
Hyperlink
=========

Word allows hyperlinks to be placed in a document wherever paragraphs can appear.

The target (URL) of a hyperlink may be external, such as a web site, or internal, to
another location in the document.

The visible text of a hyperlink is held in one or more runs. Technically a hyperlink can
have zero runs, but this occurs only in contrived cases (otherwise there would be
nothing to click on). As usual, each run can have its own distinct text formatting
(font), so for example one word in the hyperlink can be bold, etc. By default, Word
applies the built-in `Hyperlink` character style to a newly inserted hyperlink.

Note that rendered page-breaks can occur in the middle of a hyperlink.

A |Hyperlink| is a child of |Paragraph|, a peer of |Run|.


Candidate protocol
------------------

An external hyperlink has an address and an optional anchor. An internal hyperlink has
only an anchor. An anchor is also known as a *URI fragment* and follows a hash mark
("#").

Note that the anchor and URL are stored in two distinct attributes, so you need to
concatenate `.address` and `.anchor` if you want the whole thing.

.. highlight:: python

**Access hyperlinks in a paragraph**::

    >>> hyperlinks = paragraph.hyperlinks
    [<docx.text.hyperlink.Hyperlink at 0x7f...>]

**Access hyperlinks in a paragraph in document order with runs**::

    >>> list(paragraph.iter_inner_content())
    [
      <docx.text.run.Run at 0x7f...>
      <docx.text.hyperlink.Hyperlink at 0x7f...>
      <docx.text.run.Run at 0x7f...>
    ]

**Access hyperlink address**::

    >>> hyperlink.address
    'https://google.com/'

**Access hyperlinks runs**::

    >>> hyperlink.runs
    [
      <docx.text.run.Run at 0x7f...>
      <docx.text.run.Run at 0x7f...>
      <docx.text.run.Run at 0x7f...>
    ]

**Determine whether a hyperlink contains a rendered page-break**::

    >>> hyperlink.contains_page_break
    False

**Access visible text of a hyperlink**::

    >>> hyperlink.text
    'an excellent Wikipedia article on ferrets'

**Add an external hyperlink**::

    >>> hyperlink = paragraph.add_hyperlink(
          'About', address='http://us.com', anchor='about'
        )
    >>> hyperlink
    <docx.text.hyperlink.Hyperlink at 0x7f...>
    >>> hyperlink.text
    'About'
    >>> hyperlink.address
    'http://us.com'
    >>> hyperlink.anchor
    'about'

**Add an internal hyperlink (to a bookmark)**::

    >>> hyperlink = paragraph.add_hyperlink('Section 1', anchor='Section_1')
    >>> hyperlink.text
    'Section 1'
    >>> hyperlink.anchor
    'Section_1'
    >>> hyperlink.address
    None

**Modify hyperlink properties**::

    >>> hyperlink.text = 'Froogle'
    >>> hyperlink.text
    'Froogle'
    >>> hyperlink.address = 'mailto:info@froogle.com?subject=sup dawg?'
    >>> hyperlink.address
    'mailto:info@froogle.com?subject=sup%20dawg%3F'
    >>> hyperlink.anchor = None
    >>> hyperlink.anchor
    None

**Add additional runs to a hyperlink**::

    >>> hyperlink.text = 'A '
    >>> # .insert_run inserts a new run at idx, defaults to idx=-1
    >>> hyperlink.insert_run(' link').bold = True
    >>> hyperlink.insert_run('formatted', idx=1).bold = True
    >>> hyperlink.text
    'A formatted link'
    >>> [r for r in hyperlink.iter_runs()]
    [<docx.text.run.Run at 0x7fa...>,
     <docx.text.run.Run at 0x7fb...>,
     <docx.text.run.Run at 0x7fc...>]

**Iterate over the run-level items a paragraph contains**::

    >>> paragraph = document.add_paragraph('A paragraph having a link to: ')
    >>> paragraph.add_hyperlink(text='github', address='http://github.com')
    >>> [item for item in paragraph.iter_run_level_items()]:
    [<docx.text.paragraph.Run at 0x7fd...>, <docx.text.paragraph.Hyperlink at 0x7fe...>]

**Paragraph.text now includes text contained in a hyperlink**::

    >>> paragraph.text
    'A paragraph having a link to: github'


Word Behaviors
--------------

* What are the semantics of the w:history attribute on w:hyperlink? I'm
  suspecting this indicates whether the link should show up blue (unvisited)
  or purple (visited). I'm inclined to think we need that as a read/write
  property on hyperlink. We should see what the MS API does on this count.

* We probably need to enforce some character-set restrictions on w:anchor.
  Word doesn't seem to like spaces or hyphens, for example. The simple type
  ST_String doesn't look like it takes care of this.

* We'll need to test URL escaping of special characters like spaces and
  question marks in Hyperlink.address.

* What does Word do when loading a document containing an internal hyperlink
  having an anchor value that doesn't match an existing bookmark? We'll want
  to know because we're sure to get support inquiries from folks who don't
  match those up and wonder why they get a repair error or whatever.


Specimen XML
------------

.. highlight:: xml


External links
~~~~~~~~~~~~~~

The address (URL) of an external hyperlink is stored in the document.xml.rels
file, keyed by the w:hyperlink@r:id attribute::

    <w:p>
      <w:r>
        <w:t xml:space="preserve">This is an external link to </w:t>
      </w:r>
      <w:hyperlink r:id="rId4">
        <w:r>
          <w:rPr>
            <w:rStyle w:val="Hyperlink"/>
          </w:rPr>
          <w:t>Google</w:t>
        </w:r>
      </w:hyperlink>
    </w:p>

... mapping to relationship in document.xml.rels::

    <Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
      <Relationship Id="rId4" Mode="External" Type="http://..." Target="http://google.com/"/>
    </Relationships>

A hyperlink can contain multiple runs of text (and a whole lot of other
stuff, including nested hyperlinks, at least as far as the schema indicates)::

    <w:p>
      <w:hyperlink r:id="rId2">
        <w:r>
          <w:rPr>
            <w:rStyle w:val="Hyperlink"/>
          </w:rPr>
          <w:t xml:space="preserve">A hyperlink containing an </w:t>
        </w:r>
        <w:r>
          <w:rPr>
            <w:rStyle w:val="Hyperlink"/>
            <w:i/>
          </w:rPr>
          <w:t>italicized</w:t>
        </w:r>
        <w:r>
          <w:rPr>
            <w:rStyle w:val="Hyperlink"/>
          </w:rPr>
          <w:t xml:space="preserve"> word</w:t>
        </w:r>
      </w:hyperlink>
    </w:p>


Internal links
~~~~~~~~~~~~~~

An internal link provides "jump to another document location" behavior in the
Word UI. An internal link is distinguished by the absence of an r:id
attribute. In this case, the w:anchor attribute is required. The value of the
anchor attribute is the name of a bookmark in the document.

Example::

    <w:p>
      <w:r>
        <w:t xml:space="preserve">See </w:t>
      </w:r>
      <w:hyperlink w:anchor="Section_4">
        <w:r>
          <w:rPr>
            <w:rStyle w:val="Hyperlink"/>
          </w:rPr>
          <w:t>Section 4</w:t>
        </w:r>
      </w:hyperlink>
      <w:r>
        <w:t xml:space="preserve"> for more details.</w:t>
      </w:r>
    </w:p>

... referring to this bookmark elsewhere in the document::

    <w:p>
      <w:bookmarkStart w:id="0" w:name="Section_4"/>
        <w:r>
          <w:t>Section 4</w:t>
        </w:r>
      <w:bookmarkEnd w:id="0"/>
    </w:p>


Schema excerpt
--------------

.. highlight:: xml

::

    <xsd:complexType name="CT_P">
      <xsd:sequence>
        <xsd:element name="pPr" type="CT_PPr" minOccurs="0"/>
        <xsd:group   ref="EG_PContent"        minOccurs="0" maxOccurs="unbounded"/>
      </xsd:sequence>
      <xsd:attribute name="rsidRPr"      type="ST_LongHexNumber"/>
      <xsd:attribute name="rsidR"        type="ST_LongHexNumber"/>
      <xsd:attribute name="rsidDel"      type="ST_LongHexNumber"/>
      <xsd:attribute name="rsidP"        type="ST_LongHexNumber"/>
      <xsd:attribute name="rsidRDefault" type="ST_LongHexNumber"/>
    </xsd:complexType>

    <xsd:group name="EG_PContent">  <!-- denormalized -->
      <xsd:choice>
        <xsd:element name="r"         type="CT_R"/>
        <xsd:element name="hyperlink" type="CT_Hyperlink"/>
        <xsd:element name="fldSimple" type="CT_SimpleField"/>
        <xsd:element name="sdt"       type="CT_SdtRun"/>
        <xsd:element name="customXml" type="CT_CustomXmlRun"/>
        <xsd:element name="smartTag"  type="CT_SmartTagRun"/>
        <xsd:element name="dir"       type="CT_DirContentRun"/>
        <xsd:element name="bdo"       type="CT_BdoContentRun"/>
        <xsd:element name="subDoc"    type="CT_Rel"/>
        <xsd:group ref="EG_RunLevelElts"/>
      </xsd:choice>
    </xsd:group>

    <xsd:complexType name="CT_Hyperlink">
      <xsd:group ref="EG_PContent" minOccurs="0" maxOccurs="unbounded"/>
      <xsd:attribute name="tgtFrame"    type="s:ST_String"/>
      <xsd:attribute name="tooltip"     type="s:ST_String"/>
      <xsd:attribute name="docLocation" type="s:ST_String"/>
      <xsd:attribute name="history"     type="s:ST_OnOff"/>
      <xsd:attribute name="anchor"      type="s:ST_String"/>
      <xsd:attribute  ref="r:id"/>
    </xsd:complexType>

    <xsd:group name="EG_RunLevelElts">
      <xsd:choice>
        <xsd:element name="proofErr"                    type="CT_ProofErr"/>
        <xsd:element name="permStart"                   type="CT_PermStart"/>
        <xsd:element name="permEnd"                     type="CT_Perm"/>
        <xsd:element name="bookmarkStart"               type="CT_Bookmark"/>
        <xsd:element name="bookmarkEnd"                 type="CT_MarkupRange"/>
        <xsd:element name="moveFromRangeStart"          type="CT_MoveBookmark"/>
        <xsd:element name="moveFromRangeEnd"            type="CT_MarkupRange"/>
        <xsd:element name="moveToRangeStart"            type="CT_MoveBookmark"/>
        <xsd:element name="moveToRangeEnd"              type="CT_MarkupRange"/>
        <xsd:element name="commentRangeStart"           type="CT_MarkupRange"/>
        <xsd:element name="commentRangeEnd"             type="CT_MarkupRange"/>
        <xsd:element name="customXmlInsRangeStart"      type="CT_TrackChange"/>
        <xsd:element name="customXmlInsRangeEnd"        type="CT_Markup"/>
        <xsd:element name="customXmlDelRangeStart"      type="CT_TrackChange"/>
        <xsd:element name="customXmlDelRangeEnd"        type="CT_Markup"/>
        <xsd:element name="customXmlMoveFromRangeStart" type="CT_TrackChange"/>
        <xsd:element name="customXmlMoveFromRangeEnd"   type="CT_Markup"/>
        <xsd:element name="customXmlMoveToRangeStart"   type="CT_TrackChange"/>
        <xsd:element name="customXmlMoveToRangeEnd"     type="CT_Markup"/>
        <xsd:element name="ins"                         type="CT_RunTrackChange"/>
        <xsd:element name="del"                         type="CT_RunTrackChange"/>
        <xsd:element name="moveFrom"                    type="CT_RunTrackChange"/>
        <xsd:element name="moveTo"                      type="CT_RunTrackChange"/>
        <xsd:group ref="EG_MathContent" minOccurs="0" maxOccurs="unbounded"/>
      </xsd:choice>
    </xsd:group>

    <xsd:complexType name="CT_R">
      <xsd:sequence>
        <xsd:group ref="EG_RPr"             minOccurs="0"/>
        <xsd:group ref="EG_RunInnerContent" minOccurs="0" maxOccurs="unbounded"/>
      </xsd:sequence>
      <xsd:attribute name="rsidRPr" type="ST_LongHexNumber"/>
      <xsd:attribute name="rsidDel" type="ST_LongHexNumber"/>
      <xsd:attribute name="rsidR"   type="ST_LongHexNumber"/>
    </xsd:complexType>

    <xsd:simpleType name="ST_OnOff">
      <xsd:union memberTypes="xsd:boolean ST_OnOff1"/>
    </xsd:simpleType>

    <xsd:simpleType name="ST_OnOff1">
      <xsd:restriction base="xsd:string">
        <xsd:enumeration value="on"/>
        <xsd:enumeration value="off"/>
      </xsd:restriction>
    </xsd:simpleType>

    <xsd:simpleType name="ST_RelationshipId">
      <xsd:restriction base="xsd:string"/>
    </xsd:simpleType>

    <xsd:simpleType name="ST_String">
      <xsd:restriction base="xsd:string"/>
    </xsd:simpleType>
