From 39655363fa401657b8ba01fd6711edf03935a88c Mon Sep 17 00:00:00 2001
From: Magnus Hagander <magnus@hagander.net>
Date: Wed, 13 Nov 2024 14:25:44 +0100
Subject: [PATCH] Don't crash on no-data passed to svg charts

This could cause a divide-by-zero in some cases. Instead render the text
"NO DATA". Normally, the entire svg would be exluded in this case, but
in case it's not this will at least work.
---
 postgresqleu/util/templatetags/svgcharts.py | 7 +++++++
 template/util/svgbarchart.svg               | 4 ++++
 template/util/svgpiechart.svg               | 4 ++++
 3 files changed, 15 insertions(+)

diff --git a/postgresqleu/util/templatetags/svgcharts.py b/postgresqleu/util/templatetags/svgcharts.py
index 479aec02..7d73db25 100644
--- a/postgresqleu/util/templatetags/svgcharts.py
+++ b/postgresqleu/util/templatetags/svgcharts.py
@@ -98,6 +98,13 @@ def svgbarchart(svgdata, legend=True, wratio=2):
     maxval = max([d['value'] for d in svgdata])
     roundedmax = math.ceil(maxval / 2) * 2
 
+    if not roundedmax:
+        # Graph is empty
+        return t.render({
+            'height': height,
+            'width': width,
+        })
+
     for i, s in enumerate(svgdata):
         s['leftpos'] = itemwidth * i
         s['height'] = int((s['value'] / roundedmax) * graphratio * height)
diff --git a/template/util/svgbarchart.svg b/template/util/svgbarchart.svg
index 12a24c9e..a3589c3c 100644
--- a/template/util/svgbarchart.svg
+++ b/template/util/svgbarchart.svg
@@ -1,5 +1,6 @@
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1"
      viewBox="0 -10 {{width}} {{height}}">
+{% if svgdata %}
   <line x1="0" x2="{{width}}" y1="{{bottom}}" y2="{{bottom}}" stroke="black" />
 {%for label, pos in gridlines.items %}
   <line x1="8" x2="{{width}}" y1="{{pos}}" y2="{{pos}}" stroke="gray" stroke-width="0.5" />
@@ -13,4 +14,7 @@
   <text x="{{d.leftpos|add:2}}" y="{{bottom|add:2}}" writing-mode="tb" glyph-orientation-vertical="90" style="font-size: 3.7pt">{{d.label}}</text>
 {%endif%}
 {%endfor%}
+{% else %}
+ <text x="50%" y="50%" style="font-size: 8pt">NO DATA</text>
+{% endif %}
 </svg>
diff --git a/template/util/svgpiechart.svg b/template/util/svgpiechart.svg
index c8af3593..eef2f84e 100644
--- a/template/util/svgpiechart.svg
+++ b/template/util/svgpiechart.svg
@@ -1,5 +1,6 @@
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1"
      viewBox="-100 -100 {{legendwidth|add:200}} 200">
+{%if slices %}
 {%for s in slices%}{%if s.drawslice%}
   <path d="M {{s.startx}} {{s.starty}} A {{radius}} {{radius}} 0 {{s.largearc}} 1 {{s.endx}} {{s.endy}} L 0 0 L {{s.startx}} {{s.starty}}"
 	fill="{{s.color}}" stroke="white" class="pieslice">
@@ -11,4 +12,7 @@
 {%for s in slices%}
   {%if s.percent%}<text x="{{s.centerx}}" y="{{s.centery}}" class="svgpiepercent" stroke="none" fill="white">{{s.percent}}%{%if s.popup%}<title>{{s.popup}}</title>{%endif%}</text>{%endif%}
 {%endfor%}
+{% else %}
+ <text x="50%" y="50%" style="font-size: 8pt">NO DATA</text>
+{% endif %}
 </svg>
-- 
2.39.5