backport fix for #2012 don't advance image that's first child of bloc…

…k at top of page if image is taller than page

CHANGELOG.adoc

@@ -13,6 +13,7 @@ Bug Fixes::
 * decouple tests from path of PWD (#2444)
 * consider inherited styles when analyzing glyphs for fallback font support (#2463)
 * add fallback character for placeholder character when using AFM font (#2453)
+* don't advance image that's first child of block at top of page if image is taller than page (#2012)
 
 == 2.3.9 (2023-06-28) - @mojavelinux
 

lib/asciidoctor/pdf/converter.rb

@@ -1802,7 +1802,7 @@ def convert_image node, opts = {}
               end
               # NOTE: shrink image so it fits within available space; group image & caption
               if (rendered_h = svg_size.output_height) > (available_h = cursor - caption_h)
-                unless pinned || at_page_top?
+                unless pinned || at_page_top? || (node.first_child? && (node.parent.attr? 'pdf-at-top'))
                   advance_page
                   available_h = cursor - caption_h
                 end
@@ -1844,7 +1844,7 @@ def convert_image node, opts = {}
               rendered_w, rendered_h = image_info.calc_image_dimensions width: (width || [available_w, actual_w].min)
               # NOTE: shrink image so it fits within available space; group image & caption
               if rendered_h > (available_h = cursor - caption_h)
-                unless pinned || at_page_top?
+                unless pinned || at_page_top? || (node.first_child? && (node.parent.attr? 'pdf-at-top'))
                   advance_page
                   available_h = cursor - caption_h
                 end

lib/asciidoctor/pdf/ext/asciidoctor/abstract_block.rb

@@ -13,6 +13,10 @@ def last_child
     blocks[-1]
   end
 
+  def first_child?
+    self == parent.blocks[0]
+  end
+
   def last_child?
     self == parent.blocks[-1]
   end

lib/asciidoctor/pdf/ext/prawn/extensions.rb

@@ -1002,16 +1002,25 @@ def with_dry_run &block
       # start_new_page. Using start_new_page can mangle the calculation of content block's extent.
       #
       def arrange_block node, &block
-        keep_together = (node.option? 'unbreakable') && !at_page_top?
+        if at_page_top?
+          at_top = true
+        else
+          at_top = true if node.first_child? && (node.parent.attr? 'pdf-at-top')
+          keep_together = true if node.option? 'unbreakable'
+        end
+        node.set_attr 'pdf-at-top', '' if at_top
         doc = node.document
         block_for_scratch = proc do
+          at_top = node.set_attr 'pdf-at-top', '' if !at_top && at_page_top?
           push_scratch doc
           instance_exec(&block)
         ensure
           pop_scratch doc
         end
         extent = dry_run keep_together: keep_together, onto: [self, keep_together], &block_for_scratch
         scratch? ? block_for_scratch.call : (yield extent)
+      ensure
+        node.remove_attr 'pdf-at-top' if at_top
       end
 
       # This method installs an on_page_create_callback that stops processing if the first page is

spec/arrange_block_spec.rb

@@ -927,8 +927,7 @@ def content
         (expect image[:y]).to eql 742.0
       end
 
-      # NOTE: this scenario renders an example block that starts with an empty page
-      it 'should split block across pages that contains image taller than page at start of block', negative: true do
+      it 'should split block across pages that contains image taller than page at start of block' do
         input = <<~'EOS'
         ====
         image::tall-spacer.png[]
@@ -937,18 +936,16 @@ def content
         pdf = to_pdf input, pdf_theme: pdf_theme, analyze: true
         images = (to_pdf input, pdf_theme: pdf_theme, analyze: :image).images
         pages = pdf.pages
-        (expect pages).to have_size 2
+        (expect pages).to have_size 1
         page_width, page_height = (get_page_size pdf, 1).map(&:to_f)
         page_margin = pdf_theme[:page_margin].to_f
         (expect images).to have_size 1
         image = images[0]
-        (expect image[:page_number]).to be 2
-        (expect image[:y]).to eql (page_height - page_margin)
-        (expect image[:height]).to eql (page_height - page_margin * 2)
+        (expect image[:page_number]).to be 1
+        (expect image[:y]).to eql (page_height - page_margin - 12)
+        (expect image[:height]).to eql (page_height - 12 - page_margin * 2)
         p1_gs = (pdf.extract_graphic_states pages[0][:raw_content])[0]
         (expect p1_gs).to have_background color: 'FFFFCC', top_left: [page_margin, page_height - page_margin], bottom_right: [page_width - page_margin, page_margin]
-        p2_gs = (pdf.extract_graphic_states pages[1][:raw_content])[0]
-        (expect p2_gs).to have_background color: 'FFFFCC', top_left: [page_margin, page_height - page_margin], bottom_right: [page_width - page_margin, page_margin]
       end
 
       it 'should split block across pages that contains image taller than page that follows text' do
@@ -1348,8 +1345,7 @@ def content
         (expect image[:y]).to eql 711.009
       end
 
-      # NOTE: this scenario renders an example block that starts with an empty page
-      it 'should split block across pages that contains image taller than page at start of block', negative: true do
+      it 'should split block across pages that contains image taller than page at start of block' do
         input = <<~'EOS'
         before block
 
@@ -1360,19 +1356,17 @@ def content
         pdf = to_pdf input, pdf_theme: pdf_theme, analyze: true
         images = (to_pdf input, pdf_theme: pdf_theme, analyze: :image).images
         pages = pdf.pages
-        (expect pages).to have_size 3
+        (expect pages).to have_size 2
         page_width, page_height = (get_page_size pdf, 1).map(&:to_f)
         page_margin = pdf_theme[:page_margin].to_f
         (expect images).to have_size 1
         image = images[0]
-        (expect image[:page_number]).to be 3
-        (expect image[:y]).to eql (page_height - page_margin)
-        (expect image[:height]).to eql (page_height - page_margin * 2)
+        (expect image[:page_number]).to be 2
+        (expect image[:y]).to eql (page_height - page_margin - 12)
+        (expect image[:height]).to eql (page_height - 12 - page_margin * 2)
         (expect (pdf.extract_graphic_states pages[0][:raw_content])).to be_empty
         p2_gs = (pdf.extract_graphic_states pages[1][:raw_content])[0]
         (expect p2_gs).to have_background color: 'FFFFCC', top_left: [page_margin, page_height - page_margin], bottom_right: [page_width - page_margin, page_margin]
-        p3_gs = (pdf.extract_graphic_states pages[2][:raw_content])[0]
-        (expect p3_gs).to have_background color: 'FFFFCC', top_left: [page_margin, page_height - page_margin], bottom_right: [page_width - page_margin, page_margin]
       end
 
       # FIXME: this fails when block is unbreakable