add utility to conceal page top to force margin to be applied

4 files changed, 16 insertions, 13 deletions

diff --git a/lib/asciidoctor/pdf/converter.rb b/lib/asciidoctor/pdf/converter.rb
index 34abd4ab..dd3ace3f 100644
--- a/lib/asciidoctor/pdf/converter.rb
+++ b/lib/asciidoctor/pdf/converter.rb
@@ -3090,11 +3090,12 @@ module Asciidoctor
       # title (i.e., subject.title? returns true).
       def ink_caption subject, opts = {}
         if opts.delete :dry_run
-          force_top_margin = !at_page_top? if (force_top_margin = opts.delete :force_top_margin).nil?
           return (dry_run keep_together: true, single_page: :enforce do
-            # TODO: encapsulate this logic to force top margin to be applied
-            margin_box.instance_variable_set :@y, margin_box.absolute_top + 0.0001 if force_top_margin
-            ink_caption subject, opts
+            if opts.delete :force_top_margin
+              conceal_page_top { ink_caption subject, opts }
+            else
+              ink_caption subject, opts
+            end
           end).single_page_height
         end
         if ::Asciidoctor::AbstractBlock === subject
diff --git a/lib/asciidoctor/pdf/ext/prawn-table/cell/asciidoc.rb b/lib/asciidoctor/pdf/ext/prawn-table/cell/asciidoc.rb
index 01698156..0af9cd52 100644
--- a/lib/asciidoctor/pdf/ext/prawn-table/cell/asciidoc.rb
+++ b/lib/asciidoctor/pdf/ext/prawn-table/cell/asciidoc.rb
@@ -41,17 +41,10 @@ module Prawn
             extent = @pdf.dry_run keep_together: true, single_page: true do
               push_scratch parent_doc
               doc.catalog[:footnotes] = parent_doc.catalog[:footnotes]
-              if padding_y > 0
-                move_down padding_y
-              #elsif at_page_top?
-              else
-                # TODO: encapsulate this logic to force top margin to be applied
-                margin_box.instance_variable_set :@y, margin_box.absolute_top + 0.0001
-              end
               # NOTE: we should be able to use cell.max_width, but returns 0 in some conditions (like when colspan > 1)
               indent cell.padding_left, bounds.width - cell.width + cell.padding_right do
-                # TODO: truncate margin bottom of last block
-                traverse cell.content
+                move_down padding_y if padding_y > 0
+                conceal_page_top { traverse cell.content }
               end
               pop_scratch parent_doc
               doc.catalog[:footnotes] = parent_doc.catalog[:footnotes]
diff --git a/lib/asciidoctor/pdf/ext/prawn/extensions.rb b/lib/asciidoctor/pdf/ext/prawn/extensions.rb
index 713c20d5..2be47aec 100644
--- a/lib/asciidoctor/pdf/ext/prawn/extensions.rb
+++ b/lib/asciidoctor/pdf/ext/prawn/extensions.rb
@@ -252,6 +252,15 @@ module Asciidoctor
         @y == @margin_box.absolute_top
       end
 
+      # Prevents at_page_top? from returning true while yielding to the specified block.
+      #
+      def conceal_page_top
+        margin_box.instance_variable_set :@y, (old_top = margin_box.absolute_top) + 0.0001
+        yield
+      ensure
+        margin_box.instance_variable_set :@y, old_top
+      end
+
       # Returns whether the current page is the last page in the document.
       #
       def last_page?
diff --git a/spec/reference/image-svg-with-caption-scale-to-fit-page.pdf b/spec/reference/image-svg-with-caption-scale-to-fit-page.pdf
index 10e975e6..6ca95fab 100644
--- a/spec/reference/image-svg-with-caption-scale-to-fit-page.pdf
+++ b/spec/reference/image-svg-with-caption-scale-to-fit-page.pdf