From 159183c8a07697c0a73325b1c2a68c7ef217bf94 Mon Sep 17 00:00:00 2001
From: "Enrico Weigelt, metux IT consult" <info@metux.net>
Date: Wed, 19 Mar 2025 10:50:56 +0100
Subject: [PATCH] Xnamespace: create per-namespace fake root windows

For each namespace creating a fake (invisible) root window, which can be
used for storing per-namespace properties (eg. cut buffers), etc.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
---
 Xext/namespace/hook-init-rootwindow.c | 71 +++++++++++++++++++++++++++
 Xext/namespace/hooks.h                |  1 +
 Xext/namespace/meson.build            |  1 +
 Xext/namespace/namespace.c            |  1 +
 Xext/namespace/namespace.h            |  2 +
 5 files changed, 76 insertions(+)
 create mode 100644 Xext/namespace/hook-init-rootwindow.c

diff --git a/Xext/namespace/hook-init-rootwindow.c b/Xext/namespace/hook-init-rootwindow.c
new file mode 100644
index 000000000..2d7a8c067
--- /dev/null
+++ b/Xext/namespace/hook-init-rootwindow.c
@@ -0,0 +1,71 @@
+#define HOOK_NAME "initroot"
+
+#include <dix-config.h>
+
+#include <stdio.h>
+#include <X11/Xatom.h>
+#include <X11/Xmd.h>
+
+#include "dix/window_priv.h"
+
+#include "namespace.h"
+#include "hooks.h"
+
+static inline int setWinStrProp(WindowPtr pWin, Atom name, const char *text) {
+    return dixChangeWindowProperty(serverClient, pWin, name, XA_STRING,
+                                   8, PropModeReplace, strlen(text), text, TRUE);
+}
+
+void hookInitRootWindow(CallbackListPtr *pcbl, void *data, void *screen)
+{
+    ScreenPtr pScreen = (ScreenPtr)screen;
+
+    // only act on first screen
+    if (pScreen->myNum)
+        return;
+
+    /* create the virtual root windows */
+    WindowPtr realRoot = pScreen->root;
+
+    assert(realRoot);
+
+    struct Xnamespace *walk;
+
+    xorg_list_for_each_entry(walk, &ns_list, entry) {
+        if (strcmp(walk->name, NS_NAME_ROOT)==0) {
+            walk->rootWindow = realRoot;
+            XNS_LOG("<%s> actual root 0x%0x\n", walk->name, walk->rootWindow->drawable.id);
+            continue;
+        }
+
+        int rc = 0;
+        WindowPtr pWin = dixCreateWindow(
+            FakeClientID(0), realRoot, 0, 0, 23, 23,
+            0, /* bw */
+            InputOutput,
+            0, /* vmask */
+            NULL, /* vlist */
+            0, /* depth */
+            serverClient,
+            wVisual(realRoot), /* visual */
+            &rc);
+
+        if (!pWin)
+            FatalError("hookInitRootWindow: cant create per-namespace root window for %s\n", walk->name);
+
+        Mask mask = pWin->eventMask;
+        pWin->eventMask = 0;    /* subterfuge in case AddResource fails */
+        if (!AddResource(pWin->drawable.id, X11_RESTYPE_WINDOW, (void *) pWin))
+            FatalError("hookInitRootWindow: cant add per-namespace root window as resource\n");
+        pWin->eventMask = mask;
+
+        walk->rootWindow = pWin;
+
+        // set window name
+        char buf[PATH_MAX] = { 0 };
+        snprintf(buf, sizeof(buf)-1, "XNS-ROOT:%s", walk->name);
+        setWinStrProp(pWin, XA_WM_NAME, buf);
+
+        XNS_LOG("<%s> virtual root 0x%0x\n", walk->name, walk->rootWindow->drawable.id);
+    }
+}
diff --git a/Xext/namespace/hooks.h b/Xext/namespace/hooks.h
index d06408c52..9f08f6199 100644
--- a/Xext/namespace/hooks.h
+++ b/Xext/namespace/hooks.h
@@ -25,6 +25,7 @@
     struct XnamespaceClientPriv *subj = XnsClientPriv(client);
 
 void hookClientState(CallbackListPtr *pcbl, void *unused, void *calldata);
+void hookInitRootWindow(CallbackListPtr *pcbl, void *unused, void *calldata);
 void hookSelectionFilter(CallbackListPtr *pcbl, void *unused, void *calldata);
 
 #endif /* __XSERVER_NAMESPACE_HOOKS_H */
diff --git a/Xext/namespace/meson.build b/Xext/namespace/meson.build
index 165882231..75a8a12ab 100644
--- a/Xext/namespace/meson.build
+++ b/Xext/namespace/meson.build
@@ -3,6 +3,7 @@ libxserver_namespace = static_library(
 	[
 		'config.c',
 		'hook-clientstate.c',
+		'hook-init-rootwindow.c',
 		'hook-selection.c',
 		'namespace.c',
 	],
diff --git a/Xext/namespace/namespace.c b/Xext/namespace/namespace.c
index b2aa59913..496e0a87d 100644
--- a/Xext/namespace/namespace.c
+++ b/Xext/namespace/namespace.c
@@ -29,6 +29,7 @@ NamespaceExtensionInit(void)
     if (!(dixRegisterPrivateKey(&namespaceClientPrivKeyRec, PRIVATE_CLIENT,
             sizeof(struct XnamespaceClientPriv)) &&
           AddCallback(&ClientStateCallback, hookClientState, NULL) &&
+          AddCallback(&PostInitRootWindowCallback, hookInitRootWindow, NULL) &&
           AddCallback(&SelectionFilterCallback, hookSelectionFilter, NULL)))
         FatalError("NamespaceExtensionInit: allocation failure\n");
 
diff --git a/Xext/namespace/namespace.h b/Xext/namespace/namespace.h
index acabe1060..5bf9ba7f8 100644
--- a/Xext/namespace/namespace.h
+++ b/Xext/namespace/namespace.h
@@ -8,6 +8,7 @@
 #include "include/list.h"
 #include "include/privates.h"
 #include "include/window.h"
+#include "include/windowstr.h"
 
 struct Xnamespace {
     struct xorg_list entry;
@@ -18,6 +19,7 @@ struct Xnamespace {
     char *authTokenData;
     size_t authTokenLen;
     size_t refcnt;
+    WindowPtr rootWindow;
 };
 
 extern struct xorg_list ns_list;