From 88b098f6ddb413bf6ea852e4328a43568c628be1 Mon Sep 17 00:00:00 2001
From: Matthew Fernandez <matthew.fernandez@gmail.com>
Date: Tue, 7 Dec 2021 08:06:15 -0800
Subject: [PATCH] add a test case for scale precision issue

---
 rtest/1855.dot           | 71 ++++++++++++++++++++++++++++++++++++++++
 rtest/test_regression.py | 38 +++++++++++++++++++++
 2 files changed, 109 insertions(+)
 create mode 100644 rtest/1855.dot

diff --git a/rtest/1855.dot b/rtest/1855.dot
new file mode 100644
index 000000000..cda66ebfb
--- /dev/null
+++ b/rtest/1855.dot
@@ -0,0 +1,71 @@
+digraph {
+graph[size="10.0624,6.11863",ratio=fill];
+overlap=false;
+splines=true;
+node[fontname="Helvetica"];
+edge[fontname="Helvetica"];
+2->1[color=black];
+3->1[color=black];
+4->1[color=black];
+5->1[color=black];
+6->1[color=black];
+7->1[color=black];
+8->1[color=black];
+9->1[color=black];
+10->1[color=black];
+11->1[color=black];
+12->1[color=black];
+13->1[color=black];
+14->1[color=black];
+15->1[color=black];
+16->1[color=black];
+17->1[color=black];
+18->1[color=black];
+19->1[color=black];
+20->1[color=black];
+21->1[color=black];
+22->1[color=black];
+23->1[color=black];
+24->1[color=black];
+25->1[color=black];
+26->1[color=black];
+27->1[color=black];
+28->1[color=black];
+29->1[color=black];
+30->1[color=black];
+31->1[color=black];
+32->1[color=black];
+1[label=""];
+2[label=""];
+3[label=""];
+4[label=""];
+5[label=""];
+6[label=""];
+7[label=""];
+8[label=""];
+9[label=""];
+10[label=""];
+11[label=""];
+12[label=""];
+13[label=""];
+14[label=""];
+15[label=""];
+16[label=""];
+17[label=""];
+18[label=""];
+19[label=""];
+20[label=""];
+21[label=""];
+22[label=""];
+23[label=""];
+24[label=""];
+25[label=""];
+26[label=""];
+27[label=""];
+28[label=""];
+29[label=""];
+30[label=""];
+31[label=""];
+32[label="",style=filled,color=pink];
+1[style=filled,color=black,fillcolor=lightcyan2];
+}
diff --git a/rtest/test_regression.py b/rtest/test_regression.py
index 3440da693..f8abf5d01 100644
--- a/rtest/test_regression.py
+++ b/rtest/test_regression.py
@@ -832,6 +832,44 @@ def test_html(src: Path):
   assert p.returncode == 0
   assert stderr == ""
 
+@pytest.mark.xfail(strict=True)
+def test_1855():
+  """
+  SVGs should have a scale with sufficient precision
+  https://gitlab.com/graphviz/graphviz/-/issues/1855
+  """
+
+  # locate our associated test case in this directory
+  src = Path(__file__).parent / "1855.dot"
+  assert src.exists(), "unexpectedly missing test case"
+
+  # run it through Graphviz
+  svg = subprocess.check_output(["dot", "-Tsvg", src], universal_newlines=True)
+
+  # find the graph element
+  root = ET.fromstring(svg)
+  graph = root[0]
+  assert graph.get("class") == "graph", "could not find graph element"
+
+  # extract its `transform` attribute
+  transform = graph.get("transform")
+
+  # this should begin with a scale directive
+  m = re.match(r"scale\((?P<x>\d+(\.\d*)?) (?P<y>\d+(\.\d*))\)", transform)
+  assert m is not None, f"failed to find 'scale' in '{transform}'"
+
+  x = m.group("x")
+  y = m.group("y")
+
+  # the scale should be somewhere in reasonable range of what is expected
+  assert float(x) >= 0.32 and float(x) <= 0.34, "inaccurate x scale"
+  assert float(y) >= 0.32 and float(y) <= 0.34, "inaccurate y scale"
+
+  # two digits of precision are insufficient for this example, so require a
+  # greater number of digits in both scale components
+  assert len(x) > 4, "insufficient precision in x scale"
+  assert len(y) > 4, "insufficient precision in y scale"
+
 @pytest.mark.parametrize("variant", [1, 2])
 @pytest.mark.skipif(shutil.which("gml2gv") is None, reason="gml2gv not available")
 def test_1869(variant: int):
-- 
2.40.0