Add default values for w, h, x and y

doc/ctpv.1

@@ -379,11 +379,6 @@ script environment:
 .BR $y
 and
 .BR $id .
-However, they are rarely used even by built-in previews and
-are only set if corresponding arguments were passed to
-.B ctpv
-command (see
-.IR SYNOPSIS ).
 There are also
 .B $m
 and

src/ctpv.c

@@ -214,6 +214,15 @@ static RESULT preview(int argc, char *argv[])
     GET_PARG(y, 4);
     GET_PARG(id, 5);
 
+    if (!w)
+        w = "80";
+    if (!h)
+        h = "40";
+    if (!x)
+        x = "0";
+    if (!y)
+        y = "0";
+
     ERRCHK_RET_OK(init_previews());
 
     struct InputFile input_f;