Support custom site description and thumbnail image for SEO and sharing (#696)

* Add  `description` to config
* Add `sharing_image` to config

exampleSite/config.toml

@@ -48,13 +48,7 @@ enableGitInfo = false
   smartypants = true  # `false` disables all smart punctuation substitutions (e.g. smart quotes, dashes, fractions).
 
 [params]
-  # Color theme.
-  #   Choose from `default`, `ocean`, `forest`, `coffee`, `dark`, or `1950s`.
-  color_theme = "default"
-
-  # Font style.
-  #   Choose from `default`, `classic`, or `playfair`.
-  font = "default"
+  # AUTHOR SETUP
 
   # Your details.
   name = "Lena Smith"
@@ -66,25 +60,20 @@ enableGitInfo = false
 
   gravatar = false  # Get your avatar from Gravatar.com? (true/false)
   avatar = "portrait.jpg"  # Specify an avatar image (in `static/img/` folder) or delete value to disable avatar.
+  
+  # Details for the Contact Widget
   email = "test@example.org"
   address = "Building 1 Room 1, Stanford University, California, 90210, USA"
   office_hours = "Monday 10:00 to 13:00 or email for appointment"
   phone = "888 888 88 88"
-  twitter = ""
   skype = "echo123"
   telegram = ""
-
-  # Enable Keybase in Contact widget by entering your keybase.io username.
-  keybase = ""
+  keybase = ""  # Your keybase.io username.
 
   # Discussion link (e.g. link to a forum, mailing list, or chat).
   #   Uncomment line below to use.
   #   discussion = { name = "Discuss", url = "https://discourse.gohugo.io" }
 
-  # Diplay a logo in navigation bar rather than title (optional).
-  #   To enable, place an image in `static/img/` and reference its filename below. To disable, set the value to "".
-  logo = ""
-
   # Enable/disable map in Contact widget.
   # To show your address on a map in the contact widget, you need to enter your latitude, longitude and choose
   # a map provider below.
@@ -106,6 +95,29 @@ enableGitInfo = false
   longitude = "-122.1697"
   zoom = 15
 
+  # SITE SETUP
+
+  # Color theme.
+  #   Choose from `default`, `ocean`, `forest`, `coffee`, `dark`, or `1950s`.
+  color_theme = "default"
+
+  # Font style.
+  #   Choose from `default`, `classic`, or `playfair`.
+  font = "default"
+
+  # Description for social sharing and search engines. If undefined, author role is used in place.
+  description = ""
+  
+  # Default image for social sharing and search engines. Place image in `static/img/` folder and specify image name here.
+  sharing_image = ""
+
+  # Twitter username (without @). Used when a vistor shares your site on Twitter.
+  twitter = ""
+
+  # Diplay a logo in navigation bar rather than title (optional).
+  #   To enable, place an image in `static/img/` and reference its filename below. To disable, set the value to "".
+  logo = ""
+
   # Date and time format (refer to https://sourcethemes.com/academic/docs/customization/#date-format )
   #   Examples: "Mon, Jan 2, 2006" or "2006-01-02"
   date_format = "Jan 2, 2006"

layouts/partials/header.html

@@ -11,15 +11,19 @@
 
   {{ $scr := .Scratch }}
   {{/* Generate page description. */}}
-  {{ $scr.Set "description" .Site.Params.role }}
-  {{ if .Params.abstract }}
-    {{ $scr.Set "description" .Params.abstract }}
-  {{ else if .Params.summary }}
-    {{ $scr.Set "description" .Params.summary }}
+  {{ $desc := "" }}
+  {{ if .Params.summary }}
+    {{ $desc = .Params.summary }}
+  {{ else if .Params.abstract }}
+    {{ $desc = .Params.abstract }}
   {{ else if .IsPage }}
-    {{ $scr.Set "description" .Summary }}
+    {{ $desc = .Summary }}
+  {{ else if .Site.Params.description }}
+    {{ $desc = .Site.Params.description }}
+  {{ else }}
+    {{ $desc = .Site.Params.role }}
   {{ end }}
-  <meta name="description" content="{{ $scr.Get "description" }}">
+  <meta name="description" content="{{ $desc }}">
 
   {{ range .Translations }}
   <link rel="alternate" hreflang="{{ .Lang }}" href="{{ .Permalink }}">
@@ -125,8 +129,16 @@
   <meta property="og:site_name" content="{{ .Site.Title }}">
   <meta property="og:url" content="{{ .Permalink }}">
   <meta property="og:title" content="{{ if not .IsHome }}{{ .Title }} | {{ end }}{{ .Site.Title }}">
-  <meta property="og:description" content="{{ $scr.Get "description" }}">
-  {{- with .Params.header.image }}<meta property="og:image" content="{{ printf "img/%s" . | absURL }}">{{end}}
+  <meta property="og:description" content="{{ $desc }}">
+  {{ $og_image := "" }}
+  {{ if .Params.header.image }}
+    {{ $og_image = .Params.header.image }}
+  {{ else if .Site.Params.sharing_image }}
+    {{ $og_image = .Site.Params.sharing_image }}
+  {{ else }}
+    {{ $og_image = "icon-192.png" }}
+  {{ end }}
+  {{- with $og_image }}<meta property="og:image" content="{{ printf "img/%s" . | absURL }}">{{end}}
   <meta property="og:locale" content="{{ .Site.LanguageCode | default "en-us" }}">
   {{ if .IsPage }}
   {{ if not .PublishDate.IsZero }}<meta property="article:published_time" content="{{ .PublishDate.Format "2006-01-02T15:04:05-07:00" | safeHTML }}">