QAbstractItemView: Fix IM input starting edit session

Item views can open an editor widget on the first key press, and need to
take special care not to break input methods. The initial key press
starts compositing by the system input method, which is then interrupted
by the focus transfer to the editor.

To solve this problem, the widget needs to keep focus while the initial
composition is ongoing, and only transfer focus to the editor once the
composition is either accepted or cancelled by the user. Add a state flag
that is set during this initial preedit phase.

During this initial composition, the item view will receive all input
method events, and needs to forward these to the open, but not yet focused
editor for the user to get the correct visual feedback during the preedit
phase. The item view also needs to report to input method queries on
behalf of the editor to make sure that the IM UI is correctly positioned
without covering the user input.

Implement a test that simulates the sequences through synthesized
QInputMethodEvents; we can't simulate the entire system input stack.

Fixes: QTBUG-54848
Change-Id: Ief3fe349f9d7542949032905c7f9ca2beb197611
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

2 files changed, 94 insertions, 21 deletions

diff --git a/src/widgets/itemviews/qabstractitemview.cpp b/src/widgets/itemviews/qabstractitemview.cpp
index 6ee9c2c7d1..67f24f071d 100644
--- a/src/widgets/itemviews/qabstractitemview.cpp
+++ b/src/widgets/itemviews/qabstractitemview.cpp
@@ -87,6 +87,7 @@ QAbstractItemViewPrivate::QAbstractItemViewPrivate()
         selectionBehavior(QAbstractItemView::SelectItems),
         currentlyCommittingEditor(nullptr),
         pressClosedEditor(false),
+        waitForIMCommit(false),
         pressedModifiers(Qt::NoModifier),
         pressedPosition(QPoint(-1, -1)),
         pressedAlreadySelected(false),
@@ -885,10 +886,26 @@ QAbstractItemDelegate *QAbstractItemView::itemDelegate() const
 */
 QVariant QAbstractItemView::inputMethodQuery(Qt::InputMethodQuery query) const
 {
+    Q_D(const QAbstractItemView);
     const QModelIndex current = currentIndex();
-    if (!current.isValid() || query != Qt::ImCursorRectangle)
-        return QAbstractScrollArea::inputMethodQuery(query);
-    return visualRect(current);
+    QVariant result;
+    if (current.isValid()) {
+        if (QWidget *currentEditor;
+            d->waitForIMCommit && (currentEditor = d->editorForIndex(current).widget)) {
+            // An editor is open but the initial preedit is still ongoing. Delegate
+            // queries to the editor and map coordinates from editor to this view.
+            result = currentEditor->inputMethodQuery(query);
+            if (result.typeId() == QMetaType::QRect) {
+                const QRect editorRect = result.value<QRect>();
+                result = QRect(currentEditor->mapTo(this, editorRect.topLeft()), editorRect.size());
+            }
+        } else if (query == Qt::ImCursorRectangle) {
+            result = visualRect(current);
+        }
+    }
+    if (!result.isValid())
+        result = QAbstractScrollArea::inputMethodQuery(query);
+    return result;
 }
 
 /*!
@@ -2599,14 +2616,53 @@ void QAbstractItemView::timerEvent(QTimerEvent *event)
 */
 void QAbstractItemView::inputMethodEvent(QInputMethodEvent *event)
 {
-    if (event->commitString().isEmpty() && event->preeditString().isEmpty()) {
+    Q_D(QAbstractItemView);
+    // When QAbstractItemView::AnyKeyPressed is used, a new IM composition might
+    // start before the editor widget acquires focus. Changing focus would interrupt
+    // the composition, so we keep focus on the view until that first composition
+    // is complete, and pass QInputMethoEvents on to the editor widget so that the
+    // user gets the expected feedback. See also inputMethodQuery, which redirects
+    // calls to the editor widget during that period.
+    bool forwardEventToEditor = false;
+    const bool commit = !event->commitString().isEmpty();
+    const bool preediting = !event->preeditString().isEmpty();
+    if (QWidget *currentEditor = d->editorForIndex(currentIndex()).widget) {
+        if (d->waitForIMCommit) {
+            if (commit || !preediting) {
+                // commit or cancel
+                d->waitForIMCommit = false;
+                QApplication::sendEvent(currentEditor, event);
+                if (!commit) {
+                    QAbstractItemDelegate *delegate = itemDelegateForIndex(currentIndex());
+                    if (delegate)
+                        delegate->setEditorData(currentEditor, currentIndex());
+                    d->selectAllInEditor(currentEditor);
+                }
+                if (currentEditor->focusPolicy() != Qt::NoFocus)
+                    currentEditor->setFocus();
+            } else {
+                // more pre-editing
+                QApplication::sendEvent(currentEditor, event);
+            }
+            return;
+        }
+    } else if (preediting) {
+        // don't set focus when the editor opens
+        d->waitForIMCommit = true;
+        // but pass preedit on to editor
+        forwardEventToEditor = true;
+    } else if (!commit) {
         event->ignore();
         return;
     }
     if (!edit(currentIndex(), AnyKeyPressed, event)) {
-        if (!event->commitString().isEmpty())
+        d->waitForIMCommit = false;
+        if (commit)
             keyboardSearch(event->commitString());
         event->ignore();
+    } else if (QWidget *currentEditor; forwardEventToEditor
+               && (currentEditor = d->editorForIndex(currentIndex()).widget)) {
+        QApplication::sendEvent(currentEditor, event);
     }
 }
 
@@ -2685,7 +2741,10 @@ bool QAbstractItemView::edit(const QModelIndex &index, EditTrigger trigger, QEve
     if (QWidget *w = (d->persistent.isEmpty() ? static_cast<QWidget*>(nullptr) : d->editorForIndex(index).widget.data())) {
         if (w->focusPolicy() == Qt::NoFocus)
             return false;
-        w->setFocus();
+        if (!d->waitForIMCommit)
+            w->setFocus();
+        else
+            updateMicroFocus();
         return true;
     }
 
@@ -4241,6 +4300,28 @@ void QAbstractItemViewPrivate::updateGeometry()
         q->updateGeometry();
 }
 
+/*
+    Handles selection of content for some editors containing QLineEdit.
+
+    ### Qt 7 This should be done by a virtual method in QAbstractItemDelegate.
+*/
+void QAbstractItemViewPrivate::selectAllInEditor(QWidget *editor)
+{
+    while (QWidget *fp = editor->focusProxy())
+        editor = fp;
+
+#if QT_CONFIG(lineedit)
+    if (QLineEdit *le = qobject_cast<QLineEdit*>(editor))
+        le->selectAll();
+#endif
+#if QT_CONFIG(spinbox)
+    if (QSpinBox *sb = qobject_cast<QSpinBox*>(editor))
+        sb->selectAll();
+    else if (QDoubleSpinBox *dsb = qobject_cast<QDoubleSpinBox*>(editor))
+        dsb->selectAll();
+#endif
+}
+
 QWidget *QAbstractItemViewPrivate::editor(const QModelIndex &index,
                                           const QStyleOptionViewItem &options)
 {
@@ -4260,20 +4341,7 @@ QWidget *QAbstractItemViewPrivate::editor(const QModelIndex &index,
             if (w->parent() == viewport)
                 QWidget::setTabOrder(q, w);
 
-            // Special cases for some editors containing QLineEdit
-            QWidget *focusWidget = w;
-            while (QWidget *fp = focusWidget->focusProxy())
-                focusWidget = fp;
-#if QT_CONFIG(lineedit)
-            if (QLineEdit *le = qobject_cast<QLineEdit*>(focusWidget))
-                le->selectAll();
-#endif
-#if QT_CONFIG(spinbox)
-            if (QSpinBox *sb = qobject_cast<QSpinBox*>(focusWidget))
-                sb->selectAll();
-            else if (QDoubleSpinBox *dsb = qobject_cast<QDoubleSpinBox*>(focusWidget))
-                dsb->selectAll();
-#endif
+            selectAllInEditor(w);
         }
     }
 
@@ -4444,7 +4512,10 @@ bool QAbstractItemViewPrivate::openEditor(const QModelIndex &index, QEvent *even
 
     q->setState(QAbstractItemView::EditingState);
     w->show();
-    w->setFocus();
+    if (!waitForIMCommit)
+        w->setFocus();
+    else
+        q->updateMicroFocus();
 
     if (event)
         QCoreApplication::sendEvent(w->focusProxy() ? w->focusProxy() : w, event);
diff --git a/src/widgets/itemviews/qabstractitemview_p.h b/src/widgets/itemviews/qabstractitemview_p.h
index f45d642dcf..74850de992 100644
--- a/src/widgets/itemviews/qabstractitemview_p.h
+++ b/src/widgets/itemviews/qabstractitemview_p.h
@@ -140,6 +140,7 @@ public:
     bool sendDelegateEvent(const QModelIndex &index, QEvent *event) const;
     bool openEditor(const QModelIndex &index, QEvent *event);
     void updateEditorData(const QModelIndex &topLeft, const QModelIndex &bottomRight);
+    void selectAllInEditor(QWidget *w);
 
     QItemSelectionModel::SelectionFlags multiSelectionCommand(const QModelIndex &index,
                                                               const QEvent *event) const;
@@ -367,6 +368,7 @@ public:
     QBasicTimer pressClosedEditorWatcher;
     QPersistentModelIndex lastEditedIndex;
     bool pressClosedEditor;
+    bool waitForIMCommit;
 
     QPersistentModelIndex enteredIndex;
     QPersistentModelIndex pressedIndex;