Merge pull request #5413 from rldhont/server-bugfix-display

[Server][Bugfix] Test if the environ variable DISPLAY is defined

src/server/qgis_map_serv.cpp

@@ -19,6 +19,8 @@
 //for CMAKE_INSTALL_PREFIX
 #include "qgsconfig.h"
 #include "qgsserver.h"
+#include "qgslogger.h"
+#include "qgsserverlogger.h"
 #include "qgsfcgiserverresponse.h"
 #include "qgsfcgiserverrequest.h"
 
@@ -39,7 +41,25 @@ int fcgi_accept()
 
 int main( int argc, char *argv[] )
 {
-  QgsApplication app( argc, argv, getenv( "DISPLAY" ), QString(), QStringLiteral( "server" ) );
+  // Test if the environ variable DISPLAY is defined
+  // if it's not, the server is running in offscreen mode
+  // Qt supports using various QPA (Qt Platform Abstraction) back ends
+  // for rendering. You can specify the back end to use with the environment
+  // variable QT_QPA_PLATFORM when invoking a Qt-based application.
+  // Available platform plugins are: directfbegl, directfb, eglfs, linuxfb,
+  // minimal, minimalegl, offscreen, wayland-egl, wayland, xcb.
+  // https://www.ics.com/blog/qt-tips-and-tricks-part-1
+  // http://doc.qt.io/qt-5/qpa.html
+  const char *display = getenv( "DISPLAY" );
+  bool withDisplay = true;
+  if ( !display )
+  {
+    withDisplay = false;
+    qputenv( "QT_QPA_PLATFORM", "offscreen" );
+    QgsMessageLog::logMessage( "DISPLAY not set, running in offscreen mode, all printing capabilities will not be available.", "Server", QgsMessageLog::INFO );
+  }
+  // since version 3.0 QgsServer now needs a qApp so initialize QgsApplication
+  QgsApplication app( argc, argv, withDisplay, QString(), QStringLiteral( "server" ) );
   QgsServer server;
 #ifdef HAVE_SERVER_PYTHON_PLUGINS
   server.initPython();