<!DOCTYPE sect2 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
               "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
		<!ENTITY % darktable_dtd SYSTEM "../../dtd/darktable.dtd">
		%darktable_dtd;
		]>
<sect2 status="final" id="history">

  <title>History stack</title>

  <indexterm>
    <primary>darkroom panels</primary>
    <secondary>history stack</secondary>
  </indexterm>

  <indexterm>
    <primary>history stack</primary>
  </indexterm>

  <informaltable frame="none">
    <tgroup cols="2" colsep="0" rowsep="0">
      <colspec colwidth="6*"/>
      <colspec colwidth="4*"/>
      <tbody>
        <row>
          <entry>
            <para>
              The history stack lists every change of state (activate/de-activated) for all
              modules. Here you can <emphasis>select</emphasis> a point in the stack to return
              to a point in the development history. If you then activate a new module or change
              a module parameter, all modules above the selected point will be discarded.
            </para>
          </entry>
          <entry>
            <graphic fileref="darkroom/images/panel_history.png" scalefit="1" width="80%" align="center" />
          </entry>
        </row>
      </tbody>
    </tgroup>
  </informaltable>

  <para>
    <emphasis>Caution: activating any module action using key accelerators will discard all
    modules above the currently selected one. It is easy to lose all development work on an
    image this way!</emphasis>
  </para>

  <para>
    In darktable 2.0 it is safe to quit the program, leave the darkroom mode, or switch to
    another image while having selected some earlier state in the history stack panel. The
    history stack remains unchanged. When returning to the image you will find the history stack
    panel in the state where you left it.
  </para>

  <para>
    Hitting <quote>compress history stack</quote> generates the shortest history stack that
    produces the current image, i.e. suppressing all obsolete stack items. This also will
    discard all modules above the currently selected one.
  </para>

  <para>
    The button to the right
    <inlinegraphic fileref="&icon_styles;" scalefit="1" width="2%" align="center" />
    lets you create a new style for applying your history stack to other images. Use the first
    line of the popup dialog window to name your style and the second to add a searchable
    description. You are prompted for which of the current history stack modules to include in
    the style.
  </para>

  <para>
    Once created styles are then managed and applied to other images through lighttable's
    <emphasis>styles</emphasis> panel (see <xref linkend="styles"/>).
  </para>

</sect2>