From 04cd1ac05a22eb0439e00117538083d48e8b5920 Mon Sep 17 00:00:00 2001
From: "Enrico Weigelt, metux IT consult" <info@metux.net>
Date: Thu, 15 May 2025 17:47:40 +0200
Subject: [PATCH] dix: add dixPropertyUnlinkPtr()

This function shall be used for unlinking (but not destroying) property
from a property list.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
---
 dix/property.c      | 26 +++++++-------------------
 dix/property_list.c | 33 +++++++++++++++++++++++++++++++++
 dix/property_priv.h | 10 ++++++++++
 3 files changed, 50 insertions(+), 19 deletions(-)

diff --git a/dix/property.c b/dix/property.c
index d0bd18f35..872658b5e 100644
--- a/dix/property.c
+++ b/dix/property.c
@@ -430,7 +430,7 @@ dixChangeWindowProperty(ClientPtr pClient, WindowPtr pWin, Atom property,
 int
 DeleteProperty(ClientPtr client, WindowPtr pWin, Atom propName)
 {
-    PropertyPtr pProp, prevProp;
+    PropertyPtr pProp;
     int rc;
 
     rc = dixLookupProperty(&pProp, pWin, propName, client, DixDestroyAccess);
@@ -438,18 +438,9 @@ DeleteProperty(ClientPtr client, WindowPtr pWin, Atom propName)
         return Success;         /* Succeed if property does not exist */
 
     if (rc == Success) {
-        if (pWin->properties == pProp) {
-            /* Takes care of head */
-            if (!(pWin->properties = pProp->next))
-                CheckWindowOptionalNeed(pWin);
-        }
-        else {
-            /* Need to traverse to find the previous element */
-            prevProp = pWin->properties;
-            while (prevProp->next != pProp)
-                prevProp = prevProp->next;
-            prevProp->next = pProp->next;
-        }
+        dixPropertyUnlinkPtr(&pWin->properties, pProp);
+        if (!pWin->properties)
+            CheckWindowOptionalNeed(pWin);
 
         deliverPropertyNotifyEvent(pWin, PropertyDelete, pProp);
         notifyVRRMode(client, pWin, PropertyDelete, pProp);
@@ -461,16 +452,13 @@ DeleteProperty(ClientPtr client, WindowPtr pWin, Atom propName)
 void
 DeleteAllWindowProperties(WindowPtr pWin)
 {
-    PropertyPtr pProp = pWin->properties;
+    PropertyPtr pProp;
 
-    while (pProp) {
+    while ((pProp = pWin->properties)) {
         deliverPropertyNotifyEvent(pWin, PropertyDelete, pProp);
-        PropertyPtr pNextProp = pProp->next;
+        dixPropertyUnlinkPtr(&pWin->properties, pProp);
         dixPropertyFree(pProp);
-        pProp = pNextProp;
     }
-
-    pWin->properties = NULL;
 }
 
 /*****************
diff --git a/dix/property_list.c b/dix/property_list.c
index 9a7a2fc8b..b46a30a15 100644
--- a/dix/property_list.c
+++ b/dix/property_list.c
@@ -7,6 +7,7 @@
 #include "dix/property_priv.h"
 #include "include/privates.h"
 #include "include/propertyst.h"
+#include "os/bug_priv.h"
 
 void dixPropertyFree(PropertyPtr pr)
 {
@@ -41,3 +42,35 @@ PropertyPtr dixPropertyCreate(Atom type, Atom name, int format, size_t len,
 
     return pProp;
 }
+
+PropertyPtr dixPropertyUnlinkPtr(PropertyPtr *list, PropertyPtr prop)
+{
+    BUG_RETURN_VAL(!list, NULL);
+
+    if ((!prop) || (!(*list))) // nothing to do
+        return NULL;
+
+    PropertyPtr walk = *list;
+
+    // remove from head
+    if (walk == prop) {
+        *list = prop->next;
+        walk->next = NULL;
+        return prop;
+    }
+
+    // walk the list to find it
+    while (walk->next && walk->next != prop) {
+        walk = walk->next;
+    }
+
+    // didn't find it
+    if (!walk->next)
+        return NULL;
+
+    // unlink the element
+    walk->next = walk->next->next;
+    prop->next = NULL;
+
+    return prop;
+}
diff --git a/dix/property_priv.h b/dix/property_priv.h
index dad4a07a7..a5833a5d2 100644
--- a/dix/property_priv.h
+++ b/dix/property_priv.h
@@ -123,4 +123,14 @@ void dixPropertyFree(PropertyPtr pProp);
 PropertyPtr dixPropertyCreate(Atom type, Atom name, int format,
                               size_t len, const void *value);
 
+/*
+ * Unlink a property structure from a property list. The given property's next
+ * pointer is also cleared. The property structure itself is NOT destroyed.
+ *
+ * @param list pointer to the property list head (NULL on empty list)
+ * @param prop pointer to the property to unlink.
+ * @return on success, pointer to the property, NULL if not found in list
+ */
+PropertyPtr dixPropertyUnlinkPtr(PropertyPtr *list, PropertyPtr prop);
+
 #endif /* _XSERVER_PROPERTY_PRIV_H */