Backport of _XGetRequest()

To enable linking of a current libXrender libNX_X11 needs that symbol.

This is a (manual) backport of the following upstream libX11 commit
available at
https://cgit.freedesktop.org/xorg/lib/libX11/commit/src/XlibInt.c?id=4a060f993bf676cf21ad9784e010f54134da7b40:

     Commit: 4a060f993bf676cf21ad9784e010f54134da7b40
     Author: Peter Hutterer <peter.hutterer@who-t.net>
     Date: Mon, 17 Oct 2011 09:45:15 +1000
     Subject: Add _XGetRequest as substitute for GetReq/GetReqExtra

2 files changed, 47 insertions, 29 deletions

diff --git a/nx-X11/lib/X11/XlibInt.c b/nx-X11/lib/X11/XlibInt.c
index 49535fe18..64028d723 100644
--- a/nx-X11/lib/X11/XlibInt.c
+++ b/nx-X11/lib/X11/XlibInt.c
@@ -3732,6 +3732,36 @@ Screen *_XScreenOfWindow (dpy, w)
     return NULL;
 }
 
+/*
+ * WARNING: This implementation's pre-conditions and post-conditions
+ * must remain compatible with the old macro-based implementations of
+ * GetReq, GetReqExtra, GetResReq, and GetEmptyReq. The portions of the
+ * Display structure affected by those macros are part of libX11's
+ * ABI.
+ */
+void *_XGetRequest(Display *dpy, CARD8 type, size_t len)
+{
+    xReq *req;
+
+    WORD64ALIGN
+
+    if (dpy->bufptr + len > dpy->bufmax)
+       _XFlush(dpy);
+
+    if (len % 4)
+       fprintf(stderr,
+               "Xlib: request %d length %zd not a multiple of 4.\n",
+               type, len);
+
+    dpy->last_req = dpy->bufptr;
+
+    req = (xReq*)dpy->bufptr;
+    req->reqType = type;
+    req->length = len / 4;
+    dpy->bufptr += len;
+    dpy->request++;
+    return req;
+}
 
 #if defined(WIN32)
 
diff --git a/nx-X11/lib/X11/Xlibint.h b/nx-X11/lib/X11/Xlibint.h
index 474b77349..a359efca1 100644
--- a/nx-X11/lib/X11/Xlibint.h
+++ b/nx-X11/lib/X11/Xlibint.h
@@ -422,6 +422,19 @@ extern LockInfoPtr _Xglobal_lock;
 /* Leftover from CRAY support - was defined empty on all non-Cray systems */
 #define WORD64ALIGN
 
+/**
+ * Return a len-sized request buffer for the request type. This function may
+ * flush the output queue.
+ *
+ * @param dpy The display connection
+ * @param type The request type
+ * @param len Length of the request in bytes
+ *
+ * @returns A pointer to the request buffer with a few default values
+ * initialized.
+ */
+extern void *_XGetRequest(Display *dpy, CARD8 type, size_t len);
+
 /*
  * GetReq - Get the next available X request packet in the buffer and
  * return it. 
@@ -433,23 +446,10 @@ extern LockInfoPtr _Xglobal_lock;
 
 #if !defined(UNIXCPP) || defined(ANSICPP)
 #define GetReq(name, req) \
-	if ((dpy->bufptr + SIZEOF(x##name##Req)) > dpy->bufmax)\
-		_XFlush(dpy);\
-	req = (x##name##Req *)(dpy->last_req = dpy->bufptr);\
-	req->reqType = X_##name;\
-	req->length = (SIZEOF(x##name##Req))>>2;\
-	dpy->bufptr += SIZEOF(x##name##Req);\
-	dpy->request++
-
+        req = (x##name##Req *) _XGetRequest(dpy, X_##name, SIZEOF(x##name##Req))
 #else  /* non-ANSI C uses empty comment instead of "##" for token concatenation */
 #define GetReq(name, req) \
-	if ((dpy->bufptr + SIZEOF(x/**/name/**/Req)) > dpy->bufmax)\
-		_XFlush(dpy);\
-	req = (x/**/name/**/Req *)(dpy->last_req = dpy->bufptr);\
-	req->reqType = X_/**/name;\
-	req->length = (SIZEOF(x/**/name/**/Req))>>2;\
-	dpy->bufptr += SIZEOF(x/**/name/**/Req);\
-	dpy->request++
+        req = (x/**/name/**/Req *) _XGetRequest(dpy, X_/**/name, SIZEOF(x/**/name/**/Req))
 #endif
 
 /* GetReqExtra is the same as GetReq, but allocates "n" additional
@@ -457,22 +457,10 @@ extern LockInfoPtr _Xglobal_lock;
 
 #if !defined(UNIXCPP) || defined(ANSICPP)
 #define GetReqExtra(name, n, req) \
-	if ((dpy->bufptr + SIZEOF(x##name##Req) + n) > dpy->bufmax)\
-		_XFlush(dpy);\
-	req = (x##name##Req *)(dpy->last_req = dpy->bufptr);\
-	req->reqType = X_##name;\
-	req->length = (SIZEOF(x##name##Req) + n)>>2;\
-	dpy->bufptr += SIZEOF(x##name##Req) + n;\
-	dpy->request++
+        req = (x##name##Req *) _XGetRequest(dpy, X_##name, SIZEOF(x##name##Req) + n)
 #else
 #define GetReqExtra(name, n, req) \
-	if ((dpy->bufptr + SIZEOF(x/**/name/**/Req) + n) > dpy->bufmax)\
-		_XFlush(dpy);\
-	req = (x/**/name/**/Req *)(dpy->last_req = dpy->bufptr);\
-	req->reqType = X_/**/name;\
-	req->length = (SIZEOF(x/**/name/**/Req) + n)>>2;\
-	dpy->bufptr += SIZEOF(x/**/name/**/Req) + n;\
-	dpy->request++
+        req = (x/**/name/**/Req *) _XGetRequest(dpy, X_/**/name, SIZEOF(x/**/name/**/Req) + n)
 #endif