!important styles don't get overriden

[Michael DeRazon]

I have a React.js component that is setting the height of the component as an inline style and I have no control over it.
To make it work with buggyfill, I had to create a class with !important to override the precedency of the inline styles of the lib. Therefor I have something like this in my CSS file:

.map {
  height: 85vh !important;
}

When debugging on IOS7, I see the fixed px class that is the result of buggyfill, but the above class definition still takes precedency over the 3 (the buggyfill version, the inline version and the !important class version)

Any ideas how to bypass this ?

[Michael DeRazon]

found a workaround.
changed line 326
from

return (_number * _base) + 'px';

to

return (_number * _base) + 'px !important';

[Rodney Rehm]

You could try a bit more generic approach to solving the issue in replaceValues():

function replaceValues(match, number, unit, source) {
  var _base = dimensions[unit];
  var _number = parseFloat(number) / 100;
  var _important = source.indexOf('!important') !== -1 ? ' !important' : '';
  return (_number * _base) + 'px' + _important;
}

let me know if that works for you (I haven't tested it) so we may improve the buggyfill instead of dealing with custom workarounds…

[Michael DeRazon]

You've changed replaceValues signature from match, number, unit to match, number, unit, source without changing the caller function ?
Am I missing something ?

It doesn't work, tells me that variable source is undefined

[Rodney Rehm]

The caller is String.prototype.replace() and it knows the signature of the supplied callback. I was missing the offset parameter, though:

function replaceValues(match, number, unit, offset, source) {
  var _base = dimensions[unit];
  var _number = parseFloat(number) / 100;
  var _important = source.indexOf('!important') !== -1 ? ' !important' : '';
  return (_number * _base) + 'px' + _important;
}

[Michael DeRazon]

that did fix the "source undefined" issue but for some reason !important is not being passed to the source.

For example, in my stylesheet I define

.map {
    height: 75vh !important;
}

and printing source variable in replaceValues() I see

75vh

instead of

75vh !important

[Rodney Rehm]

Then we should investigate how to get that !important accessed…

[Michael DeRazon]

On line 232 you do

forEach.call(rule.style, function(name) {
  var value = rule.style.getPropertyValue(name);
  viewportUnitExpression.lastIndex = 0;
  if (viewportUnitExpression.test(value)) {
    declarations.push([rule, name, value]);
    options.hacks && options.hacks.findDeclarations(declarations, rule, name, value);
  }
});

CSSStyleDeclaration.getPropertyValue() only gets the property value,

We can use it with CSSStyleDeclaration.getPropertyPriority() (see here)

So it will be something like

forEach.call(rule.style, function(name) {
  var priority = '';
  if (rule.style.getPropertyPriority(name)) {
    priority = ' !important';
  }
  var value = rule.style.getPropertyValue(name) + priority;
  viewportUnitExpression.lastIndex = 0;
  if (viewportUnitExpression.test(value)) {
    declarations.push([rule, name, value]);
    options.hacks && options.hacks.findDeclarations(declarations, rule, name, value);
  }
});

What do you think ?

[Michael DeRazon]

tested it with my use case, and it looks like it's fine.

Tried using both

.map {
  height: 85vh !important;
}

and

.map {
  height: 85vh;
}

first one converted to 360px !important and the second one to 360px on my iphone 4 so it looks like it's working.

Also, it's safe to assume that getPropertyPriority() returns either "important" or empty string ""

Are there any other implications you're aware of ?

[Rodney Rehm]

Good Work!

I think pushing the boolean returned by rule.style.getPropertyPriority(name) onto the declarations list declarations.push([rule, name, value, priority]); is the cleaner (as in more obvious) solution, but one that requires a lot more code to be changed, whereas your propsal is limited to a single function. So I'd go with your proposal, rewritten to a 4-line change:

forEach.call(rule.style, function(name) {
  var value = rule.style.getPropertyValue(name);
  // preserve those !important rules
  if (rule.style.getPropertyPriority(name)) {
    value += ' !important';
  }

  viewportUnitExpression.lastIndex = 0;
  if (viewportUnitExpression.test(value)) {
    declarations.push([rule, name, value]);
    options.hacks && options.hacks.findDeclarations(declarations, rule, name, value);
  }
});

Do you want to send a PR for this? (If so, please also add and example to the test.css, which sort of functions as a manual test)