;+ ; NAME: ; CANCONNECT ; ; PURPOSE: ; ; This function will check to see if it is possible to make ; a connection with the window system. It is useful when ; running IDL as a CRON job or from remote logins. The program ; will establish a system variable named !FSC_Display_Connection the ; first time it is run. Programs which need to know if a connection ; can be established can consult this system variable as a faster ; way of determining a connection than running this program. The ; system variable is set to 1 if a connection can be made and to ; 0 otherwise. ; ; AUTHOR: ; ; FANNING SOFTWARE CONSULTING ; David Fanning, Ph.D. ; 1645 Sheely Drive ; Fort Collins, CO 80526 USA ; Phone: 970-221-0438 ; E-mail: david@idlcoyote.com ; Coyote's Guide to IDL Programming: http://www.idlcoyote.com ; ; CATEGORY: ; Utilities ; ; CALLING SEQUENCE: ; ; connection = CanConnect() ; ; RETURN_VALUE: ; ; connection: Will be set to 1 if a window connection is possible ; Otherwise, it will be set to 0. ; ; INPUT_PARAMETERS: ; ; None. ; ; KEYWORDS: ; ; None. ; ; NOTES: ; ; A system variable, !FSC_Display_Connection is created. ; ; MODIFICATION HISTORY: ; ; Written by David W. Fanning, 10 February 2010. ; Modified program to set the system variable !FSC_Display_Connection. This is primarily ; a way for legacy code to run in cron jobs without continually checking for ; a connection, which before this update required opening and closing a window. ; 7 October 2010. DWF. ;- ;******************************************************************************************; ; Copyright (c) 2010, by Fanning Software Consulting, Inc. ; ; All rights reserved. ; ; ; ; Redistribution and use in source and binary forms, with or without ; ; modification, are permitted provided that the following conditions are met: ; ; ; ; * Redistributions of source code must retain the above copyright ; ; notice, this list of conditions and the following disclaimer. ; ; * Redistributions in binary form must reproduce the above copyright ; ; notice, this list of conditions and the following disclaimer in the ; ; documentation and/or other materials provided with the distribution. ; ; * Neither the name of Fanning Software Consulting, Inc. nor the names of its ; ; contributors may be used to endorse or promote products derived from this ; ; software without specific prior written permission. ; ; ; ; THIS SOFTWARE IS PROVIDED BY FANNING SOFTWARE CONSULTING, INC. ''AS IS'' AND ANY ; ; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES ; ; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT ; ; SHALL FANNING SOFTWARE CONSULTING, INC. BE LIABLE FOR ANY DIRECT, INDIRECT, ; ; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED ; ; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; ; ; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ; ; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ; ; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS ; ; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ; ;******************************************************************************************; Function CanConnect ; Assume a good connection. haveConnection = 1 ; Try to open a window. If you fail, you have no window connection. Catch, theError IF theError NE 0 THEN BEGIN Catch, /CANCEL haveConnection = 0 GOTO, cleanUp ENDIF ; Try to open a window. theWindow = !D.Window Window, /FREE, XSIZE=5, YSIZE=5, /PIXMAP Catch, /CANCEL ; Come here if things go south or you actually make it here. cleanUp: IF !D.Window NE theWindow THEN BEGIN WDelete, !D.Window IF theWindow GE 0 THEN WSet, theWindow ENDIF ; Does the system variable !FSC_Display_Connection exist? If so, set its value. ; If not, create it. DefSysV, '!FSC_Display_Connection', EXISTS=sysvarExists IF sysvarExists $ THEN !FSC_Display_Connection = haveConnection $ ELSE DefSysV, '!FSC_Display_Connection', haveConnection RETURN, haveConnection END