Inherit gradient attributes from the linked/parent element

mogest · Sep 16, 2024 · 0158ec1 · 0158ec1
1 parent ba87994
commit 0158ec1
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Showing 2 changed files with 63 additions and 25 deletions.
diff --git a/lib/prawn/svg/elements/gradient.rb b/lib/prawn/svg/elements/gradient.rb
@@ -12,7 +12,6 @@ def parse
     raise SkipElementQuietly if attributes['id'].nil?
 
     @parent_gradient = document.gradients[href_attribute[1..]] if href_attribute && href_attribute[0] == '#'
-
     assert_compatible_prawn_version
     load_gradient_configuration
     load_coordinates
@@ -34,6 +33,10 @@ def gradient_arguments(element)
     arguments&.merge(base_arguments)
   end
 
+  def derive_attribute(name)
+    attributes[name] || parent_gradient&.derive_attribute(name)
+  end
+
   private
 
   def specific_gradient_arguments(element)
@@ -86,44 +89,44 @@ def assert_compatible_prawn_version
   end
 
   def load_gradient_configuration
-    @units = attributes['gradientUnits'] == 'userSpaceOnUse' ? :user_space : :bounding_box
+    @units = derive_attribute('gradientUnits') == 'userSpaceOnUse' ? :user_space : :bounding_box
 
-    if (transform = attributes['gradientTransform'])
+    if (transform = derive_attribute('gradientTransform'))
       @transform_matrix = parse_transform_attribute(transform)
     end
 
-    if (spread_method = attributes['spreadMethod']) && spread_method != 'pad'
+    if (spread_method = derive_attribute('spreadMethod')) && spread_method != 'pad'
       warnings << "prawn-svg only currently supports the 'pad' spreadMethod attribute value"
     end
   end
 
   def load_coordinates
     case [type, units]
     when [:linear, :bounding_box]
-      @x1 = parse_zero_to_one(attributes['x1'], 0)
-      @y1 = parse_zero_to_one(attributes['y1'], 0)
-      @x2 = parse_zero_to_one(attributes['x2'], 1)
-      @y2 = parse_zero_to_one(attributes['y2'], 0)
+      @x1 = parse_zero_to_one(derive_attribute('x1'), 0)
+      @y1 = parse_zero_to_one(derive_attribute('y1'), 0)
+      @x2 = parse_zero_to_one(derive_attribute('x2'), 1)
+      @y2 = parse_zero_to_one(derive_attribute('y2'), 0)
 
     when [:linear, :user_space]
-      @x1 = x(attributes['x1'])
-      @y1 = y(attributes['y1'])
-      @x2 = x(attributes['x2'])
-      @y2 = y(attributes['y2'])
+      @x1 = x(derive_attribute('x1'))
+      @y1 = y(derive_attribute('y1'))
+      @x2 = x(derive_attribute('x2'))
+      @y2 = y(derive_attribute('y2'))
 
     when [:radial, :bounding_box]
-      @cx = parse_zero_to_one(attributes['cx'], 0.5)
-      @cy = parse_zero_to_one(attributes['cy'], 0.5)
-      @fx = parse_zero_to_one(attributes['fx'], cx)
-      @fy = parse_zero_to_one(attributes['fy'], cy)
-      @radius = parse_zero_to_one(attributes['r'], 0.5)
+      @cx = parse_zero_to_one(derive_attribute('cx'), 0.5)
+      @cy = parse_zero_to_one(derive_attribute('cy'), 0.5)
+      @fx = parse_zero_to_one(derive_attribute('fx'), cx)
+      @fy = parse_zero_to_one(derive_attribute('fy'), cy)
+      @radius = parse_zero_to_one(derive_attribute('r'), 0.5)
 
     when [:radial, :user_space]
-      @cx = x(attributes['cx'] || '50%')
-      @cy = y(attributes['cy'] || '50%')
-      @fx = x(attributes['fx'] || attributes['cx'])
-      @fy = y(attributes['fy'] || attributes['cy'])
-      @radius = pixels(attributes['r'] || '50%')
+      @cx = x(derive_attribute('cx') || '50%')
+      @cy = y(derive_attribute('cy') || '50%')
+      @fx = x(derive_attribute('fx') || derive_attribute('cx'))
+      @fy = y(derive_attribute('fy') || derive_attribute('cy'))
+      @radius = pixels(derive_attribute('r') || '50%')
 
     else
       raise 'unexpected type/unit system'

diff --git a/spec/prawn/svg/elements/gradient_spec.rb b/spec/prawn/svg/elements/gradient_spec.rb
@@ -2,11 +2,11 @@
 
 describe Prawn::SVG::Elements::Gradient do
   let(:document) { Prawn::SVG::Document.new(svg, [800, 600], { width: 800, height: 600 }) }
-  let(:element)  { Prawn::SVG::Elements::Gradient.new(document, document.root, [], fake_state) }
+  let(:root_element) { Prawn::SVG::Elements::Root.new(document, document.root, []) }
+  let(:element) { document.gradients['flag'] }
 
   before do
-    allow(element).to receive(:assert_compatible_prawn_version)
-    element.process
+    root_element.process
   end
 
   describe 'object bounding box with linear gradient' do
@@ -133,4 +133,39 @@
       )
     end
   end
+
+  context 'when a gradient is linked to another' do
+    let(:svg) do
+      <<-SVG
+        <svg>
+          <linearGradient id="flag" gradientUnits="userSpaceOnUse" x1="100" y1="500" x2="200" y2="600">
+            <stop offset="0" stop-color="red"/>
+            <stop offset="1" stop-color="blue"/>
+          </linearGradient>
+
+          <linearGradient id="flag-2" href="#flag" x1="150" x2="220" />
+
+          <linearGradient id="flag-3" href="#flag-2" x1="170" />
+        </svg>
+      SVG
+    end
+
+    it 'correctly inherits the attributes from the parent element' do
+      arguments = document.gradients['flag-2'].gradient_arguments(double)
+      expect(arguments).to eq(
+        from:                  [150.0, 100.0],
+        to:                    [220.0, 0.0],
+        stops:                 [[0, 'ff0000'], [1, '0000ff']],
+        apply_transformations: true
+      )
+
+      arguments = document.gradients['flag-3'].gradient_arguments(double)
+      expect(arguments).to eq(
+        from:                  [170.0, 100.0],
+        to:                    [220.0, 0.0],
+        stops:                 [[0, 'ff0000'], [1, '0000ff']],
+        apply_transformations: true
+      )
+    end
+  end
 end