下面的代码用来查找与特定进程的PID对应的X Window窗口。关键部分是递归查找窗口的_NET_WM_PID属性。
一个进程PID可能会对应多个窗口，即使你在屏幕上只看到了一个窗口。
除了程序主窗口外，还可能有程序的“关于”等窗口。这类窗口虽然逻辑上（比如在Qt库中）应该从属于主窗口，但作为一个X Window来说，却有可能并不从属于主窗口。
#include <X11/X.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xproto.h>
#include <X11/Xatom.h>
#include <iostream>
#include <list>
/* Find X Window From PID
*
* Reference:
* http://stackoverflow.com/questions/151407/how-to-get-an-x11-window-from-a-process-id
*/
class XWindowFinder {
public:
XWindowFinder(unsigned long pid, Display *display=NULL): _display(display), _pid(pid) {
if(_display==NULL) _display = XOpenDisplay(NULL);
_atomPID = XInternAtom(_display, "_NET_WM_PID", True);
if(_atomPID == None) {
std::cout << "No such atom" << std::endl;
return;
}
Window wRoot = XDefaultRootWindow(_display);
this->search(wRoot);
}
const std::vector<Window> &result() const { return _result; }
void print(){
for(std::vector<Window>::const_iterator it=_result.begin(); it !=_result.end(); it++)
std::cout << "Window #" << (unsigned long)(*it) << std::endl;
}
private:
unsigned long _pid;
Atom _atomPID;
Display *_display;
std::vector<Window> _result;
unsigned long getPid(Window w){
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,
&type, &format, &nItems, &bytesAfter, &propPID))
{
if(propPID != 0) {
unsigned long pid = *((unsigned long *)propPID);
XFree(propPID);
return pid;
}
}
return 0;
}
bool search(Window w) {
bool found = false;
unsigned long propPID = this->getPid(w);
if(_pid == propPID){
_result.push_back(w);
return true;
}
// Recurse into child windows.
Window wRoot;
Window wParent;
Window *wChild;
unsigned nChildren;
if(0 != XQueryTree(_display, w, &wRoot, &wParent, &wChild, &nChildren)) {
for(unsigned i = 0; i < nChildren; i++){
found = search(wChild[i]) || found;
// found = found || search(wChild[i]);
//if(found) break;
}
}
return found;
}
};
int main(int argc, char **argv){
if(argc>=3 && strcmp(argv[1],"pid")==0){
int pid = atoi(argv[2]);
XWindowFinder finder(pid);
finder.print();
return 0;
}
return 0;
}