From 63485bcc026097c37047d33e1e709baf70470f8f Mon Sep 17 00:00:00 2001
From: "Enrico Weigelt, metux IT consult" <info@metux.net>
Date: Fri, 4 Oct 2024 16:05:09 +0200
Subject: [PATCH] Xext: shm: use PixmapDestroy hook

Wrapping ScreenRec's function pointers is problematic for many reasons,
so use the new pixmap destroy notify hook instead.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
---
 Xext/shm.c | 45 +++++++++++++--------------------------------
 1 file changed, 13 insertions(+), 32 deletions(-)

diff --git a/Xext/shm.c b/Xext/shm.c
index c698bb591..39ff0ca48 100644
--- a/Xext/shm.c
+++ b/Xext/shm.c
@@ -98,7 +98,6 @@ in this Software without prior written authorization from The Open Group.
 
 typedef struct _ShmScrPrivateRec {
     ShmFuncsPtr shmFuncs;
-    DestroyPixmapProcPtr destroyPixmap;
 } ShmScrPrivateRec;
 
 Bool noMITShmExtension = FALSE;
@@ -109,8 +108,6 @@ static void ShmResetProc(ExtensionEntry *extEntry);
 static void SShmCompletionEvent(xShmCompletionEvent *from,
                                 xShmCompletionEvent *to);
 
-static Bool ShmDestroyPixmap(PixmapPtr pPixmap);
-
 static unsigned char ShmReqCode;
 int ShmCompletionCode;
 int BadShmSegCode;
@@ -244,28 +241,6 @@ ShmRegisterFuncs(ScreenPtr pScreen, ShmFuncsPtr funcs)
     ShmInitScreenPriv(pScreen)->shmFuncs = funcs;
 }
 
-static Bool
-ShmDestroyPixmap(PixmapPtr pPixmap)
-{
-    ScreenPtr pScreen = pPixmap->drawable.pScreen;
-    ShmScrPrivateRec *screen_priv = ShmGetScreenPriv(pScreen);
-    void *shmdesc = NULL;
-    Bool ret = TRUE;
-
-    if (pPixmap->refcnt == 1)
-        shmdesc = dixLookupPrivate(&pPixmap->devPrivates, shmPixmapPrivateKey);
-
-    pScreen->DestroyPixmap = screen_priv->destroyPixmap;
-    if (pScreen->DestroyPixmap)
-        ret = pScreen->DestroyPixmap(pPixmap);
-    screen_priv->destroyPixmap = pScreen->DestroyPixmap;
-    pScreen->DestroyPixmap = ShmDestroyPixmap;
-
-    if (shmdesc)
-	ShmDetachSegment(shmdesc, 0);
-
-    return ret;
-}
 
 void
 ShmRegisterFbFuncs(ScreenPtr pScreen)
@@ -434,6 +409,9 @@ ShmDetachSegment(void *value, /* must conform to DeleteType */
     ShmDescPtr shmdesc = (ShmDescPtr) value;
     ShmDescPtr *prev;
 
+    if (!shmdesc)
+        return Success;
+
     if (--shmdesc->refcnt)
         return TRUE;
 #if SHM_FD_PASSING
@@ -1511,6 +1489,14 @@ SProcShmDispatch(ClientPtr client)
     }
 }
 
+static void ShmPixmapDestroy(CallbackListPtr *pcbl, ScreenPtr pScreen, PixmapPtr pPixmap)
+{
+    ShmDetachSegment(
+        dixLookupPrivate(&pPixmap->devPrivates, shmPixmapPrivateKey),
+        0);
+    dixSetPrivate(&pPixmap->devPrivates, shmPixmapPrivateKey, NULL);
+}
+
 void
 ShmExtensionInit(void)
 {
@@ -1541,13 +1527,8 @@ ShmExtensionInit(void)
                 sharedPixmaps = xFalse;
         }
         if (sharedPixmaps)
-            for (i = 0; i < screenInfo.numScreens; i++) {
-                ShmScrPrivateRec *screen_priv =
-                    ShmGetScreenPriv(screenInfo.screens[i]);
-                screen_priv->destroyPixmap =
-                    screenInfo.screens[i]->DestroyPixmap;
-                screenInfo.screens[i]->DestroyPixmap = ShmDestroyPixmap;
-            }
+            for (i = 0; i < screenInfo.numScreens; i++)
+                dixScreenHookPixmapDestroy(screenInfo.screens[i], ShmPixmapDestroy);
     }
     ShmSegType = CreateNewResourceType(ShmDetachSegment, "ShmSeg");
     if (ShmSegType &&