Attributes

Control code characters set display attributes which control the text colour, double height, flashing etc. The default attributes at the beginning of a row are white text on a black background, single height, not flashing, not boxed, not concealed, no held mosaic. Graphics, when activated, default to contiguous display. When an attribute is set it stays activated until the end of the row (generally). An attribute takes up a space unless 'hold mosaics' is active, in which case the held mosaic character is used.

To help with the control codes, the Attributes and Colour objects can be used when composing strings for setPageRows(), setRow(), writeBytes() and writeByte(). They're optional, and you can use the control codes directly when writing to the base page.

import { Attributes, Colour } from '@techandsoftware/teletext';

Attributes.charFromTextColour(colour)

Sets text mode for the specified colour. Characters following this are mapped according to the G0 character set. See below for the colours.

Attributes.charFromGraphicColour(colour)

Sets graphic mode for the specified colour. Characters following this draw block mosaics from the G1 character set if the character code is 20 to 3f or 60 to 7f; characters 40 to 5f show the character from the G0 set with the same character code.

colour is one of these:

• Colour.RED
• Colour.GREEN
• Colour.YELLOW
• Colour.BLUE
• Colour.MAGENTA
• Colour.CYAN
• Colour.WHITE
• Colour.BLACK - black was added in level 2.5, but is included here at level 1.5 and ignored at level 1

Attributes.charFromAttribute(attribute)

Gets the code for an attribute. attribute is one of these:

Attribute	Use
Attributes.NEW_BACKGROUND	set the background colour to the current foreground colour
Attributes.BLACK_BACKGROUND	set the background colour to black
Attributes.CONTIGUOUS_GRAPHICS	set the mosaic graphics to contiguous blocks
Attributes.SEPARATED_GRAPHICS	set the mosaic graphics to separated blocks
Attributes.FLASH	activate flashing for text/mosaic
Attributes.STEADY	deactivate flashing for text/mosaic
Attributes.NORMAL_SIZE	set text/mosaic to normal height
Attributes.DOUBLE_HEIGHT	set text/mosaic to double height. The row below will be hidden. Background colours on this row will be extended to the row below. Single height characters on the top row stay single height but their background colour is still extended to the lower row
Attributes.DOUBLE_WIDTH	set text/mosaic to double width. Double width characters use two cells, and the character in the next cell is hidden. Requires Level 2.5 to be set
Attributes.DOUBLE_SIZE	set text/mosaic to double size. Double size characters use four cells. The row below is hidden as per double height, and the character in the cell after a double size character is hidden as per double width. Requires Level 2.5 to be set
Attributes.CONCEAL	text/mosaic characters show as spaces until reveal is pressed. For use with toggleReveal() / ttx.reveal. The concealed atttribute is active until the next colour attribute (or the end of the row)
Attributes.HOLD_MOSAICS	stores the last mosaic character seen on a row (going left to right) so that on the next spacing attribute the held mosaic is used instead of a space. A practical use is in a row of graphics, so that the colour could be changed without a space, with the space being filled in with the mosaic before the colour change. The held mosaic is reset to a space with a change of size or text/graphics mode
Attributes.RELEASE_MOSAICS	cancels held mosaic mode, so that attributes will show a space and not the held mosaic. The held mosaic isn't reset to a space
Attributes.START_BOX	starts boxed characters (used for subtitles, newsflash). Two adjacent start box characters need to be used, with the box starting between the two. For use with toggleBoxMode()
Attributes.END_BOX	ends boxed characters. Two adjacent end box characters need to be used, with the box ending between the two.
Attributes.ESC	switch between the default G0 character set and the second G0 character set. This requires the second G0 character set to have been set with setSecondG0Charset(). If this hasn't been set, the attribute has no effect

As an example, to set red text on a yellow background, you will need:

teletext.setPageRow(0, Attributes.charFromTextColour(Colour.YELLOW) +
    Attributes.charFromAttribute(Attributes.NEW_BACKGROUND) +
    Attributes.charFromTextColour(Colour.RED) + "Red on yellow");

The attributes take up 3 spaces before the text.

If you prefer to use the control codes directly, check the source of Attributes.js or the teletext spec to get the control code values. Double height, for instance, is code 13 (or d in hexadecimal), so you could use strings like "\x0d", "\u{d}", String.fromCharCode(13).