Added support for pdf snapshots rendering to Snap package

snap/snapcraft.yaml

@@ -15,6 +15,10 @@ icon: addon/YaCy256x256.png
 
 apps:
   yacy-search:
+    environment:
+      # needed to run wkhtmltopdf from YaCy within the Snap for Snapshots generation
+      # with wkhtmltopdf 0.12.2.4 included with Ubuntu 16.04 LTS (recommended minimum system to build Snaps in 2018)
+      QT_QPA_PLATFORM_PLUGIN_PATH: "$SNAP/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms"
     command: sh "$SNAP/yacy/startYACY.sh" -f -s "$SNAP_USER_DATA"
     # Interfaces authorizations requirements
     # network-bind - to allow acting as an HTTP server and client
@@ -22,7 +26,8 @@ apps:
     # home - not strictly necessary but can be convenient for some features to have read/write access to files outside the snap data folders, notably 
     #  - to index files in Intranet mode
     #  - for index, dump, vocabulary import/export features
-    plugs: [network-bind, desktop, home]
+    # x11 - needed by wkhtmltopdf to generate Snapshots using WebKit engine - not necessary when Snapshots feature is not used
+    plugs: [network-bind, desktop, home, x11]
   passwd: # set the YaCy administrator password
     environment: 
       YACY_DATA_PATH: "$SNAP_USER_DATA/DATA"
@@ -35,7 +40,9 @@ parts:
   yacy-search:
     # Additional packages
     # curl : needed by the passwd.sh script to call a YaCy API when the server is running
-    stage-packages: [curl]
+    # wkhtmltopdf : needed by the snapshot generation feature. 
+    # Conversion from PDF snapshots to images is done using the pure java pdfbox library, as imagemagick is more difficult to propertly embed within a Snap 
+    stage-packages: [curl, wkhtmltopdf]
     plugin: ant
     ant-build-targets: 
       - clean