Merge pull request #522 from sharelatex/bg-hide-textlayer-for-performance

set text layer to display:none for faster scroll

services/web/public/coffee/ide/pdfng/directives/pdfViewer.coffee

@@ -323,6 +323,8 @@ define [
 									clearTimeout spinnerTimer
 								else
 									spinner.remove(element)
+								# stop displaying the text layer
+								element.removeClass 'pdfjs-viewer-show-text'
 								ctrl.redraw(origposition)
 								$timeout renderVisiblePages
 								scope.loadSuccess = true
@@ -405,6 +407,53 @@ define [
 						scope.adjustingScroll = true
 						element.scrollTop(currentScrollTop + delta)
 
+				element.on 'mousedown', (e) ->
+					# We're checking that the event target isn't the directive root element 
+					# to make sure that the click was within a PDF page - no point in showing
+					# the text layer when the click is outside.
+					# If the user clicks a PDF page, the mousedown target will be the canvas
+					# element (or the text layer one). Alternatively, if the event target is
+					# the root element, we can assume that the user has clicked either the 
+					# grey background area or the scrollbars.
+					if e.target != element[0] and !_hasSelection()
+						element.addClass 'pdfjs-viewer-show-text'
+						_setMouseUpHandler()
+
+				mouseUpHandler = null # keep track of the handler to avoid adding multiple times
+
+				_setMouseUpHandler = () ->
+					if not mouseUpHandler?
+						mouseUpHandler = $(document.body).one 'mouseup', _handleSelectionMouseUp
+
+				_handleSelectionMouseUp = () ->
+					mouseUpHandler = null # reset handler, has now fired
+					window.setTimeout () ->
+						removedClass = _removeClassIfNoSelection()
+						# if we still have a selection we need to keep the handler going
+						if not removedClass then _setMouseUpHandler()
+					, 10
+					return true
+
+				_removeClassIfNoSelection = () ->
+					if _hasSelection()
+						return false # didn't remove the text layer
+					else
+						element.removeClass 'pdfjs-viewer-show-text'
+						return true
+
+				_hasSelection = () ->
+					selection = window.getSelection?()
+					# check the selection collapsed state in preference to
+					# using selection.toString() as the latter is "" when 
+					# the selection is hidden (e.g. while viewing logs)
+					return selection? and _isSelectionWithinPDF(selection) and !selection.isCollapsed
+
+				_isSelectionWithinPDF = (selection) ->
+					if selection.rangeCount == 0
+						return false
+					selectionAncestorNode = selection.getRangeAt(0).commonAncestorContainer
+					return element.find(selectionAncestorNode).length > 0 or element.is(selectionAncestorNode)
+
 				element.on 'scroll', () ->
 					#console.log 'scroll event', element.scrollTop(), 'adjusting?', scope.adjustingScroll
 					#scope.scrollPosition = element.scrollTop()

services/web/public/stylesheets/app/editor/pdf.less

@@ -37,6 +37,7 @@
 			margin: 10px auto;
 			padding: 0 10px;
 			box-sizing: content-box;
+			user-select: none;
 		}
 	}
 	.progress-thin {
@@ -338,3 +339,13 @@
 	.files-dropdown {
 		display: inline-block;
 	}
+
+.plv-text-layer {
+	display: none;
+	user-select: text;
+	
+	.pdf-page-container:hover &,
+	.pdfjs-viewer-show-text & {
+		display: block;
+	}
+}

services/web/public/stylesheets/app/editor/toolbar.less

@@ -10,6 +10,7 @@
 			right: 0;
 			padding: .15em .6em .2em;
 			font-size: 60%;
+			pointer-events: none; // Labels were capturing button/anchor clicks.
 		}
 	}