ephyr: if -parent is given, check for a trailing -screen. (#24144)

If -parent is given, don't open up a new window if -screen is given as well.
The commandline option -screen allows to set the depth of the embedded
Xephry instance, even though width and height are autoscaled on -parent.

This patch checks for a -screen parameter after -parent and - if one is
found - delays initializing the screen. The parent window id is stored
temporarily but re-set after a -screen argument.
The following command is thus valid:

Xephyr -parent 1234 -screen 640x480@8 -screen 1024x768

It embeds the first 8-bit screen into window 1234 and opens up a new window
for the second screen. Multiple parent arguments are possible, the screens
are embedded in-order.

X.Org Bug 24144 <http://bugs.freedesktop.org/show_bug.cgi?id=24144>

Tested-by: Vic Lee
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

hw/kdrive/ephyr/Xephyr.man.pre

@@ -46,6 +46,11 @@ sets the screen size.
 .BI -parent " id"
 uses exiting window
 .I id .
+If a 
+.BI -screen 
+argument follows a 
+.BI -parent
+argument, this screen is embedded into the given window.
 .TP 8
 .B -host-cursor
 set 'cursor acceleration':

hw/kdrive/ephyr/ephyrinit.c

@@ -148,6 +148,7 @@ processScreenArg (char *screen_size, char *parent_id)
 int
 ddxProcessArgument (int argc, char **argv, int i)
 {
+  static char* parent = NULL;
   EPHYR_DBG("mark argv[%d]='%s'", i, argv[i] );
 
   if (i == 1)
@@ -159,6 +160,18 @@ ddxProcessArgument (int argc, char **argv, int i)
     {
       if(i+1 < argc)
 	{
+	  int j;
+	  /* If parent is specified and a screen argument follows, don't do
+           * anything, let the -screen handling init the rest */
+	  for (j = i; j < argc; j++)
+	    {
+	      if (!strcmp(argv[j], "-screen"))
+		{
+		  parent = argv[i + 1];
+		  return 2;
+		}
+	    }
+
 	  processScreenArg ("100x100", argv[i+1]);
 	  return 2;
 	}
@@ -170,7 +183,8 @@ ddxProcessArgument (int argc, char **argv, int i)
     {
       if ((i+1) < argc)
 	{
-	  processScreenArg (argv[i+1], NULL);
+	  processScreenArg (argv[i+1], parent);
+	  parent = NULL;
 	  return 2;
 	}