resolves #2156 honor caption-align when element align is not left and caption-max-width is % of element width (PR #2157)

3 files changed, 53 insertions, 7 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 4410d495..f3ea8f8d 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -17,6 +17,7 @@ Enhancements::
 
 Bug Fixes::
 
+* honor `caption-align` when element align is not `left` and `caption-max-width` is % of element width (e.g., `fit-content(50%)`) (#2156)
 * allow theme to set font style of first line of abstract to `normal_italic` (#2138)
 * add support for `:color` option to `Prawn::Text::Formatted::Box` directly and remove workarounds
 * preserve columns on subsequent pages in the index section (#2149)
diff --git a/lib/asciidoctor/pdf/converter.rb b/lib/asciidoctor/pdf/converter.rb
index 56c4cb26..5a9c1b95 100644
--- a/lib/asciidoctor/pdf/converter.rb
+++ b/lib/asciidoctor/pdf/converter.rb
@@ -3119,11 +3119,22 @@ module Asciidoctor
         if (max_width = opts.delete :max_width) && max_width != 'none'
           if ::String === max_width
             if max_width.start_with? 'fit-content'
-              if max_width.end_with? 't', '()'
-                max_width = block_width || container_width
-              else
-                max_width = (block_width || container_width) * (max_width.slice 12, max_width.length - 1).to_f / 100.0
+              block_width ||= container_width
+              unless max_width.end_with? 't', '()'
+                max_width = block_width * (max_width.slice 12, max_width.length - 1).to_f / 100.0
+                if (caption_width_delta = block_width - max_width) > 0
+                  case align
+                  when :right
+                    indent_by[0] += caption_width_delta
+                  when :center
+                    indent_by[0] += caption_width_delta * 0.5
+                    indent_by[1] += caption_width_delta * 0.5
+                  else # :left, nil
+                    indent_by[1] += caption_width_delta
+                  end
+                end
               end
+              max_width = block_width
             elsif max_width.end_with? '%'
               max_width = [max_width.to_f / 100 * bounds.width, bounds.width].min
               block_align = align
@@ -3138,11 +3149,12 @@ module Asciidoctor
           if (remainder = container_width - max_width) > 0
             case block_align
             when :right
-              indent_by = [remainder, 0]
+              indent_by[0] += remainder
             when :center
-              indent_by = [(side_margin = remainder * 0.5), side_margin]
+              indent_by[0] += remainder * 0.5
+              indent_by[1] += remainder * 0.5
             else # :left, nil
-              indent_by = [0, remainder]
+              indent_by[1] += remainder
             end
           end
         end
diff --git a/spec/image_spec.rb b/spec/image_spec.rb
index 0b57e273..704a2211 100644
--- a/spec/image_spec.rb
+++ b/spec/image_spec.rb
@@ -2059,6 +2059,39 @@ describe 'Asciidoctor::PDF::Converter - Image' do
       (expect caption_text_l1[:x]).to eql tux_image[:x]
       (expect caption_text_l2[:x]).to eql caption_text_l1[:x]
     end
+
+    it 'should align caption within width of image if alignment is fixed and max-width is percentage of image width' do
+      pdf_theme = {
+        image_caption_align: 'left',
+        image_caption_max_width: 'fit-content(50%)',
+      }
+
+      input = <<~'EOS'
+      .This is a picture of our beloved Tux.
+      image::tux.png[align=right]
+      EOS
+
+      pdf = to_pdf input, pdf_theme: pdf_theme, analyze: :image
+
+      images = pdf.images
+      (expect images).to have_size 1
+      tux_image = images[0]
+
+      pdf = to_pdf input, pdf_theme: pdf_theme, analyze: true
+
+      caption_texts = pdf.text
+      (expect caption_texts).to have_size 3
+      caption_text_l1, caption_text_l2, caption_text_l3 = caption_texts
+      (expect caption_text_l1[:y]).to be > caption_text_l2[:y]
+      (expect caption_text_l2[:y]).to be > caption_text_l3[:y]
+      (expect caption_text_l1[:string]).to start_with 'Figure 1.'
+      (expect caption_text_l1[:width]).to be < tux_image[:width] * 0.5
+      (expect caption_text_l2[:width]).to be < tux_image[:width] * 0.5
+      (expect caption_text_l3[:width]).to be < tux_image[:width] * 0.5
+      (expect caption_text_l1[:x]).to eql tux_image[:x]
+      (expect caption_text_l2[:x]).to eql caption_text_l1[:x]
+      (expect caption_text_l3[:x]).to eql caption_text_l2[:x]
+    end
   end
 
   context 'Border' do