Keep tape options across the print redirect, honour saved rotation

Printing redirected back to a bare tape page, so every option - rotation
most visibly - reverted to the default the moment you pressed Print.
Carry the chosen options through the redirect instead.

Also read tape_rotate_default so an untick can be made permanent in
Settings; it only applies to a fresh arrival, never over an explicit
choice on the page.

app/routes/labels_tape.py

@@ -36,9 +36,38 @@ def printer_config():
                  or '/ipp/print'),
         'format': (SiteSetting.get('tape_printer_format', '') or '').strip(),
         'tape': SiteSetting.get('tape_default', tape_printer.DEFAULT_TAPE),
+        'rotate': SiteSetting.get_bool('tape_rotate_default', True),
     }
 
 
+def _options_query(options, labels):
+    """
+    The chosen options as query args, so a redirect back to the tape page
+    comes back exactly as the user left it. Without this, printing bounced
+    you to a fresh page and every choice - rotation especially - reverted
+    to the default.
+    """
+    query = {
+        'ids': ','.join(str(l.id) for l in labels),
+        tape_printer.FORM_MARKER: '1',
+        'tape': options.tape,
+        'copies': options.copies,
+        'font_scale': options.font_scale,
+        'image_percent': options.image_percent,
+        'padding_mm': options.padding_mm,
+        'align': options.align,
+        'fields': options.fields,
+    }
+    # Checkboxes: only present when on, which is what the parser expects.
+    if options.rotate:
+        query['rotate'] = '1'
+    if options.outline:
+        query['outline'] = '1'
+    if options.fixed_length_mm:
+        query['fixed_length_mm'] = options.fixed_length_mm
+    return query
+
+
 def _selected_labels():
     """Resolve the selection from ids= or category=, same as sheet printing."""
     ids = request.values.getlist('ids')
@@ -69,10 +98,14 @@ def index():
         flash('Select some labels to print first.', 'warning')
         return redirect(url_for('labels.index'))
 
+    config = printer_config()
     source = request.form if request.method == 'POST' else request.args
-    options = tape_printer.options_from_form(source)
+    # rotate_default only applies when the form was not submitted, so an
+    # explicit untick on the page always wins over the saved preference.
+    options = tape_printer.options_from_form(
+        source, rotate_default=config['rotate'])
     if not source.get('tape'):
-        options.tape = printer_config()['tape']
+        options.tape = config['tape']
 
     return render_template(
         'admin/labels/tape.html',
@@ -88,7 +121,7 @@ def index():
             ('category_code', 'Category code'), ('location', 'Drawer'),
             ('colour', 'Colour name'), ('accent', 'Colour stripe'),
         ],
-        printer=printer_config(),
+        printer=config,
     )
 
 
@@ -100,7 +133,8 @@ def preview():
     if not label_id:
         abort(400, 'preview.png needs an ?id= of a label.')
     label = PartLabel.query.get_or_404(label_id)
-    options = tape_printer.options_from_form(request.args)
+    options = tape_printer.options_from_form(
+        request.args, rotate_default=printer_config()['rotate'])
     buffer = tape_printer.preview_png(
         label, options, current_app.config['UPLOAD_FOLDER'])
     return send_file(buffer, mimetype='image/png')
@@ -151,8 +185,9 @@ def print_tape():
         flash('Nothing selected to print.', 'warning')
         return redirect(url_for('labels.index'))
 
-    options = tape_printer.options_from_form(request.form)
     config = printer_config()
+    options = tape_printer.options_from_form(
+        request.form, rotate_default=config['rotate'])
     host = config['host']
     if not host:
         flash('No tape printer address configured. Set it in Label '
@@ -169,13 +204,13 @@ def print_tape():
             mime_type = info.get('usable_format')
         except ipp_client.IPPError as exc:
             flash(f'Could not reach the printer: {exc}', 'danger')
-            return redirect(url_for('tape.index', ids=','.join(
-                str(l.id) for l in labels)))
+            return redirect(url_for('tape.index',
+                                    **_options_query(options, labels)))
     if not mime_type:
         flash('The printer did not offer a format LIM can produce. Use '
               'Download PDF instead.', 'warning')
         return redirect(url_for('tape.index',
-                                ids=','.join(str(l.id) for l in labels)))
+                                **_options_query(options, labels)))
 
     upload_folder = current_app.config['UPLOAD_FOLDER']
     sent = 0
@@ -205,9 +240,7 @@ def print_tape():
     for problem in failures[:5]:
         flash(problem, 'danger')
 
-    return redirect(url_for('tape.index',
-                            ids=','.join(str(l.id) for l in labels),
-                            tape=options.tape))
+    return redirect(url_for('tape.index', **_options_query(options, labels)))
 
 
 @tape_bp.route('/download.pdf', methods=['GET', 'POST'])
@@ -221,7 +254,8 @@ def download_pdf():
         return redirect(url_for('labels.index'))
 
     source = request.form if request.method == 'POST' else request.args
-    options = tape_printer.options_from_form(source)
+    options = tape_printer.options_from_form(
+        source, rotate_default=printer_config()['rotate'])
     buffer = tape_printer.render_batch_pdf(
         labels, options, current_app.config['UPLOAD_FOLDER'])
     if buffer is None: