Fix inability to scroll content while AI is generating a response

Caused by b63fb68, we should not update the selection if it is not at the end

Author: timxx

qgitc/aichatbot.py

@@ -87,14 +87,15 @@ def appendResponse(self, response: AiResponse):
         cursor = self.textCursor()
         selectionStart = cursor.selectionStart()
         selectionEnd = cursor.selectionEnd()
+        docLength = self.document().characterCount() - 1
         cursor.movePosition(QTextCursor.End)
 
         if not response.is_delta or response.first_delta:
             self._insertRoleBlock(cursor, response.role)
             cursor.insertBlock()
         cursor.insertText(response.message)
 
-        if selectionStart != selectionEnd:
+        if selectionStart != selectionEnd and selectionEnd == docLength:
             newCursor = self.textCursor()
             newCursor.setPosition(selectionStart)
             newCursor.setPosition(selectionEnd, QTextCursor.KeepAnchor)
@@ -104,14 +105,15 @@ def appendServiceUnavailable(self):
         cursor = self.textCursor()
         selectionStart = cursor.selectionStart()
         selectionEnd = cursor.selectionEnd()
+        docLength = self.document().characterCount() - 1
         cursor.movePosition(QTextCursor.End)
 
         self._insertRoleBlock(cursor, AiRole.System)
 
         cursor.insertBlock()
         cursor.insertText(self.tr("Service Unavailable"))
 
-        if selectionStart != selectionEnd:
+        if selectionStart != selectionEnd and selectionEnd == docLength:
             newCursor = self.textCursor()
             newCursor.setPosition(selectionStart)
             newCursor.setPosition(selectionEnd, QTextCursor.KeepAnchor)

tests/test_aichatbot.py

@@ -0,0 +1,112 @@
+# -*- coding: utf-8 -*-
+from PySide6.QtGui import QTextCursor
+from PySide6.QtTest import QTest
+
+from qgitc.aichatbot import AiChatbot
+from qgitc.llm import AiResponse, AiRole
+from tests.base import TestBase
+
+
+class TestAiChatbot(TestBase):
+    def setUp(self):
+        super().setUp()
+        self.chatbot = AiChatbot()
+        self.chatbot.show()
+        QTest.qWaitForWindowExposed(self.chatbot)
+
+    def tearDown(self):
+        self.chatbot.close()
+        super().tearDown()
+
+    def doCreateRepo(self):
+        pass
+
+    def testAppendResponse_SelectionAtEnd_Preserved(self):
+        """Test that selection at document end IS preserved (prevents expansion)"""
+        # Add initial content
+        response1 = AiResponse(role=AiRole.Assistant, message="First message")
+        response1.is_delta = False
+        self.chatbot.appendResponse(response1)
+
+        # Select to the end of document
+        cursor = self.chatbot.textCursor()
+        cursor.movePosition(QTextCursor.Start)
+        cursor.movePosition(QTextCursor.NextCharacter,
+                            QTextCursor.MoveAnchor, 5)
+        cursor.movePosition(QTextCursor.End, QTextCursor.KeepAnchor)
+        self.chatbot.setTextCursor(cursor)
+
+        selectionStart = cursor.selectionStart()
+        selectionEnd = cursor.selectionEnd()
+        selectedText = cursor.selectedText()
+
+        # Verify we ARE at the document end
+        docLength = self.chatbot.document().characterCount() - 1
+        self.assertEqual(selectionEnd, docLength)
+
+        # Append new content
+        response2 = AiResponse(role=AiRole.User, message="Second message")
+        response2.is_delta = False
+        self.chatbot.appendResponse(response2)
+
+        # Verify selection is preserved (not expanded to include new text)
+        newCursor = self.chatbot.textCursor()
+        self.assertTrue(newCursor.hasSelection())
+        self.assertEqual(selectionStart, newCursor.selectionStart())
+        self.assertEqual(selectionEnd, newCursor.selectionEnd())
+        self.assertEqual(selectedText, newCursor.selectedText())
+
+    def testAppendResponse_DeltaMessages(self):
+        """Test appending delta messages (streaming responses)"""
+        # First delta
+        response1 = AiResponse(role=AiRole.Assistant, message="Hello ")
+        response1.is_delta = True
+        response1.first_delta = True
+        self.chatbot.appendResponse(response1)
+
+        cursor = self.chatbot.textCursor()
+        cursor.movePosition(QTextCursor.End)
+        endPos1 = cursor.position()
+
+        # Subsequent deltas
+        response2 = AiResponse(role=AiRole.Assistant, message="World")
+        response2.is_delta = True
+        response2.first_delta = False
+        self.chatbot.appendResponse(response2)
+
+        # Verify content is appended
+        cursor = self.chatbot.textCursor()
+        cursor.movePosition(QTextCursor.End)
+        endPos2 = cursor.position()
+        self.assertGreater(endPos2, endPos1)
+
+        # Verify text content
+        text = self.chatbot.toPlainText()
+        self.assertIn("Hello World", text)
+
+    def testAppendResponse_NoSelectionNoCursorChange(self):
+        """Test that when there's no selection and cursor is not at end, cursor stays in place"""
+        # Add initial content
+        response1 = AiResponse(role=AiRole.Assistant, message="First message")
+        response1.is_delta = False
+        self.chatbot.appendResponse(response1)
+
+        # Position cursor in the middle (no selection)
+        cursor = self.chatbot.textCursor()
+        cursor.movePosition(QTextCursor.Start)
+        cursor.movePosition(QTextCursor.NextCharacter,
+                            QTextCursor.MoveAnchor, 5)
+        self.chatbot.setTextCursor(cursor)
+        cursorPos = cursor.position()
+        self.assertFalse(cursor.hasSelection())
+
+        # Append new content
+        response2 = AiResponse(role=AiRole.User, message="Second message")
+        response2.is_delta = False
+        self.chatbot.appendResponse(response2)
+
+        # Cursor should stay at the same position since there was no selection
+        # and it wasn't at the end
+        actualCursor = self.chatbot.textCursor()
+        self.assertEqual(cursorPos, actualCursor.position())
+        self.assertFalse(actualCursor.hasSelection())