X11: Add support for _NET_WM_PING protocol

This is mainly used to allow the window manager to close locked or otherwise
misbehaving windows.  The PID and hostname properties are both required to
properly support this, but may also be used for other things.

1 files changed, 53 insertions, 14 deletions

diff --git a/src/x11.c b/src/x11.c
index 4e8d591..ce9387b 100644
--- a/src/x11.c
+++ b/src/x11.c
@@ -41,6 +41,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <unistd.h>
 
 #ifndef MIN
 #  define MIN(a, b) (((a) < (b)) ? (a) : (b))
@@ -157,14 +158,17 @@ puglInitWorldInternals(const PuglWorldType type, const PuglWorldFlags flags)
 
   // Intern the various atoms we'll need
 
-  impl->atoms.CLIPBOARD        = XInternAtom(display, "CLIPBOARD", 0);
-  impl->atoms.UTF8_STRING      = XInternAtom(display, "UTF8_STRING", 0);
-  impl->atoms.WM_PROTOCOLS     = XInternAtom(display, "WM_PROTOCOLS", 0);
-  impl->atoms.WM_DELETE_WINDOW = XInternAtom(display, "WM_DELETE_WINDOW", 0);
-  impl->atoms.PUGL_CLIENT_MSG  = XInternAtom(display, "_PUGL_CLIENT_MSG", 0);
-  impl->atoms.NET_CLOSE_WINDOW = XInternAtom(display, "_NET_CLOSE_WINDOW", 0);
-  impl->atoms.NET_WM_NAME      = XInternAtom(display, "_NET_WM_NAME", 0);
-  impl->atoms.NET_WM_STATE     = XInternAtom(display, "_NET_WM_STATE", 0);
+  impl->atoms.CLIPBOARD         = XInternAtom(display, "CLIPBOARD", 0);
+  impl->atoms.UTF8_STRING       = XInternAtom(display, "UTF8_STRING", 0);
+  impl->atoms.WM_CLIENT_MACHINE = XInternAtom(display, "WM_CLIENT_MACHINE", 0);
+  impl->atoms.WM_PROTOCOLS      = XInternAtom(display, "WM_PROTOCOLS", 0);
+  impl->atoms.WM_DELETE_WINDOW  = XInternAtom(display, "WM_DELETE_WINDOW", 0);
+  impl->atoms.PUGL_CLIENT_MSG   = XInternAtom(display, "_PUGL_CLIENT_MSG", 0);
+  impl->atoms.NET_CLOSE_WINDOW  = XInternAtom(display, "_NET_CLOSE_WINDOW", 0);
+  impl->atoms.NET_WM_NAME       = XInternAtom(display, "_NET_WM_NAME", 0);
+  impl->atoms.NET_WM_PID        = XInternAtom(display, "_NET_WM_PID", 0);
+  impl->atoms.NET_WM_PING       = XInternAtom(display, "_NET_WM_PING", 0);
+  impl->atoms.NET_WM_STATE      = XInternAtom(display, "_NET_WM_STATE", 0);
 
   impl->atoms.NET_WM_STATE_ABOVE =
     XInternAtom(display, "_NET_WM_STATE_ABOVE", 0);
@@ -583,14 +587,38 @@ puglRealize(PuglView* const view)
     puglSetWindowTitle(view, view->title);
   }
 
-  if (parent == root) {
-    XSetWMProtocols(display, impl->win, &atoms->WM_DELETE_WINDOW, 1);
-  }
-
   if (view->transientParent) {
     puglSetTransientParent(view, view->transientParent);
   }
 
+  // Set PID and hostname so the window manager can access our process
+  char       hostname[256] = {0};
+  const long pid           = (long)getpid();
+  if (pid > 0 && !gethostname(hostname, sizeof(hostname))) {
+    hostname[sizeof(hostname) - 1] = '\0';
+    XChangeProperty(display,
+                    impl->win,
+                    atoms->WM_CLIENT_MACHINE,
+                    XA_STRING,
+                    8,
+                    PropModeReplace,
+                    (const uint8_t*)hostname,
+                    (int)strlen(hostname));
+
+    XChangeProperty(display,
+                    impl->win,
+                    atoms->NET_WM_PID,
+                    XA_CARDINAL,
+                    32,
+                    PropModeReplace,
+                    (const uint8_t*)&pid,
+                    1);
+  }
+
+  // Set supported WM protocols
+  Atom protocols[] = {atoms->NET_WM_PING, atoms->WM_DELETE_WINDOW};
+  XSetWMProtocols(display, impl->win, protocols, (parent == root) ? 2 : 1);
+
   // Create input context
   if (world->impl->xim) {
     impl->xic = XCreateIC(world->impl->xim,
@@ -913,13 +941,24 @@ setClipboardFormats(PuglView* const         view,
 static PuglEvent
 translateClientMessage(PuglView* const view, XClientMessageEvent message)
 {
-  const PuglX11Atoms* const atoms = &view->world->impl->atoms;
-  PuglEvent                 event = {{PUGL_NOTHING, 0}};
+  Display* const            display = view->world->impl->display;
+  const PuglX11Atoms* const atoms   = &view->world->impl->atoms;
+  PuglEvent                 event   = {{PUGL_NOTHING, 0}};
 
   if (message.message_type == atoms->WM_PROTOCOLS) {
     const Atom protocol = (Atom)message.data.l[0];
     if (protocol == atoms->WM_DELETE_WINDOW) {
       event.type = PUGL_CLOSE;
+    } else if (protocol == atoms->NET_WM_PING) {
+      const Window root    = RootWindow(display, view->impl->screen);
+      XEvent       reply   = {ClientMessage};
+      reply.xclient        = message;
+      reply.xclient.window = root;
+      XSendEvent(display,
+                 root,
+                 False,
+                 SubstructureNotifyMask | SubstructureRedirectMask,
+                 &reply);
     }
   } else if (message.message_type == atoms->PUGL_CLIENT_MSG) {
     event.type         = PUGL_CLIENT;