resolves asciidoctor#582 display title for abstract

- display title for abstract
- allow abstract title to be customized by theme

data/themes/base-theme.yml

@@ -52,6 +52,8 @@ caption_margin_outside: 0
 abstract_font_size: 13.5
 abstract_line_height: 1.4
 abstract_padding: 0
+abstract_title_align: center
+abstract_title_font_style: bold
 admonition_border_color: 'EEEEEE'
 admonition_border_width: 0.5
 admonition_padding: [0, 12, 0, 12]

data/themes/default-theme.yml

@@ -131,6 +131,12 @@ abstract:
   line_height: $lead_line_height
   font_style: italic
   first_line_font_style: bold
+  title:
+    align: center
+    font_color: $heading_font_color
+    font_family: $heading_font_family
+    font_size: $heading_h4_font_size
+    font_style: $heading_font_style
 admonition:
   border_color: $base_border_color
   border_width: $base_border_width

docs/theming-guide.adoc

@@ -1819,6 +1819,40 @@ The keys in this category control the arrangement and style of the abstract.
 (default: 0)
 |abstract:
   padding: [0, 12, 0, 12]
+
+3+|*Key Prefix:* abstract_title
+
+|align
+|<<text-alignments,Text alignment>> +
+(default: center)
+|sidebar:
+  title:
+    align: center
+
+|font_color
+|<<colors,Color>>
+|sidebar:
+  title:
+    font_color: #333333
+
+|font_family
+|<<fonts,Font family name>>
+|sidebar:
+  title:
+    font_family: Noto Serif
+
+|font_size
+|<<values,Number>>
+|sidebar:
+  title:
+    font_size: 13
+
+|font_style
+|<<font-styles,Font style>> +
+(default: bold)
+|sidebar:
+  title:
+    font_style: bold
 |===
 
 === Thematic Break

lib/asciidoctor-pdf/converter.rb

@@ -374,6 +374,11 @@ def convert_floating_title node
   def convert_abstract node
     add_dest_for_block node if node.id
     pad_box @theme.abstract_padding do
+      if node.title?
+        theme_font :abstract_title do
+          layout_heading node.title, align: (@theme.abstract_title_align || @theme.base_align).to_sym
+        end
+      end
       theme_font :abstract do
         prose_opts = { line_height: @theme.abstract_line_height }
         # FIXME control more first_line_options using theme