Move QR generation to the browser, saving some time and effort on the server.

cara/apps/calculator/report_generator.py

 import concurrent.futures
 import base64
 import dataclasses
-from datetime import datetime, timedelta
+from datetime import datetime
 import io
+import json
 import typing
 import urllib
 import zlib
 
-import loky
 import jinja2
 import numpy as np
-import qrcode
-import json
 
 from cara import models
 from ... import monte_carlo as mc
@@ -123,7 +121,7 @@ def calculate_report_data(model: models.ExposureModel):
     }
 
 
-def generate_qr_code(base_url, calculator_prefix, form: FormData):
+def generate_permalink(base_url, calculator_prefix, form: FormData):
     form_dict = FormData.to_dict(form, strip_defaults=True)
 
     # Generate the calculator URL arguments that would be needed to re-create this
@@ -136,20 +134,9 @@ def generate_qr_code(base_url, calculator_prefix, form: FormData):
     qr_url = f"{base_url}/_c/{compressed_args}"
     url = f"{base_url}{calculator_prefix}?{args}"
 
-    qr = qrcode.QRCode(
-        version=1,
-        error_correction=qrcode.constants.ERROR_CORRECT_H,
-        box_size=10,
-        border=4,
-    )
-    qr.add_data(qr_url)
-    qr.make(fit=True)
-    img = qr.make_image(fill_color="black", back_color="white").convert('RGB')
-
     return {
-        'image': img2base64(_img2bytes(img)),
         'link': url,
-        'qr_url': qr_url,
+        'shortened': qr_url,
     }
 
 
@@ -313,7 +300,7 @@ class ReportGenerator:
         context['alternative_scenarios'] = comparison_report(
             alternative_scenarios, scenario_sample_times, executor_factory=executor_factory,
         )
-        context['qr_code'] = generate_qr_code(base_url, self.calculator_prefix, form)
+        context['permalink'] = generate_permalink(base_url, self.calculator_prefix, form)
         context['calculator_prefix'] = self.calculator_prefix
         context['scale_warning'] = {
             'level': 'yellow-2', 

cara/apps/calculator/static/js/pdf.js

-function generate_pdf_version(qr_link) {
-    const pdf_version = this.document.getElementById("body");
-
-    // PDF styling
-    var opt = {
-        filename: 'myfile.pdf',
-        image: { type: 'jpeg', quality: 0.98 },
-        html2canvas: { scale: 2, width: 1200, windowWidth: 1200 },
-        enableLinks: false,
-        jsPDF: {
-            unit: 'pt',
-            format: 'letter',
-            orientation: 'portrait',
-        },
-        pagebreak: { mode: '', avoid: '.break-avoid' },
-    };
-    html2pdf().set(opt).from(pdf_version).toPdf().get('pdf').then(function(pdf) {
-        var totalPages = pdf.internal.getNumberOfPages();
-        pdf.setPage(1);
-        pdf.link(530, 25, 60, 60, { url: qr_link }); //Hyperlink to reproduce results
-
-        for (i = 1; i <= totalPages; i++) {
-            pdf.setPage(i);
-            pdf.setFontSize(10);
-            pdf.setTextColor(150);
-            pdf.text('Page ' + i + ' of ' + totalPages, (pdf.internal.pageSize.getWidth() / 2.25), (pdf.internal.pageSize.getHeight() - 10));
-        }
-    }).save();
-};
\ No newline at end of file

cara/apps/calculator/templates/base/calculator.report.html.j2

@@ -24,8 +24,6 @@
 			<p class="mb-0"> Created {{ creation_date }} using CARA calculator version v{{ form.calculator_version }}</p>
 		</div>
 		<button type="button" class="btn btn-outline-dark align-self-center" style="margin-right: -100pt" id="download-pdf" onclick="print()">Print Report</button>
-		{# To be replaced by "Generate PDF" #}
-		<img id="pdf-qr-code" class="align-self-center invisible" src="{{ qr_code.image }}"/>
 	</div>
 
 {% endblock report_header %}
@@ -162,10 +160,10 @@
 					<div class="collapse show" id="collapseQRcode">
 						<div class="card-body">
 							<div>
-								<a href="{{ qr_code.link }}" style="float: left;"><img style="width:250pt;" id="qr_code" src="{{ qr_code.image }}"/></a>
+								<a href="{{ permalink.link }}" style="float: left;"><div id="qrcode"></div></a>
 								<span style="float: left; min-height: 250pt; line-height: 250pt; vertical-align: middle; display: inline-block;">
 								<p style="display: inline-block; vertical-align: middle; line-height: normal;">
-								Click the QR code to regenerate the report and get a shareable link.<br>Alternatively, scan to regenerate the report.<br> Mobile-friendly app coming soon!
+								Click the QR code to regenerate the report and get a shareable link.<br>Alternatively, scan to regenerate the report.<br>
 								</p>
 								</span>
 							</div>	
@@ -433,11 +431,19 @@
 	</div>
 {% endblock disclaimer_container %}
 
-<script src="{{ calculator_prefix }}/static/js/pdf.js"></script>
 <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
 <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js" integrity="sha384-ZMP7rVo3mIykV+2+9J3UJ46jBk0WLaUAdn689aCwoqbBJiSnjAK/l8WvCWPIPm49" crossorigin="anonymous"></script>
 <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js" integrity="sha384-ChfqqxuZUCnJSK3+MXmPNIyE6ZbWh2IMqE241rYiqJxyMiZ6OW/JmZQ5stwEULTy" crossorigin="anonymous"></script>
 <script src="https://cdnjs.cloudflare.com/ajax/libs/html2pdf.js/0.9.2/html2pdf.bundle.js"></script>
 
+<script src="https://cdnjs.cloudflare.com/ajax/libs/qrcodejs/1.0.0/qrcode.min.js" integrity="sha512-CNgIRecGo7nphbeZ04Sc13ka07paqdeTu0WR1IM4kNcpmBAUSHSQX0FslNhTDadL4O5SAGapGt4FodqL8My0mA==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>
+<script type="text/javascript">
+    new QRCode(document.getElementById("qrcode"), {
+        text: "{{ permalink.shortened }}",
+        width: 330,
+        height: 330}
+    );
+</script>
+
 </body>
 </html>

cara/tests/apps/calculator/test_webapp.py

@@ -4,7 +4,7 @@ import pytest
 import tornado.testing
 
 import cara.apps.calculator
-from cara.apps.calculator.report_generator import generate_qr_code
+from cara.apps.calculator.report_generator import generate_permalink
 
 _TIMEOUT = 20.
 
@@ -97,26 +97,26 @@ class TestOpenApp(tornado.testing.AsyncHTTPTestCase):
         assert response.code == 404
 
 
-async def test_qrcode_urls(http_server_client, baseline_form):
+async def test_permalink_urls(http_server_client, baseline_form):
     base_url = 'proto://hostname/prefix'
-    qr_data = generate_qr_code(base_url, "/calculator", baseline_form)
+    permalink_data = generate_permalink(base_url, "/calculator", baseline_form)
     expected = f'{base_url}/calculator?exposed_coffee_break_option={baseline_form.exposed_coffee_break_option}&'
-    assert qr_data['link'].startswith(expected)
+    assert permalink_data['link'].startswith(expected)
 
     # We should get a 200 for the link.
-    response = await http_server_client.fetch(qr_data['link'].replace(base_url, ''))
+    response = await http_server_client.fetch(permalink_data['link'].replace(base_url, ''))
     assert response.code == 200
 
     # And a 302 for the QR url itself. The redirected URL should be the same as
     # in the link.
-    assert qr_data['qr_url'].startswith(base_url)
+    assert permalink_data['shortened'].startswith(base_url)
     response = await http_server_client.fetch(
-        qr_data['qr_url'].replace(base_url, ''),
+        permalink_data['shortened'].replace(base_url, ''),
         max_redirects=0,
         raise_error=False,
     )
     assert response.code == 302
-    assert response.headers['Location'] == qr_data['link'].replace(base_url, '')
+    assert response.headers['Location'] == permalink_data['link'].replace(base_url, '')
 
 
 async def test_invalid_compressed_url(http_server_client, baseline_form):

requirements.txt

@@ -62,7 +62,6 @@ pyparsing==2.4.7
 pyrsistent==0.18.0
 python-dateutil==2.8.2
 pyzmq==22.1.0
-qrcode==7.2
 requests==2.26.0
 requests-unixsocket==0.2.0
 scikit-learn==0.24.2

setup.py

@@ -30,7 +30,6 @@ REQUIREMENTS: dict = {
         'numpy',
         'psutil',
         'python-dateutil',
-        'qrcode[pil]',
         'scipy',
         'sklearn',
         'timezonefinder',