Android: input method fixes for SwiftEdit keyboard

* Report correct pre-edit information when calling updateSelection()
  on endBatchEdit()
* Fix getExtractedText() to report the correct offset and cursor position,
* Fix setSelection() to use the correct cursor position.

Task-number: QTBUG-35689

Change-Id: I7e8427d0f5a18abf18ba2faf9d510756ddf6044b
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

src/plugins/platforms/android/qandroidinputcontext.cpp

@@ -150,12 +150,13 @@ static jobject getExtractedText(JNIEnv *env, jobject /*thiz*/, int hintMaxChars,
     if (!m_androidInputContext)
         return 0;
 
-#ifdef QT_DEBUG_ANDROID_IM_PROTOCOL
-    qDebug() << "@@@ GETEX";
-#endif
     const QAndroidInputContext::ExtractedText &extractedText =
             m_androidInputContext->getExtractedText(hintMaxChars, hintMaxLines, flags);
 
+#ifdef QT_DEBUG_ANDROID_IM_PROTOCOL
+    qDebug() << "@@@ GETEX" << hintMaxChars << hintMaxLines << QString::fromLatin1("0x") + QString::number(flags,16) << extractedText.text << "partOff:" << extractedText.partialStartOffset << extractedText.partialEndOffset << "sel:" << extractedText.selectionStart << extractedText.selectionEnd << "offset:" << extractedText.startOffset;
+#endif
+
     jobject object = env->NewObject(m_extractedTextClass, m_classConstructorMethodID);
     env->SetIntField(object, m_partialStartOffsetFieldID, extractedText.partialStartOffset);
     env->SetIntField(object, m_partialEndOffsetFieldID, extractedText.partialEndOffset);
@@ -451,7 +452,10 @@ void QAndroidInputContext::updateCursorPosition()
         // make sure it also works with editors that have not been updated to the new API
         QVariant absolutePos = query->value(Qt::ImAbsolutePosition);
         const int cursorPos = absolutePos.isValid() ? absolutePos.toInt() : query->value(Qt::ImCursorPosition).toInt();
-        QtAndroidInput::updateSelection(cursorPos, cursorPos, -1, -1); //selection empty and no pre-edit text
+        const int composeLength = m_composingText.length();
+        const int composeStart = composeLength ? cursorPos : -1;
+        QtAndroidInput::updateSelection(cursorPos + composeLength, cursorPos + composeLength, //empty selection
+                                        composeStart, composeStart + composeLength); // pre-edit text
     }
 }
 
@@ -603,19 +607,39 @@ jint QAndroidInputContext::getCursorCapsMode(jint /*reqModes*/)
 
 const QAndroidInputContext::ExtractedText &QAndroidInputContext::getExtractedText(jint hintMaxChars, jint /*hintMaxLines*/, jint /*flags*/)
 {
+    // Note to self: "if the GET_EXTRACTED_TEXT_MONITOR flag is set, you should be calling
+    // updateExtractedText(View, int, ExtractedText) whenever you call
+    // updateSelection(View, int, int, int, int)."  QTBUG-37980
+
     QSharedPointer<QInputMethodQueryEvent> query = focusObjectInputMethodQuery();
     if (query.isNull())
         return m_extractedText;
 
-    if (hintMaxChars)
+    int localPos = query->value(Qt::ImCursorPosition).toInt(); //position before pre-edit text relative to the current block
-        m_extractedText.text = query->value(Qt::ImSurroundingText).toString().right(hintMaxChars);
+    QVariant absolutePos = query->value(Qt::ImAbsolutePosition);
+    int blockPos = absolutePos.isValid() ? absolutePos.toInt() - localPos : 0; // position of the start of the current block
+    QString blockText = query->value(Qt::ImSurroundingText).toString() + m_composingText;
+    int composeLength = m_composingText.length();
+
+    int cpos = localPos + composeLength; //actual cursor pos relative to the current block
+
+    int localOffset = 0; // start of extracted text relative to the current block
+    if (hintMaxChars) {
+        if (cpos > hintMaxChars)
+            localOffset = cpos - hintMaxChars;
+        m_extractedText.text = blockText.mid(localOffset, hintMaxChars);
+    }
+
+    m_extractedText.startOffset = blockPos + localOffset; // "The offset in the overall text at which the extracted text starts."
 
-    m_extractedText.startOffset = query->value(Qt::ImCursorPosition).toInt();
     const QString &selection = query->value(Qt::ImCurrentSelection).toString();
     const int selLen = selection.length();
     if (selLen) {
-        m_extractedText.selectionStart = query->value(Qt::ImAnchorPosition).toInt();
+        m_extractedText.selectionStart = query->value(Qt::ImAnchorPosition).toInt() - localOffset;
-        m_extractedText.selectionEnd = m_extractedText.startOffset;
+        m_extractedText.selectionEnd = m_extractedText.selectionStart + selLen;
+    } else {
+        m_extractedText.selectionStart = cpos - localOffset;
+        m_extractedText.selectionEnd = cpos - localOffset;
     }
 
     return m_extractedText;
@@ -757,9 +781,17 @@ jboolean QAndroidInputContext::setComposingRegion(jint start, jint end)
 
 jboolean QAndroidInputContext::setSelection(jint start, jint end)
 {
+    QSharedPointer<QInputMethodQueryEvent> query = focusObjectInputMethodQuery();
+    if (query.isNull())
+        return JNI_FALSE;
+
+    int localPos = query->value(Qt::ImCursorPosition).toInt();
+    QVariant absolutePos = query->value(Qt::ImAbsolutePosition);
+    int blockPosition = absolutePos.isValid() ? absolutePos.toInt() - localPos : 0;
+
     QList<QInputMethodEvent::Attribute> attributes;
     attributes.append(QInputMethodEvent::Attribute(QInputMethodEvent::Selection,
-                                                   start,
+                                                   start - blockPosition,
                                                    end - start,
                                                    QVariant()));