Provide cross-browser Rects for box model dimensions for Elements.

tools/dom/src/Dimension.dart

+/** Class representing a distance measurement in CSS. */

[Jennifer Messerly, 2013/07/16 22:03:16]

fyi, I think the spec terminology is "length".

either way, might be good to link something like:
https://developer.mozilla.org/en-US/docs/Web/CSS/length
?

[Emily Fortuna, 2013/07/18 22:45:02]

Done.

+@Experimental()
+class Dimension {
+  num _value;
+  String _unit;
+
+  /** Set this CSS Dimension to a percentage `value`. */
+  Dimension.percent(this._value) : _unit = '%';
+
+  /** Set this CSS Dimension to a pixel `value`. */
+  Dimension.px(this._value) : _unit = 'px';
+
+  /** Set this CSS Dimension to a pica `value`. */
+  Dimension.pc(this._value) : _unit = 'pc';
+
+  /** Set this CSS Dimension to a point `value`. */
+  Dimension.pt(this._value) : _unit = 'pt';
+
+  /** Set this CSS Dimension to an inch `value`. */
+  Dimension.inch(this._value) : _unit = 'in';
+
+  /** Set this CSS Dimension to a centimeter `value`. */
+  Dimension.cm(this._value) : _unit = 'cm';
+
+  /** Set this CSS Dimension to a millimeter `value`. */
+  Dimension.mm(this._value) : _unit = 'mm';
+
+  /**
+   * Set this CSS Dimension to the specified number of ems.
+   *
+   * 1em is equal to the current font size. (So 2ems is equal to double the font
+   * size). This is useful for producing website layouts that scale nicely with
+   * the user's desired font size.
+   */
+  Dimension.em(this._value) : _unit = 'em';
+
+  /**
+   * Set this CSS Dimension to the specified number of x-heights.
+   *
+   * One ex is equal to the the x-height of a font's baseline to its mean line,
+   * generally the height of the letter "x" in the font, which is usually about
+   * half the font-size.
+   */
+  Dimension.ex(this._value) : _unit = 'ex';
+
+  /**
+   * Construct a Dimension object from the CSS string `cssValue`, in pixels.
+   *  This constructor is only called on output from getComputedValue, which we
+   * know to be pixels.
+   */
+  Dimension._(String pixels = '0px') {

[Jennifer Messerly, 2013/07/16 22:03:16]

make this public? It seems really useful, even if it can't handle all cases
(throwing an error for invalid data would be okay IMO). This would make the very
string-based CssStyleDelcaration a lot easier to work with.

[Emily Fortuna, 2013/07/18 22:45:02]

Updated! It originally was, but I had made it private after Pete's comments. But
I do think that's what makes this class useful. Fixed!

+    if (pixels.contains('.')) {
+      _value = double.parse(pixels.substring(0, pixels.length - 2));
+    } else {
+      _value = int.parse(pixels.substring(0, pixels.length - 2));
+    }
+    _unit = 'px';
+  }
+
+  /** Print out the CSS String representation of this value. */
+  String toString() {
+    return '${_value}${_unit}';
+  }
+
+  /** Return a unitless, numerical value of this CSS value. */
+  num get value => this._value;

[Jennifer Messerly, 2013/07/16 22:03:16]

remove this.?

+}