Edit gatsby theme

packages/gatsby-theme/decks/beep.mdx

@@ -8,3 +8,4 @@
 ---
 
 HMR *should* work now
+

packages/gatsby-theme/gatsby-node.js

@@ -43,6 +43,12 @@ const mdxResolverPassthrough = fieldName => async (
   return result
 }
 
+const resolveTitle = async (...args) => {
+  const headings = await mdxResolverPassthrough('headings')(...args)
+  const [first = {}] = headings
+  return first.value || ''
+}
+
 exports.createSchemaCustomization = ({ actions, schema }) => {
   actions.createTypes(
     schema.buildObjectType({
@@ -52,6 +58,10 @@ exports.createSchemaCustomization = ({ actions, schema }) => {
         slug: {
           type: `String!`,
         },
+        title: {
+          type: 'String!',
+          resolve: resolveTitle,
+        },
         body: {
           type: `String!`,
           resolve: mdxResolverPassthrough(`body`),
@@ -72,6 +82,7 @@ exports.createPages = async ({ graphql, actions, reporter, pathPrefix }) => {
           node {
             id
             slug
+            title
           }
         }
       }

packages/gatsby-theme/src/components/deck.js

@@ -71,7 +71,7 @@ const DefaultMode = ({ children }) => <React.Fragment children={children} />
 
 export default ({
   slides = [],
-  pageContext: { slug },
+  pageContext: { title, slug },
   theme = {},
   themes = [],
   ...props
@@ -112,6 +112,7 @@ export default ({
   return (
     <>
       <Helmet>
+        {title && <title>{title}</title>}
         {head}
       </Helmet>
       <GoogleFont theme={mergedTheme} />

packages/gatsby-theme/src/templates/deck.js

@@ -9,6 +9,7 @@ export const pageQuery = graphql`
     deck: deck(id: { eq: $id }) {
       id
       body
+      title
     }
   }
 `