fix: check directory existence when loading files (close #227)

Author: paulmueller

dcscope/gui/settings.py

@@ -0,0 +1,41 @@
+import pathlib
+from PyQt6 import QtCore
+
+
+def get_dir(topic: str,
+            settings: QtCore.QSettings
+            ) -> str:
+    """Given a QSettings instance, return a directory
+
+    If writable is `True`, return a writable directory
+    """
+    location = settings.value(f"paths/{topic}", "")
+
+    if not location:
+        # use default value
+        location = QtCore.QStandardPaths.standardLocations(
+            QtCore.QStandardPaths.StandardLocation.HomeLocation)[0]
+    else:
+        # check whether the location exists
+        path = pathlib.Path(location)
+        if not path.is_dir():
+            for pp in path.parents:
+                if pp.is_dir():
+                    location = str(pp)
+                    break
+            else:
+                location = "."
+
+    return location or "."
+
+
+def set_dir(topic: str,
+            path: pathlib.Path | str,
+            settings: QtCore.QSettings,
+            ):
+    """Given a QSettings instance, save a directory topic"""
+    path = pathlib.Path(path)
+    if path.exists():
+        if not path.is_dir():
+            path = path.parent
+        settings.setValue(f"paths/{topic}", str(path))