Release 1.4.2: load-only dialog when nothing is selected

With neither mode derivable (nothing selected, no marker rectangles,
no config) the dialog now opens anyway instead of failing with an
error figure: both radios disabled with their reasons, OK/Save
disabled, Load config… live - a saved config can bootstrap the run.

README: note that macOS/NixOS field tests last ran with plugin v1.3.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HjSRLWQ8ywBBYyakvr3YTx

fill_resistance/dialog.py

@@ -26,7 +26,11 @@ Two run modes share the dialog, chosen by a radio at the top:
 
 "Load config…" swaps the whole setup for another config file: ask()
 then returns a LoadRequest instead of a Selection and main re-derives
-everything from that file and reopens the dialog.
+everything from that file and reopens the dialog. The dialog even
+opens with NO runnable mode at all (nothing selected, no marker
+rectangles, no config) - load-only: both radios unchecked and
+disabled with their reasons, OK/Save disabled - so a saved config can
+bootstrap the run.
 
 Row identity is POSITIONAL: the tables never sort or reorder, so
 main.py zips Selection.pdn_rows with its own parallel terminal list.
@@ -205,16 +209,28 @@ class _Dialog(QDialog):
         self.mode_pdn = QRadioButton("PDN")
         self.mode_classic.setEnabled(self._classic_ok)
         self.mode_pdn.setEnabled(self._pdn_ok)
-        start_pdn = self._pdn_ok and (not self._classic_ok
-                                      or start_mode == "pdn")
-        (self.mode_pdn if start_pdn else self.mode_classic).setChecked(True)
-        reason = None
+        # with NEITHER mode derivable (nothing selected, no marker
+        # rectangles, no config terminals) the dialog still opens
+        # LOAD-ONLY: no radio checked, OK/Save disabled below - so
+        # "Load config…" can pull in a saved setup instead of the
+        # launch dying with an error figure
+        self._no_mode = not (self._classic_ok or self._pdn_ok)
+        if not self._no_mode:
+            start_pdn = self._pdn_ok and (not self._classic_ok
+                                          or start_mode == "pdn")
+            (self.mode_pdn if start_pdn
+             else self.mode_classic).setChecked(True)
+        reasons = []
         if not self._classic_ok and classic_reason:
-            reason = f"Classic unavailable: {classic_reason}"
+            reasons.append(f"Classic unavailable: {classic_reason}")
             self.mode_classic.setToolTip(classic_reason)
-        elif not self._pdn_ok and pdn_reason:
-            reason = f"PDN unavailable: {pdn_reason}"
+        if not self._pdn_ok and pdn_reason:
+            reasons.append(f"PDN unavailable: {pdn_reason}")
             self.mode_pdn.setToolTip(pdn_reason)
+        if self._no_mode and load_dir is not None:
+            reasons.append("Load config… below can still set up a run "
+                           "from a saved config file.")
+        reason = "\n".join(reasons) if reasons else None
 
         # --- shared form #1 --------------------------------------------
         form1 = QFormLayout()
@@ -387,14 +403,23 @@ class _Dialog(QDialog):
         buttons = QDialogButtonBox(QDialogButtonBox.Ok | QDialogButtonBox.Cancel)
         buttons.accepted.connect(self._try_accept)
         buttons.rejected.connect(self.reject)
+        self.ok_button = buttons.button(QDialogButtonBox.Ok)
+        self.load_button = None
+        self.save_button = None
         if load_dir is not None:
-            load_btn = buttons.addButton("Load config…",
-                                         QDialogButtonBox.ActionRole)
-            load_btn.clicked.connect(self._load_config)
+            self.load_button = buttons.addButton(
+                "Load config…", QDialogButtonBox.ActionRole)
+            self.load_button.clicked.connect(self._load_config)
         if save_callback is not None:
-            save_btn = buttons.addButton("Save config…",
-                                         QDialogButtonBox.ActionRole)
-            save_btn.clicked.connect(self._save_config)
+            self.save_button = buttons.addButton(
+                "Save config…", QDialogButtonBox.ActionRole)
+            self.save_button.clicked.connect(self._save_config)
+        if self._no_mode:
+            # nothing to run or to save until a load re-derives; Load
+            # config… and Cancel stay live
+            self.ok_button.setEnabled(False)
+            if self.save_button is not None:
+                self.save_button.setEnabled(False)
 
         content = QWidget()
         lay = QVBoxLayout(content)
@@ -405,11 +430,12 @@ class _Dialog(QDialog):
         mode_row.addWidget(self.mode_pdn)
         mode_row.addStretch(1)
         lay.addLayout(mode_row)
+        self.reason_label = None
         if reason is not None:
-            rl = QLabel(reason)
-            rl.setWordWrap(True)
-            rl.setStyleSheet("color: gray; font-size: 10px;")
-            lay.addWidget(rl)
+            self.reason_label = QLabel(reason)
+            self.reason_label.setWordWrap(True)
+            self.reason_label.setStyleSheet("color: gray; font-size: 10px;")
+            lay.addWidget(self.reason_label)
         lay.addLayout(form1)
         if self.classic_section is not None:
             lay.addWidget(self.classic_section)
@@ -997,7 +1023,9 @@ def ask(candidates: dict[str, list[str]], layer_order: list[str],
     config file); pdn: the PDN terminal setup (editable tables);
     pdn_candidates: net candidates for PDN mode (classic uses
     `candidates`); classic_reason / pdn_reason: why a mode is
-    unavailable (its radio is disabled with the reason shown);
+    unavailable (its radio is disabled with the reason shown; with
+    BOTH unavailable the dialog opens load-only - OK and Save disabled
+    until Load config… returns a LoadRequest);
     save_callback(selection, target_path) -> saved name string enables
     the "Save config…" button in both modes (the file name is asked
     per save, seeded with save_target); load_dir (the board directory)