Revert "glx: Remove pointless GLX_INTEL_swap_event paranoia"

This reverts commit 19c57ea3bf.

This commit is causing a reproducible crash of GNOME shell on Xorg
server.  Revert it for now and we may investigate it further in the
future.

Fixes #8542.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23589>

src/glx/dri2_glx.c

@@ -652,7 +652,7 @@ unsigned dri2GetSwapEventType(Display* dpy, XID drawable)
       struct glx_display *glx_dpy = __glXInitialize(dpy);
       __GLXDRIdrawable *pdraw;
       pdraw = dri2GetGlxDrawableFromXDrawableId(dpy, drawable);
-      if (!pdraw)
+      if (!pdraw || !(pdraw->eventMask & GLX_BUFFER_SWAP_COMPLETE_INTEL_MASK))
          return 0;
       return glx_dpy->codes.first_event + GLX_BufferSwapComplete;
 }

src/glx/glx_pbuffer.c

@@ -60,6 +60,10 @@ ChangeDrawableAttribute(Display * dpy, GLXDrawable drawable,
                         const CARD32 * attribs, size_t num_attribs)
 {
    struct glx_display *priv = __glXInitialize(dpy);
+#ifdef GLX_DIRECT_RENDERING
+   __GLXDRIdrawable *pdraw;
+   int i;
+#endif
    CARD32 *output;
    CARD8 opcode;
 
@@ -87,6 +91,22 @@ ChangeDrawableAttribute(Display * dpy, GLXDrawable drawable,
    UnlockDisplay(dpy);
    SyncHandle();
 
+#ifdef GLX_DIRECT_RENDERING
+   pdraw = GetGLXDRIDrawable(dpy, drawable);
+
+   if (!pdraw)
+      return;
+
+   for (i = 0; i < num_attribs; i++) {
+      switch(attribs[i * 2]) {
+      case GLX_EVENT_MASK:
+	 /* Keep a local copy for masking out DRI2 proto events as needed */
+	 pdraw->eventMask = attribs[i * 2 + 1];
+	 break;
+      }
+   }
+#endif
+
    return;
 }
 

src/glx/glxclient.h

@@ -127,6 +127,7 @@ struct __GLXDRIdrawableRec
    struct glx_screen *psc;
    GLenum textureTarget;
    GLenum textureFormat;        /* EXT_texture_from_pixmap support */
+   unsigned long eventMask;
    int refcount;
 };