Graphviz PNG rendering not working on PlantUML Online

Question

Hello,

When trying to render the following diagram on PlantUML Online:

@startuml
digraph g {
    label=""
    labelloc=t
    forcelabels=true
    graph [fontname="Helvetica"]
    graph [style=wedged colorscheme=set39]
    node [label="" shape=box fontname="Helvetica-Bold" fontsize="12pt" style=filled fillcolor="#E3FCDD:#BFF4AC" color="#336F05" gradientangle=90]
    edge [fontname="Helvetica" fontsize="10pt"]
    sx01 [label="leaf01"]
    sx02 [label="leaf02"]
    S1 [label="server01"]
    S2 [label="server02"]
    concentrate=true

    { rank = same; sx01 sx02 }
    { rank = same; S1 S2 }

    sx01 -> sx02 [minlen=4 peripheries=2 color="black:white:black" arrowhead=none
        labeldistance=4
        labelangle=0
        headlabel=<
            <table border="0">
                <tr><td></td></tr>
                <tr><td></td></tr>
                <tr><td></td></tr>
                <tr><td></td></tr>
            </table>
        >
    ]
    sx01 -> S1 [color="#1A5883" arrowhead=none labelangle=75 taillabel="" headlabel="" fontsize="8pt"]
    sx01 -> S2 [color="#00BE50" arrowhead=none labelangle=35 taillabel="" headlabel="" fontsize="8pt"]
    sx02 -> S1 [color="#1A5883" arrowhead=none labelangle=35 taillabel="" headlabel="" fontsize="8pt"]
    sx02 -> S2 [color="#00BE50" arrowhead=none labelangle=-75 taillabel="" headlabel="" fontsize="8pt"]
    S1 -> S2 [minlen=8 style=invis arrowhead=none]
}
@enduml

Here's the diagram URL: //www.plantuml.com/plantuml/png/nLJ1Rk8m4Btp5PPxHciIsAKiHYrjqTuvLXoSU21MZHtP1hfRzT_NiKaC2Ar4Bvj3IDwRuRrv7dYmZXctsyeU5nl3wWfjq4SF-Kko0YJ5EBr8NL8NNjVQb10mIvtPGG1Z--jQAwVO5YZ-1N8FJfGChquBhFijWHw0Ru2ZKajjR5c1Rx3WyljOgZG7zDfQGBPYDT12lwChtzwVQybnOApuuvb1LZkCeinQIEbbceyWHV7TIxvuUdwUtCqNY-7Z4qOjdkVV5sI46vjSW79CRIJGUn8TDNQl3dUcJBnohBVlPD1D886joI0nsJcJ7Pbbwh1Wzc2wdcLsmNGzfLQbDskOWtWK0Vr0XgatH97rPdz6Cq7tynhjTPSDbOptPqURMw4aA3f4DHXHL_u6bcPjPeLavTlaK0a7a_2C4JD67ofWd2gjuc9q2yI5TSpRfSDpF2PDEh1fZzDEFPQkgME515Hemy6h4pnBT5TYPbF7PzDlyMR-Kub76gy9Z4-hiuYRyswtR_0u6e_po_nEy_anGeu9sVqeKahuT0V7QGLRcIp9439_6P5_oUHVaCbkd-RhCZTDqxyvjMNCBEt--FXN8jHUs0kfLU-pzm2AxxRoBm00

It renders on SVG but fails on PNG, and it was working before. It still works at https://plantuml-editor.kkeisuke.com/ so I believe it's a regression.

When clicking on "Discover the future PlantUML Web Editor!  ", it fails with a Forbidden error message.

Comments

the problematic line is 
   graph [style=wedged colorscheme=set39]
in concrete, if you remove
    colorscheme=set39

then it is working again:

---

Related to the problematic font (found on the other issue too). In the orig. sample the label is empty therefore no font problem occurs in the orig. sample. But it can be reproduced with following sample:

@startuml
digraph g {
    ' label="Helvetica not working"
    ' graph [fontname="Helvetica"]

    label="Helvetica-Bold working"
    graph [fontname="Helvetica-Bold"]
}
@enduml

Helvetica not working

(detailed SVG error message:

	Error: fontconfig: Didn't find expected font family. Perhaps URW Type 1 fonts need installing?
	<?xml version="1.0" encoding="UTF-8" standalone="no"?>
	<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
	"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
	<!-- Generated by graphviz version 10.0.1 (20240210.2158)
	-->
	<!-- Title: g Pages: 1 -->
	<svg width="55pt" height="33pt"
	viewBox="0.00 0.00 55.14 32.80" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
	<g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 28.8)">
	<title>g</title>
	<polygon fill="white" stroke="none" points="-4,4 -4,-28.8 51.14,-28.8 51.14,4 -4,4"/>
	<text text-anchor="middle" x="23.57" y="-8.2" font-family="Helvetica,sans-Serif" font-size="14.00">hhhh</text>
	</g>
	</svg>

)

Helvetica-Bold is working