resolves #2219 fix layout of collapsible block (PR #2220)

3 files changed, 88 insertions, 8 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 83081150..d6771a67 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -9,6 +9,7 @@ For a detailed view of what has changed, refer to the {url-repo}/commits/main[co
 
 Bug Fixes::
 
+* indent content of collapsible block and apply bottom margin to match style of HTML output (#2219)
 * patch prawn-gmagick to reread bit depth of a PNG image if it extracts the wrong value (#2216)
 * interpret width of SVG correctly when width is defined in file using px units (#2215)
 * don't crash if inline role defines border width but not border color
diff --git a/lib/asciidoctor/pdf/converter.rb b/lib/asciidoctor/pdf/converter.rb
index c7dcce77..a5a33b79 100644
--- a/lib/asciidoctor/pdf/converter.rb
+++ b/lib/asciidoctor/pdf/converter.rb
@@ -1164,8 +1164,26 @@ module Asciidoctor
       alias convert_literal convert_code
       alias convert_listing_or_literal convert_code
 
+      def convert_collapsible node
+        id = node.id
+        title = (collapsible_marker = %(\u25bc )) + (node.title? ? node.title : 'Details')
+        indent_by = theme_font(:caption) { rendered_width_of_string collapsible_marker }
+        if !at_page_top? && (id || (node.option? 'unbreakable'))
+          arrange_block node do
+            add_dest_for_block node if id
+            tare_first_page_content_stream { ink_caption title }
+            indent(indent_by) { traverse node }
+          end
+        else
+          add_dest_for_block node if id
+          tare_first_page_content_stream { ink_caption title }
+          indent(indent_by) { traverse node }
+        end
+        theme_margin :block, :bottom, (next_enclosed_block node)
+      end
+
       def convert_example node
-        return convert_open node if node.option? 'collapsible'
+        return convert_collapsible node if node.option? 'collapsible'
         caption_bottom = @theme.example_caption_end&.to_sym == :bottom
         arrange_block node do |extent|
           add_dest_for_block node if node.id
@@ -1190,14 +1208,12 @@ module Asciidoctor
         if !at_page_top? && (has_title || id || (node.option? 'unbreakable'))
           arrange_block node do
             add_dest_for_block node if id
-            tare_first_page_content_stream do
-              node.context == :example ? (ink_caption %(\u25bc #{node.title})) : (ink_caption node, labeled: false)
-            end if has_title
+            tare_first_page_content_stream { ink_caption node, labeled: false } if has_title
             traverse node
           end
         else
           add_dest_for_block node if id
-          node.context == :example ? (ink_caption %(\u25bc #{node.title})) : (ink_caption node, labeled: false) if has_title
+          ink_caption node, labeled: false if has_title
           traverse node
         end
       end
diff --git a/spec/example_spec.rb b/spec/example_spec.rb
index 4060f655..6379ae3f 100644
--- a/spec/example_spec.rb
+++ b/spec/example_spec.rb
@@ -340,21 +340,84 @@ describe 'Asciidoctor::PDF::Converter - Example' do
     (expect (text_left - left).to_f).to eql 12.0
   end
 
-  it 'should use informal title and no border or shading if collapsible option is set' do
+  it 'should use informal title, indented content, no border or shading, and bottom margin if collapsible option is set' do
     input = <<~'EOS'
     .Reveal Answer
     [%collapsible]
     ====
     This is a PDF, so the answer is always visible.
     ====
+
+    Paragraph following collapsible block.
     EOS
 
     pdf = to_pdf input, analyze: true
     lines = pdf.lines
-    (expect lines).to eql [%(\u25bc Reveal Answer), 'This is a PDF, so the answer is always visible.']
-    (expect pdf.text[0][:x]).to eql pdf.text[1][:x]
+    expected_lines = [
+      %(\u25bc Reveal Answer),
+      'This is a PDF, so the answer is always visible.',
+      'Paragraph following collapsible block.',
+    ]
+    (expect lines).to eql expected_lines
+    (expect pdf.text[0][:x]).to eql pdf.text[2][:x]
+    (expect pdf.text[1][:x]).to be > pdf.text[2][:x]
+    (expect pdf.text[1][:y] - (pdf.text[2][:y] + pdf.text[2][:font_size])).to be > 12
 
     pdf = to_pdf input, analyze: :line
     (expect pdf.lines).to be_empty
   end
+
+  # see https://developer.mozilla.org/en-US/docs/Web/HTML/Element/summary#default_label_text
+  it 'should use fallback title for collapsible block if no title is specified' do
+    input = <<~'EOS'
+    [%collapsible]
+    ====
+    These are the details.
+    ====
+    EOS
+
+    pdf = to_pdf input, analyze: true
+    (expect pdf.text[0][:string]).to eql %(\u25bc Details)
+  end
+
+  it 'should align left margin of content of collapsible block with start of title text' do
+    input = <<~'EOS'
+    .*Spoiler*
+    [%collapsible]
+    ====
+    Now you can't unsee it.
+    Muahahahaha.
+    ====
+    EOS
+
+    pdf = to_pdf input, analyze: true
+    (expect pdf.text[0][:x]).to eql 48.24
+    (expect pdf.text[1][:x]).to be > 48.24
+    (expect pdf.text[2][:x]).to be > 48.24
+    (expect pdf.text[1][:x]).to eql pdf.text[2][:x]
+  end
+
+  it 'should insert block margin between bottom of content and next block' do
+    pdf_theme = {
+      code_background_color: 'transparent',
+      code_border_radius: 0,
+      code_border_width: [1, 0],
+    }
+    input = <<~'EOS'
+    [%collapsible]
+    ====
+    ----
+    inside
+    ----
+    ====
+
+    ----
+    below
+    ----
+    EOS
+
+    lines = (to_pdf input, pdf_theme: pdf_theme, analyze: :line).lines.sort_by {|it| -it[:from][:y] }
+    (expect lines).to have_size 4
+    (expect lines[1][:from][:y] - lines[2][:from][:y]).to eql 12.0
+  end
 end