Implement professional PDF-based label printing for boxes and locations

- Replace ZPL/image-based printing with ReportLab PDF generation
- Box labels: 8cm x 5cm landscape with 'BOX Nr:' header and CODE128 barcode
- Location labels: 8cm x 5cm landscape with 'Location nr:' header and CODE128 barcode
- Add /generate_box_label_pdf endpoint using same approach as print_module
- Update FG scan quick box creation to use PDF printing with default printer
- Switch from CDN QZ Tray to local patched version for pairing-key auth
- Improve error handling and logging throughout printing workflow
- Fix import issues (add mm unit to warehouse.py)
- Optimize barcode size and spacing for better readability

py_app/app/warehouse.py

@@ -3,7 +3,7 @@ from flask import current_app, request, render_template, session, redirect, url_
 import csv, os, tempfile
 from reportlab.lib.pagesizes import letter
 from reportlab.pdfgen import canvas
-from reportlab.lib.units import cm
+from reportlab.lib.units import cm, mm
 from reportlab.graphics.barcode import code128
 import io
 
@@ -255,7 +255,7 @@ def import_locations_csv_handler():
     return render_template('import_locations_csv.html', report=report, locations=locations)
 
 def generate_location_label_pdf():
-    """Generate PDF for location barcode label (8x4cm)"""
+    """Generate PDF for location barcode label (8cm x 5cm landscape)"""
     try:
         data = request.get_json()
         location_code = data.get('location_code', '')
@@ -263,46 +263,93 @@ def generate_location_label_pdf():
         if not location_code:
             return jsonify({'error': 'Location code is required'}), 400
         
+        print(f"DEBUG: Generating location label PDF for: {location_code}")
+        
         # Create PDF in memory
         buffer = io.BytesIO()
         
-        # Create PDF with 8x4cm page size (width x height)
-        page_width = 8 * cm
-        page_height = 4 * cm
+        # Create PDF with 8cm x 5cm page size in landscape orientation
+        page_width = 80 * mm   # 8 cm
+        page_height = 50 * mm  # 5 cm
         
         c = canvas.Canvas(buffer, pagesize=(page_width, page_height))
         
-        # Generate Code128 barcode
-        barcode = code128.Code128(location_code, barWidth=1.0, humanReadable=False)
+        # Optimize for label printer
+        c.setPageCompression(1)
+        c.setCreator("Trasabilitate Location Label System")
+        c.setTitle("Location Label - Optimized for Label Printers")
         
-        # Calculate the desired barcode dimensions (fill most of the label)
-        desired_barcode_width = 7 * cm  # Almost full width
-        desired_barcode_height = 2.5 * cm  # Most of the height
+        # Define margins and usable area
+        margin = 2 * mm
+        usable_width = page_width - (2 * margin)
+        usable_height = page_height - (2 * margin)
         
-        # Calculate scaling factor to fit the desired width
-        scale = desired_barcode_width / barcode.width
+        # Calculate vertical layout
+        # Top section: "Location nr: XXXX" text
+        # Bottom section: Barcode
+        text_height = 12 * mm  # Space for text at top
+        barcode_height = usable_height - text_height - (1 * mm)  # Rest for barcode with minimal spacing
         
-        # Calculate actual dimensions after scaling
-        actual_width = barcode.width * scale
-        actual_height = barcode.height * scale
+        # === TOP SECTION: Location Nr Label ===
+        # Position from top of usable area
+        text_y = page_height - margin - text_height
         
-        # Center the barcode on the label
-        barcode_x = (page_width - actual_width) / 2
-        barcode_y = (page_height - actual_height) / 2 + 0.3 * cm  # Slightly above center for text space
+        # Draw "Location nr:" label
+        c.setFont("Helvetica-Bold", 14)
+        label_text = "Location nr:"
+        label_width = c.stringWidth(label_text, "Helvetica-Bold", 14)
         
-        # Draw barcode with scaling
-        c.saveState()
-        c.translate(barcode_x, barcode_y)
-        c.scale(scale, scale)
-        barcode.drawOn(c, 0, 0)
-        c.restoreState()
+        # Draw location code
+        c.setFont("Helvetica-Bold", 18)
+        code_text = location_code
+        code_width = c.stringWidth(code_text, "Helvetica-Bold", 18)
         
-        # Add location code text below barcode
-        c.setFont("Helvetica-Bold", 10)
-        text_width = c.stringWidth(location_code, "Helvetica-Bold", 10)
-        text_x = (page_width - text_width) / 2
-        text_y = barcode_y - 0.5 * cm  # Below the barcode
-        c.drawString(text_x, text_y, location_code)
+        # Calculate total width and center everything
+        total_text_width = label_width + 3*mm + code_width  # 3mm spacing between label and code
+        start_x = margin + (usable_width - total_text_width) / 2
+        
+        # Draw label text
+        c.setFont("Helvetica-Bold", 14)
+        c.drawString(start_x, text_y + 5*mm, label_text)
+        
+        # Draw location code
+        c.setFont("Helvetica-Bold", 18)
+        c.drawString(start_x + label_width + 3*mm, text_y + 5*mm, code_text)
+        
+        # === BOTTOM SECTION: Barcode ===
+        barcode_y = margin
+        
+        try:
+            # Create barcode for location code
+            barcode = code128.Code128(
+                location_code, 
+                barWidth=0.4*mm,  # Thicker bars for better scanning
+                barHeight=barcode_height,
+                humanReadable=True,
+                fontSize=10
+            )
+            
+            # Calculate scaling to fit width
+            scale_factor = usable_width / barcode.width
+            
+            # Center the barcode horizontally
+            barcode_x = margin + (usable_width - (barcode.width * scale_factor)) / 2
+            
+            # Draw the barcode
+            c.saveState()
+            c.translate(barcode_x, barcode_y)
+            c.scale(scale_factor, 1)
+            barcode.drawOn(c, 0, 0)
+            c.restoreState()
+            
+            print(f"DEBUG: Barcode generated successfully with scale factor: {scale_factor}")
+            
+        except Exception as e:
+            print(f"DEBUG: Error generating barcode: {e}")
+            # Fallback: draw text if barcode fails
+            c.setFont("Helvetica-Bold", 12)
+            text_width = c.stringWidth(location_code, "Helvetica-Bold", 12)
+            c.drawString((page_width - text_width) / 2, barcode_y + barcode_height/2, location_code)
         
         # Finalize PDF
         c.save()
@@ -313,10 +360,13 @@ def generate_location_label_pdf():
         response.headers['Content-Type'] = 'application/pdf'
         response.headers['Content-Disposition'] = f'inline; filename=location_{location_code}_label.pdf'
         
+        print(f"DEBUG: Location label PDF generated successfully")
         return response
         
     except Exception as e:
         print(f"Error generating location label PDF: {e}")
+        import traceback
+        traceback.print_exc()
         return jsonify({'error': str(e)}), 500
 
 def update_location(location_id, location_code, size, description):