<sect1 id="sect-data-comment">
  <title>Comments in Cells</title>
  
  <para>
    Each cell in a worksheet can have an associated comment.
    Comments are not ordinarily visible.
    Cells having associated comments are marked with a red triangle
    in the top right corner of the cell.
    If you move the mouse cursor over the red triangle, the cursor
    changes to the left-pointing arrow.
    If the cursor remains over the triangle long enough, a pop-up
    window appears, displaying the author's name and the text of
    the comment.
    The pop-up window is removed when the mouse cursor is moved off
    the red triangle.
  </para>

  <para>
    To add a comment to a cell, first select the cell.
    Next choose <guimenuitem>Comment...</guimenuitem> from the
    <xref linkend="Insert-Menu" /> to open the <guimenu>New Cell Comment</guimenu> dialog.
    If the cell already has an associated comment, &gnum; instead opens the
    <guimenu>Edit Cell Comment</guimenu> dialog, which is shown below. The
    only difference is that the <guimenu>Edit Cell Comment</guimenu> dialog
    is initialized with the existing comment and it includes a line identifying
    the author of the existing comment.
  </para>
  <figure id="menu-insert-comment.png">
    <title>The <guimenu>Insert Comment</guimenu> dialog.</title>
    <screenshot>
      <mediaobject>
        <imageobject>
          <imagedata fileref="figures/menu-insert-comment.png" />
        </imageobject>
        <textobject>
          <phrase>An image of the Insert Comment dialog.</phrase>
        </textobject>
      </mediaobject>
    </screenshot>
  </figure>
  <para>
    To change the appearance of the comment text, select the
    text to be formatted, then click on one of the character
    attribute selectors above the comment text box. You can
    select italics, strike-through, character weight, and
    underlining. The italics and strike-through selectors toggle the
    character attributes, based on the first character of the
    selected text. For example, if the first character is
    italic, clicking on the italics selector removes the italic
    attribute from all characters of the selected text.
  </para>
  <para>
    The arrows next to the weight and underlining
    selectors open menus from which you can select a
    weight or underline style.
    Selecting a weight or underline style applies it to
    the selected text and makes it the meaning of the
    associated selector. For example, if you select
    <guimenuitem>Light</guimenuitem> from the weight menu,
    the selected text is made light. If you subsequently
    click on the weight selector, the text selected at that
    time is also made light.
    The weights may not all be visibly different,
    depending on the font in use. 
  </para>
  <para>
    "Wrap in properties window" controls word wrap in the comment
    editing box just above it.
    By default, lines are broken at spaces between words to prevent
    a line from exceeding the width of the text box.
    Click on the check-box to toggle word wrap.
    Line breaks occur in the comment pop-up only where you place
    them explicitly by pressing <keycap>Enter</keycap>.
    Turning off word wrap lets you see how the comment will be displayed
    in the pop-up.
  </para>

</sect1>


<sect1 id="sect-data-link">
  <title>Hyperlinks</title>
  
  <para>
    Each cell can have an associated hyperlink.
    A hyperlink permits the user of a spreadsheet to go directly to
    a particular cell or group of cells, to access another file on
    the local computer or on the web, or to send an email message
    to an address built into the link.
  </para>

  <para>
    To add a hyperlink to one or more cells, first select the cells.
    Next choose <guimenuitem>Hyperlink...</guimenuitem>
    from the <xref linkend="Insert-Menu" /> to open the <guimenu>HyperLink</guimenu> dialog.
  </para>
  <figure id="menu-insert-hyperlink.png">
    <title>The <guimenu>HyperLink</guimenu> dialog.</title>
    <screenshot>
      <mediaobject>
        <imageobject>
          <imagedata fileref="figures/menu-insert-hyperlink.png" />
        </imageobject>
        <textobject>
          <phrase>An image of the HyperLink dialog.</phrase>
        </textobject>
      </mediaobject>
    </screenshot>
  </figure>
  <para>
    If the selection includes a hyperlink, the dialog is initialized from
    the existing link.
    If there is more than one hyperlink in the selection, the cell in
    the first row that has a hyperlink, and the first such column of that
    row, is used to initialize the dialog.
  </para>
  <para>
    When you click on <guibutton>OK</guibutton>, the information in the
    dialog is attached to each cell in the selection, replacing any
    previously defined links.
    For any empty cells in the selection, the text of the link is set as
    the contents of the cell.
    For all cells in the selection, the cell format is modified to give
    the contents a distinctive color, and the text is underlined.
  </para>
  <para>
    If the link location text box is empty when you click on <guibutton>OK</guibutton>, 
    no hyperlink is created.
    Instead, if any cells in the selection have existing hyperlinks, those
    hyperlinks are removed.
    The distinctive format applied to links is not removed.
    For that reason it might be preferable to choose
    <xref linkend="edit-menu-clear-links" />
    from the <xref linkend="Edit-Menu" /> to remove existing hyperlinks.
  </para>
  <para>
    &gnum; supports four types of hyperlink.
    The first element of the <guimenu>HyperLink</guimenu> dialog, the
    <guimenu>Type</guimenu> menu, selects the type of hyperlink to
    be created.
    The <guimenu>HyperLink</guimenu> dialog varies slightly, depending
    on the selected hyperlink type:
    <itemizedlist>
      <listitem>
        <para>
          Internal Link: The second element of the dialog is a text box
          labeled "Target Range". You can enter a single range, with or 
          without a worksheet name.
          To select the range from the worksheet, click on the button
          at the end of the "Target Range" line. This collapses the
          dialog to a single line and makes it possible to interact with
          the cell grid. Select the desired sheet tab, if necessary,
          then select the desired cells.
          When the selection is complete, click on the button at the
          end of the Target Range input box to open the full
          <guimenu>HyperLink</guimenu> dialog again.
        </para>
        <para>
          When an internal link is activated by clicking on the cell,
          the range of cells given by the link address
          becomes the current selection. The cell closest to A1 in the
          new selection becomes the active cell.
        </para>
      </listitem>
      <listitem>
        <para>
          External Link: The second element of the dialog is a text box
          labeled "File". Enter the path to a file. You can also enter
          a Universal Resource Locator (URL) here; the URL is accessed
          as described for Web Link below.
        </para>
        <para>
          When an external link is activated by clicking on the cell,
          &gnum; launches an application to present the file,
          based on its apparent type. For example, "mypic.jpg" would
          be opened in an image viewer, while "myinfo.html" would be
          opened in a web browser.
        </para>
      </listitem>
      <listitem>
        <para>
          Email Link: The dialog provides text boxes where you can
          enter the destination address and subject line for an e-mail message.
        </para>
        <para>
          When an email link is activated by clicking on the cell,
          &gnum; launches an e-mail client to send a message. The message
          is initialized with the destination address and
          subject specified in the dialog.
        </para>
      </listitem>
      <listitem>
        <para>
          Web Link: Enter a Universal Resource Locator (URL) in the
          Web Address text box.
        </para>
        <para>
          When the link is activated by clicking on the cell,
          &gnum; launches an application to display the information
          at the specified URL, based on its apparent type. For a
          web address beginning with "http://" or "https://" the application is
          the default web browser.
        </para>
      </listitem>
    </itemizedlist>
  </para>
  <para>
    When you move the mouse pointer to a hyperlink in the cell grid,
    a tool tip appears.
    The default tip shows the link address and instructions for
    activating the link or selecting the cell.
    To define a tip specific to the link, select the radio button
    next to "Tip", then enter the tip text in the text box.
    If the link-specific tip is selected and left blank, no tip is displayed
    when the mouse pointer is on the link.
  </para>

</sect1>

<sect1 id="sect-data-names">
  <title>Defining Names</title>

  <para>
    Names are labels with a meaning defined in the spreadsheet or by &gnum;.
    Names can be defined for a whole workbook or for just a single worksheet.
    A name can refer to a numeric value, a string, a range of cells, or a formula.
    A name can be used wherever its meaning could otherwise be used.
  </para>
  <para>
    A name is a sequence of letters, digits, and underscore characters,
    beginning with a letter or underscore.
    A name cannot look like a cell identifier.
    For example, "D7" is not a permitted name, while "D_7" and "_D7" are permitted.
  </para>
  <para>
    To define a name or modify the definition of an existing name:
  </para>
  <itemizedlist>
    <listitem>
      <para>
        If you wish to define or modify a name for use within a single
        worksheet and it is not the current worksheet, click on the
	appropriate worksheet tab at the bottom of the &gnum; window.
      </para>
    </listitem>
    <listitem>
      <para>
        Open the <guimenu>Define Names</guimenu> dialog by choosing
        <guimenuitem>Modify&nbsp;&#9654; Names</guimenuitem> from
        the <xref linkend="Edit-Menu" />.
      </para>
    </listitem>
    <listitem>
      <para>
        Use the dialog to modify the defined names as desired.
        When your changes are complete, click on <guibutton>Close</guibutton>
        to close the dialog.
      </para>
    </listitem>
  </itemizedlist>
  <figure id="menu-edit-modify-names.png">
    <title>The <guimenu>Define Names</guimenu> dialog</title>
    <screenshot>
      <mediaobject>
        <imageobject>
          <imagedata fileref="figures/menu-edit-modify-names.png" />
        </imageobject>
        <textobject>
          <phrase>An image of the Define Names dialog.</phrase>
        </textobject>
      </mediaobject>
    </screenshot>
  </figure>
  <para>
    The <guimenu>Define Names</guimenu> dialog lists the
    names defined in the workbook, organized into two or more groups
    corresponding to the workbook, the active sheet, and the inactive
    sheets, if any. When the dialog is opened, only the names defined
    for the workbook and the active sheet are visible; the definitions
    for any inactive sheets are collapsed into a single line for each,
    identified by the sheet name. The definitions for the workbook or
    a sheet can be exposed or hidden by clicking on the arrow at the
    left end of the workbook or sheet line.
  </para>
  <para>
    The second column of the <guimenu>Define Names</guimenu> dialog can 
    show one of three icons. To define a new name, click on the
    plus sign in the row for the workbook or the active worksheet.
    Names defined under a worksheet name are visible
    only on that worksheet.
    Names defined for the workbook are visible to any
    worksheet that does not have its own definition of the name.
    Names are created as "&lt;new-name&gt;", which must be changed
    before the definition can be used. Click on the new line to select
    it, then click on the name field and type the new name, followed by
    the <keycap>Enter</keycap> key.
    When you press <keycap>Enter</keycap>, the name is fixed.
    Only its value can then be changed.
  </para>
  <para>
    If the second column shows a minus sign, the line is for a
    user-defined name. 
    Click on the minus sign to delete the definition of the name.
    If the second column shows a padlock icon, the definition is created 
    automatically and cannot be modified from this dialog.
  </para>
  <para>
    For user-defined names, the third column of the <guimenu>Define
    Names</guimenu> dialog contains a downward- or upward-pointing arrow.
    Click on the arrow to move the definition down to the worksheet or
    up to the workbook.
    This operation is not permitted if the moved definition would replace
    a name already defined for the destination.
    To do such a replacement, first delete the name in the destination,
    then move the definition.
  </para>
  <para>
    The last column of the dialog shows the value defined for the name. 
    When a new name is created, this field is initialized with an absolute 
    reference to the currently selected cells.
    To modify a definition, click on the value field and edit it as
    desired, then press the <keycap>Enter</keycap> key.
    To define a string value, enclose it in quotation marks, for example,
    'string one' or "string two".
    To specify a range of cells, use absolute references.
    Relative references change in meaning depending on the cell where
    they are used, which is unlikely to produce your intended result.
    You can define a name as a cell or range of cells by clearing its
    existing definition, if any, and then selecting the desired cell or
    cells on the cell grid.
    You can switch worksheets prior to selecting cells.
    The dialog continues to modify names defined for the workbook or the
    worksheet that was displayed when the dialog was opened.
    A reference created by selection in the <guimenu>Define Names</guimenu>
    dialog includes the worksheet name and uses absolute cell coordinates.
    That is, a selection would look like "Sheet1!$A$1:$B$24".
  </para>
  <para>
    Below the display of defined names is a filter box.
    If the workbook or sheet contains many defined names, you can see
    a subset of the names by typing a partial name in the filter box
    and pressing <keycap>Enter</keycap>.
    All names that do not contain the entered string are omitted from the
    display.
    Differences of case are ignored.
    For example, if &ldquo;real&rdquo; were entered in the filter box,
    names such as "Real_Value" and "Surreal" would be displayed.
    When you press <keycap>Enter</keycap> in the filter box, contexts that contain
    no matching names are automatically collapsed. You may later need 
    to manually expand the workbook line, for example, if the filter
    string is changed.
    If the line for the workbook or a worksheet begins with a
    right-pointing arrow, it contains names that pass the filter.
    Clicking on the arrow will change it to a downward-pointing arrow
    and make the names visible.
    To see all the defined names, clear the filter by clicking on the
    button at the right end of the filter box.
  </para>
  <para>
    In addition to the names defined by the user, &gnum; has some pre-defined names
    for useful elements:
  </para>
  <itemizedlist>
    <listitem>
      <para>
        Sheet_Title: The name of the current sheet.
      </para>
    </listitem>
  </itemizedlist>

  <itemizedlist>
    <listitem>
      <para>
        Print_Area: The range of cells set as the sheet's
        print area; undefined if print area is not set.
      </para>
    </listitem>
  </itemizedlist>

</sect1>
