GUI: Begin IPC mechanism to open files despite sandboxing

gui/gui.pro

@@ -4,7 +4,7 @@
 #
 #-------------------------------------------------
 
-QT       += core concurrent gui
+QT       += core concurrent gui network
 
 greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
 CONFIG += c++17
@@ -23,6 +23,8 @@ DEFINES += QT_DEPRECATED_WARNINGS
 #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
 
 SOURCES += \
+    ipcclient.cpp \
+    ipcserver.cpp \
         main.cpp \
         mainwindow.cpp \
       pdfworker.cpp \
@@ -30,6 +32,9 @@ SOURCES += \
       clicklabel.cpp
 
 HEADERS += \
+    ipc.h \
+    ipcclient.h \
+    ipcserver.h \
         mainwindow.h \
     pdfworker.h \
     pdfpreview.h \