Add Page Editor toolbar toggles and widen the default window

Edit mode, snap to grid and the widgets/properties pane are now toggles on
the main toolbar while the Page Editor is open. Outside edit mode the page
and the property sheet are read-only; drags snap to the 10px grid when
snapping is on. The default window grows by the right pane's width so the
canvas is not squeezed when the pane shows.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ox_widget_properties.py

@@ -574,6 +574,10 @@ class OxWidgetPropertiesPanel:
         self.repaint = repaint
         self.comp = None
         self.rows = []
+        # Off until the Page Editor's edit mode is switched on: every field is then shown
+        # but none of them takes input, and no write reaches `commit`.
+        self.editable = False
+        self._controls = []     # (widget, state when editable) for every input on the sheet
         self.frame = ttk.Frame(parent)
 
         self._name_font = tkfont.Font(family="Segoe UI", size=9)
@@ -637,6 +641,7 @@ class OxWidgetPropertiesPanel:
         for child in self._sheet.winfo_children():
             child.destroy()
         self.rows = []
+        self._controls = []
         self._status_var.set("")
 
         if self.comp is None:
@@ -649,9 +654,36 @@ class OxWidgetPropertiesPanel:
 
         for grid_row, prop in enumerate(build_props(self.comp)):
             self.rows.append(self._build_row(grid_row, prop))
+        self._apply_editable()
         self.reload()
         self._canvas.yview_moveto(0)
 
+    def set_editable(self, editable):
+        """Edit mode on or off: the fields take input, or only show their values."""
+        self.editable = editable
+        self._apply_editable()
+
+    def _apply_editable(self):
+        for widget, editable_state in self._controls:
+            state = editable_state if self.editable else "disabled"
+            # Combobox first: it is an Entry too, and "readonly" would still let it pick.
+            if isinstance(widget, ttk.Combobox):
+                widget.configure(state=state)
+            elif isinstance(widget, tk.Entry):
+                widget.configure(state="normal" if self.editable else "readonly")
+            else:
+                widget.state(["!disabled"] if self.editable else ["disabled"])
+        if self.comp is not None:
+            self._status_var.set("" if self.editable else
+                                 "View mode — switch on edit mode (✏) to change values.")
+
+    def _guarded(self, command):
+        """`command`, run only while the sheet is editable."""
+        def run(*args):
+            if self.editable:
+                return command(*args)
+        return run
+
     def flush_edits(self):
         """Commits a typed value still sitting in its field.
 
@@ -695,7 +727,9 @@ class OxWidgetPropertiesPanel:
         return label
 
     def _dots(self, cell, command):
-        ttk.Button(cell, text="…", width=3, command=command).pack(side=tk.RIGHT, padx=1)
+        button = ttk.Button(cell, text="…", width=3, command=self._guarded(command))
+        button.pack(side=tk.RIGHT, padx=1)
+        self._controls.append((button, None))
 
     def _build_readonly(self, cell, row):
         self._value_label(cell, row, READONLY_FG)
@@ -712,6 +746,10 @@ class OxWidgetPropertiesPanel:
 
         def commit(_event=None):
             text = var.get()
+            if not self.editable:
+                if text != row["loaded"]:
+                    var.set(row["loaded"])
+                return
             if text != row["loaded"]:
                 # Taken as loaded first: the write repaints, and the repaint must not
                 # find this same edit still pending and commit it a second time.
@@ -739,6 +777,7 @@ class OxWidgetPropertiesPanel:
                          highlightbackground=SHEET_BG)
         entry.pack(side=tk.LEFT, fill=tk.BOTH, expand=True, padx=2, pady=1)
         self._bind_commit(entry, row)
+        self._controls.append((entry, None))
 
     def _build_image(self, cell, row):
         combo = ttk.Combobox(cell, textvariable=row["var"], font=self._name_font,
@@ -746,6 +785,7 @@ class OxWidgetPropertiesPanel:
         combo.pack(fill=tk.BOTH, expand=True, padx=1)
         commit = self._bind_commit(combo, row)
         combo.bind("<<ComboboxSelected>>", commit)
+        self._controls.append((combo, "normal"))
 
     def _build_choice(self, cell, row):
         prop, var = row["prop"], row["var"]
@@ -759,6 +799,7 @@ class OxWidgetPropertiesPanel:
 
         combo.bind("<<ComboboxSelected>>", selected)
         row["load"] = lambda: var.set(prop.read())
+        self._controls.append((combo, "readonly"))
 
     def _build_colour(self, cell, row):
         prop, var = row["prop"], row["var"]
@@ -781,14 +822,14 @@ class OxWidgetPropertiesPanel:
 
         self._dots(cell, choose)
         self._value_label(cell, row, READONLY_FG)
-        swatch.bind("<Button-1>", choose)
+        swatch.bind("<Button-1>", self._guarded(choose))
         row["load"] = load
 
     def _build_dialog(self, cell, row):
         opener = getattr(self, f"_open_{row['prop'].dialog}_dialog")
         self._dots(cell, opener)
         label = self._value_label(cell, row)
-        label.bind("<Double-Button-1>", lambda e: opener())
+        label.bind("<Double-Button-1>", self._guarded(lambda e: opener()))
         row["load"] = lambda: row["var"].set(row["prop"].read())
 
     def _build_link(self, cell, row):
@@ -815,6 +856,9 @@ class OxWidgetPropertiesPanel:
     # ── writing ───────────────────────────────────────────────────
 
     def _write(self, row, text):
+        if not self.editable:
+            row["load"]()
+            return
         values, error = row["prop"].write(text)
         if error:
             self._status_var.set(f"{row['prop'].label}: {error}")