resolved illegal threading issue; close #32

dialogs/geo_agent_dialog_base.ui

@@ -18,7 +18,7 @@
     <item row="0" column="0">
      <widget class="QTabWidget" name="tabWidget">
       <property name="currentIndex">
-       <number>1</number>
+       <number>0</number>
       </property>
       <widget class="QWidget" name="tab">
        <attribute name="title">
@@ -29,23 +29,6 @@
          <layout class="QVBoxLayout" name="verticalLayout">
           <item>
            <layout class="QHBoxLayout" name="layout_custom">
-            <!-- <item>
-             <widget class="QTextEdit" name="llm_response_edit">
-              <property name="sizePolicy">
-               <sizepolicy hsizetype="Ignored" vsizetype="Ignored">
-                <horstretch>0</horstretch>
-                <verstretch>0</verstretch>
-               </sizepolicy>
-              </property>
-              <property name="html">
-               <string>&lt;!DOCTYPE HTML PUBLIC &quot;-//W3C//DTD HTML 4.0//EN&quot; &quot;http://www.w3.org/TR/REC-html40/strict.dtd&quot;&gt;
-&lt;html&gt;&lt;head&gt;&lt;meta name=&quot;qrichtext&quot; content=&quot;1&quot; /&gt;&lt;style type=&quot;text/css&quot;&gt;
-p, li { white-space: pre-wrap; }
-&lt;/style&gt;&lt;/head&gt;&lt;body style=&quot; font-family:'MS Shell Dlg 2'; font-size:7.875pt; font-weight:400; font-style:normal;&quot;&gt;
-&lt;p style=&quot;-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; font-size:7.8pt;&quot;&gt;&lt;br /&gt;&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
-              </property>
-             </widget>
-            </item> -->
             <item>
              <widget class="QTextBrowser" name="llm_response">
               <property name="sizePolicy">
@@ -290,7 +273,7 @@ p, li { white-space: pre-wrap; }
              <item>
               <widget class="QLabel" name="label_5">
                <property name="text">
-               <string>Temperature:</string>
+                <string>Temperature:</string>
                </property>
               </widget>
              </item>

geo_agent.py

@@ -27,10 +27,6 @@
     QCoreApplication,
     Qt,
     QThread,
-    QMetaObject,
-    QTimer,
-    Q_ARG,
-    QEventLoop,
 )
 from qgis.PyQt.QtGui import QIcon
 from qgis.PyQt.QtWidgets import QAction, QMessageBox, QSizePolicy, QProgressDialog
@@ -53,17 +49,9 @@
 from .llm.worker import LLMWorker
 from .prompts.system import GENERAL_SYSTEM_PROMPT
 from .utils.canvas_refresh import (
-    RefreshDispatcher,
+    set_main_runner,
     set_qgis_interface,
-    set_refresh_callback,
-)
-from .utils.layer_operations import (
-    LayerRemovalDispatcher,
-    set_layer_removal_callback,
-)
-from .utils.project_loader import (
-    ProjectLoadDispatcher,
-    set_project_load_callback,
+    MainThreadRunner
 )
 from .utils.markdown_converter import markdown_to_html
 from typing import Optional
@@ -91,15 +79,9 @@ def __init__(self, iface):
         """
         # Save reference to the QGIS interface
         self.iface = iface
-
-        # Dispatcher for main-thread canvas refresh
-        self._refresh_dispatcher = RefreshDispatcher(self.iface)
-
-        # Dispatcher for main-thread project loading
-        self._project_load_dispatcher = ProjectLoadDispatcher(self.iface)
-
-        # Dispatcher for main-thread layer removal
-        self._layer_removal_dispatcher = LayerRemovalDispatcher(self.iface)
+
+        # main runner - will be initialized in initGui() on the main thread
+        self.main_runner = None
 
         # initialize plugin directory
         self.plugin_dir = os.path.dirname(__file__)
@@ -259,94 +241,6 @@ def _on_qgis_message(self, message, tag, level):
         except Exception:
             pass
 
-    def _refresh_callback(self):
-        """Thread-safe refresh callback invoked by tools. Queues a dispatcher slot on the main thread."""
-        try:
-            ok = QMetaObject.invokeMethod(
-                self._refresh_dispatcher,
-                "doRefresh",
-                Qt.QueuedConnection,
-            )
-            if not ok:
-                QgsMessageLog.logMessage(
-                    "QMetaObject.invokeMethod('doRefresh') returned False; "
-                    "falling back to QTimer.singleShot.",
-                    "GeoAgent",
-                    level=Qgis.Warning,
-                )
-                QTimer.singleShot(0, self._refresh_dispatcher.doRefresh)
-        except Exception as e:
-            self._log_error("refresh_callback", e)
-
-    def _project_load_callback(self, path):
-        """Thread-safe project load callback using signals."""
-        try:
-
-            def on_result_ready():
-                loop.quit()
-
-            # connect signal to quit when result is ready
-            self._project_load_dispatcher.result_ready.connect(on_result_ready)
-
-            # queue the load operation on the main thread
-            QMetaObject.invokeMethod(
-                self._project_load_dispatcher,
-                "doLoadProject",
-                Qt.QueuedConnection,
-                Q_ARG(str, path),
-            )
-            # wait for the dispatcher to signal completion
-            loop = QEventLoop()
-
-            # max wait 30 seconds timeout
-            QTimer.singleShot(30000, loop.quit)
-            loop.exec_()
-
-            # disconnect signal to avoid memory leaks
-            self._project_load_dispatcher.result_ready.disconnect(on_result_ready)
-
-            # return the result that was set by the dispatcher
-            return self._project_load_dispatcher.result
-        except Exception as e:
-            error_msg = f"_project_load_callback error: {e}"
-            QgsMessageLog.logMessage(error_msg, "GeoAgent", level=Qgis.Warning)
-            return {"success": False, "error": error_msg}
-
-    def _layer_removal_callback(self, layer_id, layer_name):
-        """Thread-safe layer removal callback using signals."""
-        try:
-
-            def on_result_ready():
-                loop.quit()
-
-            # connect signal to quit when result is ready
-            self._layer_removal_dispatcher.result_ready.connect(on_result_ready)
-
-            # queue the removal operation on the main thread
-            QMetaObject.invokeMethod(
-                self._layer_removal_dispatcher,
-                "doRemoveLayer",
-                Qt.QueuedConnection,
-                Q_ARG(str, layer_id),
-                Q_ARG(str, layer_name),
-            )
-            # wait for the dispatcher to signal completion
-            loop = QEventLoop()
-
-            # max wait 10 seconds timeout
-            QTimer.singleShot(10000, loop.quit)
-            loop.exec_()
-
-            # disconnect signal to avoid memory leaks
-            self._layer_removal_dispatcher.result_ready.disconnect(on_result_ready)
-
-            # return the result that was set by the dispatcher
-            return self._layer_removal_dispatcher.result
-        except Exception as e:
-            error_msg = f"_layer_removal_callback error: {e}"
-            QgsMessageLog.logMessage(error_msg, "GeoAgent", level=Qgis.Warning)
-            return {"success": False, "error": error_msg}
-
     def _ensure_dependencies_installed(self):
         """Ensure required Python packages are installed via pyproject.toml."""
         pkg_to_import = {
@@ -589,6 +483,10 @@ def add_action(
     def initGui(self):
         """Create the menu entries and toolbar icons inside the QGIS GUI."""
 
+        # Initialize MainThreadRunner on the main Qt thread
+        # Qt objects should be created on the thread where they will live
+        self.main_runner = MainThreadRunner()
+
         icon_path = os.path.join(self.plugin_dir, "icons", "icon.png")
         self.add_action(
             icon_path,
@@ -622,21 +520,24 @@ def run(self):
         # Ensure dependencies before loading graph or message classes
         self._ensure_dependencies_installed()
 
-        # Initialize QGIS interface for tools
-        try:
-            # Register QGIS interface for tools module
-            set_qgis_interface(self.iface)
-
-            # Register thread-safe refresh callback method
-            set_refresh_callback(self._refresh_callback)
+        # Ensure MainThreadRunner is initialized (should be done in initGui())
+        # MainThreadRunner is a QObject that must be created on the main Qt thread
+        # If it's None here, initGui() was not called properly by QGIS
+        if self.main_runner is None:
+            # This should not happen in normal QGIS plugin lifecycle
+            # Log a warning as this indicates a problem with plugin initialization
+            QgsMessageLog.logMessage(
+                'MainThreadRunner was not initialized in initGui(). '
+                'This may indicate a problem with plugin initialization.',
+                'GeoAgent',
+                level=Qgis.Warning
+            )
+            # Create it here as a fallback, though this is not ideal for threading
+            self.main_runner = MainThreadRunner()
 
-            # Register thread-safe project load callback method
-            set_project_load_callback(self._project_load_callback)
-
-            # Register thread-safe layer removal callback method
-            set_layer_removal_callback(self._layer_removal_callback)
-        except Exception as e:
-            self._log_error("initialize_tools_interface", e)
+        # Set global main runner for canvas refresh utility
+        set_main_runner(self.main_runner)
+        set_qgis_interface(self.iface)
 
         # Create the dialog with elements (after translation) and keep reference
         # Only create GUI ONCE in callback, so that it will only load when the plugin is started
@@ -824,9 +725,7 @@ def send_message(self):
             # self.dlg.send_chat.setText("Processing...")
 
             # Create and start worker thread for non-blocking inference
-            self._worker_thread = LLMWorker(
-                self.app, self.thread_id, msgs, invoke_app_async
-            )
+            self._worker_thread = LLMWorker(self.app, self.thread_id, msgs, invoke_app_async)
             self._worker_thread.result_ready.connect(self._on_invoke_result)
             self._worker_thread.error.connect(self._on_invoke_error)
             self._worker_thread.finished.connect(self._on_invoke_finished)

metadata.txt

@@ -6,7 +6,7 @@
 name=GeoAgent
 qgisMinimumVersion=3.2
 description=Plugin for QGIS interaction using LLM. Enables geospatial analysis and data processing through natural language commands.
-version=0.1.1
+version=0.2.0
 author=Tek Kshetri, Rabin Ojha
 email=iamtekson@gmail.com, rabenojha@gmail.com
 
@@ -16,6 +16,10 @@ license=MIT
 tracker=https://github.com/iamtekson/GeoAgent/issues
 repository=https://github.com/iamtekson/GeoAgent
 changelog=
+    v0.2.0
+        - Improved UI help messages and user notifications.
+        - Enhanced error handling for project operations.
+        - Resolved issue with illegal threading (QGIS crash) during project load/save/create/delete operations.
     v0.1.1
         - Fixed dependency installation issues on some systems.
     v0.1

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "geo-agent"
-version = "0.1.1"
+version = "0.2.0"
 description = "Plugin for QGIS interaction using LLM. Enables geospatial analysis and data processing through natural language commands."
 readme = "README.md"
 requires-python = ">=3.13"

tools/__init__.py

@@ -15,12 +15,13 @@
     select_by_geometry,
 )
 
+# for easy importing geoprocessing tools later
 from .geoprocessing import (
     execute_processing,
     list_processing_algorithms,
     get_algorithm_parameters,
     find_processing_algorithm,
-)
+    )
 
 # Aggregate all tools for easy import
 TOOLS = {

tools/filters.py

@@ -1,4 +1,4 @@
-from ..utils.canvas_refresh import refresh_map_canvas
+from ..utils.canvas_refresh import get_qgis_interface, qgis_main_thread
 from typing import Optional
 from qgis.core import (
     QgsProject,
@@ -8,9 +8,12 @@
 )
 
 from langchain_core.tools import tool
+from ..logger.processing_logger import get_processing_logger
 
+_logger = get_processing_logger()
 
 @tool
+@qgis_main_thread
 def select_by_attribute(
     layer_name: str,
     field_name: str,
@@ -34,6 +37,7 @@ def select_by_attribute(
         - select_by_attribute('roads', 'type', '=', 'highway')
         - select_by_attribute('names', 'name', 'starts_with', 'New')
     """
+    _logger.info(f"Selecting by attribute on layer '{layer_name}', field '{field_name}', operator '{operator}', value '{value}'")
     try:
         project = QgsProject.instance()
 
@@ -54,6 +58,7 @@ def select_by_attribute(
         field_index = layer.fields().indexFromName(field_name)
         if field_index == -1:
             available_fields = [f.name() for f in layer.fields()]
+            _logger.error(f"Field '{field_name}' not found in layer '{layer_name}'. Available fields: {', '.join(available_fields)}")
             return f"**Error:** Field **{field_name}** not found. Available fields: {', '.join(available_fields)}"
 
         # Build expression based on operator
@@ -98,16 +103,19 @@ def select_by_attribute(
 
         layer.selectByIds(selected_ids)
 
-        # Highlight on map
-        refresh_map_canvas()
+        iface = get_qgis_interface()
+        iface.mapCanvas().refresh()
 
+        _logger.info(f"Selected {len(selected_ids)} features in layer '{layer_name}' using attribute filter.")
         return f"**Success:** Selected {len(selected_ids)} features in **{layer_name}** where **{field_name}** {operator} '{value}'."
 
     except Exception as e:
+        _logger.error(f"Error selecting by attribute: {str(e)}", exc_info=True)
         return f"**Error:** selecting by attribute: {str(e)}"
 
 
 @tool
+@qgis_main_thread
 def select_by_geometry(
     layer_name: str,
     geometry_filter: str,
@@ -129,6 +137,7 @@ def select_by_geometry(
         - select_by_geometry('roads', 'intersecting', 'study_area')
         - select_by_geometry('points', 'inside', 'boundary')
     """
+    _logger.info(f"Selecting by geometry on layer '{layer_name}' using filter '{geometry_filter}' with reference layer '{reference_layer_name}'")
     try:
         project = QgsProject.instance()
 
@@ -223,17 +232,20 @@ def select_by_geometry(
                     selected_ids.append(feature.id())
 
         else:
+            _logger.error(f"Unknown geometry filter '{geometry_filter}'")
             return f"**Error:** Unknown geometry filter **{geometry_filter}**. Use: 'largest', 'smallest', 'intersecting', 'inside', 'touching'."
 
         # Apply selection
         layer.selectByIds(selected_ids)
 
-        # Highlight on map
-        refresh_map_canvas()
+        iface = get_qgis_interface()
+        iface.mapCanvas().refresh()
 
+        _logger.info(f"Selected {len(selected_ids)} features in layer '{layer_name}' using geometry filter.")
         return f"**Success:** Selected {len(selected_ids)} features in **{layer_name}** using **{geometry_filter}** filter."
 
     except Exception as e:
+        _logger.error(f"Error selecting by geometry: {str(e)}", exc_info=True)
         return f"**Error:** selecting by geometry: {str(e)}"
 
 

tools/geoprocessing.py

@@ -15,7 +15,7 @@
 from ..config.constants import RASTER_EXTENSIONS
 
 
-# TODO: test this function for both raster and vector outputs
+
 @tool
 def execute_processing(algorithm: str, parameters: dict, **kwargs) -> dict:
     """