qquicktextinput: Fix validation for IM event

If validation did not pass after text pre-editing is finished, it need
to be roll back to state before pre-editing started.

Before this change, if validation did not pass, text was always rolled
back to previous state. In pre-editing text case, it means back to the
state in which part of the text was removed (and later changed to
pre-edited text). It may cause a situation of removing part of the text
that was already validated

Fixes: QTBUG-90239
Change-Id: I3ec39e0f6b8a93d4e6fd190af30d4c80a0e495eb
Reviewed-by: Rami Potinkara <rami.potinkara@qt.io>
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>
(cherry picked from commit b1ae151acc80254ab0ec2937c55b99223205875c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 19 insertions, 1 deletions

diff --git a/src/quick/items/qquicktextinput.cpp b/src/quick/items/qquicktextinput.cpp
index b1945e9eb8..419ac4a2bb 100644
--- a/src/quick/items/qquicktextinput.cpp
+++ b/src/quick/items/qquicktextinput.cpp
@@ -3471,8 +3471,12 @@ void QQuickTextInputPrivate::processInputMethodEvent(QInputMethodEvent *event)
     }
     QString oldPreeditString = m_textLayout.preeditAreaText();
     m_textLayout.setPreeditArea(m_cursor, event->preeditString());
-    if (oldPreeditString != m_textLayout.preeditAreaText())
+    if (oldPreeditString != m_textLayout.preeditAreaText()) {
         emit q->preeditTextChanged();
+        if (!event->preeditString().isEmpty() && m_undoPreeditState == -1)
+            // Pre-edit text started. Remember state for undo purpose.
+            m_undoPreeditState = priorState;
+    }
     const int oldPreeditCursor = m_preeditCursor;
     m_preeditCursor = event->preeditString().length();
     hasImState = !event->preeditString().isEmpty();
@@ -3515,6 +3519,11 @@ void QQuickTextInputPrivate::processInputMethodEvent(QInputMethodEvent *event)
         q->updateInputMethod(Qt::ImCursorRectangle | Qt::ImAnchorRectangle
                             | Qt::ImCurrentSelection);
     }
+
+    // Empty pre-edit text handled. Clean m_undoPreeditState
+    if (event->preeditString().isEmpty())
+        m_undoPreeditState = -1;
+
 }
 #endif // im
 
@@ -3591,6 +3600,12 @@ bool QQuickTextInputPrivate::finishChange(int validateFromState, bool update, bo
         if (m_maskData)
             checkIsValid();
 
+#if QT_CONFIG(im)
+        // If we were during pre-edit, validateFromState should point to the state before pre-edit
+        // has been started. Choose the correct oldest remembered state
+        if (m_undoPreeditState >= 0 && (m_undoPreeditState < validateFromState || validateFromState < 0))
+                validateFromState = m_undoPreeditState;
+#endif
         if (validateFromState >= 0 && wasValidInput && !m_validInput) {
             if (m_transactions.count())
                 return false;
@@ -3663,6 +3678,9 @@ void QQuickTextInputPrivate::internalSetText(const QString &txt, int pos, bool e
     }
     m_history.clear();
     m_undoState = 0;
+#if QT_CONFIG(im)
+    m_undoPreeditState = -1;
+#endif
     m_cursor = (pos < 0 || pos > m_text.length()) ? m_text.length() : pos;
     m_textDirty = (oldText != m_text);