Get rid of copypasted code between isWindowBlocked's overrides

The code in QGuiApplication::isWindowBlocked and
QApplication::isWindowBlocked is very similar, a result of copying and
pasting. Due to the copying it is difficult to modify the code and the
implementation is hard to comprehend, too.
There are ultimately only two parts that are different. First is that
QApplication's override may also specify a certain window as
non-blockable if it is a popup window. Second, default modality is
computed in QApplication if a modal window does not have one assigned.
The differing parts have been extracted following the template method
design pattern.

Pick-to: 6.4
Change-Id: I3b9aa206a3c7211fe022730943bf6f76aa5ae6d2
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

2 files changed, 34 insertions, 30 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 7887db8534..0814339150 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -852,6 +852,17 @@ void QGuiApplicationPrivate::hideModalWindow(QWindow *window)
     }
 }
 
+Qt::WindowModality QGuiApplicationPrivate::defaultModality() const
+{
+    return Qt::NonModal;
+}
+
+bool QGuiApplicationPrivate::windowNeverBlocked(QWindow *window) const
+{
+    Q_UNUSED(window);
+    return false;
+}
+
 /*
     Returns \c true if \a window is blocked by a modal window. If \a
     blockingWindow is non-zero, *blockingWindow will be set to the blocking
@@ -859,49 +870,40 @@ void QGuiApplicationPrivate::hideModalWindow(QWindow *window)
 */
 bool QGuiApplicationPrivate::isWindowBlocked(QWindow *window, QWindow **blockingWindow) const
 {
+    Q_ASSERT_X(window, Q_FUNC_INFO, "The window must not be null");
+
     QWindow *unused = nullptr;
     if (!blockingWindow)
         blockingWindow = &unused;
+    *blockingWindow = nullptr;
 
-    if (modalWindowList.isEmpty()) {
-        *blockingWindow = nullptr;
+    if (modalWindowList.isEmpty() || windowNeverBlocked(window))
         return false;
-    }
 
     for (int i = 0; i < modalWindowList.count(); ++i) {
         QWindow *modalWindow = modalWindowList.at(i);
 
         // A window is not blocked by another modal window if the two are
         // the same, or if the window is a child of the modal window.
-        if (window == modalWindow || modalWindow->isAncestorOf(window, QWindow::IncludeTransients)) {
-            *blockingWindow = nullptr;
+        if (window == modalWindow || modalWindow->isAncestorOf(window, QWindow::IncludeTransients))
             return false;
-        }
 
-        Qt::WindowModality windowModality = modalWindow->modality();
-        switch (windowModality) {
+        switch (modalWindow->modality() == Qt::NonModal ? defaultModality()
+                                                        : modalWindow->modality()) {
         case Qt::ApplicationModal:
-        {
-            if (modalWindow != window) {
-                *blockingWindow = modalWindow;
-                return true;
-            }
-            break;
-        }
-        case Qt::WindowModal:
-        {
-            QWindow *w = window;
+            *blockingWindow = modalWindow;
+            return true;
+        case Qt::WindowModal: {
+            // Find the nearest ancestor of window which is also an ancestor of modal window to
+            // determine if the modal window blocks the window.
+            auto *current = window;
             do {
-                QWindow *m = modalWindow;
-                do {
-                    if (m == w) {
-                        *blockingWindow = m;
-                        return true;
-                    }
-                    m = m->parent(QWindow::IncludeTransients);
-                } while (m);
-                w = w->parent(QWindow::IncludeTransients);
-            } while (w);
+                if (current->isAncestorOf(modalWindow, QWindow::IncludeTransients)) {
+                    *blockingWindow = current;
+                    return true;
+                }
+                current = current->parent(QWindow::IncludeTransients);
+            } while (current);
             break;
         }
         default:
@@ -909,7 +911,6 @@ bool QGuiApplicationPrivate::isWindowBlocked(QWindow *window, QWindow **blocking
             break;
         }
     }
-    *blockingWindow = nullptr;
     return false;
 }
 
diff --git a/src/gui/kernel/qguiapplication_p.h b/src/gui/kernel/qguiapplication_p.h
index 3b30c14dbe..8309e2bfa7 100644
--- a/src/gui/kernel/qguiapplication_p.h
+++ b/src/gui/kernel/qguiapplication_p.h
@@ -188,7 +188,10 @@ public:
     static void showModalWindow(QWindow *window);
     static void hideModalWindow(QWindow *window);
     static void updateBlockedStatus(QWindow *window);
-    virtual bool isWindowBlocked(QWindow *window, QWindow **blockingWindow = nullptr) const;
+
+    virtual Qt::WindowModality defaultModality() const;
+    virtual bool windowNeverBlocked(QWindow *window) const;
+    bool isWindowBlocked(QWindow *window, QWindow **blockingWindow = nullptr) const;
     virtual bool popupActive() { return false; }
     virtual bool closeAllPopups() { return false; }