samples/snippets/visualbasic/VS_Snippets_Wpf/FindText/VisualBasic/Content/FlowDocumentSample2.xaml - main - aprogrammer/dotnet-docs

samples/snippets/visualbasic/VS_Snippets_Wpf/FindText/VisualBasic/Content/FlowDocumentSample2.xaml
76 строк4 KB
Andy De George
Move snippets from samples repo to this repo (#17296)
03 мар 2020, 19:23
03 мар 2020, 19:23dbbeda1
<FlowDocument xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  TextAlignment="Justify" 
  IsOptimalParagraphEnabled="True"
  IsHyphenationEnabled="True"
  IsColumnWidthFlexible="True"
  Background="AliceBlue"
  ColumnWidth="300"
  ColumnGap="20"
>
  <Paragraph>
    <Italic>
      "One of the most important operations necessary when text materials
      are prepared for printing or display is the task of dividing long
      paragraphs into individual lines. When this job has been done well,
      people will not be aware of the fact that the words they are reading
      have been broken apart arbitrarily and placed into a somewhat rigid
      and unnatural rectangular framework; but if the job has been done
      poorly, readers will be distracted by bad breaks that interrupt
      their train of thought."
    </Italic>
  </Paragraph>
  <Paragraph>
    <Hyperlink NavigateUri="http://www-cs-faculty.stanford.edu/~knuth/">
      - Donald E. Knuth
    </Hyperlink>
  </Paragraph>
  <Paragraph>
    <Bold>
      Principle of Optimal Paragraph
    </Bold>
  </Paragraph>
  <Paragraph>
    Knuth started his revolutionary work of developing a computer program to
    produce high quality publication in the late ’70. The program he developed
    called TEX (pronounced "tek") is highly regarded as the work that helps
    shape the field of digital typography and desktop publishing. It is still
    being widely used and constantly extended by many others up to today. One
    of the most intriguing inventions in this program is its ability to produce
    superior quality paragraph layout for printing and reading purpose – arguably
    comparable to the work manually done by most respectable publishers of the
    modern times.  This typographically beautiful paragraph layout is driven by
    a line breaking algorithm known as <Italic>total-fit</Italic> or
    <Italic>optimum-fit</Italic> algorithm. Some call the kind of paragraph
    produced by this algorithm <Italic>Optimal Paragraph</Italic>.
  </Paragraph>
  <Paragraph>
    In principle, the task of text formatting consists of two main components:
    choosing where to end individual lines and how to justify the lines. The first
    component may involve the task of word division called <Italic>hyphenation</Italic>.
    Line justification is the task of fitting a line into a desired width. Usually
    it is done by distributing the extra space into or taking out excess space
    from inter-word spaces in the line. Line justification is strongly dependent
    to line breaking. When line breaking is done properly, justification can be
    done without the need to change the spacing too much and thereby avoiding
    holes between words that would distress the eyes of the reader.
  </Paragraph>
  <Paragraph>
    Unlike a standard line breaking algorithm which breaks the line without taking
    into account the line that may come after it, the total-fit algorithm breaks
    line by looking ahead on what may come later in the paragraph and make a single
    decision to break all the lines at once.  The main idea of the algorithm is to
    provide a way to break a paragraph into lines so that the inter-word spacing is
    balanced between all the lines of the paragraph. This is attained by choosing
    the sequence of breakpoints with the minimal total cost over all lines. The
    cost of a line depends on many factors that can affect the visual appearance
    of the line, such as the measure of inter-word space changing, the division of
    the last word of the line, etc.
  </Paragraph>

  <Paragraph>
    A paragraph is considered optimal when all inter-word spaces over all lines are set as
    close as possible to the ideal inter-word spaces. Therefore, an optimum paragraph is in
    fact a paragraph composed in such a way that the total contrast of inter-word spaces set
    in all lines with the ideal inter-word spaces cannot be reduced anymore.
  </Paragraph>
</FlowDocument>