How to use SASS logic within a CSS 3 media query [duplicate]

Question

I'm using saas via the compass framework and the blueprint/grid dependency. I want to be able to set the width of a column using a media query, like so:

// /src/partials/_base.scss
$blueprint-grid-columns: 18;

@media screen and (max-width: 1024px){
    // If screen res is 1024 or lower, then set grid width to 46px
    $blueprint-grid-width: 46px;
}
@media screen and (max-width: 1280px){
    $blueprint-grid-width: 50px;
}
@media screen and (max-width: 1600px){
    $blueprint-grid-width: 76px;
}

$blueprint-grid-margin: 8px;

This compiles to in /stylesheets/screen.css:

@media screen and (max-width: 1024px) {}
@media screen and (max-width: 1280px) {}
@media screen and (max-width: 1600px) {}

But the values in the rest of screen.css are not set accordingly. I guess that makes sense, since the $blueprint-grid-width variable is read at compile time, not run time.

Is there a way to output a layout with different grid widths by using a media query to get screen resolution?

Related github issue:
https://github.com/chriseppstein/compass/issues/302

Answer 1

This was a bug in SASS. It's been fixed as of version 3.1.0:

http://sass-lang.com/docs/yardoc/file.SASS_CHANGELOG.html#310

Answer 2

I'm trying to figure out the same thing but there doesn't seem to be a good way to get this working the way I want it to. Like you said, the variables get set at compile time, not runtime so it's hard to figure. I think you could do something like this:

@media screen and (max-width: 1024px) {
    $blueprint-grid-width: 46px;
    @import 'blueprint';
    // do everything else you need to with this size
}

But then you'd have to do this same, brute force kind of reset of Blueprint for every media query you want to run.