *popup = QApplication::activePopupWidget();
if (!popup) {
return false;
QWindow *window = qobject_cast<QWindow *>(watched);
if (popup->windowHandle() == window) {
// The popup window handles mouse events before the widget.
return false;
QWidget *widget = qobject_cast<QWidget *>(watched);
if (widget) {
// Let the popup widget handle the mouse press event.
return false;
m_filterMouseEvents = true;
return true;
} else if (event->type() == QEvent::MouseButtonRelease) {
if (m_filterMouseEvents) {
// Eat events until all mouse buttons are released.
QMouseEvent *mouseEvent = static_cast<QMouseEvent *>(event);
if (mouseEvent->buttons() == Qt::NoButton) {
m_filterMouseEvents = false;
return true;
return false;
void ShellCorona::setupWaylandIntegration()
if (!KWindowSystem::isPlatformWayland()) {
......@@ -2052,6 +2145,7 @@ void ShellCorona::setupWaylandIntegration()
qApp->installEventFilter(new DismissPopupEventFilter(this));
KWayland::Client::PlasmaShell *ShellCorona::waylandPlasmaShellInterface() const
......@@ -2169,4 +2263,5 @@ void ShellCorona::activateTaskManagerEntry(int index)
#include "moc_shellcorona.cpp"
#include "shellcorona.moc"
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