la barre de navigation de lucianoa modio m'a bien plu (possibilité d'arréter le slideshow depuis un bouton dans la barre de navigation)
(http://www.lucianoamodio.it/portfolio/p … play-false)
je l'ai reproduit chez moi (rien de trop compliqué mais il me reste encore un peu de boulot css pour arriver à faire coller les boutons) et à toutes fins utiles je vous livre le contenu du template-extention, si ça intéresse d'autres personnes...

serait-il possible de l'intégrer nativement dans le core piwigo (simplification de la page slideshow) ?

<div class="navButtons">
 
{if isset($last)}
    <a class="navButton" href="{$last.U_IMG}" title="{'last_page'|@translate} : {$last.TITLE}" rel="last"><img src="{$ROOT_URL}{$themeconf.icon_dir}/last.png" class="button" alt="{'last_page'|@translate}"></a>
{else}
    <a class="navButton"><img src="{$ROOT_URL}{$themeconf.icon_dir}/last_unactive.png" class="button" alt=""></a>
{/if}
 
{if isset($next)}
    <a class="navButton" href="{$next.U_IMG}" title="{'next_page'|@translate} : {$next.TITLE}" rel="next"><img src="{$ROOT_URL}{$themeconf.icon_dir}/right.png" class="button" alt="{'next_page'|@translate}"></a>
{else}
    <a class="navButton"><img src="{$ROOT_URL}{$themeconf.icon_dir}/right_unactive.png" class="button" alt=""></a>
{/if}

{if isset($slideshow.U_START_PLAY)}
    <a class="navButton" href="{$slideshow.U_START_PLAY}" title="{'start_play'|@translate}"><img src="{$ROOT_URL}{$themeconf.icon_dir}/play.png" class="button" alt="{'start_play'|@translate}"></a>
{/if}

{if isset($slideshow.U_STOP_PLAY)}
     <a class="navButton" href="{$slideshow.U_STOP_PLAY}" title="{'stop_play'|@translate}"><img src="{$ROOT_URL}{$themeconf.icon_dir}/pause.png" class="button" alt="{'stop_play'|@translate}"></a>
{/if}

{if isset($U_UP) and !isset($slideshow)}
    <a class="navButton" href="{$U_UP}" title="{'thumbnails'|@translate}" rel="up"><img src="{$ROOT_URL}{$themeconf.icon_dir}/up.png" class="button" alt="{'thumbnails'|@translate}"></a>
{/if}

{if isset($U_SLIDESHOW_STOP) }
    <a class="navButton" href="{$U_SLIDESHOW_STOP}" title="{'slideshow_stop'|@translate}" rel="nofollow"><img src="{$ROOT_URL}{$themeconf.icon_dir}/stop_selected.png" class="button" alt="{'slideshow_stop'|@translate}"></a>
{/if}
 
{if isset($previous)}
    <a class="navButton" href="{$previous.U_IMG}" title="{'previous_page'|@translate} : {$previous.TITLE}" rel="prev"><img src="{$ROOT_URL}{$themeconf.icon_dir}/left.png" class="button" alt="{'previous_page'|@translate}"></a>
{else}
    <a class="navButton"><img src="{$ROOT_URL}{$themeconf.icon_dir}/left_unactive.png" class="button" alt=""></a>
{/if}
 
{if isset($first)}
    <a class="navButton" href="{$first.U_IMG}" title="{'first_page'|@translate} : {$first.TITLE}" rel="first"><img src="{$ROOT_URL}{$themeconf.icon_dir}/first.png" class="button" alt="{'first_page'|@translate}"></a>
{else}
    <a class="navButton"><img src="{$ROOT_URL}{$themeconf.icon_dir}/first_unactive.png" class="button" alt=""></a>
{/if}

{if isset($slideshow.U_START_REPEAT)}
    <a class="navButton" href="{$slideshow.U_START_REPEAT}" title="{'start_repeat'|@translate}"><img src="{$ROOT_URL}{$themeconf.icon_dir}/start_repeat.png" class="button" alt="{'start_repeat'|@translate}"></a>
{/if}

{if isset($slideshow.U_STOP_REPEAT)}
    <a class="navButton" href="{$slideshow.U_STOP_REPEAT}" title="{'stop_repeat'|@translate}"><img src="{$ROOT_URL}{$themeconf.icon_dir}/stop_repeat.png" class="button" alt="{'stop_repeat'|@translate}"></a>
{/if}


{if isset($slideshow)}
  {if isset($slideshow.U_DEC_PERIOD)}
    <a class="navButton" href="{$slideshow.U_DEC_PERIOD}" title="{'dec_period'|@translate}"><img src="{$ROOT_URL}{$themeconf.icon_dir}/dec_period.png" class="button" alt="{'dec_period'|@translate}"></a>
  {else}
    <a class="navButton"> <img src="{$ROOT_URL}{$themeconf.icon_dir}/dec_period_unactive.png" class="button" alt=""></a>
  {/if}

  {if isset($slideshow.U_INC_PERIOD)}
    <a class="navButton" href="{$slideshow.U_INC_PERIOD}" title="{'inc_period'|@translate}"><img src="{$ROOT_URL}{$themeconf.icon_dir}/inc_period.png" class="button" alt="{'inc_period'|@translate}"></a>
  {else}
    <a class="navButton"> <img src="{$ROOT_URL}{$themeconf.icon_dir}/inc_period_unactive.png" class="button" alt=""></a>
  {/if}
{/if}

</div>