Solved

Merging pthreads with X Windows

Posted on 1997-10-21
1
379 Views
Last Modified: 2013-12-26
I am currently developing a multi-threaded C++ apllication on a HP workstation (HP-UX 10.20). The application contains a series of X windows (X11R5) that have been developed using UIM/X. The application receives input data from a variety of external sources. The input is received on a combination of CORBA interfaces, TCP/IP sockets and one serial port. I have set up threads to process the input data, but that data needs to be displayed in the applications windows. Since X11R5 is not thread-safe (and the possibility of being able to upgrade to X11R6 is very unlikely), I need to find a reliable, safe way of getting the application's input data from the various threads that process it into the main "default" thread that contains the X event main loop.

It has been suggested to me that I read the input data into a buffer and then use XSendEvent to generate a X event to pass a pointer to that buffer to a event handler routine for display processing. However, XSendEvent requires a display pointer and window ID, and some of my input will be requests to create a window that does not yet exist. Therefore, I may not always have a window ID to target the X event to.

Another suggestion has been to use UNIX pipes or TCP/IP sockets to pass the pointers to a callback routine to do the display processing. However, I am very unfamiliar with both pipes and sockets, and I am very concerned about error handling and error recovery (i.e. how do I receover if a pipe is broken?).

Therefore, what I am looking for is some information about the benefits and pitfalls of each of these approaches, as well as any suggestions and/or examples of other approaches that I may have not considered.
0
Comment
Question by:EdMosher
1 Comment
 
LVL 2

Accepted Solution

by:
lockhart earned 100 total points
ID: 1295401
The first suggestion is the best. Since all threads can share global memory, just place the display pointer and window id into globals, if they don't exist yet (you'll need to initialize them to NULL) then put your data into another global area and have your X initializer code check it to display the latest data. You'll have to semaphore the global area to make your app thread safe.

Another consideration you might look into is running the X application as a separate process and let the globals reside in shared memory (shmget, etc.) so you don't have to worry about thread safety on the X side.
0

Featured Post

Free Tool: Postgres Monitoring System

A PHP and Perl based system to collect and display usage statistics from PostgreSQL databases.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
repeateFront java challenge 31 94
Folder Comparison 12 54
Whole sheet autoscrub still needed 19 51
Problem to App 4 97
This is to be the first in a series of articles demonstrating the development of a complete windows based application using the MFC classes.  I’ll try to keep each article focused on one (or a couple) of the tasks that one may meet.   Introductio…
Introduction: Load and Save to file, Document-View interaction inside the SDI. Continuing from the second article about sudoku.   Open the project in visual studio. From the class view select CSudokuDoc and double click to open the header …
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
Although Jacob Bernoulli (1654-1705) has been credited as the creator of "Binomial Distribution Table", Gottfried Leibniz (1646-1716) did his dissertation on the subject in 1666; Leibniz you may recall is the co-inventor of "Calculus" and beat Isaac…

860 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question