$Y

The National Language Support (NLS) utility $X/$Y tab defines the $X and $Y cursor movement characters for the current locale. For further details, refer to the section on “System Classes for National Language Support” in Caché Specialized System Tools and Utilities.

The following table shows the effects of different characters on $Y.

The S(ecret) protocol of the OPEN and USE commands turns off echoing. It also prevents $Y from being changed during input, so it indicates the true cursor position.

A WRITE $CHAR() that changes vertical position also changes $Y. A WRITE * that changes vertical position does not change $Y. For example, WRITE $Y,$CHAR(10),$Y performs the line feed and increments $Y. In contrast, WRITE $Y,*10,$Y performs the line feed but does not increment $Y. (See the WRITE command for further details.)

Because WRITE * does not change $Y, you can send a control sequence to your terminal and $Y will still reflect the true cursor position. Since some control sequences do move the cursor, you can use the SET command to set $Y directly. For example, the following commands move the cursor to column 20 and line 10 on a VT100-type terminal and set $X and $Y accordingly:

  SET dy=10,dx=20
  WRITE *27,*91,dy+1,*59,dx+1,*72
  SET $Y=dy,$X=dx

ANSI standard control sequences (such as escape sequences) that the device acts on but does not output can produce a discrepancy between the $X and $Y values and the true cursor position. To avoid this problem, use the WRITE * statement and specify the ASCII value of each character in the string. For example, instead of using the following code:

   WRITE $CHAR(27)_"[1m"

use this equivalent form:

   WRITE *27,*91,*49,*109

As a rule, after any escape sequence that explicitly moves the cursor, you should update $X and $Y to reflect the actual cursor position.