Avoid endless wait cursors

Author: m-kuhn

python/plugins/MetaSearch/dialogs/maindialog.py

@@ -46,6 +46,7 @@
                        QgsCoordinateTransform, QgsGeometry, QgsPointXY,
                        QgsProviderRegistry, QgsSettings)
 from qgis.gui import QgsRubberBand
+from qgis.utils import OverrideCursor
 
 from owslib.csw import CatalogueServiceWeb # spellok
 from owslib.fes import BBox, PropertyIsLike
@@ -281,8 +282,6 @@ def connection_info(self):
         if not self._get_csw():
             return
 
-        QApplication.restoreOverrideCursor()
-
         if self.catalog:  # display service metadata
             self.btnCapabilities.setEnabled(True)
             metadata = render_template('en', self.context,
@@ -490,25 +489,22 @@ def search(self):
         # TODO: allow users to select resources types
         # to find ('service', 'dataset', etc.)
         try:
-            self.catalog.getrecords2(constraints=self.constraints,
-                                     maxrecords=self.maxrecords, esn='full')
+            with OverrideCursor(Qt.WaitCursor):
+                self.catalog.getrecords2(constraints=self.constraints,
+                                         maxrecords=self.maxrecords, esn='full')
         except ExceptionReport as err:
-            QApplication.restoreOverrideCursor()
             QMessageBox.warning(self, self.tr('Search error'),
                                 self.tr('Search error: {0}').format(err))
             return
         except Exception as err:
-            QApplication.restoreOverrideCursor()
             QMessageBox.warning(self, self.tr('Connection error'),
                                 self.tr('Connection error: {0}').format(err))
             return
 
         if self.catalog.results['matches'] == 0:
-            QApplication.restoreOverrideCursor()
             self.lblResults.setText(self.tr('0 results'))
             return
 
-        QApplication.restoreOverrideCursor()
         self.display_results()
 
     def display_results(self):
@@ -675,25 +671,20 @@ def navigate(self):
                 else:
                     return
 
-        QApplication.setOverrideCursor(QCursor(Qt.WaitCursor))
-
         try:
-            self.catalog.getrecords2(constraints=self.constraints,
-                                     maxrecords=self.maxrecords,
-                                     startposition=self.startfrom, esn='full')
+            with OverrideCursor(Qt.WaitCursor):
+                self.catalog.getrecords2(constraints=self.constraints,
+                                         maxrecords=self.maxrecords,
+                                         startposition=self.startfrom, esn='full')
         except ExceptionReport as err:
-            QApplication.restoreOverrideCursor()
             QMessageBox.warning(self, self.tr('Search error'),
                                 self.tr('Search error: {0}').format(err))
             return
         except Exception as err:
-            QApplication.restoreOverrideCursor()
             QMessageBox.warning(self, self.tr('Connection error'),
                                 self.tr('Connection error: {0}').format(err))
             return
 
-        QApplication.restoreOverrideCursor()
-
         self.display_results()
 
     def add_to_ows(self):
@@ -727,8 +718,6 @@ def add_to_ows(self):
             stype = ['ESRI:ArcGIS:FeatureServer', 'afs', 'arcgisfeatureserver']
             data_url = item_data['afs'].split('FeatureServer')[0] + 'FeatureServer'
 
-        QApplication.restoreOverrideCursor()
-
         sname = '%s from MetaSearch' % stype[1]
 
         # store connection
@@ -820,26 +809,22 @@ def show_metadata(self):
         identifier = get_item_data(item, 'identifier')
 
         try:
-            QApplication.setOverrideCursor(QCursor(Qt.WaitCursor))
-            cat = CatalogueServiceWeb(self.catalog_url, timeout=self.timeout, # spellok
-                                      username=self.catalog_username,
-                                      password=self.catalog_password)
-            cat.getrecordbyid(
-                [self.catalog.records[identifier].identifier])
+            with OverrideCursor(Qt.WaitCursor):
+                cat = CatalogueServiceWeb(self.catalog_url, timeout=self.timeout, # spellok
+                                          username=self.catalog_username,
+                                          password=self.catalog_password)
+                cat.getrecordbyid(
+                    [self.catalog.records[identifier].identifier])
         except ExceptionReport as err:
-            QApplication.restoreOverrideCursor()
             QMessageBox.warning(self, self.tr('GetRecords error'),
                                 self.tr('Error getting response: {0}').format(err))
             return
         except KeyError as err:
             QMessageBox.warning(self,
                                 self.tr('Record parsing error'),
                                 self.tr('Unable to locate record identifier'))
-            QApplication.restoreOverrideCursor()
             return
 
-        QApplication.restoreOverrideCursor()
-
         record = cat.records[identifier]
         record.xml_url = cat.request
 
@@ -902,21 +887,20 @@ def _get_csw(self):
         """convenience function to init owslib.csw.CatalogueServiceWeb""" # spellok
 
         # connect to the server
-        try:
-            QApplication.setOverrideCursor(QCursor(Qt.WaitCursor))
-            self.catalog = CatalogueServiceWeb(self.catalog_url, # spellok
-                                               timeout=self.timeout,
-                                               username=self.catalog_username,
-                                               password=self.catalog_password)
-            return True
-        except ExceptionReport as err:
-            msg = self.tr('Error connecting to service: {0}').format(err)
-        except ValueError as err:
-            msg = self.tr('Value Error: {0}').format(err)
-        except Exception as err:
-            msg = self.tr('Unknown Error: {0}').format(err)
+        with OverrideCursor(Qt.WaitCursor):
+            try:
+                self.catalog = CatalogueServiceWeb(self.catalog_url, # spellok
+                                                   timeout=self.timeout,
+                                                   username=self.catalog_username,
+                                                   password=self.catalog_password)
+                return True
+            except ExceptionReport as err:
+                msg = self.tr('Error connecting to service: {0}').format(err)
+            except ValueError as err:
+                msg = self.tr('Value Error: {0}').format(err)
+            except Exception as err:
+                msg = self.tr('Unknown Error: {0}').format(err)
 
-        QApplication.restoreOverrideCursor()
         QMessageBox.warning(self, self.tr('CSW Connection error'), msg)
         return False
 

python/plugins/db_manager/db_manager.py

@@ -32,6 +32,8 @@
 
 from qgis.gui import QgsMessageBar
 from qgis.core import QgsSettings, QgsMapLayer
+from qgis.utils import OverrideCursor
+
 from .info_viewer import InfoViewer
 from .table_viewer import TableViewer
 from .layer_preview import LayerPreview
@@ -72,29 +74,23 @@ def closeEvent(self, e):
         QMainWindow.closeEvent(self, e)
 
     def refreshItem(self, item=None):
-        QApplication.setOverrideCursor(Qt.WaitCursor)
-        try:
-            if item is None:
-                item = self.tree.currentItem()
-            self.tree.refreshItem(item)  # refresh item children in the db tree
-        except BaseError as e:
-            DlgDbError.showError(e, self)
-            return
-        finally:
-            QApplication.restoreOverrideCursor()
+        with OverrideCursor(Qt.WaitCursor):
+            try:
+                if item is None:
+                    item = self.tree.currentItem()
+                self.tree.refreshItem(item)  # refresh item children in the db tree
+            except BaseError as e:
+                DlgDbError.showError(e, self)
 
     def itemChanged(self, item):
-        QApplication.setOverrideCursor(Qt.WaitCursor)
-        try:
-            self.reloadButtons()
-            # clear preview, this will delete the layer in preview tab
-            self.preview.loadPreview(None)
-            self.refreshTabs()
-        except BaseError as e:
-            DlgDbError.showError(e, self)
-            return
-        finally:
-            QApplication.restoreOverrideCursor()
+        with OverrideCursor(Qt.WaitCursor):
+            try:
+                self.reloadButtons()
+                # clear preview, this will delete the layer in preview tab
+                self.preview.loadPreview(None)
+                self.refreshTabs()
+            except BaseError as e:
+                DlgDbError.showError(e, self)
 
     def reloadButtons(self):
         db = self.tree.currentDatabase()
@@ -114,14 +110,11 @@ def reloadButtons(self):
             self._lastDb.registerAllActions(self)
 
     def tabChanged(self, index):
-        QApplication.setOverrideCursor(Qt.WaitCursor)
-        try:
-            self.refreshTabs()
-        except BaseError as e:
-            DlgDbError.showError(e, self)
-            return
-        finally:
-            QApplication.restoreOverrideCursor()
+        with OverrideCursor(Qt.WaitCursor):
+            try:
+                self.refreshTabs()
+            except BaseError as e:
+                DlgDbError.showError(e, self)
 
     def refreshTabs(self):
         index = self.tabs.currentIndex()
@@ -300,17 +293,12 @@ def invokeCallback(self, callback, *params):
                 This method takes care to override and restore the cursor,
                 but also catches exceptions and displays the error dialog.
         """
-        QApplication.setOverrideCursor(Qt.WaitCursor)
-        try:
-            callback(self.tree.currentItem(), self.sender(), self, *params)
-
-        except BaseError as e:
-            # catch database errors and display the error dialog
-            DlgDbError.showError(e, self)
-            return
-
-        finally:
-            QApplication.restoreOverrideCursor()
+        with OverrideCursor(Qt.WaitCursor):
+            try:
+                callback(self.tree.currentItem(), self.sender(), self, *params)
+            except BaseError as e:
+                # catch database errors and display the error dialog
+                DlgDbError.showError(e, self)
 
     def unregisterAction(self, action, menuName):
         if not hasattr(self, '_registeredDbActions'):

python/plugins/processing/algs/qgis/ui/FieldsCalculatorDialog.py

@@ -40,6 +40,7 @@
                        QgsMapLayerProxyModel,
                        QgsMessageLog)
 from qgis.gui import QgsEncodingFileDialog
+from qgis.utils import OverrideCursor
 
 from processing.core.ProcessingConfig import ProcessingConfig
 from processing.core.ProcessingLog import ProcessingLog
@@ -220,10 +221,9 @@ def getParamValues(self):
 
     def accept(self):
         keepOpen = ProcessingConfig.getSetting(ProcessingConfig.KEEP_DIALOG_OPEN)
-        try:
-            parameters = self.getParamValues()
-            if parameters:
-                QApplication.setOverrideCursor(QCursor(Qt.WaitCursor))
+        parameters = self.getParamValues()
+        if parameters:
+            with OverrideCusor(Qt.WaitCursor):
                 context = dataobjects.createContext()
                 ProcessingLog.addToLog(self.alg.asPythonCommand(parameters, context))
 
@@ -235,8 +235,6 @@ def accept(self):
                                            not keepOpen)
                 if not keepOpen:
                     QDialog.reject(self)
-        finally:
-            QApplication.restoreOverrideCursor()
 
     def reject(self):
         self.executed = False

python/plugins/processing/gui/ConfigDialog.py

@@ -51,6 +51,7 @@
                       QgsSpinBox,
                       QgsOptionsPageWidget)
 from qgis.core import NULL, QgsApplication, QgsSettings
+from qgis.utils import OverrideCursor
 
 from processing.core.ProcessingConfig import (ProcessingConfig,
                                               settingsWatcher,
@@ -293,10 +294,9 @@ def accept(self):
                         return
                 setting.save(qsettings)
 
-        QApplication.setOverrideCursor(QCursor(Qt.WaitCursor))
-        for p in QgsApplication.processingRegistry().providers():
-            p.refreshAlgorithms()
-        QApplication.restoreOverrideCursor()
+        with OverrideCursor(Qt.WaitCursor):
+            for p in QgsApplication.processingRegistry().providers():
+                p.refreshAlgorithms()
 
         settingsWatcher.settingsChanged.emit()
 

python/utils.py

@@ -625,6 +625,28 @@ def spatialite_connect(*args, **kwargs):
     return dbapi2.connect(*args, **kwargs)
 
 
+class OverrideCursor():
+    """
+    Executes a code block with a different cursor set and makes sure the cursor
+    is restored even if exceptions are raised or an intermediate ``return``
+    statement is hit.
+
+    Example:
+    ```
+    with OverrideCursor(Qt.WaitCursor):
+        do_a_slow(operation)
+    ```
+    """
+
+    def __init__(self, cursor):
+        self.cursor = cursor
+
+    def __enter__(self):
+        QApplication.setOverrideCursor(self.cursor)
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        QApplication.restoreOverrideCursor()
+
 #######################
 # IMPORT wrapper