box-sizing

box-sizing
==========
Utility module to accept a variety of left, top, width, height combinations and output true left, top, width, height positions as valid numbers.

This module exposes a single function which is intended to be used as an assistant for positioning screen widgets such as Windows in a similar way to how CSS block elements work.

var boxSizing = require('box-sizing');

var coords = boxSizing({
left: "20",
top: -20,
width: '50%',
height: 50,
}, {
maxWidth: 100,
maxHeight: 100,
});

// coords = {
// left: 20, // Straight forward copy (with type conversion to Number)
// top: 40, // (i.e. negative values are bottom aligned)
// width: 50, // (i.e. 50% of maxWidth)
// height: 50, // Another straight copy
// }

The boxSizing function can also take predefined default values:

var coords = boxSizing({
left: 20,
}, {
top: 30,
height: 40,
width: 50,
});

// coords = {
// left: 20,
// top: 30,
// width: 40,
// height: 50,
// }

Valid input formats
-------------------
The four main keys can be specified in the following format:

* Number - The value is used as is. E.g. '10' => '10px' offset
* String + "%" The value is used as a percentage of the whole. E.g. '10%' => '10%' of horizontal or vertical space (depending on context)
* "middle" / "center" - (only applicable for 'left' and 'top' positions) Tries to center the window based on 'width' and 'height' keys.
* -Number - Any negative value will be right or bottom aligned. E.g. -10 => 10 pixels from the right or bottom of the screen