Gerbview: show a message instead of an error when trying to open a job file as plot file.

Fixes #4844
https://gitlab.com/kicad/code/kicad/issues/4844

gerbview/files.cpp

@@ -316,7 +316,17 @@ bool GERBVIEW_FRAME::loadListOfGerberAndDrillFiles( const wxString& aPath,
         }
         else
         {
-            if( Read_GERBER_File( filename.GetFullPath() ) )
+            if( filename.GetExt() == GerberJobFileExtension.c_str() )
+            {
+                //We cannot read a gerber job file as a gerber plot file: skip it
+                wxString txt;
+                txt.Printf(
+                    _( "<b>A gerber job file cannot be loaded as a plot file</b> <i>%s</i>" ),
+                    filename.GetFullName() );
+                success = false;
+                reporter.Report( txt, RPT_SEVERITY_ERROR );
+            }
+            else if( Read_GERBER_File( filename.GetFullPath() ) )
             {
                 UpdateFileHistory( m_lastFileName );
 
@@ -545,6 +555,18 @@ bool GERBVIEW_FRAME::unarchiveFiles( const wxString& aFullFileName, REPORTER* aR
             continue;
         }
 
+        if( curr_ext == GerberJobFileExtension.c_str() )
+        {
+            //We cannot read a gerber job file as a gerber plot file: skip it
+            if( aReporter )
+            {
+                msg.Printf( _( "Info: skip file \"%s\" (gerber job file)\n" ), entry->GetName() );
+                aReporter->Report( msg, RPT_SEVERITY_WARNING );
+            }
+
+            continue;
+        }
+
         int layer = GetActiveLayer();
 
         if( layer == NO_AVAILABLE_LAYERS )

gerbview/tools/gerbview_actions.cpp

@@ -57,8 +57,8 @@ OPT<TOOL_EVENT> GERBVIEW_ACTIONS::TranslateLegacyId( int aId )
 //
 TOOL_ACTION GERBVIEW_ACTIONS::openGerber( "gerbview.Control.openGerber",
         AS_GLOBAL, 0, "",
-        _( "Open Gerber File(s)..." ),
-        _( "Open Gerber file(s) on the current layer. Previous data will be deleted" ),
+        _( "Open Gerber Plot File(s)..." ),
+        _( "Open Gerber plot file(s) on the current layer. Previous data will be deleted" ),
         load_gerber_xpm );
 
 TOOL_ACTION GERBVIEW_ACTIONS::openDrillFile( "gerbview.Control.openDrillFile",
@@ -70,7 +70,7 @@ TOOL_ACTION GERBVIEW_ACTIONS::openDrillFile( "gerbview.Control.openDrillFile",
 TOOL_ACTION GERBVIEW_ACTIONS::openJobFile( "gerbview.Control.openJobFile",
         AS_GLOBAL, 0, "",
         _( "Open Gerber Job File..." ),
-        _( "Open a Gerber job file and its associated gerber files" ),
+        _( "Open a Gerber job file and its associated gerber plot files" ),
         gerber_job_file_xpm );
 
 TOOL_ACTION GERBVIEW_ACTIONS::openZipFile( "gerbview.Control.openZipFile",