From 2881f3defa1d89b2c6808db2344ea6e525aefd28 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sun, 8 Jan 2023 09:37:26 -0500
Subject: 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.
---
 src/x11.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++-------------
 src/x11.h |  3 +++
 2 files changed, 56 insertions(+), 14 deletions(-)

(limited to 'src')

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;
diff --git a/src/x11.h b/src/x11.h
index e90694a..b2c0e54 100644
--- a/src/x11.h
+++ b/src/x11.h
@@ -21,11 +21,14 @@
 typedef struct {
   Atom CLIPBOARD;
   Atom UTF8_STRING;
+  Atom WM_CLIENT_MACHINE;
   Atom WM_PROTOCOLS;
   Atom WM_DELETE_WINDOW;
   Atom PUGL_CLIENT_MSG;
   Atom NET_CLOSE_WINDOW;
   Atom NET_WM_NAME;
+  Atom NET_WM_PID;
+  Atom NET_WM_PING;
   Atom NET_WM_STATE;
   Atom NET_WM_STATE_ABOVE;
   Atom NET_WM_STATE_BELOW;
-- 
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