CP-14715 - Fix auto-detected form fields on rotated PDFs

lib/templates/find_acro_fields.rb

@@ -29,6 +29,9 @@ module FindAcroFields
       2 => 'right'
     }.freeze
 
+    # /Rotate values that swap media width and height in visual space.
+    SWAP_DIMENSION_ROTATIONS = [90, 270].freeze
+
     module_function
 
     # rubocop:disable Metrics
@@ -59,6 +62,14 @@ def call(pdf, attachment, data)
           page_width = media_box[2] - media_box[0]
           page_height = media_box[3] - media_box[1]
 
+          # Transform media-space Rect into visual (post-rotation) space so
+          # areas match Pdfium previews and fill-time page.rotate(flatten: true).
+          rotation = (page[:Rotate] || 0).to_i % 360
+          if rotation != 0
+            x0, y0, x1, y1 = apply_page_rotation(x0, y0, x1, y1, rotation, page_width, page_height)
+            page_width, page_height = page_height, page_width if SWAP_DIMENSION_ROTATIONS.include?(rotation)
+          end
+
           x = x0
           y = y0
           w = x1 - x0
@@ -77,6 +88,9 @@ def call(pdf, attachment, data)
 
           next if attrs[:w].zero? || attrs[:h].zero?
 
+          # Comb cell_w still divides visual width by MaxLen. On 90/270 pages a comb
+          # whose cells ran along media-x can get the wrong axis; pre-existing, not
+          # fixed by the rotation map above (would need axis-aware cell spacing).
           if child_field[:MaxLen] && child_field.try(:concrete_field_type) == :comb_text_field
             attrs[:cell_w] = w / page_width.to_f / child_field[:MaxLen].to_f
           end
@@ -124,6 +138,20 @@ def correct_coordinates(x_coord, y_coord, shift, media_box_start)
       [corrected_x, corrected_y]
     end
 
+    # Map a media-space Rect through PDF /Rotate (clockwise degrees) into visual
+    # page space. Mirrors HexaPDF::Type::Page#rotate(0, flatten: true) corner math.
+    # HexaPDF builds its flatten matrix from absolute box edges; this takes width/
+    # height extents and only matches that math because correct_coordinates has
+    # already shifted the Rect onto a 0-origin box before we get here.
+    def apply_page_rotation(llx, lly, urx, ury, rotation, width, height)
+      case rotation
+      when 90  then [lly, width - urx, ury, width - llx]
+      when 180 then [width - urx, height - ury, width - llx, height - lly]
+      when 270 then [height - ury, llx, height - lly, urx]
+      else          [llx, lly, urx, ury]
+      end
+    end
+
     def build_field_properties(field)
       field_name = field.full_field_name if field.full_field_name.to_s.match?(FIELD_NAME_REGEXP)
 

spec/lib/templates/find_acro_fields_spec.rb

@@ -0,0 +1,138 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Templates::FindAcroFields do
+  # Letter media box; field Rect chosen so expected fractions are simple.
+  let(:page_w) { 612.0 }
+  let(:page_h) { 792.0 }
+  let(:field_rect) { [100.0, 100.0, 300.0, 130.0] } # x0, y0, x1, y1 (PDF bottom-left origin)
+  let(:attachment) { instance_double(ActiveStorage::Attachment, uuid: SecureRandom.uuid) }
+
+  def build_pdf(rotate: nil, media_box: nil, crop_box: nil, rect: nil)
+    doc = HexaPDF::Document.new
+    page = doc.pages.add(media_box || [0, 0, page_w, page_h])
+    page[:CropBox] = crop_box if crop_box
+    page[:Rotate] = rotate if rotate && rotate != 0
+
+    form = doc.acro_form(create: true)
+    form.create_text_field('name').create_widget(page, Rect: (rect || field_rect).dup)
+
+    doc
+  end
+
+  def extract_area(rotate: nil, media_box: nil, crop_box: nil, rect: nil)
+    pdf = build_pdf(rotate:, media_box:, crop_box:, rect:)
+    fields = described_class.call(pdf, attachment, '')
+    expect(fields).not_to be_empty
+    fields.first[:areas].first
+  end
+
+  def expect_area(area, expected_x:, expected_y:, expected_w:, expected_h:)
+    expect(area[:x]).to be_within(1e-6).of(expected_x)
+    expect(area[:y]).to be_within(1e-6).of(expected_y)
+    expect(area[:w]).to be_within(1e-6).of(expected_w)
+    expect(area[:h]).to be_within(1e-6).of(expected_h)
+    expect(area[:page]).to eq(0)
+    expect(area[:attachment_uuid]).to eq(attachment.uuid)
+  end
+
+  describe '.call with page rotation' do
+    it 'preserves media-normalized coords when /Rotate is absent' do
+      area = extract_area(rotate: nil)
+
+      expect_area(
+        area,
+        expected_x: 100 / page_w,
+        expected_y: (page_h - 130) / page_h,
+        expected_w: 200 / page_w,
+        expected_h: 30 / page_h
+      )
+    end
+
+    it 'preserves media-normalized coords when /Rotate is 0' do
+      area = extract_area(rotate: 0)
+
+      expect_area(
+        area,
+        expected_x: 100 / page_w,
+        expected_y: (page_h - 130) / page_h,
+        expected_w: 200 / page_w,
+        expected_h: 30 / page_h
+      )
+    end
+
+    it 'maps fields into visual space for /Rotate 90' do
+      # Visual rect: [100, 312, 130, 512], visual dims 792×612
+      area = extract_area(rotate: 90)
+
+      expect_area(
+        area,
+        expected_x: 100 / page_h,
+        expected_y: (page_w - 512) / page_w,
+        expected_w: 30 / page_h,
+        expected_h: 200 / page_w
+      )
+    end
+
+    it 'maps fields into visual space for /Rotate 180' do
+      # Visual rect: [312, 662, 512, 692], visual dims 612×792
+      area = extract_area(rotate: 180)
+
+      expect_area(
+        area,
+        expected_x: 312 / page_w,
+        expected_y: (page_h - 692) / page_h,
+        expected_w: 200 / page_w,
+        expected_h: 30 / page_h
+      )
+    end
+
+    it 'maps fields into visual space for /Rotate 270' do
+      # Visual rect: [662, 100, 692, 300], visual dims 792×612
+      area = extract_area(rotate: 270)
+
+      expect_area(
+        area,
+        expected_x: 662 / page_h,
+        expected_y: (page_w - 300) / page_w,
+        expected_w: 30 / page_h,
+        expected_h: 200 / page_w
+      )
+    end
+
+    it 'maps fields for /Rotate 90 when MediaBox is not 0-origin' do
+      # Offsets [10, 20]; absolute Rect chosen so correct_coordinates yields the
+      # same 0-origin rect as the base cases ([100, 100, 300, 130]). Extents-based
+      # rotation only matches HexaPDF flatten after that normalization.
+      media_box = [10.0, 20.0, 10.0 + page_w, 20.0 + page_h]
+      rect = [110.0, 120.0, 310.0, 150.0]
+      area = extract_area(rotate: 90, media_box:, rect:)
+
+      expect_area(
+        area,
+        expected_x: 100 / page_h,
+        expected_y: (page_w - 512) / page_w,
+        expected_w: 30 / page_h,
+        expected_h: 200 / page_w
+      )
+    end
+
+    it 'uses CropBox extents for /Rotate 90 when CropBox differs from MediaBox' do
+      # media_box up top is CropBox whenever present. Larger MediaBox must not
+      # change width/height or the post-correct_coordinates origin.
+      media_box = [0.0, 0.0, 700.0, 900.0]
+      crop_box = [10.0, 20.0, 10.0 + page_w, 20.0 + page_h]
+      rect = [110.0, 120.0, 310.0, 150.0]
+      area = extract_area(rotate: 90, media_box:, crop_box:, rect:)
+
+      expect_area(
+        area,
+        expected_x: 100 / page_h,
+        expected_y: (page_w - 512) / page_w,
+        expected_w: 30 / page_h,
+        expected_h: 200 / page_w
+      )
+    end
+  end
+end