Added information about dropping a PDF to present it.

src/styles/components/_presentation.scss

@@ -27,12 +27,18 @@
   top: 0;
 }
 
+.presentation-target {
+  width: 100%;
+  font-size: 10em;
+  text-align: center;
+  margin-top: 30px;
+}
+
 .mainPresentation #presentation {
   display: block;
 }
 
 .presentationpane {
-  background: black;
   bottom: 0;
   left: 0;
   overflow: auto;

static/partials/presentation.html

@@ -1,6 +1,10 @@
 <div class="presentation">
 	<div class="presentationpane nicescroll">
-		<pdfcanvas/>
+		<pdfcanvas ng-hide="maxPageNumber === -1" />
+		<div class="welcome container-fluid" ng-hide="maxPageNumber !== -1">
+			<h1>{{_('Please drop a PDF document here to present it to the other participants.')}}</h1>
+			<div class="presentation-target fa fa-file-pdf-o"></div>
+		</div>
 	</div>
 	<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>