read padding from correct box when creating new page

resolves prawnpdf#1121

CHANGELOG.md

@@ -1,5 +1,13 @@
 ## PrawnPDF master branch
 
+## Unreleased
+
+### Apply correct margin box when creating or switching pages
+
+When creating a new page or returning to a page previously created, compute the margin box correctly.
+
+(Dan Allen, [#1122](https://github.com/prawnpdf/prawn/pull/1022))
+
 ## PrawnPDF 2.3.0
 
 ### Added OpenType Font Support

lib/prawn/document.rb

@@ -720,15 +720,17 @@ def generate_margin_box
           (page.margins[:top] + page.margins[:bottom])
       )
 
-      # This check maintains indentation settings across page breaks
+      # update bounding box if not flowing from the previous page
+      unless @bounding_box&.parent
+        old_margin_box = @bounding_box
+        @bounding_box = @margin_box
+      end
+
+      # maintains indentation settings across page breaks
       if old_margin_box
         @margin_box.add_left_padding(old_margin_box.total_left_padding)
         @margin_box.add_right_padding(old_margin_box.total_right_padding)
       end
-
-      # we must update bounding box if not flowing from the previous page
-      #
-      @bounding_box = @margin_box unless @bounding_box&.parent
     end
 
     def apply_margin_options(options)