Macros for printer common tasks

[cesarreyes3]

It would be very helpful if we could create macros on the printer class, it could simplify common tasks, for example:

Here, you create 'Item' class for formating a line

escpos-php/example/rawbt-receipt.php

Lines 16 to 21 in f414320

	$items = array(
	new item("Example item #1", "4.00"),
	new item("Another thing", "3.50"),
	new item("Something else", "1.00"),
	new item("A final item", "4.45"),
	);

escpos-php/example/rawbt-receipt.php

Lines 126 to 138 in f414320

	public function getAsString($width = 48)
	{
	$rightCols = 10;
	$leftCols = $width - $rightCols;
	if ($this->dollarSign) {
	$leftCols = $leftCols / 2 - $rightCols / 2;
	}
	$left = str_pad($this->name, $leftCols);
	$sign = ($this->dollarSign ? '$ ' : '');
	$right = str_pad($sign . $this->price, $rightCols, ' ', STR_PAD_LEFT);
	return "$left$right\n";
	}

With a macro we can do

Printer::macro('item', function($name = '', $price = '', $dollarSign = false, $width = 48){
        $rightCols = 10;
        $leftCols = $width - $rightCols;
        if ($dollarSign) {
            $leftCols = $leftCols / 2 - $rightCols / 2;
        }
        $left = str_pad($name, $leftCols);

        $sign = ($dollarSign ? '$ ' : '');
        $right = str_pad($sign . $price, $rightCols, ' ', STR_PAD_LEFT);
        return "$left$right\n";
});

//Example
$printer->item('Total', '14.25', true);

@mike42 I could add some test and examples if they are needed