From 8ea3300a0862320259614dbb7387b2353a04e7e1 Mon Sep 17 00:00:00 2001
From: Vova Mshanetskiy <vovams163@gmail.com>
Date: Wed, 8 May 2019 13:56:29 +0300
Subject: QAndroidInputContext: Fix getTextBefore/AfterCursor() in mid. of
 preedit

getTextBeforeCursor() and getTextAfterCursor() were not properly
handling the case when the cursor is in the middle of preedit string
(just as TODO comments inside these functions were saying). This was
causing problems with Gboard when the user focuses a text editor by
tapping in the middle of a word.

Fixes: QTBUG-58063
Change-Id: I4a580a74d79965816557bfb342337975348d1c45
Reviewed-by: Andy Shaw <andy.shaw@qt.io>
---
 .../platforms/android/qandroidinputcontext.cpp     | 77 +++++++++++++---------
 1 file changed, 47 insertions(+), 30 deletions(-)

diff --git a/src/plugins/platforms/android/qandroidinputcontext.cpp b/src/plugins/platforms/android/qandroidinputcontext.cpp
index 064bfbbce3..db40c30d7d 100644
--- a/src/plugins/platforms/android/qandroidinputcontext.cpp
+++ b/src/plugins/platforms/android/qandroidinputcontext.cpp
@@ -1129,46 +1129,63 @@ QString QAndroidInputContext::getSelectedText(jint /*flags*/)
 
 QString QAndroidInputContext::getTextAfterCursor(jint length, jint /*flags*/)
 {
-    //### the preedit text could theoretically be after the cursor
-    QVariant textAfter = QInputMethod::queryFocusObject(Qt::ImTextAfterCursor, QVariant(length));
-    if (textAfter.isValid()) {
-        return textAfter.toString().left(length);
-    }
-
-    //compatibility code for old controls that do not implement the new API
-    QSharedPointer<QInputMethodQueryEvent> query = focusObjectInputMethodQuery();
-    if (query.isNull())
+    if (length <= 0)
         return QString();
 
-    QString text = query->value(Qt::ImSurroundingText).toString();
-    if (!text.length())
-        return text;
+    QString text;
+
+    QVariant reportedTextAfter = QInputMethod::queryFocusObject(Qt::ImTextAfterCursor, length);
+    if (reportedTextAfter.isValid()) {
+        text = reportedTextAfter.toString();
+    } else {
+        // Compatibility code for old controls that do not implement the new API
+        QSharedPointer<QInputMethodQueryEvent> query =
+                focusObjectInputMethodQuery(Qt::ImCursorPosition | Qt::ImSurroundingText);
+        if (query) {
+            const int cursorPos = query->value(Qt::ImCursorPosition).toInt();
+            text = query->value(Qt::ImSurroundingText).toString().mid(cursorPos);
+        }
+    }
+
+    // Controls do not report preedit text, so we have to add it
+    if (!m_composingText.isEmpty()) {
+        const int cursorPosInsidePreedit = m_composingCursor - m_composingTextStart;
+        text = m_composingText.midRef(cursorPosInsidePreedit) + text;
+    }
 
-    int cursorPos = query->value(Qt::ImCursorPosition).toInt();
-    return text.mid(cursorPos, length);
+    text.truncate(length);
+    return text;
 }
 
 QString QAndroidInputContext::getTextBeforeCursor(jint length, jint /*flags*/)
 {
-    QVariant textBefore = QInputMethod::queryFocusObject(Qt::ImTextBeforeCursor, QVariant(length));
-    if (textBefore.isValid())
-        return textBefore.toString().rightRef(length) + m_composingText;
-
-    //compatibility code for old controls that do not implement the new API
-    QSharedPointer<QInputMethodQueryEvent> query = focusObjectInputMethodQuery();
-    if (query.isNull())
+    if (length <= 0)
         return QString();
 
-    int cursorPos = query->value(Qt::ImCursorPosition).toInt();
-    QString text = query->value(Qt::ImSurroundingText).toString();
-    if (!text.length())
-        return text;
+    QString text;
 
-    //### the preedit text does not need to be immediately before the cursor
-    if (cursorPos <= length)
-        return text.leftRef(cursorPos) + m_composingText;
-    else
-        return text.midRef(cursorPos - length, length) + m_composingText;
+    QVariant reportedTextBefore = QInputMethod::queryFocusObject(Qt::ImTextBeforeCursor, length);
+    if (reportedTextBefore.isValid()) {
+        text = reportedTextBefore.toString();
+    } else {
+        // Compatibility code for old controls that do not implement the new API
+        QSharedPointer<QInputMethodQueryEvent> query =
+                focusObjectInputMethodQuery(Qt::ImCursorPosition | Qt::ImSurroundingText);
+        if (query) {
+            const int cursorPos = query->value(Qt::ImCursorPosition).toInt();
+            text = query->value(Qt::ImSurroundingText).toString().left(cursorPos);
+        }
+    }
+
+    // Controls do not report preedit text, so we have to add it
+    if (!m_composingText.isEmpty()) {
+        const int cursorPosInsidePreedit = m_composingCursor - m_composingTextStart;
+        text += m_composingText.leftRef(cursorPosInsidePreedit);
+    }
+
+    if (text.length() > length)
+        text = text.right(length);
+    return text;
 }
 
 /*
-- 
cgit v1.2.3