1 files changed, 25 insertions, 0 deletions
diff --git a/graph/web/legacy.js b/graph/web/legacy.js
new file mode 100644
index 00000000..4c1b7ef8
--- /dev/null
+++ b/graph/web/legacy.js
@@ -0,0 +1,25 @@
+// Only earlier chapters need Graphviz. Load it on the first bare-DOT frame.
+let dotView;
+async function drawDot(dot) {
+  if (!dotView) {
+    dotView = (async () => {
+      for (const src of ["vendor/graphviz.umd.js", "vendor/d3-graphviz.js"]) {
+        await new Promise((resolve, reject) => {
+          const script = document.createElement("script");
+          script.src = src; script.onload = resolve;
+          script.onerror = () => reject(new Error("Cannot load " + src));
+          document.head.append(script);
+        });
+      }
+      return new Promise((resolve, reject) => {
+        const view = d3.select("#dot").graphviz({useWorker: false, fit: true})
+          .onerror(reject).on("initEnd", () => resolve(view))
+          .transition(() => d3.transition("main").ease(d3.easeLinear).duration(500));
+      });
+    })();
+  }
+  const view = await dotView;
+  const host = document.getElementById("dot");
+  view.width(host.clientWidth).height(host.clientHeight);
+  await new Promise((resolve, reject) => view.onerror(reject).renderDot(dot, resolve));
+}