Revert "xwin: drop duplicate OsVendorVErrorF()"

This reverts commit 9652bc73e2.

Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2036>

hw/xwin/InitOutput.c

@@ -633,6 +633,9 @@ OsVendorInit(void)
 
     winFixupPaths();
 
+    if (!OsVendorVErrorFProc)
+        OsVendorVErrorFProc = OsVendorVErrorF;
+
     if (!g_fLogInited) {
         /* keep this order. If LogInit fails it calls Abort which then calls
          * ddxGiveUp where LogInit is called again and creates an infinite

hw/xwin/win.h

@@ -742,6 +742,10 @@ void
  * winerror.c
  */
 
+void
+OsVendorVErrorF(const char *pszFormat, va_list va_args)
+_X_ATTRIBUTE_PRINTF(1, 0);
+
 void
 winMessageBoxF(const char *pszError, UINT uType, ...)
 _X_ATTRIBUTE_PRINTF(1, 3);

hw/xwin/winerror.c

@@ -39,6 +39,23 @@
 
 #include "dix/input_priv.h"
 
+void
+OsVendorVErrorF(const char *pszFormat, va_list va_args)
+{
+    /* make sure the clipboard and multiwindow threads do not interfere the
+     * main thread */
+    static pthread_mutex_t s_pmPrinting = PTHREAD_MUTEX_INITIALIZER;
+
+    /* Lock the printing mutex */
+    pthread_mutex_lock(&s_pmPrinting);
+
+    /* Print the error message to a log file, could be stderr */
+    LogVMessageVerb(X_NONE, 0, pszFormat, va_args);
+
+    /* Unlock the printing mutex */
+    pthread_mutex_unlock(&s_pmPrinting);
+}
+
 /*
  * os/log.c:FatalError () calls our vendor ErrorF, so the message
  * from a FatalError will be logged.

hw/xwin/winprocarg.c

@@ -225,6 +225,12 @@ ddxProcessArgument(int argc, char *argv[], int i)
 
     /* Initialize once */
     if (!s_fBeenHere) {
+        /*
+         * This initialises our hook into VErrorF () for catching log messages
+         * that are generated before OsInit () is called.
+         */
+        OsVendorVErrorFProc = OsVendorVErrorF;
+
         s_fBeenHere = TRUE;
 
         /* Initialize only if option is not -help */

os/log.c

@@ -105,6 +105,8 @@ OR PERFORMANCE OF THIS SOFTWARE.
 #pragma clang diagnostic ignored "-Wformat-nonliteral"
 #endif
 
+void (*OsVendorVErrorFProc) (const char *, va_list args) = NULL;
+
 /* Default logging parameters. */
 #define DEFAULT_LOG_VERBOSITY		0
 #define DEFAULT_LOG_FILE_VERBOSITY	3
@@ -890,7 +892,10 @@ FatalError(const char *f, ...)
 void
 VErrorF(const char *f, va_list args)
 {
-    LogVMessageVerb(X_NONE, -1, f, args);
+    if (OsVendorVErrorFProc)
+        OsVendorVErrorFProc(f, args);
+    else
+        LogVMessageVerb(X_NONE, -1, f, args);
 }
 
 void

os/osdep.h

@@ -174,6 +174,10 @@ int os_move_fd(int fd);
    depending on whether multithreading is used */
 int xthread_sigmask(int how, const sigset_t *set, sigset_t *oldest);
 
+/* callback for DDX specific error printing, if any (may be NULL) */
+extern void (*OsVendorVErrorFProc) (const char *, va_list args)
+    _X_ATTRIBUTE_PRINTF(1, 0);
+
 typedef void (*OsSigHandlerPtr) (int sig);
 
 /* install signal handler */