FocusAboutToChange event to be send before focus changes

Focus change happen as: FocusAboutToChange event -> focus change
-> FocusOut event -> FocusIn event.

Input method need to have focus when calling commit(). Notification
on focus about to be lost allows QWindow implementations to commit in
time.

Also changes QWidget documentation to match code reality.

Change-Id: I17a8a374a33dd700909f79e370b42348869261a6
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>

4 files changed, 72 insertions, 29 deletions

diff --git a/src/widgets/kernel/qapplication.cpp b/src/widgets/kernel/qapplication.cpp
index 7441d55865..ce57e2868d 100644
--- a/src/widgets/kernel/qapplication.cpp
+++ b/src/widgets/kernel/qapplication.cpp
@@ -1760,16 +1760,6 @@ void QApplicationPrivate::setFocusWidget(QWidget *focus, Qt::FocusReason reason)
         }
         QWidget *prev = focus_widget;
         focus_widget = focus;
-#ifndef QT_NO_IM
-        if (prev && ((reason != Qt::PopupFocusReason && reason != Qt::MenuBarFocusReason
-                      && prev->testAttribute(Qt::WA_InputMethodEnabled))
-                     // Do reset the input context, in case the new focus widget won't accept keyboard input
-                     // or it is not created fully yet.
-                     || (focus_widget && (!focus_widget->testAttribute(Qt::WA_InputMethodEnabled)
-                                          || !focus_widget->testAttribute(Qt::WA_WState_Created))))) {
-            qApp->inputMethod()->reset();
-        }
-#endif //QT_NO_IM
 
         if(focus_widget)
             focus_widget->d_func()->setFocus_sys();
@@ -1798,7 +1788,6 @@ void QApplicationPrivate::setFocusWidget(QWidget *focus, Qt::FocusReason reason)
                     QApplication::sendEvent(that->style(), &in);
             }
             emit qApp->focusChanged(prev, focus_widget);
-            emit qApp->focusObjectChanged(focus_widget);
         }
     }
 }
@@ -2051,6 +2040,14 @@ void QApplication::setActiveWindow(QWidget* act)
         }
     }
 
+    if (QApplicationPrivate::focus_widget) {
+        if (QApplicationPrivate::focus_widget->testAttribute(Qt::WA_InputMethodEnabled))
+            qApp->inputMethod()->reset();
+
+        QFocusEvent focusAboutToChange(QEvent::FocusAboutToChange, Qt::ActiveWindowFocusReason);
+        QApplication::sendEvent(QApplicationPrivate::focus_widget, &focusAboutToChange);
+    }
+
     QApplicationPrivate::active_window = window;
 
     if (QApplicationPrivate::active_window) {
diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 6418ba63e1..63eb2540ff 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -5875,9 +5875,10 @@ bool QWidget::hasFocus() const
     If the window is not active, the widget will be given the focus when
     the window becomes active.
 
-    First, a focus out event is sent to the focus widget (if any) to
-    tell it that it is about to lose the focus. Then a focus in event
-    is sent to this widget to tell it that it just received the focus.
+    First, a focus about to change event is sent to the focus widget (if any) to
+    tell it that it is about to lose the focus. Then focus is changed, a
+    focus out event is sent to the previous focus item and a focus in event is sent
+    to the new item to tell it that it just received the focus.
     (Nothing happens if the focus in and focus out widgets are the
     same.)
 
@@ -5930,23 +5931,11 @@ void QWidget::setFocus(Qt::FocusReason reason)
     }
 #endif
 
-    QWidget *w = f;
-    if (isHidden()) {
-        while (w && w->isHidden()) {
-            w->d_func()->focus_child = f;
-            w = w->isWindow() ? 0 : w->parentWidget();
-        }
-    } else {
-        while (w) {
-            w->d_func()->focus_child = f;
-            w = w->isWindow() ? 0 : w->parentWidget();
-        }
-    }
-
 #ifndef QT_NO_GRAPHICSVIEW
     // Update proxy state
     if (QWExtra *topData = window()->d_func()->extra) {
         if (topData->proxyWidget && !topData->proxyWidget->hasFocus()) {
+            f->d_func()->updateFocusChild();
             topData->proxyWidget->d_func()->focusFromWidgetToProxy = 1;
             topData->proxyWidget->setFocus(reason);
             topData->proxyWidget->d_func()->focusFromWidgetToProxy = 0;
@@ -5955,6 +5944,21 @@ void QWidget::setFocus(Qt::FocusReason reason)
 #endif
 
     if (f->isActiveWindow()) {
+        QWidget *prev = QApplicationPrivate::focus_widget;
+        if (prev) {
+            if (reason != Qt::PopupFocusReason && reason != Qt::MenuBarFocusReason
+                && prev->testAttribute(Qt::WA_InputMethodEnabled)) {
+                qApp->inputMethod()->reset();
+            }
+
+            if (reason != Qt::NoFocusReason) {
+                QFocusEvent focusAboutToChange(QEvent::FocusAboutToChange, reason);
+                QApplication::sendEvent(prev, &focusAboutToChange);
+            }
+        }
+
+        f->d_func()->updateFocusChild();
+
         QApplicationPrivate::setFocusWidget(f, reason);
 #ifndef QT_NO_ACCESSIBILITY
 # ifdef Q_OS_WIN
@@ -5999,6 +6003,30 @@ void QWidget::setFocus(Qt::FocusReason reason)
             }
         }
 #endif
+    } else {
+        f->d_func()->updateFocusChild();
+    }
+
+    if (QTLWExtra *extra = f->window()->d_func()->maybeTopData())
+        emit extra->window->focusObjectChanged(f);
+}
+
+// updates focus_child on parent widgets to point into this widget
+void QWidgetPrivate::updateFocusChild()
+{
+    Q_Q(QWidget);
+
+    QWidget *w = q;
+    if (q->isHidden()) {
+        while (w && w->isHidden()) {
+            w->d_func()->focus_child = q;
+            w = w->isWindow() ? 0 : w->parentWidget();
+        }
+    } else {
+        while (w) {
+            w->d_func()->focus_child = q;
+            w = w->isWindow() ? 0 : w->parentWidget();
+        }
     }
 }
 
@@ -6015,8 +6043,8 @@ void QWidget::setFocus(Qt::FocusReason reason)
     Takes keyboard input focus from the widget.
 
     If the widget has active focus, a \link focusOutEvent() focus out
-    event\endlink is sent to this widget to tell it that it is about
-    to lose the focus.
+    event\endlink is sent to this widget to tell it that it has
+    lost the focus.
 
     This widget must enable focus setting in order to get the keyboard
     input focus, i.e. it must call setFocusPolicy().
@@ -6027,6 +6055,14 @@ void QWidget::setFocus(Qt::FocusReason reason)
 
 void QWidget::clearFocus()
 {
+    if (hasFocus()) {
+        if (testAttribute(Qt::WA_InputMethodEnabled))
+            qApp->inputMethod()->reset();
+
+        QFocusEvent focusAboutToChange(QEvent::FocusAboutToChange);
+        QApplication::sendEvent(this, &focusAboutToChange);
+    }
+
     QWidget *w = this;
     while (w) {
         if (w->d_func()->focus_child == this)
diff --git a/src/widgets/kernel/qwidget_p.h b/src/widgets/kernel/qwidget_p.h
index 38314c234b..8107b6ca74 100644
--- a/src/widgets/kernel/qwidget_p.h
+++ b/src/widgets/kernel/qwidget_p.h
@@ -336,6 +336,7 @@ public:
     void stackUnder_sys(QWidget *);
 
     void setFocus_sys();
+    void updateFocusChild();
 
     void updateFont(const QFont &);
     inline void setFont_helper(const QFont &font) {
diff --git a/src/widgets/kernel/qwidgetwindow_qpa.cpp b/src/widgets/kernel/qwidgetwindow_qpa.cpp
index f58dddb70f..7a13e2032e 100644
--- a/src/widgets/kernel/qwidgetwindow_qpa.cpp
+++ b/src/widgets/kernel/qwidgetwindow_qpa.cpp
@@ -99,6 +99,15 @@ bool QWidgetWindow::event(QEvent *event)
     case QEvent::FocusOut:
         return false;
 
+    case QEvent::FocusAboutToChange:
+        if (QApplicationPrivate::focus_widget) {
+            if (QApplicationPrivate::focus_widget->testAttribute(Qt::WA_InputMethodEnabled))
+                qApp->inputMethod()->commit();
+
+            QGuiApplication::sendSpontaneousEvent(QApplicationPrivate::focus_widget, event);
+        }
+        return true;
+
     case QEvent::KeyPress:
     case QEvent::KeyRelease:
         handleKeyEvent(static_cast<QKeyEvent *>(event));