Class: HexaPDF::Layout::TextFragment

Inherits:
Object
  • Object
show all
Defined in:
lib/hexapdf/layout/text_fragment.rb

Overview

A TextFragment describes an optionally kerned piece of text that shares the same font, font size and other properties.

Its items are either glyph objects of the font or numeric values describing kerning information. All returned measurement values are in text space units. If the items or the style are changed, the #clear_cache has to be called. Otherwise the measurements may not be correct!

The items of a text fragment may be frozen to indicate that the fragment is potentially used multiple times.

The rectangle with the bottom left corner (#x_min, #y_min) and the top right corner (#x_max, #y_max) describes the minimum bounding box of the whole text fragment and is usually not equal to the box (0, 0)-(#width, #height).

Constant Summary collapse

PRECISION =

The precision used to determine whether two floats represent the same value.

0.000001

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(items, style) ⇒ TextFragment

Creates a new TextFragment object with the given items and style.

The argument style can either be a Style object or a hash of style options.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 107

def initialize(items, style)
  @items = items
  @style = (style.kind_of?(Style) ? style : Style.new(**style))
end

Instance Attribute Details

#items ⇒ Object

The items (glyphs and kerning values) of the text fragment.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 74

def items
  @items
end

#style ⇒ Object (readonly)

The style to be applied.

Only the following properties are used:

  • Style#font

  • Style#font_size

  • Style#horizontal_scaling

  • Style#character_spacing

  • Style#word_spacing

  • Style#text_rise

  • Style#text_rendering_mode

  • Style#subscript

  • Style#superscript

  • Style#underline

  • Style#strikeout

  • Style#fill_color

  • Style#fill_alpha

  • Style#stroke_color

  • Style#stroke_alpha

  • Style#stroke_width

  • Style#stroke_cap_style

  • Style#stroke_join_style

  • Style#stroke_miter_limit

  • Style#stroke_dash_pattern

  • Style#underlay_callback

  • Style#overlay_callback



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# File 'lib/hexapdf/layout/text_fragment.rb', line 102

def style
  @style
end

Class Method Details

.create(text, style = nil, **options) ⇒ Object

Creates a new TextFragment object for the given text, shapes it and returns it.

The needed style of the text fragment can either be specified by the style argument or via the options (in which case a new Style object is created). Regardless of the way, the resulting style object needs at least the font set.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 67

def self.create(text, style = nil, **options)
  style = (style.nil? ? Style.new(**options) : style)
  fragment = new(style.font.decode_utf8(text), style)
  TextShaper.new.shape_text(fragment)
end

Instance Method Details

#clear_cache ⇒ Object

Clears all cached values.

This method needs to be called if the fragment’s items or attributes are changed!



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# File 'lib/hexapdf/layout/text_fragment.rb', line 268

def clear_cache
  @x_min = @x_max = @exact_y_min = @exact_y_max = @width = @height = nil
  self
end

#draw(canvas, x, y, ignore_text_properties: false) ⇒ Object

Draws the text onto the canvas at the given position.

This method is the main styled text drawing facility and therefore some optimizations are done:

  • The text is drawn using HexaPDF::Content;:Canvas#show_glyphs_only which means that the text matrix is not updated. Therefore the caller must not rely on it!

  • All text style properties mentioned in the description of #style are set except if ignore_text_properties is set to true. Note that this only applies to style properties that directly affect text drawing, so, for example, underlays/overlays and underlining/strikeout is always done.

    The caller should set ignore_text_properties to true if the graphics state hasn’t been changed. This is the case, for example, if the last thing drawn was a text fragment with the same style.

  • It is assumed that the text matrix is not rotated, skewed, etc. so that setting the text position can be done using the optimal method.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 134

def draw(canvas, x, y, ignore_text_properties: false)
  style.underlays.draw(canvas, x, y + y_min, self) if style.underlays?

  # Set general font related graphics state if necessary
  unless ignore_text_properties
    canvas.font(style.font, size: style.calculated_font_size).
      horizontal_scaling(style.horizontal_scaling).
      character_spacing(style.character_spacing).
      word_spacing(style.word_spacing).
      text_rise(style.calculated_text_rise).
      text_rendering_mode(style.text_rendering_mode)

    # Set fill and/or stroke related graphics state
    canvas.opacity(fill_alpha: style.fill_alpha, stroke_alpha: style.stroke_alpha)
    trm = canvas.text_rendering_mode
    if trm.value.even? # text is filled
      canvas.fill_color(style.fill_color)
    end
    if trm == :stroke || trm == :fill_stroke || trm == :stroke_clip || trm == :fill_stroke_clip
      canvas.stroke_color(style.stroke_color).
        line_width(style.stroke_width).
        line_cap_style(style.stroke_cap_style).
        line_join_style(style.stroke_join_style).
        miter_limit(style.stroke_miter_limit).
        line_dash_pattern(style.stroke_dash_pattern)
    end
  end

  canvas.begin_text
  tlm = canvas.graphics_state.tlm
  tx = x - tlm.e
  ty = y - tlm.f
  if tx.abs < PRECISION
    if (ty + canvas.graphics_state.leading).abs < PRECISION
      canvas.move_text_cursor
    else
      canvas.move_text_cursor(offset: [0, ty], absolute: false)
    end
  elsif ty.abs < PRECISION
    canvas.move_text_cursor(offset: [tx, 0], absolute: false)
  else
    canvas.move_text_cursor(offset: [x, y])
  end
  canvas.show_glyphs_only(items)

  if style.underline? && style.underline
    y_offset = style.calculated_underline_position
    canvas.save_graphics_state do
      canvas.stroke_color(style.fill_color).
        line_width(style.calculated_underline_thickness).
        line_cap_style(:butt).
        line_dash_pattern(0).
        line(x, y + y_offset, x + width, y + y_offset).
        stroke
    end
  end

  if style.strikeout? && style.strikeout
    y_offset = style.calculated_strikeout_position
    canvas.save_graphics_state do
      canvas.stroke_color(style.fill_color).
        line_width(style.calculated_strikeout_thickness).
        line_cap_style(:butt).
        line_dash_pattern(0).
        line(x, y + y_offset, x + width, y + y_offset).
        stroke
    end
  end

  style.overlays.draw(canvas, x, y + y_min, self) if style.overlays?
end

#exact_y_max ⇒ Object

The maximum y-coordinate of any item.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 233

def exact_y_max
  @exact_y_max ||= (@items.max_by(&:y_max)&.y_max || 0) *
    style.calculated_font_size / 1000.0 + style.calculated_text_rise
end

#exact_y_min ⇒ Object

The minimum y-coordinate of any item.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 227

def exact_y_min
  @exact_y_min ||= (@items.min_by(&:y_min)&.y_min || 0) *
    style.calculated_font_size / 1000.0 + style.calculated_text_rise
end

#height ⇒ Object

The height of the text fragment.

It is calculated as the difference of the maximum of the y_max values and the minimum of the y_min values of the items. However, the text rise value is also taken into account so that the baseline is always inside the bounds. For example, if a large negative text rise value is used, the baseline will be equal to the top boundary; if a large positive value is used, it will be equal to the bottom boundary.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 254

def height
  @height ||= [y_max, 0].max - [y_min, 0].min
end

#inspect ⇒ Object

:nodoc:



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# File 'lib/hexapdf/layout/text_fragment.rb', line 274

def inspect
  "#<#{self.class.name} #{items.inspect}>"
end

#valign ⇒ Object

Returns the vertical alignment inside a line which is always :text for text fragments.

See Line for details.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 261

def valign
  :text
end

#width ⇒ Object

The width of the text fragment.

It is the sum of the widths of its items and is calculated by using the algorithm presented in PDF1.7 s9.4.4. By using kerning values as the first and/or last items, the text contained in the fragment may spill over the left and/or right boundary.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 243

def width
  @width ||= @items.sum {|item| style.scaled_item_width(item) }
end

#x_max ⇒ Object

The maximum x-coordinate of the last glyph.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 212

def x_max
  @x_max ||= calculate_x_max
end

#x_min ⇒ Object

The minimum x-coordinate of the first glyph.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 207

def x_min
  @x_min ||= calculate_x_min
end

#y_max ⇒ Object

The maximum y-coordinate, calculated using the scaled ascender of the font.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 222

def y_max
  style.scaled_y_max
end

#y_min ⇒ Object

The minimum y-coordinate, calculated using the scaled descender of the font.



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# File 'lib/hexapdf/layout/text_fragment.rb', line 217

def y_min
  style.scaled_y_min
end