Add documentation for XML format

README.md

@@ -119,6 +119,7 @@ const buffer = EscPos.getBufferFromTemplate(template, input);
 
 ## Useful links / resources
 
+- [XML Schema](doc/xml.md)
 - [ESC / POS Commands manual](./resources/ESCPOS_Command_Manual.pdf) 
 - A [blog post](https://www.visuality.pl/posts/thermal-printer-protocols-for-image-and-text#:~:text=How%20can%20we%20print%20an,command%20language%20of%20thermal%20printers) explaiing about printing images with ESCPOS 
 - Similar library for serverside - [node-escpos](https://github.com/song940/node-escpos).

doc/xml.md

@@ -0,0 +1,214 @@
+# XML Schema for xml-escpos-helper
+
+## `<document>` Element
+
+This is the root XML element of an ESC/POS template.
+
+### Attributes
+
+#### `reverse`
+
+If set, enables reverse (upside-down) printing.
+
+## `<align>` Element
+
+Sets the alignment of text contained by this element.
+
+### Attributes
+
+#### `mode`
+
+`mode=`  | Effect
+---------|-------
+`left`   | Contents are left justified.
+`right`  | Contents are right justified.
+`center` | Contents are centered.
+
+## `<barcode>` Element
+
+Prints the contained text in barcode form.
+
+### Attributes
+
+#### `system`
+
+The bar code system to print. Required. One of:
+
+- `CODABAR`
+- `CODE_39`
+- `CODE_93`
+- `CODE_128`
+- `EAN_8`
+- `EAN_13`
+- `ITF`
+- `UPC_A`
+- `UPC_E`
+
+#### `width`
+
+The width of the bar code when printed. One of:
+
+- `DOT_250`
+- `DOT_375` (default)
+- `DOT_560`
+- `DOT_625`
+- `DOT_750`
+
+
+#### `labelFont`
+
+The font used to print the textual label that accompanies the bar code. One of:
+
+- `FONT_A` (default)
+- `FONT_B`
+
+#### `labelPosition`
+
+The position of the textual label that accompanies the bar code. One of:
+
+`labelPostion=` | Effect
+----------------|-------
+`NOT_PRINT`     | Disables printing the label.
+`ABOVE`         | Print the label above the bar code.
+`BOTTOM`        | Print the label below the bar code (default).
+`ABOVE_BOTTOM`  | Print the label both above and below the bar code.
+
+#### `height`
+
+The height of the bar code, in dots. If specified, must be a positive integer.
+If not specified, defaults to 162 dots.
+
+#### `leftSpacing`
+
+How many dots to pad the bar code with on the left side.
+If specified, must be a positive integer. Defaults to 0 dots.
+
+## `<bold>` Element
+
+Prints the contents in bold.
+
+## `<break-line>` Element
+
+Inserts one or more line breaks, usually after printing one or more `<text>` elements.
+
+### Attributes
+
+#### `lines`
+
+The number of lines to insert. Must be a positive integer. Default value is 1.
+
+## `<image>` Element
+
+Prints the image contained by this element.
+Image data should be URL-encoded base-64 PNG; it should be prefixed with
+"data:image/png;base64,"
+
+### Attributes
+
+#### `mode`
+
+The print mode for the image.
+
+`mode=`               | Effect
+----------------------|-------
+`NORMAL`              | Print image with no scaling (default).
+`DOUBLE_WIDTH`        | Print image at 2x width.
+`DOUBLE_HEIGHT`       | Print image at 2x height.
+`DOUBLE_WIDTH_HEIGHT` | Print image at 2x width and height.
+
+## `<line-feed>` Element
+
+Inserts a single line break.
+
+## `<open-cash-drawer>` Element
+
+Opens the cash drawer on so-equipped printers.
+
+## `<paper-cut>` Element
+
+Cuts the paper on printers with an automated cutter.
+
+## `<print-mode>` Element
+
+Sets the print mode for specific printer models.
+
+### Attributes
+
+#### `mode`
+
+If mode is 'U220', enables support for that printer model.
+Supports generic printers otherwise.
+
+## `<qrcode>` Element
+
+Prints the contained text in QR code form.
+
+### Attributes
+
+#### `model`
+
+Selects the model of QR code
+
+`model=` | Effect
+---------|-------
+1        | Model 1 QR code.
+2        | Model 2 QR code (default).
+
+#### `size`
+
+Sets the size of each QR code module (pixel), in dots.
+Must be a positive integer, default value is 8.
+
+#### `ecl`
+
+Sets the error correction level. One of:
+
+`ecl=` | Effect
+-------|-------
+`L`    | Low error correction (default).
+`M`    | Medium error correction.
+`Q`    | "Quality" error correction.
+`H`    | High error correction.
+
+## `<small>` Element
+
+Prints its contents in small font.
+
+## `<text>` Element
+
+Prints its context, without a line feed at the end.
+
+### Attributes
+
+#### `size`
+
+Sets the size of the text.
+Must be in "x:y" format, where x and y are the horizontal and vertical character sizes.
+Both x and y must be non-negative integers. Default size is "0:0".
+
+## `<text-line>` Element
+
+Prints its contents as a line of text, with a line feed at the end.
+
+### Attributes
+
+Accepts the same attributes as `<text>`
+
+## `<underline>` Element
+
+Prints its contents underlined.
+
+### Attributes
+
+#### `mode`
+
+Controls the thickness of the line:
+
+`mode=`      | Effect
+-------------|-------
+`one-point`  | Underline is one dot thick.
+`two-points` | Underline is two dots thick (default).
+
+## `<white-mode>` Element
+
+Prints its contents color-inverted (i.e. white on black).