Make sure control overlay always has a fixed height.

src/styles/components/_presentation.scss

@@ -99,6 +99,10 @@
   line-height: 28px;
 }
 
+.overlaybar-content .pagecontrol {
+  height: 30px;
+}
+
 .presentation .overlaybar a.btn-prev {
   left: 40px;
 }

static/partials/presentation.html

@@ -20,10 +20,12 @@
 	<div class="overlaybar form-horizontal" ng-class="{notvisible: hideControlsBar}">
 		<a class="overlaybar-button" ng-model="hideControlsBar" btn-checkbox btn-checkbox btn-checkbox-true="0" btn-checkbox-false="1" title="{{_('Presentation controls')}}"><i class="fa fa-cogs"></i></a>
 		<div class="overlaybar-content">
-			<div class="clearfix" ng-show="maxPageNumber !== -1 && !downloading">
-				<a class="overlaybar-button btn-prev" ng-click="prevPage()" ng-show="currentPageNumber &gt; 1" title="{{_('Prev')}}"><i class="fa fa-backward"></i></a>
-				<div class="pageinfo center-block"><input class="form-control input-sm" type="number" ng-model="currentPageNumber" /> / {{ maxPageNumber }}</div>
-				<a class="overlaybar-button btn-next" ng-click="nextPage()" ng-show="currentPageNumber &lt; maxPageNumber" title="{{_('Next')}}"><i class="fa fa-forward"></i></a>
+			<div class="pagecontrol" ng-show="(maxPageNumber !== -1 && !downloading) || visibleSharedFiles.length">
+				<div class="clearfix" ng-show="maxPageNumber !== -1 && !downloading">
+					<a class="overlaybar-button btn-prev" ng-click="prevPage()" ng-show="currentPageNumber &gt; 1" title="{{_('Prev')}}"><i class="fa fa-backward"></i></a>
+					<div class="pageinfo center-block"><input class="form-control input-sm" type="number" ng-model="currentPageNumber" /> / {{ maxPageNumber }}</div>
+					<a class="overlaybar-button btn-next" ng-click="nextPage()" ng-show="currentPageNumber &lt; maxPageNumber" title="{{_('Next')}}"><i class="fa fa-forward"></i></a>
+				</div>
 			</div>
 			<div class="presentations nicescroll" ng-show="visibleSharedFiles.length">
 				<div class="thumbnail" ng-repeat="info in visibleSharedFiles | orderBy : 'sortkey'" ng-click="selectPresentation(info)" title="{{ info.name }}">