Add offline converter cancel logic

Author: gounux

libqfieldsync/offline_converter.py

@@ -83,6 +83,9 @@ class OfflineConverter(QObject):
     task_progress_updated = pyqtSignal(int, int)
     total_progress_updated = pyqtSignal(int, int, str)
 
+    # feedback used for basemap generation processing algorithm
+    _feedback = QgsProcessingFeedback()
+
     def __init__(
         self,
         project: QgsProject,
@@ -638,28 +641,32 @@ def _export_basemap_as_mbtiles(
                 layer_tree_model,
             )
 
-        feedback = QgsProcessingFeedback()
         context = QgsProcessingContext()
         context.setProject(cloned_project)
 
         # connect subtask feedback progress signal
-        feedback.progressChanged.connect(self._on_tiles_gen_alg_progress_changed)
+        self._feedback.progressChanged.connect(self._on_tiles_gen_alg_progress_changed)
 
-        results, ok = alg.run(params, context, feedback)
+        try:
+            results, ok = alg.run(params, context, self._feedback)
 
-        if not ok:
-            self.warning.emit(
-                self.tr("Failed to create mbtiles basemap"), feedback.textLog()
-            )
-            return False
+            if not ok:
+                self.warning.emit(
+                    self.tr("Failed to create mbtiles basemap"),
+                    self._feedback.textLog(),
+                )
+                return False
+
+            new_layer = QgsRasterLayer(results["OUTPUT_FILE"], self.tr("Basemap"))
 
-        new_layer = QgsRasterLayer(results["OUTPUT_FILE"], self.tr("Basemap"))
+            self.project_configuration.project.addMapLayer(new_layer, False)
+            layer_tree = QgsProject.instance().layerTreeRoot()
+            layer_tree.insertLayer(len(layer_tree.children()), new_layer)
 
-        self.project_configuration.project.addMapLayer(new_layer, False)
-        layer_tree = QgsProject.instance().layerTreeRoot()
-        layer_tree.insertLayer(len(layer_tree.children()), new_layer)
+            return True
 
-        return True
+        finally:
+            self._feedback.progressChanged.disconnect()
 
     def _on_tiles_gen_alg_progress_changed(self, revision: float) -> None:
         """
@@ -701,6 +708,13 @@ def on_original_project_write(doc):
     def _on_offline_editing_task_progress(self, progress):
         self.task_progress_updated.emit(progress, self.__max_task_progress)
 
+    def cancel(self) -> None:
+        """
+        Cancels the offline export of a QField project.
+        Typically used when the QField export dialog is closed.
+        """
+        self._feedback.cancel()
+
     def convertorProcessingProgress(self):
         """
         Will create a new progress object for processing to get feedback from the basemap