Text Book

Text Book is a file format used in Sonic the Hedgehog (2006) for storing text with friendly names and variables.

These files are located in cache.arc and text.arc under the ./text/ directory from platform root as *.mst files.

Specification

Text Book uses a Binary Resource container. The text to be displayed is encoded as UTF-16, whereas the names and variables are encoded as Shift-JIS.

Header

The header consists of the following data structure:

Length: 0x0C

Offset	Type	Name	Description
0x00	Char[4]	Signature	Always "WTXT" (referring to UTF-16).
0x04	UInt32	NameOffset	The offset of the name of this Text Book.
0x08	UInt32	CardCount	The total number of Text Cards in this Text Book.

Text Card

Text Cards consist of the following data structure:

Length: 0x0C

Offset	Type	Name	Description
0x00	UInt32	NameOffset	The offset of the name of this Text Card.
0x04	UInt32	TextOffset	The offset of the UTF-16 text for this Text Card.
0x08	UInt32	VariablesOffset	The offset of the variables for this Text Card.

Control Characters

The text stored in Text Cards support using control characters for certain interactive or visual behaviours.

Character	Description
\f	Creates a new page in the message window. The next page is switched to automatically after the voice line started by a sound variable has finished, otherwise it waits for player input.
\n	Creates a new line in the text entity.
$	Creates a placeholder marker for a variable to be inserted in the text entity. If no variable exists for this marker, it'll display as $.

Variables

Variables are stored as comma-separated values, there should be one for each '$' character in the actual text to be displayed.

Variable	Parameters	Description
blue	None	Once encountered, starts colouring characters blue.
color	None	Once encountered, starts colouring characters white.
color!	None	Once encountered, starts colouring characters yellow. Presumably this is meant as the "warning" colour, hence the exclamation mark.
gray	None	Once encountered, starts colouring characters grey.
green	None	Once encountered, starts colouring characters green.
picture	String	Once encountered, draws the specified picture defined in the game's Text Font Picture file.
red	None	Once encountered, starts colouring characters red.
rgba	Byte, Byte, Byte	Once encountered, starts colouring characters the specified colour. Despite the name, this does not support setting the alpha colour of the text.
sound	String	Once encountered, plays the specified sound effect if the Sound Bank containing it is loaded.
text	Unknown	Unknown.
value	Unknown	Unknown.
yellow	None	Once encountered, starts colouring characters yellow.

Example

With the following text:

$The quick $brown$ fox jumps over the $lazy$ dog.\nPress the $ button to continue.

And the following variables:

sound(all01_a00_sn),rgba(127,51,0),color,red,color,picture(button_a)

The game should first play the sound all01_a00_sn, then draw something akin to the following text:

The quick brown fox jumps over the lazy dog. Press the Ⓐ button to continue.