class HexaPDF::Layout::TextFragment

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).

Attributes

items[RW]

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

Public Class Methods

create(text, style = nil, **options) click to toggle source

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.

# File lib/hexapdf/layout/text_fragment.rb, line 66
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
new(items, style) click to toggle source

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.

# File lib/hexapdf/layout/text_fragment.rb, line 106
def initialize(items, style)
  @items = items
  @style = (style.kind_of?(Style) ? style : Style.new(**style))
end

Public Instance Methods

clear_cache() click to toggle source

Clears all cached values.

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

# File lib/hexapdf/layout/text_fragment.rb, line 267
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) click to toggle source

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.

# File lib/hexapdf/layout/text_fragment.rb, line 133
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() click to toggle source

The maximum y-coordinate of any item.

# File lib/hexapdf/layout/text_fragment.rb, line 232
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() click to toggle source

The minimum y-coordinate of any item.

# File lib/hexapdf/layout/text_fragment.rb, line 226
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() click to toggle source

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.

# File lib/hexapdf/layout/text_fragment.rb, line 253
def height
  @height ||= [y_max, 0].max - [y_min, 0].min
end
valign() click to toggle source

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

See Line for details.

# File lib/hexapdf/layout/text_fragment.rb, line 260
def valign
  :text
end
width() click to toggle source

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.

# File lib/hexapdf/layout/text_fragment.rb, line 242
def width
  @width ||= @items.sum {|item| style.scaled_item_width(item) }
end
x_max() click to toggle source

The maximum x-coordinate of the last glyph.

# File lib/hexapdf/layout/text_fragment.rb, line 211
def x_max
  @x_max ||= calculate_x_max
end
x_min() click to toggle source

The minimum x-coordinate of the first glyph.

# File lib/hexapdf/layout/text_fragment.rb, line 206
def x_min
  @x_min ||= calculate_x_min
end
y_max() click to toggle source

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

# File lib/hexapdf/layout/text_fragment.rb, line 221
def y_max
  style.scaled_y_max
end
y_min() click to toggle source

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

# File lib/hexapdf/layout/text_fragment.rb, line 216
def y_min
  style.scaled_y_min
end