gui: Add fix for wxGUI Data import Python error (#4504)

This fixes #648 by adding a command tracker queue. When the queue is not empty, closing the dialog is prevented to ensure the completion callback can still access UI elements.

gui/wxpython/modules/import_export.py

@@ -18,9 +18,11 @@
 
 @author Martin Landa <landa.martin gmail.com>
 @author Anna Kratochvilova <kratochanna gmail.com> (GroupDialog, SymbolDialog)
+@author William Welch <ww.dev icloud.com> (commands running queue)
 """
 
 import os
+from collections import deque
 
 from pathlib import Path
 
@@ -60,6 +62,8 @@ def __init__(
 
         self.commandId = -1  # id of running command
 
+        self._commands_running = deque()
+
         wx.Dialog.__init__(
             self, parent, id, title, style=style, name="MultiImportDialog"
         )
@@ -122,16 +126,17 @@ def __init__(
         # buttons
         #
         # cancel
+        self._DEFAULT_CLOSE_BTN_TEXT = _("Close dialog")
         self.btn_close = CloseButton(parent=self.panel)
-        self.btn_close.SetToolTip(_("Close dialog"))
+        self.btn_close.SetToolTip(_(self._DEFAULT_CLOSE_BTN_TEXT))
         self.btn_close.Bind(wx.EVT_BUTTON, self.OnClose)
         # run
         self.btn_run = Button(parent=self.panel, id=wx.ID_OK, label=_("&Import"))
         self.btn_run.SetToolTip(_("Import selected layers"))
         self.btn_run.SetDefault()
         self.btn_run.Bind(wx.EVT_BUTTON, self.OnRun)
 
-        self.Bind(wx.EVT_CLOSE, lambda evt: self.Destroy())
+        self.Bind(wx.EVT_CLOSE, self._handleCloseEvent)
 
         self.notebook = GNotebook(parent=self, style=globalvar.FNPageDStyle)
 
@@ -270,6 +275,33 @@ def _validateOutputMapName(self):
                 return False
         return True
 
+    def _handleCloseEvent(self, event: wx.CloseEvent):
+        if event.CanVeto() and len(self._commands_running) > 0:
+            # prevent dialog close while async commands are running
+            event.Veto()
+            return
+        self.Destroy()
+
+    def _addToCommandQueue(self):
+        self._commands_running.append(True)
+
+        # disable the dialog close button
+        self.btn_close.SetToolTip(
+            _("Dialog cannot be closed while command is running.")
+        )
+        self.btn_close.Disable()
+
+    def _removeFromCommandQueue(self):
+        try:
+            self._commands_running.pop()
+        except IndexError:
+            pass
+        finally:
+            if len(self._commands_running) == 0:
+                # enable the dialog close button
+                self.btn_close.Enable()
+                self.btn_close.SetToolTip(self._DEFAULT_CLOSE_BTN_TEXT)
+
     def OnClose(self, event=None):
         """Close dialog"""
         self.Close()
@@ -518,6 +550,7 @@ def OnRun(self, event):
             ):
                 cmd.append("--overwrite")
 
+            self._addToCommandQueue()
             # run in Layer Manager
             self._giface.RunCmd(
                 cmd, onDone=self.OnCmdDone, userData=userData, addLayer=False
@@ -526,9 +559,11 @@ def OnRun(self, event):
     def OnCmdDone(self, event):
         """Load layers and close if required"""
         if not hasattr(self, "AddLayers"):
+            self._removeFromCommandQueue()
             return
 
         self.AddLayers(event.returncode, event.cmd, event.userData)
+        self._removeFromCommandQueue()
 
         if event.returncode == 0 and self.closeOnFinish.IsChecked():
             self.Close()
@@ -663,6 +698,7 @@ def OnRun(self, event):
             ):
                 cmd.append("--overwrite")
 
+            self._addToCommandQueue()
             # run in Layer Manager
             self._giface.RunCmd(
                 cmd, onDone=self.OnCmdDone, userData=userData, addLayer=False
@@ -671,10 +707,13 @@ def OnRun(self, event):
     def OnCmdDone(self, event):
         """Load layers and close if required"""
         if not hasattr(self, "AddLayers"):
+            self._removeFromCommandQueue()
             return
 
         self.AddLayers(event.returncode, event.cmd, event.userData)
 
+        self._removeFromCommandQueue()
+
         if self.popOGR:
             os.environ.pop("GRASS_VECTOR_OGR")
 
@@ -873,16 +912,20 @@ def OnRun(self, event):
             ):
                 cmd.append("--overwrite")
 
+            self._commands_running.append(True)
             # run in Layer Manager
             self._giface.RunCmd(cmd, onDone=self.OnCmdDone, addLayer=False)
 
     def OnCmdDone(self, event):
         """Load layers and close if required"""
         if not hasattr(self, "AddLayers"):
+            self._removeFromCommandQueue()
             return
 
         self.AddLayers(event.returncode, event.cmd)
 
+        self._removeFromCommandQueue()
+
         if self.closeOnFinish.IsChecked():
             self.Close()