Merge pull request #31 from blocknotes/css-initial-values

Handle CSS `initial` values

Author: blocknotes

README.md

@@ -90,6 +90,8 @@ CSS attributes (dimensional units are ignored and considered in pixel):
 - **top**: see *position (absolute)*
 - **width**: for *img* tag, support also percentage, ex. `<img src="image.jpg" style="width: 50%; height: 200px"/>`
 
+The above attributes supports the `initial` value to reset them to their original value.
+
 For colors, the supported formats are:
 - 3 hex digits, ex. `color: #FB1`;
 - 6 hex digits, ex. `color: #abcdef`;

lib/prawn_html/attributes.rb

@@ -1,10 +1,11 @@
 # frozen_string_literal: true
 
 require 'ostruct'
+require 'set'
 
 module PrawnHtml
   class Attributes < OpenStruct
-    attr_reader :styles
+    attr_reader :initial, :styles
 
     STYLES_APPLY = {
       block: %i[align bottom leading left margin_left padding_left position right top],
@@ -19,13 +20,13 @@ class Attributes < OpenStruct
       'color' => { key: :color, set: :convert_color },
       'font-family' => { key: :font, set: :unquote },
       'font-size' => { key: :size, set: :convert_size },
-      'font-style' => { key: :styles, set: :append_styles },
-      'font-weight' => { key: :styles, set: :append_styles },
+      'font-style' => { key: :styles, set: :append_styles, values: %i[italic] },
+      'font-weight' => { key: :styles, set: :append_styles, values: %i[bold] },
       'href' => { key: :link, set: :copy_value },
       'letter-spacing' => { key: :character_spacing, set: :convert_float },
       'list-style-type' => { key: :list_style_type, set: :unquote },
-      'text-decoration' => { key: :styles, set: :append_text_decoration },
-      'vertical-align' => { key: :styles, set: :append_styles },
+      'text-decoration' => { key: :styles, set: :append_styles, values: %i[underline] },
+      'vertical-align' => { key: :styles, set: :append_styles, values: %i[subscript superscript] },
       'white-space' => { key: :white_space, set: :convert_symbol },
       # tag opening styles
       'break-before' => { key: :break_before, set: :convert_symbol },
@@ -44,7 +45,9 @@ class Attributes < OpenStruct
       'position' => { key: :position, set: :convert_symbol },
       'right' => { key: :right, set: :convert_size, options: :width },
       'text-align' => { key: :align, set: :convert_symbol },
-      'top' => { key: :top, set: :convert_size, options: :height }
+      'top' => { key: :top, set: :convert_size, options: :height },
+      # special styles
+      'text-decoration-line-through' => { key: :callback, set: :callback_strike_through }
     }.freeze
 
     STYLES_MERGE = %i[margin_left padding_left].freeze
@@ -53,6 +56,7 @@ class Attributes < OpenStruct
     def initialize(attributes = {})
       super
       @styles = {} # result styles
+      @initial = Set.new
     end
 
     # Processes the data attributes
@@ -74,6 +78,33 @@ def merge_text_styles!(text_styles, options: {})
       process_styles(hash_styles, options: options) unless hash_styles.empty?
     end
 
+    # Remove an attribute value from the context styles
+    #
+    # @param context_styles [Hash] hash of the context styles that will be updated
+    # @param rule [Hash] rule from the STYLES_LIST to lookup in the context style for value removal
+    def remove_value(context_styles, rule)
+      if rule[:set] == :append_styles
+        context_styles[rule[:key]] -= rule[:values] if context_styles[:styles]
+      else
+        default = Context::DEFAULT_STYLES[rule[:key]]
+        default ? (context_styles[rule[:key]] = default) : context_styles.delete(rule[:key])
+      end
+    end
+
+    # Update context styles applying the initial rules (if set)
+    #
+    # @param context_styles [Hash] hash of the context styles that will be updated
+    #
+    # @return [Hash] the update context styles
+    def update_styles(context_styles)
+      initial.each do |rule|
+        next unless rule
+
+        remove_value(context_styles, rule)
+      end
+      context_styles
+    end
+
     class << self
       # Merges attributes
       #
@@ -105,29 +136,30 @@ def parse_styles(styles)
     def process_styles(hash_styles, options:)
       hash_styles.each do |key, value|
         rule = evaluate_rule(key, value)
+        next unless rule
+
         apply_rule!(merged_styles: @styles, rule: rule, value: value, options: options)
       end
       @styles
     end
 
     def evaluate_rule(rule_key, attr_value)
-      rule = STYLES_LIST[rule_key]
-      if rule && rule[:set] == :append_text_decoration
-        return { key: :callback, set: :callback_strike_through } if attr_value == 'line-through'
-
-        return { key: :styles, set: :append_styles }
-      end
-      rule
+      key = nil
+      key = 'text-decoration-line-through' if rule_key == 'text-decoration' && attr_value == 'line-through'
+      key ||= rule_key
+      STYLES_LIST[key]
     end
 
     def apply_rule!(merged_styles:, rule:, value:, options:)
-      return unless rule
+      return (@initial << rule) if value == 'initial'
 
       if rule[:set] == :append_styles
-        (merged_styles[rule[:key]] ||= []) << Utils.normalize_style(value)
+        val = Utils.normalize_style(value)
+        (merged_styles[rule[:key]] ||= []) << val if val
       else
         opts = rule[:options] ? options[rule[:options]] : nil
-        merged_styles[rule[:key]] = Utils.send(rule[:set], value, options: opts)
+        val = Utils.send(rule[:set], value, options: opts)
+        merged_styles[rule[:key]] = val if val
       end
     end
   end

lib/prawn_html/context.rb

@@ -2,7 +2,9 @@
 
 module PrawnHtml
   class Context < Array
-    DEF_FONT_SIZE = 16 * PX
+    DEFAULT_STYLES = {
+      size: 16 * PX
+    }.freeze
 
     attr_reader :previous_tag
     attr_accessor :last_text_node
@@ -54,9 +56,9 @@ def block_styles
     # @return [Hash] the hash of merged styles
     def merged_styles
       @merged_styles ||=
-        each_with_object(base_styles) do |element, res|
+        each_with_object(DEFAULT_STYLES.dup) do |element, res|
           evaluate_element_styles(element, res)
-          element.update_styles(res) if element.respond_to?(:update_styles)
+          element.update_styles(res)
         end
     end
 
@@ -71,12 +73,6 @@ def remove_last
 
     private
 
-    def base_styles
-      {
-        size: DEF_FONT_SIZE
-      }
-    end
-
     def evaluate_element_styles(element, res)
       styles = element.styles.slice(*Attributes::STYLES_APPLY[:text_node])
       styles.each do |key, val|

lib/prawn_html/document_renderer.rb

@@ -129,7 +129,7 @@ def apply_callbacks(buffer)
     def adjust_leading(buffer, leading)
       return leading if leading
 
-      (buffer.map { |item| item[:size] || Context::DEF_FONT_SIZE }.max * 0.055).round(4)
+      (buffer.map { |item| item[:size] || Context::DEFAULT_STYLES[:size] }.max * 0.055).round(4)
     end
 
     def bounds(buffer, options, block_styles)

lib/prawn_html/tag.rb

@@ -2,12 +2,17 @@
 
 module PrawnHtml
   class Tag
+    extend Forwardable
+
     CALLBACKS = {
       'Background' => Callbacks::Background,
       'StrikeThrough' => Callbacks::StrikeThrough
     }.freeze
+
     TAG_CLASSES = %w[A B Blockquote Body Br Code Del Div H Hr I Img Li Mark Ol P Pre Small Span Sub Sup U Ul].freeze
 
+    def_delegators :@attrs, :styles, :update_styles
+
     attr_accessor :parent
     attr_reader :attrs, :tag
 
@@ -55,13 +60,6 @@ def tag_close_styles
       styles.slice(*Attributes::STYLES_APPLY[:tag_close])
     end
 
-    # Styles hash
-    #
-    # @return [Hash] hash of styles
-    def styles
-      attrs.styles
-    end
-
     # Styles to apply on tag opening
     #
     # @return [Hash] hash of styles to apply

lib/prawn_html/tags/small.rb

@@ -5,10 +5,10 @@ module Tags
     class Small < Tag
       ELEMENTS = [:small].freeze
 
-      def update_styles(styles)
-        size = (styles[:size] || Context::DEF_FONT_SIZE) * 0.85
-        styles[:size] = size
-        styles
+      def update_styles(context_styles)
+        size = (context_styles[:size] || Context::DEFAULT_STYLES[:size]) * 0.85
+        context_styles[:size] = size
+        super(context_styles)
       end
     end
   end

spec/integrations/blocks_spec.rb

@@ -2,7 +2,7 @@
 
 RSpec.describe 'Blocks' do
   let(:pdf) { Prawn::Document.new(page_size: 'A4', page_layout: :portrait) }
-  let(:size) { PrawnHtml::Context::DEF_FONT_SIZE }
+  let(:size) { PrawnHtml::Context::DEFAULT_STYLES[:size] }
 
   before do
     PrawnHtml.append_html(pdf, html)

spec/support/test_utils.rb

@@ -3,7 +3,7 @@
 module TestUtils
   extend self
 
-  def adjust_leading(size = PrawnHtml::Context::DEF_FONT_SIZE)
+  def adjust_leading(size = PrawnHtml::Context::DEFAULT_STYLES[:size])
     (size * 0.055).round(4)
   end
 
@@ -16,7 +16,7 @@ def default_font_family
   end
 
   def default_font_size
-    PrawnHtml::Context::DEF_FONT_SIZE
+    PrawnHtml::Context::DEFAULT_STYLES[:size]
   end
 
   def font_ascender(font_family: 'Helvetica', font_size: default_font_size)

spec/units/prawn_html/attributes_spec.rb

@@ -71,6 +71,44 @@
     end
   end
 
+  describe '#remove_value' do
+    subject(:remove_value) { attributes.remove_value(context_styles, rule) }
+
+    let(:context_styles) { { size: 9.6, styles: %i[bold italic] } }
+
+    context 'with a missing rule' do
+      let(:rule) { { key: :color, set: :convert_color } }
+
+      it "doesn't change the context styles" do
+        expect { remove_value }.not_to change(context_styles, :values)
+      end
+    end
+
+    context 'with an applied rule' do
+      let(:rule) { { key: :styles, set: :append_styles, values: %i[bold] } }
+
+      it "changes the context styles" do
+        expect { remove_value }.to change(context_styles, :values).from([9.6, %i[bold italic]]).to([9.6, %i[italic]])
+      end
+    end
+  end
+
+  describe '#update_styles' do
+    subject(:update_styles) { attributes.update_styles(context_styles) }
+
+    let(:context_styles) { { size: 9.6 } }
+    let(:rule) { { key: :styles, set: :append_styles, values: %i[bold] } }
+
+    before do
+      allow(attributes).to receive_messages(initial: Set.new([rule]), remove_value: nil)
+    end
+
+    it 'asks to the attributes to remove the value from the context styles that match the specified rule' do
+      update_styles
+      expect(attributes).to have_received(:remove_value).with(context_styles, rule)
+    end
+  end
+
   describe '.merge_attr!' do
     context 'with an empty key' do
       let(:key) { nil }

spec/units/prawn_html/context_spec.rb

@@ -121,12 +121,12 @@ def on_context_remove(context)
     subject(:merged_styles) { context.merged_styles }
 
     context 'with no elements' do
-      it { is_expected.to eq(size: PrawnHtml::Context::DEF_FONT_SIZE) }
+      it { is_expected.to eq(size: PrawnHtml::Context::DEFAULT_STYLES[:size]) }
     end
 
     context 'with some elements' do
-      let(:tag1) { instance_double(PrawnHtml::Tag, styles: { color: 'fb1', size: 12.34 }) }
-      let(:tag2) { instance_double(PrawnHtml::Tag, styles: { color: 'abc' }) }
+      let(:tag1) { instance_double(PrawnHtml::Tag, styles: { color: 'fb1', size: 12.34 }, update_styles: nil) }
+      let(:tag2) { instance_double(PrawnHtml::Tag, styles: { color: 'abc' }, update_styles: nil) }
 
       before do
         context << tag1 << tag2
@@ -145,7 +145,7 @@ def update_styles(res)
           end
         end
       end
-      let(:tag1) { instance_double(PrawnHtml::Tag, styles: { color: 'fb1', size: 12.34 }) }
+      let(:tag1) { instance_double(PrawnHtml::Tag, styles: { color: 'fb1', size: 12.34 }, update_styles: nil) }
       let(:tag2) { some_tag_class.new(:some_tag) }
 
       before do