Prevent ending up in a state where focus is perpetually grabbed.

Mouse / enter / leave / key events etc are all blocked when a window has
the blockedByModalWindow flag set. The problem appears if a QWindow is
created and only later directly or indirectly parented to a modal window
that's currently showing. Since the decision on whether a window should
be blocked or not is based on its parent / transient parent chain, we
need to reevaluate the blocked status each time the parent or transient
parent of a window changes.

Task-number: QTBUG-26112
Change-Id: Ida6b118b556fe26d17fa86335a0fe7baddc7eaf8
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>

3 files changed, 25 insertions, 10 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 3cd8d5f800..e22ccc762d 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -402,18 +402,30 @@ QWindow *QGuiApplication::modalWindow()
     return QGuiApplicationPrivate::self->modalWindowList.first();
 }
 
-void QGuiApplicationPrivate::showModalWindow(QWindow *window)
+void QGuiApplicationPrivate::updateBlockedStatus(QWindow *window)
 {
-    self->modalWindowList.prepend(window);
+    bool shouldBeBlocked = false;
+    if (window->windowType() != Qt::Tool && !self->modalWindowList.isEmpty())
+        shouldBeBlocked = self->isWindowBlocked(window);
+
+    if (shouldBeBlocked != window->d_func()->blockedByModalWindow) {
+        QEvent e(shouldBeBlocked ? QEvent::WindowBlocked : QEvent::WindowUnblocked);
+
+        window->d_func()->blockedByModalWindow = shouldBeBlocked;
+        QGuiApplication::sendEvent(window, &e);
+    }
+}
+
+void QGuiApplicationPrivate::showModalWindow(QWindow *modal)
+{
+    self->modalWindowList.prepend(modal);
 
     QEvent e(QEvent::WindowBlocked);
     QWindowList windows = QGuiApplication::topLevelWindows();
     for (int i = 0; i < windows.count(); ++i) {
         QWindow *window = windows.at(i);
-        if (!window->d_func()->blockedByModalWindow && window->windowType() != Qt::Tool && self->isWindowBlocked(window)) {
-            window->d_func()->blockedByModalWindow = true;
-            QGuiApplication::sendEvent(window, &e);
-        }
+        if (!window->d_func()->blockedByModalWindow)
+            updateBlockedStatus(window);
     }
 }
 
@@ -425,10 +437,8 @@ void QGuiApplicationPrivate::hideModalWindow(QWindow *window)
     QWindowList windows = QGuiApplication::topLevelWindows();
     for (int i = 0; i < windows.count(); ++i) {
         QWindow *window = windows.at(i);
-        if (window->d_func()->blockedByModalWindow && window->windowType() != Qt::Tool && !self->isWindowBlocked(window)) {
-            window->d_func()->blockedByModalWindow = false;
-            QGuiApplication::sendEvent(window, &e);
-        }
+        if (window->d_func()->blockedByModalWindow)
+            updateBlockedStatus(window);
     }
 }
 
diff --git a/src/gui/kernel/qguiapplication_p.h b/src/gui/kernel/qguiapplication_p.h
index 76f0a71270..a564120a3b 100644
--- a/src/gui/kernel/qguiapplication_p.h
+++ b/src/gui/kernel/qguiapplication_p.h
@@ -168,6 +168,7 @@ public:
     QWindowList modalWindowList;
     static void showModalWindow(QWindow *window);
     static void hideModalWindow(QWindow *window);
+    static void updateBlockedStatus(QWindow *window);
     virtual bool isWindowBlocked(QWindow *window, QWindow **blockingWindow = 0) const;
 
     static Qt::MouseButtons buttons;
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index f30a794b55..d6f0aab50d 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -360,6 +360,8 @@ void QWindow::setParent(QWindow *parent)
     }
 
     d->parentWindow = parent;
+
+    QGuiApplicationPrivate::updateBlockedStatus(this);
 }
 
 /*!
@@ -784,6 +786,8 @@ void QWindow::setTransientParent(QWindow *parent)
 {
     Q_D(QWindow);
     d->transientParent = parent;
+
+    QGuiApplicationPrivate::updateBlockedStatus(this);
 }
 
 /*!