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POHow to get an X11 Window from a Process ID?
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  1. POHow to get an X11 Window from a Process ID?
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    copied!<p>Under Linux, my C++ application is using fork() and execv() to launch multiple instances of OpenOffice so as to view some powerpoint slide shows. This part works.</p> <p>Next I want to be able to move the OpenOffice windows to specific locations on the display. I can do that with the XMoveResizeWindow() function but I need to find the Window for each instance.</p> <p>I have the process ID of each instance, how can I find the X11 Window from that ?</p> <hr> <p><strong>UPDATE</strong> - Thanks to Andy's suggestion, I have pulled this off. I'm posting the code here to share it with the Stack Overflow community.</p> <p>Unfortunately Open Office does not seem to set the _NET_WM_PID property so this doesn't ultimately solve my problem but it does answer the question.</p> <pre><code>// Attempt to identify a window by name or attribute. // by Adam Pierce &lt;adam@doctort.org&gt; #include &lt;X11/Xlib.h&gt; #include &lt;X11/Xatom.h&gt; #include &lt;iostream&gt; #include &lt;list&gt; using namespace std; class WindowsMatchingPid { public: WindowsMatchingPid(Display *display, Window wRoot, unsigned long pid) : _display(display) , _pid(pid) { // Get the PID property atom. _atomPID = XInternAtom(display, "_NET_WM_PID", True); if(_atomPID == None) { cout &lt;&lt; "No such atom" &lt;&lt; endl; return; } search(wRoot); } const list&lt;Window&gt; &amp;result() const { return _result; } private: unsigned long _pid; Atom _atomPID; Display *_display; list&lt;Window&gt; _result; void search(Window w) { // Get the PID for the current Window. Atom type; int format; unsigned long nItems; unsigned long bytesAfter; unsigned char *propPID = 0; if(Success == XGetWindowProperty(_display, w, _atomPID, 0, 1, False, XA_CARDINAL, &amp;type, &amp;format, &amp;nItems, &amp;bytesAfter, &amp;propPID)) { if(propPID != 0) { // If the PID matches, add this window to the result set. if(_pid == *((unsigned long *)propPID)) _result.push_back(w); XFree(propPID); } } // Recurse into child windows. Window wRoot; Window wParent; Window *wChild; unsigned nChildren; if(0 != XQueryTree(_display, w, &amp;wRoot, &amp;wParent, &amp;wChild, &amp;nChildren)) { for(unsigned i = 0; i &lt; nChildren; i++) search(wChild[i]); } } }; int main(int argc, char **argv) { if(argc &lt; 2) return 1; int pid = atoi(argv[1]); cout &lt;&lt; "Searching for windows associated with PID " &lt;&lt; pid &lt;&lt; endl; // Start with the root window. Display *display = XOpenDisplay(0); WindowsMatchingPid match(display, XDefaultRootWindow(display), pid); // Print the result. const list&lt;Window&gt; &amp;result = match.result(); for(list&lt;Window&gt;::const_iterator it = result.begin(); it != result.end(); it++) cout &lt;&lt; "Window #" &lt;&lt; (unsigned long)(*it) &lt;&lt; endl; return 0; } </code></pre>
 

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