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>

1 files changed, 75 insertions, 0 deletions

diff --git a/tests/auto/widgets/itemviews/qabstractitemview/tst_qabstractitemview.cpp b/tests/auto/widgets/itemviews/qabstractitemview/tst_qabstractitemview.cpp
index 2ac1e927d9..d904f97d82 100644
--- a/tests/auto/widgets/itemviews/qabstractitemview/tst_qabstractitemview.cpp
+++ b/tests/auto/widgets/itemviews/qabstractitemview/tst_qabstractitemview.cpp
@@ -164,6 +164,8 @@ private slots:
     void mouseSelection_data();
     void mouseSelection();
     void scrollerSmoothScroll();
+    void inputMethodOpensEditor_data();
+    void inputMethodOpensEditor();
 
 private:
     static QAbstractItemView *viewFromString(const QByteArray &viewType, QWidget *parent = nullptr)
@@ -3102,5 +3104,78 @@ void tst_QAbstractItemView::scrollerSmoothScroll()
     QTest::mouseRelease(view.viewport(), Qt::LeftButton, Qt::NoModifier, dragPosition);
 }
 
+/*!
+    Verify that starting the editing of an item with a key press while a composing
+    input method is active doesn't break the input method. See QTBUG-54848.
+*/
+void tst_QAbstractItemView::inputMethodOpensEditor_data()
+{
+    QTest::addColumn<QPoint>("editItem");
+    QTest::addColumn<QString>("preedit");
+    QTest::addColumn<QString>("commit");
+
+    QTest::addRow("IM accepted") << QPoint(1, 1) << "chang" << QString("长");
+    QTest::addRow("IM cancelled") << QPoint(25, 25) << "chang" << QString();
+}
+
+void tst_QAbstractItemView::inputMethodOpensEditor()
+{
+    QTableWidget tableWidget(50, 50);
+    tableWidget.setEditTriggers(QAbstractItemView::AnyKeyPressed);
+    for (int r = 0; r < 50; ++r) {
+        for (int c = 0; c < 50; ++c )
+            tableWidget.setItem(r, c, new QTableWidgetItem(QString("Item %1:%2").arg(r).arg(c)));
+    }
+
+    tableWidget.show();
+    QVERIFY(QTest::qWaitForWindowActive(&tableWidget));
+
+    const auto sendInputMethodEvent = [](const QString &preeditText, const QString &commitString = {}){
+        QInputMethodEvent imEvent(preeditText, {});
+        imEvent.setCommitString(commitString);
+        QApplication::sendEvent(QApplication::focusWidget(), &imEvent);
+    };
+
+    QCOMPARE(QApplication::focusWidget(), &tableWidget);
+
+    QFETCH(QPoint, editItem);
+    QFETCH(QString, preedit);
+    QFETCH(QString, commit);
+
+    tableWidget.setCurrentCell(editItem.y(), editItem.x());
+    const QString orgText = tableWidget.currentItem()->text();
+    const QModelIndex currentIndex = tableWidget.currentIndex();
+    QCOMPARE(tableWidget.inputMethodQuery(Qt::ImCursorRectangle), tableWidget.visualRect(currentIndex));
+
+    // simulate the start of input via a composing input method
+    sendInputMethodEvent(preedit.left(1));
+    QCOMPARE(tableWidget.state(), QAbstractItemView::EditingState);
+    QLineEdit *editor = tableWidget.findChild<QLineEdit*>();
+    QVERIFY(editor);
+    QCOMPARE(editor->text(), QString());
+    // the focus must remain with the tableWidget, as otherwise the compositing is interrupted
+    QCOMPARE(QApplication::focusWidget(), &tableWidget);
+    // the item view delegates input method queries to the editor
+    const QRect cursorRect = tableWidget.inputMethodQuery(Qt::ImCursorRectangle).toRect();
+    QVERIFY(cursorRect.isValid());
+    QVERIFY(tableWidget.visualRect(currentIndex).intersects(cursorRect));
+
+    // finish preediting, then commit or cancel the input
+    sendInputMethodEvent(preedit);
+    sendInputMethodEvent(QString(), commit);
+    // editing continues, the editor now has focus
+    QCOMPARE(tableWidget.state(), QAbstractItemView::EditingState);
+    QVERIFY(editor->hasFocus());
+    // finish editing
+    QTest::keyClick(editor, Qt::Key_Return);
+    if (commit.isEmpty()) {
+        // if composition was cancelled, then the item's value is unchanged
+        QCOMPARE(tableWidget.currentItem()->text(), orgText);
+    } else {
+        // otherwise, the item's value is now the commit string
+        QTRY_COMPARE(tableWidget.currentItem()->text(), commit);
+    }
+}
+
 QTEST_MAIN(tst_QAbstractItemView)
 #include "tst_qabstractitemview.moc"