D    Using DECterm Localization Features in Programs

This appendix discusses programming features for local language support that are available in the the DECterm terminal emulator.

D.1    Drawing Ruled Lines in a DECterm Window

Programming guides for video terminals discuss how you use ANSI escape sequences to perform operations, such as inserting and deleting characters, inserting and removing blank lines, and requesting character display in double height and width. Because a DECterm window is a terminal emulator, these escape sequences also apply to programs that display text and graphics in a DECterm window.

Operating system enhancements for Asian languages include additional escape sequences for drawing and removing ruled lines in a specified area of a DECterm window. These additional escape sequences allow applications to construct tables and diagrams.

The following sections describe the escape sequences that draw and erase lines according to pattern and area parameters.

D.1.1    Drawing Ruled Lines in a Pattern

The escape sequence identified by the mnemonic DECDRLBR draws ruled lines on the boundaries of a rectangular area according to a specified pattern. The following table provides format information:

When the DECDRLBR escape sequence is received from an application, DECterm software draws ruled lines on one or more of the boundaries of the area between the coordinates(Px,Py ) and(Px+Plx-1, Py+Ply -1) according to the pattern specified in P1. Consider the following example:

CSI 15 ; 1 ; 5 ; 1 ; 2 , r
 

The preceding escape sequence causes the DECterm software to draw ruled lines as shown in Figure D-1.

Figure D-1:  Drawing Ruled Lines with the DECDRLBR Sequence

DECterm software draws ruled lines that are one pixel in width. When the display scrolls, these lines correctly scroll as if text.

Figure D-2 and the table following the figure describe the bit pattern that the DECDRLBR parameters map to.

Figure D-2:  Bit Pattern for DECDRLBR Parameters

The DECDRLBR parameters are more completely described in the following list:

• Pattern of ruled lines(P1 )

  The pattern is a bitmask that controls how the ruled lines are drawn on the boundaries of the area. Ruled lines are drawn according to whether the bits for the boundaries are set on or off. For example, ruled lines are drawn on all boundaries if P1 is set to 15 and on the top and bottom boundary if P1 is set to 5:

  Boundary : Bottom   Right   Top    Left
  P1       = Bit0   + Bit1  + Bit2 + Bit3
  P1       = 1      + 2     + 4    + 8      = 15
  P1       = 1              + 4             =  5
  

• Absolute position of the start point(Px,Py )

  Px is the starting column position and Py is the starting row position. If you omit these parameters or explicitly set them to 0 (zero), the starting position is at column 1 and row 1. In other words, the upper left corner of the rectangle is at the coordinates (1,1).

• Size of the area(Plx,Ply )

  Plx is the width of the area in columns and Ply is the height of the area in rows. If you omit these parameters or explicitly set them to 0 (zero), the area is 1 column in width and 1 row in height.

D.1.2    Erasing Ruled Lines in a Pattern

The DECERLBRP escape sequence erases ruled lines on the boundaries of a rectangular area according to a specified pattern. The following table provides format information:

D.1.3    Erasing All Ruled Lines in an Area

The escape sequence DECERLBRA erases all ruled lines, not just those drawn on the area boundaries, in a rectangular area. The following table provides format information:

D.1.4    Interaction of Ruled Lines and Other DECterm Escape Sequences

Table D-1 describes the effect of using standard DECterm escape sequences when ruled lines are drawn on the screen.

Table D-1:  Behavior of Standard Escape Sequences with Ruled Lines

Mnemonic	Description	Effect on Ruled Lines
DECDWL, DECDHLT, DECDHLB	Display as double width or double height	These escape sequences have no effect on ruled lines, whose width is always one pixel. Furthermore, the parameter units for the escape sequences controlling ruled line display are always specified in terms of single width and single height columns and rows, even when the escape sequences are used with those that double the height and width of text.
GSM	Modify graphic size	These escape sequences have no effect on ruled lines, whose width is always one pixel. Comments made in the entry for DECDWL, DECDHLT, and DECDHLB also apply to GSM.
ED, EL, ECH	Erase display, erase line, and erase character	These escape sequences do not erase ruled lines, only the characters within the boundaries of the ruled lines. For example:
DL	Delete line	This escape sequence erases both lines of characters and ruled lines at the active position of deletion. The text lines and accompanying ruled lines that follow the deletion point scroll up the screen. For example:
IL	Insert line	This escape sequence causes insertion of blank lines at the active position. It causes both text and accompanying ruled lines currently at the active position to scroll down the screen. For example:
DCH	Delete character	This escape sequence does not delete ruled lines. The following example shows the result of deleting four characters at the third column position:
ICH	Insert character	This escape sequence causes blank spaces to be inserted at the active position but has no effect on ruled lines. The following example shows the result of inserting four characters at the third column position:
IRM	Invoke insert/replace mode	Insert/replace mode has no effect on ruled lines. The following example shows the result of inserting the characters w, x, y, and z at the third column position and replacing the character f with s:
DECCOLM	Invoke column mode	Ruled lines are erased with accompanying text when column mode is in effect.
RIS, DECSTR	Reset to initial state and soft terminal, invoke reset SETUP mode	The RIS sequence erases all ruled lines displayed on the screen while the DECSTR sequence does not. Note that the Clear Display option on the DECterm Commands menu erases all ruled lines whereas the Reset Terminal option does not.

D.1.5    Determining if the DECterm Device Setting Supports Ruled Lines

The feature that allows applications to draw ruled lines is enabled only when a DECterm window is emulating a terminal type that supports this feature. Your application can check for device support by requesting primary device attributes from DECterm software.

VT terminals and DECterm software return a primary device attributes report on request from applications. If the extension value 43 is included in this report, drawing ruled lines is enabled for the device. This extension is valid at a level-2 video display or higher. For example, if a DECterm window is emulating a VT382-J terminal, which is the Japanese version of a VT382, the primary device attributes are generated as follows:

CSI ? 63 ; 1 ; 2 ; 4 ; 5 ; 6 ; 7 ; 8 ; 10 ; 15 ; 43 c

Applications can send either the CSI c or CSI 0 c escape sequence to a VT terminal or DECterm software to request a device attributes report.

D.2    DECterm Programming Restrictions

This section discusses DECterm software restrictions with respect to terminal programming features discussed in hardware manuals.

D.2.1    Downline Loadable Characters

DECterm software does not support the downline loadable characters that are used for preloading and on-demand loading of terminals. The software ignores the escape sequence for these characters.

D.2.2    DRCS Characters

DECterm software supports only the Standard Character Set (SCS) component of the DIGITAL Replacement Character Set (DRCS). When DECterm software receives the SCS characters, it searches the X window server for the fonts with XLFD named as -*-dec-drcs and treats them as a soft character set. The software ignores the DECDLD control string sent by the terminal programming application.